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Fields : Petroleum - Bitumen - Chemical Industry - Polymer - Food Industry - Search - Biochemistry
Petroleum
| Magazine |
J. Phys. Chem. B 2009, 113, 13788–13799 |
| Year |
2009 |
| Autors |
Vincent J. Verrutoa, Rosemary K. Lea and Peter K. Kilpatricka |
| Estb. |
a North Carolina State UniVersity, Dept. of Chemical Engineering, 911 Partners Way, Raleigh, North Carolina 27625 |
| Abstract |
The formation of stable water-in-petroleum emulsions is a costly challenge when transporting, processing, and refining heavy crude oil and bitumen. The stability of these emulsions is attributed to interfacial films with well-documented viscoelastic properties that are known to vary with concentration, solvent quality, and asphaltene chemistry. In this study, we explore the impact of aqueous phase pH and salinity on the transient interfacial rheological properties of asphaltenic films. Using two chemically unique asphaltenes, interfacial shear rheology revealed an apparent salt-induced retardation of the interfacial consolidation processes that ultimately engender elasticity to the film. For Hondo asphaltenes at pH 7, a linear dependence of this retardation on the Debye parameter (κ) suggested that shielding of electrostatic attraction was responsible. Further investigation with dynamic oscillating drop tensiometry at pH 3, 7, and 10 illustrated that intralayer repulsive and attractive electrostatic interactions can significantly influence the evolution of the interfacial structure. More specifically, the transient tension and dilatational modulus profiles indicated several interfacial processes were affected by the addition of salt, including (i) interfacial activity and the extent of adsorption, (ii) interfacial rearrangement and consolidation, and (iii) interfacial transport or displacement or both. Furthermore, the observed asphaltene interfacial behavior was consistent with those published for interfacial structure-forming amphoteric proteins, such as lysozyme and β-casein. |
| Magazine |
Journal of colloid and interface science 270(2004) 295-298 |
| Year |
2003 |
| Autors |
Alain Cagnaa, Yang Lib, Shengxiang Jiangc, Huanquan Sunb, Xulong Caoc and Lixia Doub |
| Estb. |
a I.T. Concept, Parc de Chancdan, 69770 Longessaigne, France
b Geological Research Institute of Shengli Oilfield, SINOPEC, Dongying 257015, China
c Lanzhou Institute of Chemical Physics, Chinese Academy of Science, Lanzhou 730000, China |
| Abstract |
Viscoelastic properties of two polymers, partially hydrolyzed polyacrylamide and partially hydrolyzed modified polyacrylamide, widely used in chemical flooding in the petroleum industry, were investigated at three interfaces, water–air, water–dodecane, and water–crude oil, by means of a dilational method provided by I.T. Concept, France, at 85 ◦C. Polymer solutions were prepared in brine with 10,000 mg/l sodium chloride and 2000 mg/l calcium chloride. It has been shown that the viscoelastic modulus increases with the increment of polymer concentration in the range of 0–1500 mg/l at the water–air interface. Each polymer shows different viscoelatic behavior at different interfaces. Generally speaking, values of the viscoelastic modulus (E), the real part (E ′), and the imaginary part (E ″) at the crude oil–water interface for each polymer are lower than at the air–water or water–dodecane interface. The two polymers display different interfacial properties at the same interface. Polymer No. 2 gives more viscous interfaces than polymer No. 1. All the information obtained from this paper will be helpful in understanding the interfacial rheology of ultra-high-molecular-weight polymer solutions. |
| Magazine |
Energy conversion and management 48 (2007) 736-744 |
| Year |
2006 |
| Autors |
Pierre Chiqueta, Jean-luc Daridona, Daniel Brosetaa and Sylvain Thibeaub |
| Estb. |
a Lab. des fluides complexes, UMR 5150, université de Pau et des Pays de l'Adour, 64013 Pau-Cedex, France
b Centre Scientifique et technique Jean Feger, Totoal, Avenue Larribau, 64018 Pau Cedex, France |
| Abstract |
CO2 storage in aquifers and depleted hydrocarbon reservoirs is one of the most promising options for reducing CO2 atmospheric concentration. However, its implementation in a given reservoir requires demonstration that CO2 leakage through the reservoir seal (caprock) is extremely limited. One possible cause of rapid leakage is capillary failure of the caprock, which is to a large extent controlled by the CO2/water interfacial tension (IFT). This paper presents pendant drop measurements of IFTs between water and CO2 in a range of temperatures (308–383 K) and pressures (5–45 MPa) relevant to CO2 storage in deep geological formations. Phase densities were measured simultaneously, allowing precise IFT determinations. Increasing the pressure along a given isotherm, IFTs were observed to decrease sharply, then to level off and reach, for pressures above 20 MPa, a pseudo-plateau that decreases slightly with temperature, from around 30 mN/m at 308 K to 23 mN/m at 383 K. The presence of salt (20 g/l NaCl) in the water phase has a negligible effect on the IFT. An important conclusion for CO2 storage is that CO2/brine IFTs have low but reasonable values (higher than 20 mN/m) even at the highest pressures and temperatures examined, and that, neglecting all other possible effects, CO2 storage can, therefore, be considered even in deep geological formations. |
| Magazine |
Journal of dispersion science and technology vol.23,No 6, 809-825, 2002 |
| Year |
2002 |
| Autors |
Narve Askea, Robert Orrb and Johan Sjöblomc |
| Estb. |
a The norwegian university of science and technology, ugelstad labo, Dept of chemical engineering, N-7491 trondheim, Norway
b NorskHydro ASA, Research Park,N-3907 Porsgrumm,Norway
c Statoil R&D Centre, Rotvoll, N-7005 Trondheim, Norway |
| Abstract |
The oscillating pendant drop instrument was used to measure the dilatational elasticity modulus and dynamic interfacial tension of 21 crude oils and condensates originating from different production fields. The samples were diluted in different heptane/toluene solvents at concentrations of 0.002, 0.01, and 0.02mL oil/mL solvent. Both the solvent composition and oil concentration were found to have a great influence on the measurements. Higher aromaticity solvents reduced the interfacial activity of the natural surfactants in the crude oil. Different time dependences in the buil up of the elastic interfaces for the crude oils were also found. The samples have also been subjected to SARA analysis and TAN (Total Acid Number) determination, and the results have been correlated to the oscillating pendant drop measurements. Especially the influence of the crude oil surfactants, resins, and asphaltenes, on the interfacial properties was studied. Indications of both interfacial active and non-interfacial active asphaltenes were found. Asphaltene interfacial coverage values of 2.3 and 3.1 mg/m² have been reported. |
| Magazine |
Energy & Fuels 2007, 21, 1343-1349 |
| Year |
2007 |
| Autors |
Xiaoli Yanga, Vincent J. Verrutoa and Peter K. Kilpatricka |
| Estb. |
a Department of Chemical and Biomolecular Engineering, North Carolina State UniVersity,Raleigh, North Carolina 27695-7905 |
| Abstract |
The critical electric field (CEF) technique was used to determine the time-dependent stability of water-inoil emulsions in which asphaltenes stabilize the film. Stabilizing films comprising purely asphaltenes were observed to increase monotonically in stability with time. However, in the presence of resins, particularly in mass ratios of resins to asphaltenes of 0.5-1.0, the stability of the emulsions as probed by CEF were observed to exhibit a very sharp local maximum. Similar behavior was observed in dilatational interfacial rheology experiments using an oscillating drop tensiometer. The dilatational modulus (E) for the stabilizing film, as obtained from the variation of interfacial tension with interfacial area, of an aging asphaltene/resin model oil droplet in water exhibited a time-dependent local maximum. Values of E were nominally lower for asphaltene/ resin model oil systems than asphaltene model oil systems, qualitatively similar to CEF trends. These observed phenomena are similar to the “Vroman effect”, observed in competitive protein adsorption. One plausible explanation is that resin-solvated asphaltenic aggregates are able to diffuse and adsorb to the interface more quickly than larger pure asphaltenic aggregates, but then a molecular rearrangement occurs in which resins become the primary adsorbent in the monolayer by reptation through the consolidated asphaltene network, displacing the asphaltenes and reducing the stability and the dilatational elasticity. |
| Magazine |
Journal of colloid and interface science 239,501-508 (2001) |
| Year |
2001 |
| Autors |
Fabrice Baugeta, Dominique Langevinb and Roland Lenormanda |
| Estb. |
aInstitute français du pétrole,1&4, avenue de bois-préau,92852 Rueil-Molmaison Cedex,France
bLab. de physique des solides, université Paris-sud, Bât510,91405 Orsay Cedex, France |
| Abstract |
Because of the existence of large reserves, the production of heavy oils is presently the object of much interest. Some heavy oil reservoirs show anomalous behavior in primary production, with rates of production better than predicted. In Canada and Venezuela some heavy oils are produced in the form of "bubbly" oil, which is stable for several hours in open vessels. These crude oils are therefore commonly called "foamy oils". Since the presence of bubbles could be responsible for an enhanced rate of production, a better knowledge of the properties of the gas-oil interface is desirable. We have experimentally studied the effect of concentration of asphaltenes and resins on static and dynamic properties of oil-air interfaces and also on bulk viscosity. The experiments include surface tension measurements using the pendant-drop method, surface viscosity by the oscillating-drop method, foamability by continuous gas injection, and film lifetime. All the experiments were performed using resins and asphaltenes in toluene solutions at 20°C. At first asphaltenes enhance foamability and film lifetime. All the experiments performed showed a change in regime for asphaltene concentrations around 10% by weight, possibly due to clustering. At the studied concentrations, the adsorption process at the air-oil interface is not diffusion controlled but rather involves a reorganization of asphaltene molecules in a network structure. The formation of a solid skin is well identified by the increase of the elastic modulus. The elastic modulus is also an important property for foam stability, since a rigid interface limits bubble rupture. The interface rigidity at long times decreases with increases in resin fraction, which could decrease foam stability as well as emulsion stability. |
| Magazine |
Energy & Fuels |
| Year |
2011 |
| Autors |
Siwar Trabelsi a, Jean Francois Argillier a, Christine Dalmazzone a, Anthony Hutin a, Brigitte Bazin b and Dominique Langevin b |
| Estb. |
a IFP Energies nouvelles, 1-4 avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
b Laboratoire de Physique des Solides, Université Paris-Sud, CNRS UMR8502, Bâtiment 510, 91405 Orsay Cedex, France
|
| Abstract |
We report an experimental study of surfactant-enhanced alkaline/diluted heavy oil systems in order to understand the combined effect of different parameters such as pH, salinity, surfactant type, and concentration on diluted heavy oil/brine phase interfacial behaviour. The interfacial tension (IFT) was measured using pendant drop and spinning drop tensiometers. Different surfactants (Triton X405, SDS, SDBS) were tested. SDBS was by far the most efficient surfactant, reducing the IFT to ultra-low values ~ 4×10-4 mN/m at a concentration of only 0.05% and a pH of 11. This efficiency is due to a synergistic effect between the in situ surfactant (produced by saponification of the acids groups present in the crude oil) and the added surfactant (SDBS). |
| Magazine |
Colloids and SurfacesA:Physicochem.Eng.Aspects270–271(2005)257–262 |
| Year |
2005 |
| Autors |
Delphine Daniel-Davida, Isabelle Pezrona, Christine Dalmazzoneb, Christine Noïkb, Danièle Claussea and Ljepsa Komunjera |
| Estb. |
a Lab. Génie des Procédés Industriels, UMR CNRS 6067, Université de Technologie de Compiègne,60205 Compiègne Cedex, France
b Institut Fran¸cais du Pétrole, 1 & 4 Avenue de Bois-Pr´eau, 92852 Rueil Malmaison, France |
| Abstract |
Emulsions are formed during oil exploitation due to the presence of natural surfactants, such as asphaltenes and resins. These molecules strongly stabilise the water/oil interface and prevent coalescence of water droplets. As water/oil phase separation is necessary before oil refining, surfactants are used to break water-in-oil emulsions. Formulations based on non-toxic silicone copolymers are found to be effective in promoting emulsion breaking. Moreover, those polysiloxane copolymers can destabilise any kind of crude oil whatever its nature and origin. Thus, the understanding of their molecular action has become essential in order to develop their use in oil exploitation. In present study we use three linear copolymers with very different demulsification efficiency. Two of them are PEO–PDMS–PEO block copolymers, while the third one is a PPO–PDMS–PPO block copolymer. The kinetics of emulsion destabilisation has been followed by turbidimetric measurements. The PEO–PDMS–PEO copolymers gave better results. In order to characterize their elasticity, oscillations of the copolymer monolayers at the water/air interface have been performed. The measured values correspond to two-dimensional condensed film. The liquid/liquid Langmuir balance allowed the determination of the elastic modulus in presence and in absence of copolymer at the water/crude oil interface. The results obtained contribute to a better understanding of the molecular interactions leading to the demulsification process. |
| Magazine |
Energy & Fuels 2009, 23, 294–299 |
| Year |
2009 |
| Autors |
Gabriela Alvareza, Sandrine Poteaua, Jean-François Argilliera, Dominique Langevinb and Jean-Louis Salagerc |
| Estb. |
a Institut Franc¸ais du Pétrole, 1-4 aVenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
b Laboratoire de Physique des Solides, UniVersite´ Paris-Sud, CNRS UMR8502, Bâtiment 510, 91405 Orsay Cedex, France
c Laboratorio FIRP, Ingenierı´a Quimica, UniVersidad de los Andes, Merida, Venezuela |
| Abstract |
We have performed a study of dynamic interfacial tension and rheology of interfaces between water and either crude oil diluted in toluene or in a model oil consisting of toluene, in which pentane-extracted asphaltenes were redissolved. We show that the break point of the curve interfacial tension versus asphaltene concentration is not related to an eventual critical aggregation concentration but rather to the collapse of the asphaltene surface layer. As for other amphiphilic species that adsorb irreversibly at an oil-water interface, the corresponding emulsion stability increases with the amphiphile concentration, even above the collapse point. The behavior of diluted crude oil and model oil are quite similar. However, the surface layers evolve over longer time scales in the case of diluted crude oil, probably because of the contribution of resins that form less polar aggregates with asphaltenes. This results in less stable emulsions, especially before the collapse point. |
| Magazine |
Petrophase |
| Year |
|
| Autors |
S. Poteaua, J-F. Argilliera and D. Langevinb |
| Estb. |
a Institut Français du Pétrole, Rueil Malmaison, France
b Lab. de Physique des Solides, Université Paris -Sud, Orsay, France |
| Abstract |
Oil in water emulsions are currently being investigated to facilitate the transport of viscous heavy oils. The behavior of these emulsions is largely controlled by the interfaces between oil drops and water. The surfaceactive components of crude oil such as asphaltenes and naphtenic acids compete among themselves at these interfaces and also with possibly added synthetic surfactant emulsifier. We present here, as a function of the pH, a study of dynamic interfacial tension and viscoelasticity of interfaces between water and toluene as a model oil in which variable amounts of asphaltenes are solubilised. Influence of lower molecular surfactants, like natural naphtenic acids or synthetic surfactants has been investigated. Some results of SANS experiments on emulsions and micropipette experiments will be presented. The comparison between the microscopic properties of the interface and the macroscopic behavior of the emulsion will also be described. |
| Magazine |
Langmuir 2004, 20, 7459-7464 |
| Year |
2004 |
| Autors |
Patrick Bouriata, Nabil El Kerria, Alain Graciaaa and Jean Lachaisea |
| Estb. |
a Labo des Fluides Complexes, UMR5150, Université de Pau, 64013 Pau Cedex, France |
| Abstract |
Static and dynamic tensiometries show that a newly prepared water/asphaltenated cyclohexane interface behaves as expected: the mean area occupied per asphaltene molecule is 2 nm2, and variations of interfacial tension and dilatational elastic modulus with time indicate that equilibrium is reached more slowly than that for usual surfactants. The use of the time/temperature superposition principle allows a detailed rheological study of a 2 day old interface of the same type which has reached equilibrium. It is found that the two-dimensional asphaltene network exhibits a glass transition zone, behaves as a gel near its gelation point, and is built by a universal process of aggregation. |
| Magazine |
Langmuir 2005, 21, 11651-11658 |
| Year |
2005 |
| Autors |
Danuta M. Sztukowskia and Harvey W. Yarrantonb |
| Estb. |
a Shell Canada Research, 3655 36 StreetNW,Calgary,Alberta, Canada T2L 1Y8.
b Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta, Canada T2N 1N4 |
| Abstract |
The stability of water-in-crude oil emulsions is frequently attributed to a rigid asphaltene film at the water/oil interface. The rheological properties of these films and their relationship to emulsion stability are ill defined. In this study, the interfacial tension, elastic modulus, and viscous modulus were measured using a drop shape analyzer for model oils consisting of asphaltenes dissolved in toluene for concentrations varying from 0.002 to 20 kg/m3. The effects of oscillation frequency, asphaltene concentration, and interface aging time were examined. The films exhibited viscoelastic behavior. The total modulus increased as the interface aged at all asphaltene concentrations. An attempt was made to model the rheology for the full range of asphaltene concentration. The instantaneous elasticity was modeled with a surface equation of state (SEOS), and the elastic and viscous moduli, with the Lucassen-van den Tempel (LVDT) model. It was found that only the early-time data could be modeled using the SEOS-LVDT approach; that is, the instantaneous, elastic, and viscous moduli of interfaces aged for at most 10 minutes. At longer interface aging times, theSEOS-LVDTapproach was invalid, likely because of irreversible adsorption of asphaltenes on the interface and the formation of a network structure. |
| Magazine |
Langmuir, 2009, 25 (7), pp 3985–399 |
| Year |
2009 |
| Autors |
G. Alvareza J. Jestinb J. F. Argilliera D. Langevinc |
| Estb. |
aInstitut Français du Pétrole, 1-4 avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
bLaboratoire de Physique des Solides, Université Paris-Sud, CNRS UMR8502, Bâtiment 510, 91405 Orsay, Cedex, France
cLaboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette, Cedex, France |
| Abstract |
We have used SANS techniques to study in situ interfaces between crude oil and water in emulsions. These emulsions were stabilized by asphaltenes, which are natural surface-active molecules in viscous crude oils. By combining SANS and UV-vis spectrometry, we measured both the interfacial thickness and the adsorbed amount as well as the size of the asphaltene aggregates in the oil phase. We found that this size is comparable to the interfacial thickness, suggesting that the interface is covered by adsorbed aggregates. The thickness is a minimum at the pH at which the charge of asphaltenes in contact with water is zero (IEP). This suggests that asphaltene layers in contact with water are swollen and stretched at both low and high pH. The effect of salt addition on the interfacial characteristics is minor at the IEP, but a clear swelling is seen at high pH for 0.1 M salt, an effect that remains to be understood. Emulsion stability was found to correlate well with large interfacial thicknesses. |
| Magazine |
International journalof greenhouse gas control |
| Year |
2008 |
| Autors |
Virenkumar Shaha,b, Daniel Brosetaa, Gerard Mouronvalb and Franc¸ois Montelb |
| Estb. |
a Lab. des Fluides Complexes, UMR 5150, Université de Pau et des Pays de l'Adour, BP 1155, 64013 Pau, Cedex, France
b TOTAL SA, Centre Scientifique et Technique Jean Feger, 64018 Pau, Cedex, France |
| Abstract |
Acid gas geological disposal is a promising process to reduce CO2 atmospheric emissions and an environment-friendly and economic alternative to the transformation of H2S into sulphur by the Claus process. Acid gas confinement in geological formations is to a large extent controlled by the capillary properties of the water/acid–gas/caprock system, because a significant fraction of the injected gas rises buoyantly and accumulates beneath the caprock. These properties include the water/acid gas interfacial tension (IFT), to which the so-called capillary entry pressure of the gas in the water-saturated caprock is proportional. In this paper we present the first ever systematic water/acid gas IFT measurements carried out by the pendant drop technique under geological storage conditions. We performed IFT measurements for water/H2S systems over a large range of pressure (up to P = 15 MPa) and temperature (up to T = 120 °C). Water/H2S IFT decreases with increasing P and levels off at around 9–10 mN/m at high T (≥70 °C) and P (>12 MPa). The latter values are around 30–40% of water/CO2 IFTs, and around 20% of water/CH4 IFTs at similar T and P conditions. The IFT between water and a CO2 + H2S mixture at T = 77 °C and P > 7.5 MPa is observed to be approximately equal to the molar average IFT of the water/CO2 and water/H2S binary mixtures. Thus, when the H2S content in the stored acid gas increases the capillary entry pressure decreases, together with the maximum height of acid gas column and potential storage capacity of a given geological formation. Hence, considerable attention should be exercised when refilling with a H2S-rich acid gas a depleted gas reservoir, or a depleted oil reservoir with a gas cap: in the case of hydrocarbon reservoirs that were initially (i.e., at the time of their discovery) close to capillary leakage, acid gas leakage through the caprock will inevitably occur if the refilling pressure approaches the initial reservoir pressure. |
| Magazine |
Langmuir 2008, 24, 12807-12822 |
| Year |
2008 |
| Autors |
Vincent J. Verrutoa and Peter K. Kilpatrickb |
| Estb. |
aDepartment of Chemical & Biomolecular Engineering, North Carolina State UniVersity, Raleigh, North Carolina 27695
bDepartment of Chemical & Biomolecular Engineering, UniVersity of Notre Dame, Notre Dame, Indiana 46556 |
| Abstract |
The ever-increasing worldwide demand for energy has led to the upgrading of heavy crude oil and asphaltene-rich feedstocks becoming viable refining options for the petroleum industry. Traditional problems associated with these feedstocks, particularly stable water-in-petroleum emulsions, are drawing increasing attention. Despite considerable research on the interfacial assembly of asphaltenes, resins, and naphthenic acids, much about the resulting interfacial films is not well understood. Here, we describe the use of small-angle neutron scattering (SANS) to elucidate interfacial film properties from model emulsion systems. Modeling the SANS data with both a polydisperse core/shell form factor as well as a thin sheet approximation, we have deduced the film thickness and the asphaltenic composition within the stabilizing interfacial films of water-in-model oil emulsions prepared in toluene, decalin, and 1-methylnaphthalene. Film thicknesses were found to be 100-110 Å with little deviation among the three solvents. By contrast, asphaltene composition in the film varied significantly, with decalin leading to the most asphaltene-rich films (30% by volume of the film), while emulsions made in toluene and methylnaphthalene resulted in lower asphaltenic contents (12-15%). Through centrifugation and dilatational rheology, we found that trends of decreasing water resolution (i.e., increasing emulsion stability) and increasing long-time dilatational elasticity corresponded with increasing asphaltene composition in the film. In addition to the asphaltenic composition of the films, here we also deduce the film solvent and water content. Our analyses indicate that 1:1 (O/W) emulsions prepared with 3% (w/w) asphaltenes in toluene and 1 wt % NaCl aqueous solutions at pH 7 and pH 10 resulted in 80-90 Å thick films, interfacial areas around 2600-3100 cm2/mL, and films that were roughly 25% (v/v) asphaltenic, 60-70% toluene, and 8-12% water. The increased asphaltene and water film composition at pH 10 versus pH 7, along with unique dynamic interfacial tension profiles, suggested that the protonation state of carboxylic moieties within asphaltenes impacts the final film properties. This was further supported when we characterized similar asphaltenic emulsions that also contained 9-anthracence carboxylic acid (ACA). Addition of this aromatic acid led to slightly thinner films (70-80 Å) that were characteristically more aqueous (up to 20% by volume) and 5-6% (v/v) ACA. This unique in situ characterization (deduced entirely from SANS data from emulsion samples) of the entire film composition calls for further investigation regarding the role this film-based water plays in emulsion stability. |
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Bitumen
| Magazine |
2nd Eurasphalt& Eurobitume congress barcelona 2000-Proc,0254.UK |
| Year |
2002 |
| Autors |
Loeber La,b, Muller Gb, Héritier Bc, Jolivet Yd and Malot Md |
| Estb. |
a Université du Havre, Labo de chimie, 76600 Le Havre
b UMR 6522 CNRS and université de Rouen, 76821 Mt.St.Aignan Cedex
c Appia, 3 Av Morane saulnier,78142 Velizy Cedex
d TOTALFINA Raffinage et marketing, centre de recherches BP 27, 76700 Harfleur |
| Abstract |
Surface tension measurements and microscopic observations were undertaken to understand the film formation mechanism of some micrometer fine bitumen droplets in an aqueous phase. After evaporation, the formed bituminous film showed a more hydrophilic behaviour compared to pure bitumen films. By means of atomic force microscopy the film thickness of adsorbed bitumen could be determined and residual surfactant could be localised. Obtained structural information was related to the contact angle measurements: the presence of surfactant in the interstices between bitumen domains could explain the change of the surface properties of the film. |
| Magazine |
Bulletin des laboratoire des point et chaussée, 2001/235 |
| Year |
2001 |
| Autors |
Alain CAGNAa, Christian BOINONa, Patrick VERLHACb, Kathleen VAN NIEUWENHUYZEb and Francis VERZAROc |
| Estb. |
a IT Concept, Parc de Chancolan, 69770 Longessaigne, France
b Lab. émulsion,Nynas NV
c Groupement de recherches de Lacq, CECA SA |
| Abstract |
La tension interfaciale entre du bitume et de l’eau savonneuse est un paramètre déterminant pour l’interprétation de phénomènes physico-chimiques se produisant à l’interface bitume/eau, notamment pendant le processus d’émulsification. La compréhension et la prédiction du comportement de l’émulsion à partir des propriétés interfaciales ont été l’un des objectifs du projet européen OPTEL. La tension interfaciale a été mesurée avec un tensiomètre à goutte par analyse de la forme de la goutte de bitume. Nous présentons la précision de cette méthode (en goutte pendante ou posée) et montrons plus particulièrement l’importance de la densité du bitume et du facteur de forme. Afin d’améliorer la précision de cette mesure, un certain nombre de recommandations pratiques sont données. La tension interfaciale mesurée pour différentes concentrations en émulsifiant permet d’obtenir une isotherme d’adsorption dont l’interprétation (au moyen du modèle de Szyskowski-Langmuir) montre l’importance du choix du point correspondant à la Concentration Micellaire Critique (CMC). |
| Magazine |
Bulletin des laboratoire des point et chaussée,2002/235 |
| Year |
2002 |
| Autors |
Alain CAGNAa, Christian BOINONa, Patrick VERLHACb, Kathleen VAN NIEUWENHUYZEb and Francis VERZAROc |
| Estb. |
a IT Concept, Parc de Chancolan, 69770 Longessaigne, France
b Lab. émulsion,Nynas NV
c Groupement de recherches de Lacq, CECA SA |
| Abstract |
The interfacial tension between bitumen and soapy water is a decisive parameter for interpreting physicochemical phenomena at the bitumen/water interface, during the emulsification process in particular. Understanding and predicting the behaviour of the emulsion on the basis of interfacial properties were among the objectives of the European OPTEL project. The interfacial tension was measured using a drop tensiometer by analyzing the shape of the bitumen drop. This paper describes the accuracy of this method (both pendant drop and rising drop) and in particular shows the importance of the density of the bitumen and the shape factor. A number of practical suggestions are made with a view to improving measurement accuracy. Interfacial tension measurements for different emulsifier concentrations have provided an adsorption isotherm. Interpreting this (using the Szyskowski-Langmuir model) shows the importance of selecting the point that corresponds to the Critical Micelle Concentration (CMC). |
| Magazine |
Energy Fuels, 22 (2), 790–798, 2008 |
| Year |
2008 |
| Autors |
Alain Cagnaa, P. Chaverotb, Sylvie Glitac and Francis Rondelezb |
| Estb. |
a IT Concept-Teclis, Parc de Chancolan, 69770 Longessaigne, France
b Total Company, CReS, BP 22, 69360 Solaize, France
c EuroVia, St. Jean de l’Eure, France |
| Abstract |
We have studied the time dependence of the interfacial tension between acidic aqueous solutions (pH 2) and commercial straight-run bitumen droplets of different origins by the pendent drop method. Because of the existence in bitumen of naturally occurring surface-active species, significant changes of the interfacial tension are observed over timescales of several thousands of seconds. The kinetics of the decrease is consistent with the exodiffusion of endogenous surfactants toward the bitumen-water interface and throughout the bitumen matrix. At T ) 90 °C, one observes that the interfacial tension decreases as t1/2 at short times and as t-1/2 at long times when the interface becomes nearly saturated. Combining these two kinetic data allows for a direct estimate of the surface concentration of these endogenous surfactants. If one makes the assumption that they organize in a dense, close-packed monolayer, their size and concentration in bulk bitumen can also be readily derived. At T ) 140 °C, the viscosity of bitumen is 20 times lower than at 90 °C and the short time kinetics can no longer be resolved with our experimental apparatus. This restricts the data analysis, but we can nevertheless obtain an estimate of the size of the surfactant molecules if one makes the reasonable hypothesis that the bulk concentration of surfactants remains unchanged between 90 and 140 °C. Our results suggest that the surface-active species at pH 2 are asphaltene moieties of basic character. They are probably in an aggregated form because the measured, nanometric size decreases at elevated temperatures. Quite remarkably, they correspond to a very small fraction of the total asphaltenes contained in bitumen, which explains why they are extremely difficult to detect analytically. To the best of our knowledge, this is the first time that quantitative data on the endogenous surfactants are obtained in industrial bitumen. The present results thus complete the numerous existing observations on model oil–water systems. |
| Magazine |
Eurasphalt&Eurobitume congress-Barcelona-09/2000 |
| Year |
2000 |
| Autors |
Kathleen Van Nieuwenhuyzea, Tine Tanghea, Patrick Verlhaca and Bernard Echmannb |
| Estb. |
a Nynas NV (Belgium)
b AB Nynas Petroleum-GCC |
| Abstract |
|
Top
Chemical Industry
| Magazine |
|
| Year |
|
| Autors |
Hairis Retsosa, Ganna Gorodyskab, Anton Kiriyb, Manfred Stammb and Costantino Cretona |
| Estb. |
a Physico-chimie des polymères et des milieux dispersés, UMR 7615, Ecole supérieure,physique et de chimie industrielles, 10 rue Vauquelin-75231 Paris, France
b Leibniz-institut für polymerforschung dresden, hohe strabe 6, 01069 Dresden, Germany |
| Abstract |
We investigated the adhesive properties of binary heterogeneous plymer brushes made from end functionalized polystyrene (PS) and poly(2-vinylpyridine) (P2VP) chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for PS (toluene) and for P2VP (acidic water). This exposure results in reversible switching of adhesive and wetting properties. The manner in which the adhesion switching occurs can be tuned by the composition of mixed brushes. However, the outer surface composition could be enriched more effectively in PS after the toluene treatment than in P2VP after the acidic water treatment. As a result, the mixed brush compositions that showed the largest difference in properties between an exposure to toluene and an exposure to water were the P2VP-rich compositions. Adhesive properties, tested against a soft hydrophobic pressure-sensitive-adhesive (PSA) using a probe test, always showed smaller differences between solvent treatments than wetting properties with water, suggesting a much higher sensitivity of the hydrophobic / hydropholic brushes to polar molecules than to non-polar molecules. |
| Magazine |
Dyes and Pigments 74 (2007) 410e415 |
| Year |
2007 |
| Autors |
Ma1gorzata Bielskaa and Krystyna Prochaskaa |
| Estb. |
a Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Sklodowskiej-Curie 2, 60-965 Poznan, Poland |
| Abstract |
Separation of organic dyes from micellar solutions was studied in a cross-flow SEPA CF Osmonics module. Several model dyes (methylene blue, mordant black 11 and mordant black 17) were investigated. Sodium dodecylsulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), oxyethylated coconut fatty acid methyl esters (OMC-10) and binary mixtures of ionic and nonionic surfactants were used as surfactants. Membranes made of cellulose acetate (CQ), polysulfone (PES) and polyvinylidene fluoride (PVDF) (cut-off 15e30 kDa) were used. Ultrafiltration of micellar solutions could be considered as a research method, helpful in determining important parameters such as: (i) the micelle loading and (ii) micelle binding constant used to characterize micellar solutions, and (iii) the distribution coefficient employed in extraction studies. It was found that the type of surfactant is the main factor affecting the rejection. The best separation of the dyes was obtained when the ionic surfactant, charged opposite to dye, was used alone or in the mixture with the nonionic surfactant. Moreover, the introduction of nonionic surfactant into ionic surfactants decreased the CMC of mixed micelles and then the concentration of surfactants in the permeate. |
| Magazine |
Journal of Colloid and Interface Science 277 (2004) 443–449 |
| Year |
2004 |
| Autors |
Elzbieta Tataraa, Katarzyna Maternaa, Hans Bartb, Achim Schaadtb and Jan Szymanowskia |
| Estb. |
a Poznan University of Technology, Institute of Chemical Technology and Engineering Poznan, Pl. M. Sklodowskiej-Curie 2, 60-965 Poznan, Poland
b Kaiserslautern University, Institute of Thermal Process-Engineering, Kaiserslautern, Gottlieb-Daimler St., Postfach 3049, 67663 Kaiserslautern, Germany |
| Abstract |
Cloud point separation of selected dyes was studied. The use of dyes made possible observation of the dynamics of surfactant-rich phase separation by color video. The pictures were interpreted by means of ImageC software and degrees of whiteness were calculated. It was found that separation was slow and equilibrium was not achieved even after a period of more than 10 h. The separated surfactant-rich phase had a heterogeneous structure. The globules of the surfactant-rich phase were also observed in the micellar aqueous phase. The surfactant concentration could be as high as one or two orders of magnitude above the expected cmc values and was not decreased to critical micelle concentration by centrifugation. The presence of sodium chloride was important and improved separation. Separation of dyes was in the range 73–98% and depended upon the surfactant, the temperature, the electrolyte content, and the dye. In each system considered, appropriate conditions had to be selected to obtain high recovery of the dye. The presence of the electrolyte was the most important parameter and it improved the separation of dyes. However, addition of the electrolyte could also account for precipitation of the dyes, as observed for the systems containing Direct Pink. The best recoveries were observed for Direct Yellow and oxyethylated nonylphenol (98% at 55 °C in the presence of NaCl). Centrifugation gave recoveries similar to those for prolonged heating but it shortened the time of phase separation. |
| Magazine |
Colloids and Surfaces A: Physicochem. Eng. Aspects 263 (2005) 226–232 |
| Year |
2005 |
| Autors |
George C. Sawickia |
| Estb. |
a Dow Corning Ltd., Cardiff Road, Barry CF63 2YL, Wales, UK |
| Abstract |
Foam control agents are commonly present in household laundry cleaning products to prevent excessive foam formation in horizontal axis washing machines. However, their effectiveness is highly dependent on the composition of the foaming medium and, in particular, the specific surfactants present. The reasons for this high surfactant selectivity are still poorly understood. This study examined the impact of both the composition of the surfactant solution and the chemical structure of the individual surfactants on the foam control effectiveness of a polydimethylsiloxane-based antifoam compound. Whilst high addition levels of the antifoam compound were required to control the foam of combinations of linear alkylbenzenesulphonate and alkyl sulphates, the inclusion of alcohol ethoxylates was shown to dramatically enhance the ability of the antifoam compound to control foam. Further, that the chemical composition of the alcohol ethoxylate and the structure of the hydrophobe chain played an important role. In contrast, the chemical composition and structure of the alkyl sulphate surfactants appeared to have relatively little impact. |
| Magazine |
Journal of Colloid and Interface Science 327 (2008) 451–458 |
| Year |
2008 |
| Autors |
Lei Zhanga,b, Xiao-Chun Wanga, Qing-Tao Gonga, Lu Zhanga, Lan Luoa, Sui Zhaoa and Jia-Yong Yua |
| Estb. |
a Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, No. 2 North 1 Alley, Zhong guan cun, P.O. Box 2711, 61 section, Beijing 100080, PR China
b Graduate School, Chinese Academy of Sciences, Beijing 100039, PR China |
| Abstract |
The dilational rheological properties of absorbed film of three pairs of structural isomers, tri-substituted alkyl benzene sulfonates, at the air–water and decane–water interfaces have been investigated by drop shape analysis method. The influences of bulk concentration on dilational elasticity and viscosity were expounded. Interfacial tension relaxation method was employed to obtain dilational parameters in a reasonably broad frequency range. The experimental results showed that the meta-alkyl to sulfonate group plays a crucial role in the interfacial dilational properties: the longer meta-alkyl will lead to higher dilational parameters for air–water interface and lower ones for decane–water interface when the total alkyl carbon numbers are equal. For alkyl benzene sulfonates with shorter meta-alkyl, the surface dilational properties are similar to interfacial dilational properties, whereas the surface dilational parameters are obviously higher than the interfacial dilational parameters for alkyl benzene sulfonates with longer meta-alkyl in general. The possible mechanism has been proposed and ensured by Cole–Cole plots. |
| Magazine |
Langmuir 2003, 19, 7354-7361 |
| Year |
2003 |
| Autors |
Charles M. Kauscha, Yongsin Kima, Vernon M. Russella, Robert E. Medskera and Richard R. Thomasa |
| Estb. |
a OMNOVA Solutions, Incorporated, 2990 Gilchrist Road, Akron, Ohio 44305-4489 |
| Abstract |
Interfacial rheological studies were performed on a series of bolaamphiphilic α,ω-(diammonium disulfato)- poly(fluorooxetane)s of several perfluoroalkyl chain lengths. Similar measurements were performed on a small-molecule, anionic fluorosurfactant with a-C8F17 perfluoroalkyl group that is known to be an effective flow and leveling aid in aqueous coatings. Dilational viscoelasticities were measured for the fluorosurfactants as a function of concentration and oscillation rate. Elasticities were found to increase with increasing perfluoroalkyl chain length. All elasticities exhibited a strain rate dependence indicative of the influence of diffusional relaxation on elasticity values. Phase angles were found to be in the range for diffusional relaxation and decreased with increasing concentration and strain rate. Using interfacial rheological data, characteristic fluid dynamics numbers were calculated for the fluorosurfactants. Among these was the Marangoni number. Calculated Marangoni numbers for the poly(fluorooxetane)s were of the same order of magnitude as that for the small-molecule, long perfluoroalkyl chain surfactant. The poly(fluorooxetane)s all have equilibrium surface tensions greater than that of the small-molecule, long perfluoroalkyl chain surfactant, yet show similar abilities to aid in flow and leveling in aqueous coatings at comparable concentrations. Rheological measurements demonstrate that equilibrium surface tension alone is not enough to explain the fluid dynamics processes occurring during flow and leveling. |
| Magazine |
Langmuir 2005, 21, 617-621 |
| Year |
2005 |
| Autors |
Ashwin Raoa, Jongdae Kimb and Richard R. Thomasc |
| Estb. |
a Department of Polymer Science, The University of Akron, Akron, Ohio 44325
b Department of Polymer Engineering, The University of Akron, Akron, Ohio 44325
c OMNOVA Solutions, Incorporated, 2990 Gilchrist Road,Akron, Ohio 44305 |
| Abstract |
The dilational rheological behavior of gelatin molecules adsorbed at the air-water interface has been studied as a function of sodium dodecyl sulfate (SDS) concentration for a 7 wt % gelatin-SDS solution at 40 °C. Binding of SDS molecules to the gelatin strands disrupts the cross-linked network structure of adsorbed gelatin molecules and results in a reduction of the surface elastic modulus of the adsorbed layer that continues until the bulkSDSconcentration reaches 1mM.Beyond thisSDSconcentration, the dilational rheological properties of the adsorbed gelatin layer are indistinguishable from those of pure SDS adsorbed layers. |
| Magazine |
Journal of Supercritical Fluids 36 (2005) 81–90 |
| Year |
2005 |
| Autors |
E. Badensa, O. Boutina and G. Charbita |
| Estb. |
a Lab. de Procédés Propres et Environnement (UMR 6181–CNRS), Université Paul Cézanne, Aix Marseille III,LPPE Bâtiment Laennec, BP 80, 13 545 Aix-en-Provence, France |
| Abstract |
Laminar jet dispersion and more particularly jet atomization of water, methylene chloride and ethyl alcohol into pressurized carbon dioxide are investigated under experimental conditions of pressure, temperature and liquid flowrate commonly used for supercritical anti solvent (SAS) precipitation processes. The different modes of dispersion are characterized as a function of the jet velocity. Axisymmetrical, asymmetrical and atomized jets are observed at 308 K, under a pressure ranging from 6 to 9MPa, and for a liquid jet velocity ranging from to 0.14 to 8.02ms−1. A new correlation is given between the jet Reynolds number and the Ohnesorge number, determining the transition to the atomization regime. Experimental values of dynamic interfacial tensions are used to elaborate the correlation. |
| Magazine |
Int. J. Miner. Process. 80 (2006) 43–57 |
| Year |
2006 |
| Autors |
D. Beneventia X. Roussetb E. Zenob |
| Estb. |
a LGP2-UMR5518, Ecole Française de Papeterie et des Industries Graphiques (INPG), 461 rue de la Papeterie, DU, BP. 65, 38402 St. Martin d'Hères, France
b Centre Technique du Papier, Domaine Universitaire, B.P. 251, 38044 Grenoble CEDEX 9, France |
| Abstract |
A laboratory flotation column using Venturi aerators and a vacuum system to remove froth was used to investigate the contribution of gas flow, pulp flow, cell volume and froth retention time on the ink removal efficiency and on cellulose fibres and mineral fillers loss. The increase in the gas flow from 4 to 8L/min gave a general rise of particle transport from the pulp slurry to the froth with an ensuing strong increase in ink removal, from 75% to 85%, and water and total loss, from 10% to 40% and 15% to 30%, respectively. Whereas, the increase of the cell volume from 14 to 24L improved ink removal from 72% to 80% without considerably affecting flotation loss. The rise of the froth retention time in the flotation cell from 5 to 20 s before removal gave a general decrease in the flotation loss from 20% to 11% without a corresponding decrease in ink removal. This trend was interpreted as reflecting poor ink drainage through the froth. The increase of both pulp and froth retention time in the flotation cell appeared as the most favourable way to improve ink flotation selectivity. A mathematical model, describing particle removal during flotation in terms of true flotation, entrainment and drainage, was proposed and used to fit experimental data. |
| Magazine |
Colloids and Surfaces A:Physicochem.Eng.Aspects263(2005)210-218 |
| Year |
2005 |
| Autors |
Cécile Damea Christelle Fritzb Olivier Pitoisb Sylvain Faurea |
| Estb. |
a Lab. des Procédés Avancés de Décontamination, CEA (French Atomic Energy Commission), Marcoule, Bâtiment 37,30207 Bagnols-sur-Cèze, France a UMR 8108 Laboratoire de Physique des Matériaux Divisés et des Interfaces, Université de Marne-la-Vallée, 5 Bd Descartes,Champs-sur-Marnes 77454 Marne-la-Vallée,France |
| Abstract |
The addition of dodecanol as a co-surfactant in sodium dodecyl sulfate (SDS) solution is known to stabilize the foam. This paper presents complementary studies of this system: foam liquid fraction andwall-film thickness, viscoelastic and Plateau border pressure drop measurements for foams stabilized by SDS, SDS + dodecanol and SDS + dodecanol + xanthan gum in free drainage. It shows out that the addition of dodecanol and xanthan gum in a SDS foaming solution causes not only a deceleration of the foam drainage, but of the wall-film drainage also. In a second study, results are presented for nuclear decontamination foams stabilized by alkyl polyglucosides. Preliminary results are given for co-surfactant research with the influence of the addition of decanol and dodecanol in the alkyl polyglucoside solution and the foam stabilization effect of the addition of xanthan gum is pointed out. |
| Magazine |
Desalination 172 (2005) 19–26 |
| Year |
2005 |
| Autors |
M. Bielskaa, L. Garcia-Diezb, K. Maternaa, H.J. Bartb and J. Szymanowskia |
| Estb. |
a Institute of Chemical Technology and Engineering, Poznan University of Technology,Pl. Sklodowskiej-Curie 2, 60-965 Poznan, Poland b Institute of Thermal Process-Engineering, Kaiserslautern University,Postfach 3049/Gottlieb-Daimler-Str., 67663 Kaiserslautern, Germany |
| Abstract |
The effects of the composition of a surfactant colloidal solution containing nonylphenylpolyoxyethylene ether, the racemic mixture of L,D-phenylalanine, trans-4-hydroxy-L-proline and/or their copper complexes upon the flux of permeate and the resistance of the hydrophilic membrane and additional layer formed during ultrafiltration were studied. It was found that colloidal solutions containing the nonionic surfactant and additionally phenylalanine, the selector and their complexes with copper can be ultrafiltrated through hydrophilic membranes made of regenerated cellulose with a cut-off of 10 kDa with satisfactory fluxes. Both the permeate flux and resistance depend upon the concentration of the surfactant, but the effect of phenylalanine and the selector is negligible. The decisive effect was observed for copper complexes with phenylalanine and the selector as the complexes significantly decrease the permeate flux and increase the resistance of the additional layer. |
| Magazine |
Langmuir 2003, 19, 5763-5770 |
| Year |
2003 |
| Autors |
Richard R. Thomasa |
| Estb. |
a OMNOVA Solutions, Inc., 2990 Gilchrist Road, Akron, Ohio 44305 |
| Abstract |
Contact angle relaxation of partially wetting drops was studied on native and base hydrolyzed pyromellitic dianhydride (PMDA)-4,4′-oxydianiline (ODA) polyimide surfaces as a function of wetting liquid pH. Upon base hydrolysis, followed by acid neutralization, carboxylic acid groups are formed on the native polyimide surface. The areal density of incipient carboxylic acid groups is proportional to base hydrolysis time. Wetting kinetics were examined on polyimide surfaces as a function of hydrolysis time and wetting liquid pH using the molecular-kinetic theoretical approach. The results of parametric fitting of experimental contact angle relaxation data using the molecular-kinetic approach indicate that the kinetics and thermodynamics of wetting were nearly invariant when using a pH 2 probe liquid for native compared to hydrolyzed surfaces. In contrast, the kinetics and thermodynamics of wetting using a pH11 probe liquid exhibited large differences based on the extent of modification and ionization of the surface. The differences in kinetics appear to be due to a lesser interaction of the pH 11 probe liquid with modified surfaces. |
Top
Polymer
| Magazine |
Langmuir, 2003, 19 (24), pp 10086–10094 |
| Year |
2003 |
| Autors |
F. Michauta, P. Hébrauda, P. Perrina and F. Lafumaa |
| Estb. |
a Laboratoire de Physico-Chimie Macromoléculaire, ESPCI, CNRS, UPMC, UMR7615, 10 rue Vauquelin, 75231 Paris Cedex 05 Paris, France |
| Abstract |
A long flexible poly(dimethylsiloxane) (PDMS) backbone has been grafted with poly(ethylene oxide) (PEO) chains to obtain an amphiphilic oil-associative copolymer (PDMS-g-PEO). The copolymer exhibits interesting bulk-thickening properties in apolar organic oils (n-dodecane) thanks to the intermolecular association of PEO chains. We show that the hydrophilic association is considerably strengthened by the addition of small amounts of water, with the consequence that PDMS-g-PEO dodecane solutions exhibit solidlike behavior. The PDMS-g-PEO chains adsorb at the water-dodecane interface as shown by tensiometry. Moreover, we show that the copolymer provides good stability to both concentrated and nonconcentrated inverse emulsions. This is due to the design, the choice of the anchor and stabilizing moieties, and the balance of the hydrophilic-lipophilic properties of the polymeric surfactant, which allows not only the steric protection of the water droplets but also their trapping into a viscoelastic external phase. |
| Magazine |
Journal of Colloid and Interface Science 336 (2009) 40–45 |
| Year |
2009 |
| Autors |
Ayça Ertekina, Yongsin Kimb, Charles M. Kauschb and Richard R. Thomasb |
| Estb. |
a Department of Polymer Engineering, Polymer Engineering Academic Center, The University of Akron, Akron, OH 44325-0301, USA
b OMNOVA Solutions Inc., 2990 Gilchrist Road, Akron, OH 44305-4418, USA |
| Abstract |
ABA triblock copolymers, where A is an oligo(fluorooxetane) and B is poly(ethylene oxide) (PEO), are prepared easily using an a,x-dihydroxy PEO initiator and cationic, ring-opening polymerization of a fluorinated oxetane monomer. Terminal hydroxyl groups can be converted readily and quantitatively to acetate groups using acetic anhydride. Both types of triblock copolymers are surface active in water. The hydroxyl- and acetate-terminated triblocks exhibit differences in adsorption behavior. Both materials show similar surface tension reduction efficiencies (minimum surface tension at aggregation limit); however, the acetate-terminated triblock copolymer is much more effective (surface tension reduction at a given concentration to the aggregation limit). This behavior is explained by the influence of hydrogen bonding on adsorption properties of the hydroxyl-terminated triblock copolymer compared to the acetate- terminated version. |
| Magazine |
European Polymer Journal |
| Year |
2009 |
| Autors |
Houjian GONGa, Guiying XUa, Hui DINGa, Fengxiao SHIa and Yebang TANa |
| Estb. |
a Key Laboraory of Colloid and Interface Chemistry, Ministry of Education, Shandong University, Jinan 250100, PR China |
| Abstract |
The block polyethers with various branch structure, such as TEPA[(PO)36(EO)100]7, TEPA- [(PO)36(EO)100(PO)36]7, and TEPA[(PO)36(EO)100(PO)56]7 were synthesized. Moreover, the aggregation behavior was investigated via the measurements of equilibrium surface tension, dynamic surface tension, and surface dilational viscoelasticity, in order to probe the effect of the block structure on the property of the branched block polyethers. The surface tension results show that the efficiency and effectiveness of the block polyethers to lower surface tension increase with the increase of the PO group numbers. The maximum surface excess concentration (Τmax) values and the minimum occupied area per molecule at the air/water interface (Amin) values of the branched block polyethers obtained from Gibbs adsorption equations increase and decrease with the increases of the PO group numbers, respectively. The dynamic parameters n and t* representing the diffusion speed of the polyether molecules from bulky solution to the subsurface and from the subsurface to the air/ water surface are obtained according to the equation proposed by Rosen. The results show that the n values firstly increase and then decrease and t* values decrease with the increase of the polyether concentrations. The results of surface dilational viscoelasticity show that the dilational modulus of TEPA[(PO)36(EO)100(PO)56]7 is the largest among the three block copolymers at the low concentration (<1 mg L-1) but that of TEPA[(PO)36(EO)100]7 is the largest at the high concentration (>1 mg L-1). |
| Magazine |
Journal of Colloid and Interface Science 279 (2004) 68–77 |
| Year |
2004 |
| Autors |
E. Rotureaua, M. Leonarda, E. Dellacheriea and A. Duranda |
| Estb. |
a Lab. de Chimie Physique Macromoléculaire, UMR CNRS-INPL 7568, Groupe ENSIC, BP 451, 54001 Nancy Cedex, France |
| Abstract |
Ionic amphiphilic dextran derivatives were synthesized by the attachment of sodium sulfopropyl and phenoxy groups on the native polysaccharide. A family of dextran derivatives was thus obtained with varying hydrophobic content and charge density in the polymer chains. The surface-active properties of polymers were studied at the air–water and dodecane–water interfaces using dynamic surface/interfacial tension measurements. The adsorption was shown to begin in a diffusion-limited regime at low polymer concentrations, that is to say, with the diffusion of macromolecules in the bulk solution. In contrast, at long times the interfacial adsorption is limited by interfacial phenomena: adsorption kinetics or transfer into the adsorbed layer. A semiempirical equation developed by Filippov was shown to correctly fit the experimental curves over the whole time range. The presence of ionic groups in the chains strongly lowers the adsorption kinetics. This effect can be interpreted by electrostatic interactions between the free molecules and the already adsorbed ones. The adsorption kinetics at air–water and oil–water interfaces are compared. |
| Magazine |
Colloids and Surfaces A: Physicochem.Eng.Aspects345(2009)58–64 |
| Year |
2009 |
| Autors |
Xiaoqiang DONGa Dejun SUNa Guopeng LIUa,b Chengbo CAOc Xiren JIANGd |
| Estb. |
a Key Laboratory for Colloid & Interface Chemistry of Education Ministry, Shandong University, Jinan, Shandong 250100, PR China
b Department of Chemistry and Chemical Engineering, Shandong Institute of Education, Jinan, Shandong 250013, PR China
c School of Chemistry and Chemical Engineering, Shandong University, 73 Jingshi Road, Jinan, Shandong 250061, PR China
d North China Sea Environmental Monitoring Center of State Oceanic Administration, Qingdao, Shandong 266033, PR China |
| Abstract |
The foam prepared by sodium dodecyl polyoxyethyl sulfate (AES) with hydrophobically modified cellulose (HMHEC) solution in the presence and absence of electrolytes (NaCl, CaCl2) is evaluated by foam stability (drainage half-life) and the configuration variations of AES–HMHEC complexes at the air/water interface. The configurations of the surfactant–polymer complexes at the air/water interface as a function of surfactant concentration are speculated by the surface tension isotherm and dilatational viscoelastic behavior. It is concluded that the configuration of AES–HMHEC complexes significantly affects drainage half-life and foam decay. When the surfactant concentration is lower than the critical aggregation concentration (CAC), the surfactant molecules are dispersed in the bulk solution but they are gradually associated at the air/water interface of the foam film which contributes to retard the foam decay. With the further increase of surfactant concentration (between CAC and the saturation concentration of surfactant associated with polymer), the association of surfactants with polymers improves the foam stability and the stability of adsorbed surfactant–polymer complexes layer. When the surfactant concentration is higher than the saturated concentration, the air/water interface is mainly covered by the surfactants rather than the surfactant–polymer complexes and hence the stability of adsorbed surfactants layer decreases. In addition, the stability of adsorbed surfactant–polymer complexes layer is enhanced by the addition of electrolytes due to the screening effects. Furthermore, compared with monovalent ions (Na+), the solution containing higher valent ions (divalent Ca2+) stabilizes the foam film more efficiently due to the higher packing density of the complex at the air/water interface. |
| Magazine |
Colloids and Surfaces A: Physicochem. Eng.Aspects338(2009)40–46 |
| Year |
2009 |
| Autors |
Qian LIUa, Shuiyan ZHANGa, Dejun SUNa and Jian XUa |
| Estb. |
a Key Laboratory for Colloid & Interface Chemistry of Education Ministry, Shandong University, Jinan, Shandong 250100, PR China |
| Abstract |
Stable foams have been generated in low concentration aqueous dispersions of hexylamine-modified Laponite particles. The particles are of primary size 30 nm, modified with hexylamine molecules to render them partially hydrophobic or moderate flocculants. Infrared adsorption spectra and zeta potential measurements confirm the adsorption of hexylamine molecules on the Laponite particles. The foamability, drainage behavior and microstructure ofwet foamswere studied in terms of their dependence on the content of Laponite particles and the concentration of hexylamine. Laser-induced confocal microscopy observations confirm that stable bubbles appear to be surrounded by a thin layer of hexylamine-modified Laponite particles, which is crucial to the stability of foams. The interfacial rheology of the same systems has been also investigated by measuring the dilational viscoelasticity as a function of hexylamine concentrations. The adsorption of particles at the air–water interface has the effect of increasing dilational surface elasticity, indicating that the gel-like layer at the interface inhibits foam drainage and bubble coalescence. |
| Magazine |
Mendeleev commun, 2005, 15(1), 35–38 |
| Year |
2005 |
| Autors |
Valery G. Babaka and Jacques Desbrièresb |
| Estb. |
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation. b CERMAV–CNRS, BP53, 38041 Grenoble cedex 9, France |
| Abstract |
Two-dimensional dilational rheology has been applied to a comparative study of the kinetics of structure formation in the adsorption layers of cationic polysoaps (alkylated chitosans) and dynamic associates (surfactant-polyelectrolyte complexes, SPECs) formed between a cationic polyelectrolyte (chitosan) and an anionic surfactant (SDS). |
| Magazine |
Langmuir 2007, 23,9929 - 9932 |
| Year |
2007 |
| Autors |
Guifeng Lia, Shishir Prasada and Ali Dhinojwalaa |
| Estb. |
a Department of Polymer Science, The UniVersity of Akron, Akron, Ohio 44325-3909 |
| Abstract |
We have used dynamic interfacial tension measurements to understand the structure of the ordered monolayer at the hexadecane/water interface induced by the presence of surfactant molecules. No abrupt changes in the interfacial tension (γ) are observed during the expansion and contraction cycle below the interfacial ordering temperature (Ti) as observed for alkanes in contact with air. The lack of an abrupt change in γ and the magnitude of this change during the expansion process indicate that the ordered phase may not be crystalline. The change in the interfacial tension is due to an increase in contact between water and hexadecane molecules and the disordering of the interfacial ordered layer. At low surfactant concentrations, the recovery of the interfacial tension is slower below Ti, suggesting that there is a critical surfactant concentration necessary to nucleate an ordered phase at the interface. |
| Magazine |
Colloids and surface A-2004 |
| Year |
2004 |
| Autors |
Valery G.Babaka,b, Jacques Desbrièresb,c and Vladimir E.Tilhonova |
| Estb. |
a A.N.Nesmeyanov institute of organoelement compounds, Russian academy of sciences,28,Vavilova Str,117813 Moscow,Russia
b CERMAV – CNRS, affiliated with Joseph Fourier university, BP53, 601, Rue de la Chimie, 38041 Grenoble cedex 9, France
c Laboratory of Polymeric Physico Chemistry (LPCP, UMR 5067), University of Pau and Pays de l’Adour, Helioparc Pyrenees, 2 Avenue President Angot, 64053 PAU cedex 09, France |
| Abstract |
The kinetics of the adsorption at the air-water interface and the processes of the structure formation inside the adsorption layers of the alkylated chitosan (the cationic polysoap) have been studied in function of its bulk concentration and the ageing time of the adsorption layers. It has been shown that the dynamic surface tension γ(t) of this polysoap aqueous solution measured by the axisymmetric rising bubble shape analysis is characterised by several stages with different characteristic relaxation times. During the lag-stage and the post lag-stage the adsorption is the diffusion-controlled process of macromolecules from the bulk of the solution to the interface. At the final stage the adsorption is characterised by much lower rate due to the steric hindrance exerted by the yet formed adsorption layer on newly adsorbing macromolecules.
The structure (physical gel) formation inside the adsorption layers of the alkylated chitosan via intermolecular hydrophobic interaction or by hydrogen bonding in function of the ageing time (up to t f~5.10 4 s) has been studied with the help of the two dimensional dilational rheology by applying sinusoidal deformation to the bubble area within the frequency range w=0,05-0,4 rad/s. One characteristic relaxation frequency rheological model of Maxwell has been applied to determine two dimensional “storage” E’ and “loss” E” elasticity modules, as well as the intrinsic elasticity module Eo and the characteristic relaxation frequency ωo (or the intrinsic viscosity ηo = Eoωo/2π) of the adsorption layer in function of the bulk polymer concentration Cp. It has been shown that the parameters Eo and ηo sharply decrease with increasing Cp . This finding is interpreted on the basis of proposed mechanism explaining the effect of the conformational state of the macroions inside the adsorption layers on the Gibbs elasticity and the Marangony relaxation time. |
| Magazine |
Colloids and polymer science |
| Year |
2005 |
| Autors |
Valery G. Babaka and Jacques Desbrieresb |
| Estb. |
a A.N.Nesmeyanov institute of organoelement compounds, Russian academy of sciences,28,Vavilova Str,117813 Moscow,Russia b
Lab. of Polymeric Physico Chemistry (LPCP,UMR 5067,IPREM FR 2606),University of Pau and Pays de l'Adour,Helioparc Pyrenees,2 Avenue President Angot,64053 Pau France |
| Abstract |
The kinetics of the adsorption at the air-water interface and the processes of the structure formation inside the adsorption layers of hydrophobically modified systems [al kylated chitosans (Ch) and sodium dodecyl sulfate (SDS)–Ch complexes] have been studied by the tensiometric method based on the axisymmetric rising-bubble-shape analysis as a function of the bulk concentration of polymers and the ageing time of their adsorption layers. The kinetics of the adsorption of chitosan, alkylated chitosans (ChC3, ChC8, and ChC12), and surfactant–polyelectrolyte (PE) complexes formed by the chitosan and the polysoaps with oppositely charged anionic surfactant SDS is characterized by an induction time (the socalled lag time), τlag, corresponding to the diffusion stage of the formation of adsorption layers. During this time, the decrease in the surface tension (or the increase in the surface pressure π) does not exceed several millinewtons per meter that corresponds to the “gaseous” state of adsorption layers. The postlag stage of the formation of the adsorption layer is characterized by the remarkable rate of increase in the surface pressure π that corresponds to the conformational rearrangement of PEs inside the adsorption layer by increasing the number of hydrophobic groups (adsorbing centres) in contact with the non-polar phase at the interface. It has been found that during the lag time, the adsorption of alkylated chitosans (cationic polysoaps) increases with increasing alkyl chain length, whereas during the postlag time, the adsorption of the ChC3 is maximal with regard to other polysoaps. It has been confirmed that at equal content of alkyl groups in the system, the surface activity of the SDS–Ch complexes is much higher with regard to that of the polysoaps. The viscoelasticity of adsorption layers of individual PEs and their complexes continuously increases with the ageing time, giving evidence for the interaction between the polymers inside the adsorption layers. It has been found that the rate of increase in the dilational storage module E′ of the adsorption layers of SDS–Ch complexes is much higher than for the polysoaps that correlates with the higher surface activity of the former with regard to the latter. For the mentioned systems, the module E′ is much higher than the loss module E′ that confirms the solid-like properties of their adsorption ayers. On the other hand, the adsorption layers of the chitosan are liquid-like, while E′<<E″ |
| Magazine |
Mendeleev conmmun, 2004,14(2),66-68 |
| Year |
2004 |
| Autors |
Valery G. Babaka,b and Jacques Desbrieresb |
| Estb. |
a A.N.Nesmeyanov institute of organoelement compounds, Russian academy of sciences,28,Vavilova Str,117813 Moscow,Russia
b CERMAV–CNRS, affiliated with Joseph Fourier university, BP53, 601, Rue de la Chimie, 38041 Grenoble cedex 9, France |
| Abstract |
Dynamic tensiometry has been applied to a comparative study of the kinetics of adsorption of cationic polysoaps (alkylated chitosans) and dynamic associates (surfactant–polyelectrolyte complexes, SPECs) between chitosan and the anionic surfactant SDS at the air–water interface. |
| Magazine |
Langmuir, 2006, 22 (19), pp 7964–7968 |
| Year |
2006 |
| Autors |
Ashwin Raoa, Yongsin Kimb, Charles M. Kauschb and Richard R. Thomasb |
| Estb. |
a Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909
b OMNOVA Solutions Inc., 2990 Gilchrist Road, Akron, Ohio 44305-4418 |
| Abstract |
The effect of binding of an oligomeric cationic fluorooxetane surfactant on the interfacial properties of adsorbed gelatin-fluorooxetane complexes has been studied using dynamic surface tension and dilational rheological measurements. Adsorption kinetics of gelatin-fluorooxetane complexes are reminiscent of a mixed (barrier/diffusion limited) process, while the dilational rheological properties of the interface exhibit a strong dependence on surfactant concentration. At low surfactant concentrations, dilational surface moduli as well as phase angles are relatively insensitive to the presence of the fluorooxetane. However, at the critical aggregation concentration of the polymersurfactant system, there is a sharp increase in the complex modulus. Further increase in the fluorooxetane concentration does not significantly affect the complex modulus. The phase angle, however, does increase with increasing fluorooxetane concentration due to the transport of bound fluorooxetane from the subsurface to the solution-air interface. These results indicate that, at fluorooxetane concentrations exceeding the critical aggregation concentration, the polymersurfactant complexes adsorb to form cross-linked multilayers at the solution-air interface. |
| Magazine |
Journal of physical chemistry B 2007,111,9519-9529 |
| Year |
2007 |
| Autors |
Valery G. Babaka Rachel Auzelyb Marguerite Rinaudob |
| Estb. |
a 28, Vavilova str., Moscow 117813,Russian Federation
b Centre de Recherches sur les Macromolécules Végétales, CNRS, Laboratoire Associé à l’UniVersité Joseph,Fourier,BP53-38041 Grenoble cedex 9,France |
| Abstract |
The effect of an external salt (AcONa) on the kinetics of adsorption and structure formation inside the adsorption layers (ALs) of chitosan (Ch) and dodecyl chitosan (C12Ch) as well as on the frequency dependence of the complex dilational elasticity modulus of these layers has been studied. The complex dilational elasticity modulus of adsorption layers of polymers has been measured on the drop tensiometer (Tracker, IT Concept, France) upon applying a small sinusoidal variation of the drop area with a given frequency, ω, in the range from 10-2 to 0.63 rad/s and recording the variation of the surface pressure. It has been found that, in the absence of the salt, the dilational storage modulus, E′(ω), of ALs of both Ch and C12Ch is lower with regard to the loss modulus, E″(ω), in the whole range of frequencies used, testifying for the liquidlike rheological behavior of these layers. With an increase of the salt concentration up to CAcONa > 0.1 M, the ALs become solidlike, as shown when E′(ω) > E″(ω). Consequently, the characteristic frequency, ωc, corresponding to the intercept between the E′(ω) and E″(ω) curves, gradually varies from ωc > 1 rad/s to ωc < 0.01 rad/s when the salt concentration is increased from zero to CAcONa = 1 M. Hydrophobically modified C12Ch, having long grafted alkyl chains, exhibited a higher sensitivity to the presence of salt than Ch: the former solidifies more readily and at lower salt concentrations than the latter. It has been found that the experimental E′(ω) and E″(ω) curves exhibit two characteristic relaxation frequencies, ω01 ~ 1 rad/s and ω02 ~ 10-3-10-2 rad/s, whose physical meaning and values were related to the structure of the ALs and to the competitive contribution of electrostatic and hydrophobic interactions between amino and nonpolar groups of Ch and C12Ch to the formation of a gel-like network inside the polymeric film at the interface. |
and Laurent Billon d
| Magazine |
Polymer 52 (2011) 606e616 |
| Year |
2011 |
| Autors |
Damien Tastet a, Maud Save a, Fatima Charrier b, Bertrand Charrier b, Jean-Bernard Ledeuil c, Jean-Charles Dupinc |
| Estb. |
a IPREM, UMR 5254, CNRS, Université de Pau et des Pays de L’Adour, Technopole Helioparc, 2 Avenue P. Angot, 64053 Pau Cedex 9, France
b Sylvadour, IUT des Pays de l’Adour, Université de Pau et des Pays de L’Adour, 40 004 Mont de Marsan Cedex, France
cEquipe de Chimie Physique (ECP), IPREM, CNRS, UPPA, France
dEquipe de Physique et Chimie des Polymères (EPCP), IPREM, CNRS, UPPA, 64053, France
|
| Abstract |
Crude wood fibers represent a wide class of renewable resources. The surface modification of such materials via covalent grafting of polymer offers new surface properties with non-leaching coating. The grafting of the polymer chains was achieved by surface-initiated controlled radical polymerization through a grafted xanthate chain transfer agent. Macromolecular design via interchange of xanthate (MADIX) technique was chosen to graft poly(vinyl acetate), polystyrene, poly(n-butyl acrylate) and poly (4-vinylbenzyl chloride)-polystyrene amphiphilic cationic copolymers. Water contact angle measurements highlighted the hydrophobization of the wood fiber surface with a nanoscaled polymer monolayer indicating the appropriate coverage of the fiber. X-ray photoelectron spectroscopy showed the successful grafting of the polymer after drastic washing procedure. The quaternization of the grafted polystyreneco- poly(4-vinyl benzyl chloride) copolymers with tertiary amine allows the introduction of biocide quaternary ammonium functions while preserving the hydrophobic character of the modified wood fiber when introducing a long alkyl chain in the statistical copolymer. Finally, the cationic copolymer was subjected to Coniophora Puteana to evaluate its propensity to limit the fungi expansion. |
| Magazine |
Langmuir 2009, 25(12), 6923–6928 |
| Year |
2009 |
| Autors |
J. Sprakel a |
| Estb. |
a Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands and Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
|
| Abstract |
In this paper, we discuss the hierarchical adsorption of micelles formed from network-forming, telechelic,associative polymers at an air-water interface. We propose an interfacial mechanism that involves three distinct steps: (i) adsorption of the micellar coronas at the interface, (ii) unfolding of the micelles to anchor the hydrophobic tails at the interface, and (iii) formation of a secondary adsorption layer by bridging between the primary layer and micelles in the bulk. While the first, transport-limited process is relatively fast, the latter processes are surprisingly slow; it may take up to 106 s for the adsorption to complete. |
| Magazine |
Macromolecules 2010, 43, 6166–6173 |
| Year |
2010 |
| Autors |
A. Testouria, C. Honoreza, A. Barilleca, D. Langevina and W. Drenckhana |
| Estb. |
a Laboratoire de Physique des Solides, Université Paris-Sud, UMR8502 Orsay, France |
| Abstract |
We demonstrate how to generate highly ordered, solidified foam structures from chitosan hydrogels using millifluidic cross-flow techniques. In this, aqueous chitosan solutions (containing surfactant) and air are injected simultaneously at constant flow rates in a millimetric T-junction device, in which the gas thread breaks up to form extremely monodisperse bubbles. These bubbles travel along a tube in which the cross-linker glyoxal is added at constant flow rate via another T-junction in order to start the gelification of the chitosan. The bubbles are collected in appropriate devices, where they form hexagonally close-packed structures under the influence of gravity and/or confinement before the gelification process freezes the foam structure. The successful application of this technique requires the optimization of foam stability in conjunction with an appropriate choice of gelification time and the viscosity of the solution, both being strongly dependent on the chitosan concentration. Furthermore, reliable generation of monodisperse foams calls for a thorough calibration of the bubbling device for highly viscous and non-Newtonian fluids. Both aspects are presented here, relying in particular on rheological investigations, along with some resulting foam structures. |
| Magazine |
Colloids and Surfaces A: Physicochem. Eng. Aspects 331 (2008) 48–55 |
| Year |
2008 |
| Autors |
S. Domeneka, E. Petita, F. Ducepta, S. Mezdoura, N. Brambatib, C. Ridouxb, S. Guedjb and C. Michona |
| Estb. |
a UMR Ingénierie Procédé Aliment, AgroParisTech-INRA-CNAM-CEMAGREF, 1 avenue des Olympiades, 91744 Massy Cedex, France
b Rousselot, Chemin Moulin Premier, 84808 Isle sur la Sorgue Cedex, France |
| Abstract |
The adsorption kinetics of gelatin to the air/water interface is still not fully understood. We investigated two samples of gelatin having different gel strength (65 Bloom and 280 Bloom), named, respectively gelatin 65B and 280B. The gelatin samples in solution were characterised by viscosimetric methods. We evidence a chain expansion of gelatin upon dilution due to the polyelectrolyte effect. The measurement of the intrinsic viscosity inwater gave values of 22 mL/g for the sample 65B and 70 mL/g for the sample 280B. Although gelatin is a highly polymolecular polymer containing branched chains, the normalisation of the concentration by the intrinsic viscosity allowed the construction of a master curve of viscosity, giving the reduced critical overlap concentrations c*~0.6 and c**~5. All concentrations of the gelatin solutions used for the determination of the adsorption behaviour were within the range of the dilute regime. The analysis of the adsorption behaviour leads us to the hypothesis that there are two different phenomena: first, a step governed by diffusion to the interface which lasts until full coverage of the interfacial film. The length of this induction period seemed to be dependent on the gelatin chain length, with larger chains taking more time. Second, the adsorption of the chains to the air/water interface leads to the formation of an encumbered subsurface layer which opposes steric hindrance to newly arriving chains. This causes a continuous slow down of the rate of surface pressure increase, which was linear on the logarithmic time scale and showed a slope of −1. The adsorption kinetics was independent of the salt concentration of the solvent and of the gelatin chain size measured by the intrinsic viscosity. The gelatin sample 65B shows furthermore higher equilibrium surface pressures at high bulk concentrations (>0.01 wt%) than sample 280B, while the contrary was observed at small concentrations. |
| Magazine |
Langmuir 2008, 24, 12892-12898 |
| Year |
2008 |
| Autors |
Mauro Moglianettia, Peixun Lia, Fred L. G. Maletb, Steven P. Armesb, Robert K. Thomasa and Simon Titmussa |
| Estb. |
a Department of Chemistry, Physical and Theoretical Chemistry Laboratory, UniVersity of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K
b Department of Chemistry, UniVersity of Sheffield, Brook Hill, Sheffield, S3 7HF, U.K. |
| Abstract |
The interactions between the weak polyelectrolyte, poly(2-(dimethylamino) ethyl methacrylate) or PDMAEMA, and the anionic surfactant sodium dodecyl sulfate (SDS) at the air-water interface have been investigated at pH = 3 and 9 using a combination of neutron reflectivity and surface tension measurements. By using deuteratedPDMAEMA in combination with h-SDS and d-SDS, we have been able to directly determine the distribution of both the polymer and the surfactant at the air-water interface. At pH = 3, the polyelectrolyte is positively charged while at pH = 9 it is essentially uncharged. The enhancement in the adsorption of SDS at low coverage suggests that surface active polymer surfactant complexes are forming and adsorbing at the interface. This leads to close to monolayer adsorption of SDS, suggesting that it is surfactant monomers that are complexing with polymers that are in extended conformations parallel to the surface. As the concentration of SDS in the mixtures changes so does the surfactant content of the complexes, which affects the surface activity and hence the coverage of the complexes. Multilayer structures are formed at SDS concentrations of 0.1 and 1 mM, for pH = 3 and 9, respectively. |
| Magazine |
Journal Central South University of Technology(2007)s1−0238−04 |
| Year |
2007 |
| Autors |
GUO Longa,b and DOU Li-xiab |
| Estb. |
a College of Petroleum Engineering, China University of Petroleum, Donging 257061, China
b Geological Research Institute of Shengli Oilfield Co Ltd, SINOPEC, Dongying 257015, China |
| Abstract |
The change of interfacial viscoelasticity along with measuring time, the effect of polymer concentration and the type of polymer on interfacial viscoelasticity at the interface between polymer and dodecane were investigated by means of dilatational method. Moreover different viscoelasticity at different interfaces for polymer solution was also found. The result shows that the response of interfacial adsorption process can be made by interfacial viscoelasticity. Elasticity plays an important role in polymer/dodecane system even though contribution of viscosity in viscoelasticity goes up along with the increase of polymer concentration. Among those three interfaces, numerical value of viscoelasticity at polymer/air interface is the largest one, numerical value of viscoelasticity at polymer/dodecane interface the second, numerical value of viscoelasticity at polymer/crude oil interface the smallest. In addition, measurement of interfacial rheology is a useful method to evaluate polymer solution. |
| Magazine |
Langmuir 2003, 19, 7354-7361 |
| Year |
2003 |
| Autors |
Charles M. Kauscha, Yongsin Kima, Vernon M. Russella, Robert E. Medskera and Richard R. Thomasa |
| Estb. |
a OMNOVA Solutions, Incorporated, 2990 Gilchrist Road, Akron, Ohio 44305-4489 |
| Abstract |
Interfacial rheological studies were performed on a series of bolaamphiphilicR,ö-(diammonium disulfato)- poly(fluorooxetane)s of several perfluoroalkyl chain lengths. Similar measurements were performed on a small-molecule, anionic fluorosurfactant with a-C8F17 perfluoroalkyl group that is known to be an effective flow and leveling aid in aqueous coatings. Dilational viscoelasticities were measured for the fluorosurfactants as a function of concentration and oscillation rate. Elasticities were found to increase with increasing perfluoroalkyl chain length. All elasticities exhibited a strain rate dependence indicative of the influence of diffusional relaxation on elasticity values. Phase angles were found to be in the range for diffusional relaxation and decreased with increasing concentration and strain rate. Using interfacial rheological data, characteristic fluid dynamics numbers were calculated for the fluorosurfactants. Among these was the Marangoni number. Calculated Marangoni numbers for the poly(fluorooxetane)s were of the same order of magnitude as that for the small-molecule, long perfluoroalkyl chain surfactant. The poly(fluorooxetane)s all have equilibrium surface tensions greater than that of the small-molecule, long perfluoroalkyl chain surfactant, yet show similar abilities to aid in flow and leveling in aqueous coatings at comparable concentrations. Rheological measurements demonstrate that equilibrium surface tension alone is not enough to explain the fluid dynamics processes occurring during flow and leveling. |
| Magazine |
Langmuir, 2005, 21 (8), pp 3629–3634 |
| Year |
2005 |
| Autors |
Zuzanna T. Cygana, João T. Cabrala, Kathryn L. Beersa and Eric J. Amisa |
| Estb. |
a Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 |
| Abstract |
Rapid prototyping photolithography of a thiolene-based resin was used to fabricate microfluidic devices stable to aliphatic and aromatic organic solvents. The swelling of the cross-linked polymer matrix in various organic solvents was quantified, and the solvent resistance properties of these microfluidic devices are described. Discrete droplets of hexanes and toluene of uniform size were generated in microfluidic devices inside a water matrix containing SDS surfactant (SDS ) sodium dodecyl sulfate). Variation of water and organic flow rates in the fluidic channels was used to control droplet size and separation. Droplet composition could be controlled by varying flow rates of two joined organic streams. Organic-phase synthetic reactions within the droplets were demonstrated with the bromination of alkenes inside benzene droplets. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 74 (2009) 238–243 |
| Year |
2009 |
| Autors |
Krystyna Prochaskaa, Emilia Konowała, Joanna Sulej-Chojnackaa and Grazyna Lewandowiczb |
| Estb. |
aInstitute of Chemical Technology and Engineering, Pozna´n University of Technology, Pl. M. Skłodowskiej Curie 2, 60-965 Pozna´n, Poland
bDepartment of Biotechnology and Food Microbiology, The August Cieszkowski Agricultural University of Pozna´n, ul. Wojska Polskiego 48, 60-627 Pozna´n, Poland |
| Abstract |
The aim of the present work was to study the physicochemical properties of doubly modified, by crosslinking and acetylating, starches as well as the products of their enzymatic hydrolysis. A two step procedure of hydrolysis, including the batch and membrane reactors, were investigated. The second step of enzymatic processes were carried out in a continuous recycle membrane reactor (CRMR). Three kinds of commercial starches – two preparations of acetylated distarch adipate E1422 of different degrees of cross-linking, as well as one preparation of acetylated distarch phosphate E1414 were examined. It was found that the degree of substitution of acetyl groups in the macromolecules of starch did not influence the effectiveness of hydrolysis. However, the degree of cross-linking with adipate groups slightly decreased the efficiency of processing in the CRMR. Additionally, the relationship between the type of hydrocolloid and its adsorption activity in the air/water and oil/water systemswas considered. All obtained derivatives revealed adsorption properties and reduced the surface/interface tension in the air/water and oil/water systems. The efficiency and effectiveness of adsorption of the investigated hydrocolloids were affected by the type of modification as well as the degree of substitution of acetyl groups in the macromolecules of starch. Particle size distributions formed in aqueous solutions for all investigated hydrolyses were determined and compared with results obtained for commercial products. |
| Magazine |
Physical review letters 95, 117801 (2005) |
| Year |
2005 |
| Autors |
Shishir Prasada and Ali Dhinojwalaa |
| Estb. |
a Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA |
| Abstract |
We have studied the breaking of a two-dimensional alkane crystal above the disordered melt using an oscillating bubble rheometer. Surface tension changes abruptly during the expansion and contraction cycle. We postulate that this is due to rupture of the 2D crystal at grain boundaries. The magnitude of the abrupt change in surface tension decreases with a decrease in the rate of change of bubble surface area with a power law exponent of 0.8. The interfacial area formed after rupture decreases with a decrease in rate. These results provide new insights in understanding defect-mediated rupture in confined geometry. |
| Magazine |
Mendeleev commun,2003,13(5),217-219 |
| Year |
2003 |
| Autors |
Valery G. Babaka, Vladimir E. Tikhonova, Alexander R. Lachashvilia, Olga E. Philippovab, Alexei R. Khokhlovb and Margueritte Rinaudoc |
| Estb. |
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation
b Department of Physics, M. V. Lomonosov Moscow State University, 119992 Moscow, Russian Federation
c CERMAV–CNRS, 38041 Grenoble, France |
| Abstract |
The ‘bubble-flotation chromatography’ technique was proposed and successfully applied to the selective separation of chitosan samples of different hydrophobicity from their mixed aqueous solutions. |
| Magazine |
Langmuir 2006, 22, 4811-4817 |
| Year |
2006 |
| Autors |
Ashwin Raoa, Yongsin Kimb, Charles M. Kauschb, Vernon M. Russella and Richard R. Thomasb |
| Estb. |
a Department of Polymer Science, The UniVersity of Akron, Akron, Ohio 44325-3909
b OMNOVA Solutions, Inc., 2990 Gilchrist Road, Akron, Ohio 44305-4418 |
| Abstract |
The synthesis and characterization of a cationic oligo(fluorooxetane) surfactant with pendant -C4F9 groups are reported. Molecular area demand at saturation was determined to be 55.6 ± 0.3 Å2/molecule and characteristic of an oligomer. The adsorption of the cationic oligo(fluorooxetane) to the air-water interface appears to be diffusionlimited, and dilational rheological properties of the adsorbed molecules are representative of a “soluble” monolayer. Adsorption dynamics have been measured yielding diffusion coefficients that are dependent on concentration and in the 10-7-10-8 cm2/s range. Complex moduli from dilational interfacial rheological measurements as a function of oscillation frequency were well fitted to the Lucassen-van den Tempel equation, providing an estimate of the Gibbs elasticity. The combination of the oligomeric nature of the fluorosurfactant, short perfluoroalkyl chain and its interfacial properties suggests that this synthetic approach is an attractive route to the development of fluorinated surfactants that avoid the environmental concerns of small-molecule, long perfluoroalkyl-chain surfactants. |
Top
Food Industry
| Magazine |
Colloids and surfaces A:Physicochem,Eng.Aspects 2008 |
| Year |
2008 |
| Autors |
Veronique Bosca,b, Ilaria Ferraric and Camille Michona,b |
| Estb. |
a Agro Paris Tech, UMR ingenterte procédé, altment N°1145 no,11, Avenue des olymptades, 91744 Massy, France
b INRA, UMR ingenterte procede altment n°1145, 11 avenue des olymptades 91744 Massy,France
c The faculty of agrtculture of milan, department of food science, technology and microbiology,Italy |
| Abstract |
The adhesiveness of iota–carrageenan gels was evaluated versus their rheological properties such as storage modulus and loss tangent levels and the solid surface in contact (steel or plastics). Different viscoelastic behaviours were obtained by varying iota–carrageenan concentration or temperature. Furthermore, gels were added with casein without changing their rheological properties measured in dynamic mode (small deformation), to study the influence of solid surface tension of gels on adhesiveness. After the determination of rheological parameters of gels with dynamic rheological method, the level of adhesion was measured by a pull off test. The maximum force and the energy of adhesion measured during the separation of the gel from the solid surface were studied. Both were inversely related to the storage modulus of the gel. They increase with decreasing loss tangent (corresponding to an increase of the level of structure of the gel). Moreover, the maximum force measured during separation increases with the solid surface tension (steel or plastic) and the more structured the gel, the higher is the adhesiveness differences between surfaces.
When 0.2–0.3% (w/v) of casein are added to gels with high enough storage modulus (>90 Pa), the maximum separation force increases whereas the energy of adhesion is not affected. Casein may facilitate the propagation of the rupture at the interface. |
| Magazine |
Journal of colloid and interface science 308 (2007) 508-513 |
| Year |
2007 |
| Autors |
Lars Nilssona and Björn Bergenstahla |
| Estb. |
a Division of food Technology, centre for chemistry and chemical engineering, Lund university, P.O.Box 124,S-221 00 Lund, SWeden |
| Abstract |
In this paper we study the adsorption at cationic emulsion droplets of starch which had been hydrophobically modified with octenyl succinic anhydride (OSA), a modification which also renders the starch anionic. Emulsions were formed with didodecyldimethylammonium bromide (DDAB) after which the OSA-starch was added. The emulsions were separated by centrifugation and the surface load of OSA-starch was determined through serum depletion. The results show the adsorbed amounts can become very high, in some cases reaching approximately 40 mg/m2. The surface load correlates positively with the surface charge density of the starch which depends on the degree of substitution, rms radius and molar mass. Furthermore, the surface load obtained depends on the ratio between polymer surface charge density and the interface charge density which could be varied experimentally by combining various amounts of DDAB and dioleoyl phosphatidylcholine (DOPC) in the formation of the emulsion. The very high surface loads should correspond to very thick adsorbed layers. Thus, OSA-starch should be appropriate for encapsulation applications provided a suitable adhesion substance is employed. |
| Magazine |
Food Hydrocolloids 22(2008) 323-335 |
| Year |
2008 |
| Autors |
D.M.Dresselhuisa, E.H.A.de Hoogb, M.A.Cohen Stuartc and G.A.van Akenb |
| Estb. |
a Wageningen centre for food sciences,P.O.Box 557,6700 AN Wageningen,The netherlands
b NIZO food research B.V.P.O.Box 20,6710 BA Ede, The Netherlands
c Labo of physical chemistry and colloid science, wageningen University and research centre, P.O.Box 8038,6700 EK Wageningen, The Netherlands |
| Abstract |
Tribological measurements are indicated to be a tool in predicting the creamy in-mouth sensation of a food product. Tribological measurements relating lubricational behaviour of a food product to perception are often conducted with artificial surfaces. In this work we used pig’s tongue to mimic the human tongue, which has the advantage of having surface characteristics similar to a human tongue. Using biological material has also some drawbacks. The most important drawbacks are the limited availability, the individual differences between the tongues, and the relative fast degradation of the tissue. The aim of this study was to identify the characteristics of the tongue in terms of surface roughness, deformability and wetting properties. The knowledge on these characteristics can serve as reference when using modified poly dimethyl siloxane (PDMS) in tribological experiments relating perception to in-mouth friction. Furthermore, we demonstrated that these characteristics are crucial in tribological studies to draw rightful conclusions. Tribological measurements were performed with an experimental set-up combining friction measurement with confocal scanning laser microscope (CSLM) observations. We identified the importance of these characteristics for tribology measurements performed in relation to sensory perception.
It is shown that the tongue surface has some very typical characteristics, including the presence of papillae and a hydrophilic mucus layer, and an elastic modulus that is at least two orders of magnitude smaller than that of smooth PDMS surfaces. The different surface characteristics appear to lead to completely different lubricational behaviour of the food emulsions between these surfaces. Furthermore, for food emulsions differences in the occurrence of coalescence were found between shearing with pig’s tongue and PDMS surfaces. Therefore, we conclude that for studies relating sensory properties of food systems to lubricational behaviour, a careful choice of representative surfaces is essential and that modification of smooth PDMS can result in surfaces having characteristics closer to tongue tissue. |
| Magazine |
Advances in Colloid and Interface Science 88 (2000).19-36 |
| Year |
2000 |
| Autors |
A.Cagnaa, N. Pérona, M. Valadeb, R. Marchalc, A. Maujeanc, B. Robillardd, V. Aguie-Beghine and R. Douillarde |
| Estb. |
a I.T. Concept, Parc de Chancolan, 69770 Longessaigne, France
b Comite Interprofessionnel du Vin de Champagne, 5 rue Henri-Martin, BP 135, 51204 Epernay Cedex, France
c Lab. d’OEnologie, URCA, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2, France
d Möet et Chandon, 6 rue Croix de Bussy, 51200 Epernay, France
e INRA, Equipe de Biochimie des Macromolecules Vegetales, CRA, 2 Espl. R. Garros, BP 224, 51686 Reims Cedex 2, France |
| Abstract |
A foam ring composed of small bubbles on the surface of a champagne glass is one of its hallmarks. The equilibrium state of that ring is linked with the rate of formation and of disappearance of bubbles. The stability of bubbles is usually ascribed to the occurrence and to the properties of an adsorption layer formed at the gasrliquid interface. Our goal is to characterise such an adsorption layer at the gasrwine interface in order to understand its role in bubble stability. Alcohol in wine lowers the surface tension to 49 mNrm. The adsorption of other molecules may cause a further decrease of 2 mNrm. Such a situation makes the study of adsorption by surface tension measurement inaccurate. To overcome this problem, we have diluted the wine four times with water before its surface tension measurement by pendant drop shape analysis. In these conditions, ethanol lowers the surface tension to 64 mNrm and the adsorption of other molecules of the wine can be monitored over 6]8 mNrm. The usual behaviour of such a diluted wine is a lowering of the surface tension during at least 20 min after drop formation. Since the role of macromolecules on the foaming properties of wine had been previously observed, we have chosen to evaluate the effect of this fraction of the wine molecules on its surface properties. Thus, wines were ultrafiltrated on a membrane with a 10 000 molecular mass cut-off. The ultrafiltrate (UF) does not show any decrease of its surface tension over a 20-min period while the ultraconcentrate (UC) has a kinetics similar to that of unfiltered wine. Mixtures of UF and UC have behaviours intermediate between those of these products. A technological treatment of the wine with bentonite, believed to lower the content of macromolecules, yields a wine similar to UF. The effect of ultrafiltration was also analysed by spectroscopic ellipsometry. UF has a spectrum similar to that of a waterralcohol mixture with the same ethanol content and its ellipticity is stable during at least 20 min. On the contrary, wine or UC show spectra with the features of an adsorption layer and those characteristics increase during more than 20 min. Two varieties of vine were compared: ‘Chardonnay’ and ‘Pinot noir’. The former is known to have better foaming properties than the latter. Its surface properties measured in this study are also more pronounced than those of Pinot noir. However, the representation of the dilational modulus against the surface pressure (which, in some instances, may be a mathematical transformation of the state equation) puts all the samples (wines, UF and UC of each) on the same master curve, a fact in favour of a common nature for all the adsorption layers. It can be concluded that surface properties of champagne wines are mostly determined by ethanol and by macromolecules with a molecular mass larger than 10 000. Moreover, the adsorption layers seem to have the same nature, irrespective of the vine variety and of the concentration ratio of the wine. |
| Magazine |
Langmuir 2004, 20, 3574-3582 |
| Year |
2004 |
| Autors |
Raffaele Mezzengaa, Britta M. Folmera and Eric Hughesa |
| Estb. |
a Nestlé Research Center, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland |
| Abstract |
A method was developed allowing in situ adjustment of water-in-oil-in-water double emulsion (W/O/W) morphologies by tailoring the osmotic pressure of the water phases. The control of internal droplet size is achieved by altering the chemical potential of the external and internal water phases by dissolving neutral linear polysaccharides of suitable molecular weights. As a consequence of the different chemical potentials in the two aqueous phases, transport of water takes place modifying the initial morphology of the double emulsion. Self-diffusion 1Hnuclear magnetic resonance (1HNMR) was used to assess transport mechanisms of water in oil, while a numerical model was developed to predict the swelling/shrinking behavior ofW/O/Wdouble emulsions. The model was based on a two-step procedure in which the equilibrium size of a single internal water droplet was first predicted and then the results of the single droplet were extended to the entire double emulsion. The prediction of the equilibrium size of an internal droplet was derived by the equalization of the Laplace pressure with the osmotic pressure difference of the two aqueous phases, as modeled by mean-field theory. The double emulsion equilibrium morphologies were then predicted by upscaling the results of a single drop to the droplet size distribution of the internal W/O emulsion. Good agreement was found between the theoretical predictions and the measurement of double emulsion droplet size distribution. Therefore, the present model constitutes a valuable tool for in situ control of double emulsion morphology and enables new possible applications of these colloidal systems. |
| Magazine |
Journal of Food Engineering 78 (2007) 802–809 |
| Year |
2007 |
| Autors |
C. Balerina, P. Aymardb, ,F. Duceptc, S. Vaslinb and G. Cuveliera |
| Estb. |
a ENSIA, UMR 1211 SCALE, 1 avenue des Olympiades, 91744 Massy Cedex, France
b Danone Vitapole, Technovaleur, Route De´partementale 128, 91767 Palaiseau Cedex, France
c ENSIA, UMR GENIAL, 1 avenue des Olympiades, 91744 Massy Cedex, France |
| Abstract |
The aim of this work was to determine the phenomena affecting bubble size, according to process conditions (pressure, flow rates, whipping rotation speed) and formulation properties. Model fluids were formulated in order to get simple and well-defined rheology. An instrumented foaming pilot-scale line was built and allowed us to monitor the process and to characterise bubble size under pressure, at the exit of the mixer.
Viscosity and rotation speed of the whipping head are the most influent parameters on foam morphology: interaction between these factors have been highlighted. Experimental measurements obtained were consistent with the critical Weber number since a corrected fluid viscosity is used. It seems indeed that the fluid viscosity is reduced in the whipping head, due to the presence of local heating. These temperature variations consequent to the shear of viscous fluids in a narrow-gap geometry were quantified and modelled as a function of shear rate and fluid viscosity. |
| Magazine |
Colloids and Surfaces A: Physicochem. Eng. Aspects 279 (2006) 159–166 |
| Year |
2006 |
| Autors |
Eric Kolodziejczyka, Vera Petkovab, Jean-Jacques Benattarb, Martin E. Lesera and Martin Michela |
| Estb. |
a Nestlé Research Center Lausanne, Nestec Ltd., Vers-chez-les Blanc, CH-1000 Lausanne 26, Switzerland
b CEA-Saclay, DSM/DRECAM, Service de Physique de l’Etat Condense, F-91191 Gif sur Yvette, France |
| Abstract |
When using fluorescence microscopy for the investigation of β-lactoglobulin (BLG) stabilized thin liquid films and monolayers, it is necessary to label the protein sample with a fluorescent dye. In the present study, we discuss the effect of labeling β-lactoglobulin with either Rhodamine iso-thiocyanate (RITC) or Fluorescein iso-thiocyanate (FITC) on the BLG properties at the air–water interface and in thin films. RITC and FITC are the two most frequently used dyes in fluorescence microscopy. Two different Rhodamine concentrations were used, namely the concentration conventionally used in fluorescence microscopy, and a two times higher Rhodamine concentration. Interfacial tension and rheology measurements, and thin film investigations using X-ray reflectivity or the diminishing bubble method showed that the labeling procedure of the β-lactoglobulin using Rhodamine at the lowest concentration does not change the viscoelastic properties of the air–water interface, as well as the film thickness and gas permeability. However, when taking the higher Rhodamine concentration the films are thicker and more permeable for gas. Similarly, Fluorescein at a concentration equivalent to the highest concentration of Rhodamine induced also a modification of the protein film properties. However, the labeling did not influence the BLG monolayer viscoelastic characteristics.
Labeling β-lactoglobulin with Rhodamine allows nowusing confocal fluorescence microscopy (CSLM) for the elucidation of structure formation in thin films and at water–air surfaces. As an example, images from thin films as formed in the diminishing bubble experiment and stabilized with labeled BLG show that the formed BLG aggregates are highly surface active, i.e., enriched at the water–air interface. The obtained images reveal that the aggregates are also present in the film. In general, CSLM combined with the diminishing bubble method seems to be an excellent experimental set-up to visualize the distribution of labeled components throughout a thin film and its adjacent monolayers. This is not possible using the diminishing bubble method in combination with conventional microscopy. |
| Magazine |
10.1016/j.foodhyd.2010.07.019 |
| Year |
2010 |
| Autors |
S. Mezdoura, S. Desplanquesa and P. Relkina |
| Estb. |
a AgroParisTech, – UMR 1145, Engineering-Food-Processes, 1 avenue des Olympiades 91300 Massy-France |
| Abstract |
Vinegar sauces’ type emulsions were prepared from water-alcohol mixture (90:10) and three different sunflower oil samples (Reference oil, SUN 1 and SUN 3) at 20 wt.% with sunflower lecithin as O/W emulsifier. Besides the addition of lecithins at 0 to 2 wt.%, the oil composition varied based on the minor components present in each oil due to the different crushing and refining process. Reference oil sample was nutrient-free while SUN oil contained nutrient components sterols, tocopherols, phosphorus and phenols. Interfacial tension of the different systems was monitored using an automated tensiometer. The vinegar sauces’ type oil-in water emulsions were prepared by a two–step homogenization procedure (10,000 rpm for 10 min, followed by a passage through an homogenizer at 400 bar pressure), the lipid droplets stability against aggregation/coalescence was monitored using integrated light scattering (particle size distribution) and multiple light scattering (creaming) measurements for two months storage at 4°C . In the absence of added lecithins, SUN oil sample containing phospholipids presented lower interfacial tension values than the Reference oil. Equilibrium values obtained are ~ 4.4 mN.m-1 for SUN3, ~ 10.5 mN.m-1 for SUN 1 , instead of 13.7 mN.m-1 for Reference sample. Addition of phospholipids (lecithin) to the Reference sample led to a similar trend of adsorption kinetics observed in the SUN sample (nutrient rich oil). SUN3 showed the best ability to form elastic film and Reference oil showed lowest ability, which could be attributed to concentration and the compostion of phospholipids.
In addition, the SUN emulsions (stored at 4°C and 22°C) were more stable against creaming and smaller in droplet size with increased concentration of added lecithins. |
| Magazine |
Langmuir 2005, 21, 7786-7795 |
| Year |
2005 |
| Autors |
Christophe Schmitta Tânia Palma da Silvaa Claudine Bovaya Sabrina Rami-Shojaeib Philippe Frossarda Eric Kolodziejczyka Martin E. Lesera |
| Estb. |
a Department of Food Science, Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland
b Department of Bioanalytical Science,Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland |
| Abstract |
The electrostatic complexation between â-lactoglobulin and acacia gum was investigated at pH 4.2 and 25 °C. The binding isotherm revealed a spontaneous exothermic reaction, leading to a ΔHobs = -2108 kJ mol-1 and a saturation protein to polysaccharide weight mixing ratio of 2:1. Soluble electrostatic complexes formed in these conditions were characterized by a hydrodynamic diameter of 119 ± 0.6 nm and a polydispersity index of 0.097. The effect of time on the interfacial and foaming properties of these soluble complexes was investigated at a concentration of 0.1 wt % at two different times after mixing (4 min, referred as t ~ 0 h and t = 24 h). At t ~ 0 h, the mixture is mainly made of aggregating soluble electrostatic complexes, whereas after 24 h these complexes have already insolubilize to form liquid coacervates. The surface elasticity, viscosity and phase angle obtained at low frequency (0.01 Hz) using oscillating bubble tensiometry revealed higher fluidity and less rigidity in the film formed at t ~ 0 h. This observation was confirmed by diminishing bubble experiments coupled with microscopy of the thin film. It was thicker, more homogeneous and contained more water at t ~ 0 h as compared to t = 24 h (thinner film, less water). This led to very different gas permeability’s of Kt=0h=0.021cms-1 and Kt24h=0.449cms-1, respectively. Aqueous foams produced with theâ-lactoglobulin/acaciagumelectrostatic complexes or coacervates exhibited very different stability. The former (t ~ 0 h) had a stable volume, combining low drainage rate and mainly air bubble disproportionation as the destabilization mechanism. By contrast, using coacervates aged for 24 h, the foam was significantly less stable, combining fast liquid drainage and air bubble destabilization though fast gas diffusion followed by film rupture and bubble coalescence. The strong effect of time on the air/water interfacial properties of the β-lactoglobulin/acaciagumelectrostatic complexes can be understood by their reorganization at the interface to form a coacervate phase that is more fluid/viscous at t ~ 0 h vs rigid/elastic at t = 24 h. |
| Magazine |
Journal of Food Engineering 58 (2003) 227–238 |
| Year |
2003 |
| Autors |
Juliane Flourya, Anne Desrumauxa, Monique A.V. Axelosb and Jack Legrandc |
| Estb. |
a GEPEA-ENITIAA-UMR-CNRS 6144, Rue de la Géraudière, BP 82225, 44322 NantesCedex 03, France
b INRA LPCM, Rue de la Géraudière, BP 71627, 44316 NantesCedex 03, France
c GEPEA-UMR-CNRS 6144, Université de Nantes-IUT de Saint-Nazaire, CRTT, BP 406, 44602 Saint-Nazaire Cedex, France |
| Abstract |
A new high pressure homogeniser going up to 350 MPa was used to produce fine emulsions stabilised by methylcellulose for food applications. The objective of this study was to evaluate the effect of homogenising pressure on emulsifying and stabilising properties of methylcellulose, a food macromolecule extensively used as stabiliser in emulsions. Oil droplet size distributions of the emulsions were measured by laser-light scattering; rheological properties were characterised with a coaxial cylinder rheometer; and stability was evaluated by heating of the emulsions. Influence of homogenising pressure on interfacial properties (adsorption kinetics, interfacial tension and rheological behaviour) of the polymer was also studied at different pressure treatments. The results showed significant modifications in the structure and the texture of emulsions with increasing homogenising pressure. Homogenised methylcellulose solutions showed weaker thickening and stabilising properties compared to the one of the native methylcellulose. |
| Magazine |
J. Agric. Food Chem. 2007, 55, 1469-1474 1469 |
| Year |
2007 |
| Autors |
LARS NILSSONa and BJOIRN BERGENSTÅHLa |
| Estb. |
a Division of Food Technology, Centre for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-22100 Lund, Sweden |
| Abstract |
In this paper, we studied the adsorption at emulsion droplets of potato starch, which was hydrophobically modified with octenyl succinate anhydride (OSA), a surface active macromolecule containing ultrahigh molar mass components. The results show that the substance works as an efficient emulsifier and that it can in some cases generate high surface loads (10 mg/m2). The results can be explained as an interplay between kinetic factors during the formation of the emulsion and the physicalchemical properties of the hydrophobically modified starch, such as the degree of substitution, molar mass, and radius. In turbulent flow fields, such as in a high-pressure homogenizer, the mass transport to the interface favors the adsorption of larger molecules as they are transported more rapidly to the interface. The larger molecules are also likely to have a higher substituent density and adsorption energy than smaller ones. This in turn is likely to give high surface loads and strengthen the effect of kinetic adsorption factors, as the large molecules will be overrepresented at the surface. |
| Magazine |
|
| Year |
2007 |
| Autors |
Victor Pizones Ruiz-Henestrosaa, Cecilio Carrera Sancheza and Juan M.Rodriguez Patinoa |
| Estb. |
a Departamento de Ingenieria Quimica, Facultad de Quı´mica, Universidad de Sevilla, C/ Prof. Garcia Gonzalez,1,E-41012-Sevilla,Spain |
| Abstract |
In this contribution, we have analyzed the effect of different strategies, such as change of pH (5 or 7) or ionic strength (at 0.05 and 0.5 M), and addition of sucrose (at 1 M) and Tween 20 (at 1.10-4 M) on interfacial characteristics (adsorption, structure, dynamics of adsorption, and surface dilatational properties) and foam properties (foam capacity and stability) of soy globulins (7S and 11S at 0.1 wt %). We have observed that (1) the adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depends on the modification in the 11S/7S ratio and on the level of association/dissociation of these proteins by varying the pH and ionic strength (Ι), the effect of sucrose on the unfolding of the protein, and the competitive adsorption between protein and Tween 20 in the aqueous phase. The rate of adsorption increases at pH 7, at high ionic strength, and in the presence of sucrose. (2) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior but do not have the capacity to form a gel-like elastic film. The surface dilatational modulus increases at pH 7 and at high ionic strength but decreases with the addition of sucrose or Tween 20 into the aqueous phase. (3) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface plays an important role in the formation of foams generated from aqueous solutions of soy globulins. However, the dynamic surface pressure and dilatational modulus are not enough to explain the stability of the foam. |
| Magazine |
Food Hydrocolloids 19 (2005) 1005–1015 |
| Year |
2005 |
| Autors |
R.J. Redgwella, C. Schmitta, M. Beaulieua and D. Curtia |
| Estb. |
a Nestlé Research Centre, Nestec Ltd, Vers-chez-les-Blanc, P.O. Box 44, CH-1000, Lausanne 26, Switzerland |
| Abstract |
The arabinogalactan–protein (AGP) fraction of green coffee beans accounts for ~15% of the dry bean. A procedure was developed to solubilise most of the AGP content of the beans so that its properties as a hydrocolloid could be investigated. An AGP fraction was partially purified from green arabica coffee beans, its rheological properties characterised and compared to those of some commercially important hydrocolloids, particularly acacia gum. The coffee AGP fraction dissolved readily in water to give colourless clear solutions. The polymer was a polyelectrolyte with a high molecular weight (Mw 3.78×106), characterised by a narrow polydispersity index (Mw/Mn 1.3). The intrinsic viscosity was close to that of acacia gum ([η]=0.23 dL g-1), but a 1 wt% solution of coffee AGP was three times more viscous than acacia gum at the same concentration. Coffee AGP showed Newtonian flow for concentrations below 6 wt%, but above this concentration the flow behaviour entered a shear-thinning regime. The coffee AGP fraction possessed interesting foaming properties providing that the biopolymer concentration was high enough to initially stabilize the interface that is created. The high molecular weight of coffee AGP combined with its globular structure conferred upon it a high ability to retain water within a foam thin film. However, the structure of the interfacial film was less effective than that of acacia gum to entrap efficiently the gas into the foam. In summary, coffee AGP shows some interesting rheological features which suggest that coffee beans could be used as an alternative source of the class of surface-active polymers which find many commercial applications. |
| Magazine |
Colloids and Surfaces A: Physicochem.Eng.Aspects 237(2004)113-118 |
| Year |
2004 |
| Autors |
M.Mellemaa and J.Benjaminsa |
| Estb. |
a Unilever R&D P.D.Box 114,3130 AC Vlaardingen,The Netherlands |
| Abstract |
Oil/air interfacial elasticities were measured to explain the foaming behaviour of triacylglycerol (TAG) oils at high temperature, in the presence of phospholipids. Measurements were done by dynamic drop tensiometry (DDT), and by identifying the type of Bénard-Marangoni (BM) convection patterns are formed in a shallow layer of the same oil/phospholipid mixture heated from below.
The foam stability at high temperatures appears to be determined by the rate of drainage, which is in turn determined by the Marangoni-effect. The interfacial elasticity as measured by DDT, can be used as a measure of the Marangoni effect. The type of BM convection pattern can also be used to estimate the Marangani effect.
The relation observed between the Bénard-Marangoni patterns, interfacial elasticities and foaming behaviour is shown to be physically consistent and has potential merits in the study of foaming of complex systems. In the future the work could be extended more quantitatively and verified using defined model systems. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 42 (2005) 97–106 |
| Year |
2005 |
| Autors |
A. Malzert-Fréona, O. Abillonb, J.E. Proustc, R. Grefd, J.P. Benoîtc and F. Bouryc |
| Estb. |
a Lab. de Pharmacie Galénique, UFR de Sciences Pharmaceutiques, bd Becquerel, 14032 Caen, France
b Lab. de Physique Statistique de l’Ecole Normale Supérieure, 24 rue de Lhomond, 75231 Paris, France
c UMR Inserm U646 “Ingénierie de la Vectorisation Particulaire”, Immeuble IBT, 10 rue Andr´e Boquel, 49100 Angers, France
d Physico-Chimie,Pharmacotechnie,Biopharmacie,UMR CNRS 8612, Université Paris Sud,Centre d’Etudes Pharmaceutiques,5 rue J.B. Clément, 92290 Châtenay Malabry,France
|
| Abstract |
In this paper, we compared the efficiency of polymer films, made of a poly(ethylene glycol) (PEG2,000)/poly(η,l-lactide) (PLA50) mixture, or a PEG2,000-PLA50 copolymer, to prevent adsorption of a model protein, the hen egg-white lysozyme (HEWL), at the air–water interface. This was achieved by analyzing the surface pressure/surface area curves, and the X-ray reflectivity data of the polymer films spread on a Langmuir trough, obtained in absence or in presence of the protein. For both the mixture and the copolymer, the amount of protein adsorbed at the air–water interface decreases when the density of the polymer surface coverage increases. It was shown that even in a condensed state, the polymer film made by the mixture can not totally prevent HEWL molecules to adsorb and penetrate the polymer mixed film, but however, protein molecules would not be directly exposed to the more hydrophobic phase, i.e. the air phase. It was also shown that the configuration adopted by the copolymer at the interface in its condensed state would prevent adsorption of HEWL molecules for several hours; this would be due in particular to the presence of PEG segments in the interfacial film. |
| Magazine |
Langmuir, 2001,17 (3), 791 -797, |
| Year |
2000 |
| Autors |
Alain Cagnaa, Nicolas Pérona, Michel Valadeb, Christophe Bliardc, Véronique Aguié-Béghind and Roger Douillardd |
| Estb. |
a IT. Concept, Parc de Chancolan, 69770 Longessaigne, France
b Comité Interprofessionnel du Vin de Champagne, 5 rue Henri-Martin, BP 135, 51204 Epernay Cedex, France
c CNRS,Groupe de Glycotechnie, Laboratoire de Pharmacognosie, ESA 6013, Moulin de la Housse,BP 1039, 51687 Reims Cedex 2, France
d INRA, Equipe de Biochimie des Macromolécules Végétales, CRA, 2 Espl. R. Garros, BP 224, 51686 Reims Cedex 2, France |
| Abstract |
Adsorption layers formed at the air/degassed champagne interface were characterized by ellipsometry and by surface tension measurements of the samples diluted four times with water. Ultrafiltration of the samples showed that the adsorption layer is mainly formed by macromolecules with molecular masses in the range 104 to 105. Nonsparkling base wine was ultrafiltrated with a molecular mass cutoff of 104, and the resulting ultraconcentrate and ultrafiltrate were combined to yield experimental base wines with adjusted macromolecular content. These samples were submitted to bottle fermentation. The resulting experimental champagnes were tested for the extent of their bubble collar and for their surface properties. A good correlation was found between the two sets of data. |
| Magazine |
AVH Association - 9th Symposium-Reims, 03/2002 |
| Year |
2002 |
| Autors |
A. CAGNAa, R. BELHAMRI1b, V. AGUIÉ – BEGUINc, R. DOUILLARDc and M. MATHLOUTHIb |
| Estb. |
a IT Concept, Parc de Chancolan, 69770 Longessaigne, France
b Lab. de Chimie Physique Industrielle, UMR FARE Université de Reims
c Équipe Parois Végétales et Matériaux Fibreux, UMRFARE, INRA de Reims |
| Abstract |
|
| Magazine |
Colloids and Surfaces A: Physicochem. Eng.Aspects344(2009)72–78 |
| Year |
2009 |
| Autors |
Peter A.Wierengaa, Lianne van Noréla and Elka S. Bashevab |
| Estb. |
a Food Physics Group, Wageningen University and Research Centre, Wageningen, The Netherlands
b Laboratory of Chemical Physics and Engineering, Sofia University, Sofia, Bulgaria |
| Abstract |
In food industry, protein isolates are often used to help in the formation and stabilisation of food foams. Subsequently there is great interest in (1) understanding the effect of processing parameters on the functional properties of the isolate, and (2) methods and techniques that can help to predict the foam properties. This article describes the foaming properties of proteins that were modified in the Maillard reaction. From these relatively simple experiments results were obtained that indicate that for certain protein solutions the foam properties can vary significantly, while the interfacial properties are constant.
Commercial protein isolates originate fromonly a few sources, mainly egg white and whey, and sometimes plant proteins (e.g. soy). Despite these limited sources a large variety of isolates with a wide range of properties is produced. One source of variation is the isolation procedure, but at least equally important are the conditions used before, during and after drying the protein solution to form the dry powder.
From the literature it was found that one of the major changes to the protein during processing of the isolates is the covalent coupling of sugars via the Maillard reaction. To study the effects of these reactions, a model system was produced that consists of proteins that were glycated to different degrees using Maillardreaction. For eachsample, interfacial properties (e.g. surface pressure, dilatational modulus)were determined, and foam experiments were performed. The results show that at constant concentration of both the protein (0.5 g/L) and sugar (0.7 g/L), the foam-ability and stability could be significantly improved (e.g. non-modified lysozyme does not foam, the highest modification is easily foamed and the foam has a half-life time of 200 s).
Interestingly, the improved foam properties could not be related to any change in interfacial properties. While foam stability improved with increasing modification, the measured interfacial properties were not significantly affected. These observations seem to go against the general view that changes in foam behaviour should be reflected in changes in the interfacial properties. Additional experiments on thin liquid films were performed, where the disjoining isotherm was measured. These isotherms did not show significant differences in the interactions between the adsorbed layers. This indicates that the electrostatic and steric interactions between the adsorbed layers do not depend on the degree of modification. Only the thin film stability against rupturewas found to increase with increasing modification. The thin film experiments lead to the hypothesis that aggregates (or oligomeric proteins) formed during modification might become trapped in the film. The presence of these oligomeric proteins could result in an increase of the apparent viscosity in these films, or in gelling or jamming of the liquid phase between the two interfaces. In other words, the observed behaviour is the result of the confined geometry of the thin films.
The results confirm other observations that Maillard reactions improve foaming properties. Moreover, strong indicationswere found that to predict foam stabilitywe need more than the traditional parameters (i.e. (dynamic) surface pressure, interfacial reology, and disjoining pressure). |
| Magazine |
Langmuir, 2009, 25 (20), pp 12066–12072 |
| Year |
2009 |
| Autors |
Sébastien Marzea |
| Estb. |
a Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland |
| Abstract |
The rheological properties of PolyGlycerol PolyRicinoleate (PGPR) at the oil/water interface were studied using a drop-shaped tensiometer. Small deformation oscillations of the drop area allow the measurement of the interfacial viscoelasticity spectrum, that is, the elastic and viscous moduli as a function of frequency. Another way to obtain such a spectrum is to perform a transient relaxation measurement from which the relaxation modulus as a function of time is deduced and interpreted. Several models containing one or more relaxation times were considered, and their resulting spectra were compared to the oscillatory ones. Similar results suggest that one could in principle use oscillatory or transient relaxations indifferently. However, the transient relaxation technique proved to be more adapted for the determination of the relaxation times. At low PGPR concentrations in oil, the behavior is controlled by long relaxation times, whereas short ones take over when approaching and exceeding the saturation interfacial concentration. This was understood as a shift from a diffusion-dominated regime to a rearrangements-dominated regime. |
| Magazine |
Food biophysics 1 (2006) 2 |
| Year |
2006 |
| Autors |
Cristina Primo-Martina, Robert J. Hamera and Harmen H. J. de Jongha |
| Estb. |
a Wageningen Centre for Food Sciences,Diedenweg 20, 6700 AN Wageningen, The Netherlands |
| Abstract |
Gas cell stability during bread making is controlled by both surface and bulk properties. This paper is focused on studying the surface properties of the water-soluble phase of the dough, the dough liquor (with and without lipids), as well as the composition of the air/water interface. Using infrared reflection measurements, we showed that in lipid-poor liquor, proteins are the dominant species present at the air/water interface. With complete liquor (including the lipids), a mixed interface of protein and lipids is obtained. However, the presence of lipids in the surface layer did not significantly affect the surface pressure. We also added enzymes to the flour to evaluate in what way the surface-active properties of the liquor components can be affected. These results were compared to the effect of adding a surfactant [diacetyl tartaric esters of monoand diglycerides (DATEM)]. Biobake 10804, a xylanase that increased the arabinoxylan content of the dough liquor, decreased the surface pressure and increased the dilational modulus in lipid-poor liquor. This effect was not observed with the liquor including the lipids. Lipopan 50 BG, a 1,3-specific lipase, increased the surface pressure of the liquor that included the lipids. Lipopan F BG, which converts polar lipids to their lyso form, strongly increased the surface pressure not only in the lipid-containing liquor but also in the lipid-poor liquor. DATEM, as expected, increased the surface pressure while strongly decreasing the dilational modulus. Results of these studies were used to help explain changes in loaf volume observed in a series of baking tests, using the same enzymes and additives. This led to the conclusion that the effect of surface-active components alone cannot account for the larger loaf volumes observed. Clearly, both the effect of bulk and interfacial rheological properties should be considered together when explaining gas cell stability. |
| Magazine |
Food Hydrocolloids 21 (2007) 776–781 |
| Year |
2007 |
| Autors |
S. Mezdoura, G. Cuveliera, M.J. Cashb and C. Michona |
| Estb. |
a UMR SCALE n1 1211 (ENSIA, CNAM, INRA)—Food Science Department, Massy cedex, France
b HERCULES INCORPORATED, Aqualon Division, Delaware, USA |
| Abstract |
Hydroxypropyl cellulose (HPC) is a neutral polysaccharide derived from cellulose. It is, notably, added to non-dairy whipped topping. However, if the function of HPC is well recognized, its behavior is not well known. The interaction of HPC with each component (dispersed fat droplets, emulsifiers, proteins) should be studied step by step. In order to understand better the function of HPC, air–water interfacial rheology was used to characterize the behavior of HPC at this interface, with and without emulsifier. As HPC is a flexible polymer, it shows, at room temperature, a medium value of intrinsic viscosity, which is of the same order as of galactomannan ones. Addition of HPC in the aqueous phase leads to a decrease of the air–water surface tension (down to about 45–41 mN/m) where xanthan and guar gum have smaller or negligible effect. The time to reach the equilibrium of surface tension is reached after several hours. The smaller the concentration, the longer it is to reach the equilibrium. The competition between HPC and palmitic ester (E473) was studied. Kinetics of surface tension evolution of E473/HPC systems are different from that of HPC alone: mixed systems and HPC show an evolution of surface tension in three steps that could be explained through E473/HPC competition for the air/continuous phase interface. |
| Magazine |
Journal of Dairy Science Vol.83, No.11, 2000 |
| Year |
2000 |
| Autors |
J. M. Girardeta, L. Debomya, J.-L. Courthaudonb, L. Micloa, G. Humberta and J.-L. Gaillarda |
| Estb. |
a Lab. des BioSciences de l'Aliment, Unité associe´e à l'INRA,Université Henri Poincaré-Nancy 1, B.P. 239,54506 Vandoeuvre-le`s-Nancy, France
b Lab. d'Ingénierie Moléculaire et Sensorielle de l'Aliment,ENSBANA, 1 Esplanade Erasme, 21000 Dijon, France |
| Abstract |
A combination of proteolysis and dilational rheology has been used to study the behavior of films of β-casein (β-CN) and of peptides spread at the oil-water interface. Identification of the peptides produced by trypsin hydrolysis of β-CN in emulsion at 37°C provided information on the structure of β-CN adsorbed at the oil-water interface. Good interface properties were observed for β- CNor its peptides, probably because of the amphipathic nature of β-CN or a synergistic effect between hydrophilic and hydrophobic peptides. Remarkable surface activity was found for the amphipathic peptide β-CN (f114–169). Rheological studies had shown that interface films made with peptide fractions or with β-CN were elastic rather than viscous. Film made with the purified peptide β-CN (f114–169) was merely elastic at the triolein-water interface. A decrease of the viscoelastic modulus was observed for aging β-CN film but not for aging peptide films; The β-CN decrease was related to the flexibility of its structure. When the interface is increased by the dilation of an aqueous droplet plunged into oil, β-CN may expose new polypeptide trains to cover the increased interface, unlike peptides with simpler structures. |
Top
Protein
| Magazine |
Colloids and Surfaces B: Biointerfaces 71 (2009) 230–237 |
| Year |
2009 |
| Autors |
Maria J. Martineza, Celilio Carrera Sanchezb, Juan M, Rodriguez Patinob and Ana M.R Pilosofa |
| Estb. |
a Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires, Argentina
b Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, C/Prof. García González 1 (41012), Seville, Spain |
| Abstract |
Caseinoglycomacropeptide (GMP) is a hydrophilic glycopeptide released frommilk ĸ-casein by chymosin hydrolysis during cheese making. GMP is thought to be a potential ingredient for specific dietary applications with several health benefits. In this study GMP was characterized at the air–water interface and its behaviour was related with the self-assembly of GMP in solution as affected by pH. This GMP selfassemblywas investigated by dynamic light scattering and the interfacial propertieswere determined by tensiometry and surface dilatational measurements at pH 4, 5 and 7. At pH 5 GMP exhibited higher surface pressure at equilibrium than at pH 7. At pH 4 the behaviour was more complex due to self-assembly close to GMP pI. Dynamic measurement showed that the adsorption/penetration rate constant (Kads) is facilitated at higher GMP bulk concentrations, while the rate constant of rearrangement (Kr) decreased at higher GMP concentrations which could be attributed to the existence of a steric restriction due to the higher GMP load at the interface. Kr was higher at pH 5 because of lower electrostatic interactions close to the pI. The viscoelastic properties showed a complex behaviour due to the existence of protein–protein interactions depending on the GMP concentration, on the pH of the bulk and on the rates of diffusion, adsorption and rearrangement of GMP at the air–water interface. |
| Magazine |
Langmuir 2006, 22, 6181-6188 |
| Year |
2006 |
| Autors |
J.Benjaminsa, J.Lyklemab and E.H.Lucassen-reyndersc |
| Estb. |
a Wageningen centre for food sciences,P.O.Box 557,6700 AN Wageningen,The netherlands
b Lab. of physical chemistry and colloid science, wageningen university,Dreijenplein 66703HB, Wageningen, The Netherlands
c Mathenesselaan 11,2343 HA Oegstgeest, The Netherlands |
| Abstract |
Dynamic interfacial tensions and surface dilational moduli were measured for four proteins at three fluid interfaces, as a function of time and concentration. The proteins―β-casein, β-lactoglobulin, bovine serum albumin, and ovalbumins were adsorbed from aqueous solution against air, n-tetradecane, and a triacylglycerol oil. The sinusoidal interfacial compression/expansion, at frequencies ranging from 0.005 to 0.5 Hz, was effected in a dynamic drop tensiometer suited to viscous oil phases. Generally, at interfacial pressures up to 15 mN/m, dilational moduli were purely elastic at frequencies from 0.1 Hz. In this elastic range, in-surface relaxation either was essentially completed or had not yet started within a time on the order of 10 s. Within this time span, protein exchange with the bulk solution was negligible. In cases where in-surface relaxation was completed in the imposed time, the moduli depended only on the equilibrium Π(Γ) relationship. We interpret these results in terms of a simple two-dimensional solution model, based on a Gibbs dividing surface, accounting for nonideal mixing to the first order with respect to both entropy and enthalpy. Interfacial mixing enthalpy is shown to have a major effect on the elasticity, with both quantities increasing in the sequence triacylglycerol < tetradecane < air. We also suggest a strong correlation between enthalpy and clean-interface tension that increases in the same order. At each interface, the enthalpy increases with increasing molecular rigidity: β-casein < β-lactoglobulin < bovine serum albumin < ovalbumin. Best agreement with the experimental data was obtained with a recently extended version of the model accounting for proteins adopting smaller molecular areas with increasing surface pressure. For interfacial pressures above 15 mN/m, the moduli were generally no longer purely elastic, with viscous loss angles ranging up to 36 degrees. In this range of high pressures, the moduli depended on relaxation mechanisms for which specific kinetic models must be developed. |
| Magazine |
Langmuir 2005, 21,9689-9697 |
| Year |
2005 |
| Autors |
Alexandre I. Romoscanua and Raffaele Mezzengaa |
| Estb. |
a Nestlé Research Center, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland |
| Abstract |
The dilatational rheological properties of cross-linked protein layers adsorbed at the oil-water interface were investigated with help of a modified drop tensiometer allowing successive replacements of the external phase. This setup enables one to perform cross-linking reactions at the interface only, that is, without any contact between the cross-linking agent and protein molecules in solution, under continuous monitoring of the interfacial tension. The mechanical properties of the resulting interface were investigated with dilatational large strain experiments. Measured rheological properties were related to the expected stability ofanemulsion against disproportionation by considering the ratio of the interfacial elasticity to the interfacial tension. Inanattempt to increase this ratio to improve the resistance against disproportionation, experiments were performed with densified protein layers obtained via reduction of the droplet area prior to cross linking. To highlight the influence of the protein morphology on the dilatational rheological properties of the cross-linked adsorbed layers, experiments were performed with random coil (β-casein) as well as globular (β-lactoglobulin) proteins. Glutaraldehyde was used as a cross-linking agent. Experiments were performed at 55 °C and pH 7.0 in 20 mM imidazole buffer for later comparison with enzymatically crosslinked adsorbed protein layers. The present work demonstrated substantial qualitative and quantitative differences in the interfacial rheological properties of cross-linked random coil and globular proteins. |
| Magazine |
Journal of Food Engineering 68 (2005) 429–437 |
| Year |
2005 |
| Autors |
Juan M. Rodriguez Patinoa, Ma Rosario Rodriguez Ninoa, Cecilio Carrera Sancheza, Sara E. Molina Ortizb and Ma Cristina Anonb |
| Estb. |
a Departamento de Ingenieria Quimica, Facultad de Quimica, Universidad de Sevilla. c/. Prof. Garcia Gonzalez, 1.41012-Sevilla, Spain
b Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos,Facultad de Ciencias Exactas,Universidad Nacional de la Plata,Calle 47y116,1900 La Plata,Argentina |
| Abstract |
In this paper we present surface dilatational properties of soy globulins (β-conglycinin,glycinin, and reduced glycinin with 10 mM of dithiothreitol (DTT)) adsorbed on the air–water interface,as a function of adsorption time. The surface rheological parameters (surface dilatational modulus, E,its elastic and viscous components,and phase angle) were measured as a function of protein concentration (ranging from 1 to 1 × 10-3%,wt/wt) at pH 2.0 and 5.0. We found that the surface dilatational modulus, E,increases with time, θ. This phenomenon has been related to protein adsorption,unfolding, and/or protein–protein interactions (at long-term adsorption). The dilatational properties of the adsorbed films depend on the molecular structure of the protein,the pH,and on the protein concentration in the aqueous phase. Soy globulins are adsorbed at the air–water interface with different degrees of association at different concentrations in the bulk phase and at different aqueous phase pH. |
| Magazine |
J. of Supercritical Fluids 37 (2006) 375–383 |
| Year |
2006 |
| Autors |
Frederic Tewesa and Frank Bourya |
| Estb. |
a Inserm U646, Ingénierie de la Vectorisation Particulaire, Université d’Angers, Bat. IBT, 10 rue A. Boquel, Angers F-49100, France |
| Abstract |
For the first time, rheological and dynamical properties of various interfacial layers separating an aqueous phase and a carbon dioxide phase under supercritical conditions have been measured by means of a drop tensiometer, applying either sinusoidal or ramp interfacial area perturbation. Those approaches have been largely developed on liquid–air and liquid–liquid interface but very few studies were performed in pressurized conditions [F. Tewes, F. Boury, Formation and rheological properties of the supercritical CO2–water pure interface, J. Phys. Chem. B 109 (2005) 3990–3997; F. Tewes, F. Boury, Effect of H2O–CO2 organization on ovalbumin adsorption at the supercritical CO2–water interface, J. Phys. Chem. B 109 (2005) 1874–1881].
For small surfactants, such as Tween® molecules, same results for equilibrium elasticity (Ee) values were obtained whatever the perturbation mode. However, non-equilibrium elasticity values (Ene) were in some cases significantly influenced by the kind of perturbation. Rheological measurements evidenced the effect of the size of the alkyl tail upon the rheological properties of the interface. In particular, an alkyl chain composed of 16 carbon atoms facilitated the formation of a mixed interface constituted from Tween® molecules and a network of structured H2O–CO2 molecules.
Polymeric molecules like human serum albumin (HSA), produced interfacial films with an important elasticity. For these systems, Ee and Ene varied with CO2 pressure and with the type of protein. |
| Magazine |
Journal of Oleo science 57, (9) 485-494 (2008) |
| Year |
2008 |
| Autors |
Lok Kumar Shresthaa, Yohei Matsumotoa, Keiichi Iharab and Kenji Aramakia |
| Estb. |
a Graduate school of environment and information sciences, yokohama national university (79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8510, Japan)
b Food research and development laboratory, Morinaga milk industry Co., Ltd (1-83, 5-chome, Higashihara, Zama-city 228-8583, Kanagawa, Japan) |
| Abstract |
We present the study on dynamic surface tension and surface dilatational elasticity properties of dilute aqueous systems of pentaglycerol fatty acid esters (pentaglycerol monostearate, C18G5, and pentaglycerol monooleate, C18:1G5), whey protein, sodium caseinate, and mixed surfactant and protein at room temperature. The absorption kinectics at the air-liquid interface has been studied by bubble pressure tensiometer and the oscillation bubble (rising drop) method. It has been shown that the dynamic surface tension curve basically presents two-regions; namely induction region and rapid fall region. During the induction time the absorption is the diffusion-controlled process of amphiphilic surfactant or protein molecules from the bulk of the solution to the interface. Whey protein and sodium caseinate showed longer induction time ˜~ 10000 ms compared to the surfactant systems, where induction time was estimated to be ˜~ 1000 ms. However, in both the protein and surfactant systems, the induction time goes on decreasing with increasing the concentrations. The similar behavior was observed in the mixed system, and lower surface tension values were observed at higher concentrations. The fitting of the experimental data to the theoretical equation shows the presence of two relaxation mechanisms of widely different time scale for the concentrations following the power law, and at fixed concentration it was the highest for whey protein and the lowest for C18:1G5 system. The surface dilatational elasticity determined within the frequency range of ~ 0.1 to 1 cycle/s supports the dynamic surface tension data. |
| Magazine |
Food Hydrocolloids 19 (2005) 165–170 |
| Year |
2005 |
| Autors |
E. Casesa and P. Cayota |
| Estb. |
a Laboratoire Ingeénierie Moléculaire et Sensorielle de l’Aliment-ENSBANA-université de Bourgogne campus Montmuzard-1,Esplanade Erasme, Dijon 21000, France |
| Abstract |
In this work, we hypothesized that the difference in the dielectric constant value existing between two non-miscible phases such as oil and water could be partially responsible for both protein unfolding and reorganization of the protein structure at the interface. So, we replaced the oil phase, whose dielectric constant value is 2, by organic solvents chosen for both their non-miscibility with water and their range of dielectric constant values higher (range 6.1–7.2) than that of oil. Using a dynamic drop tensiometer, we studied both surface activity and viscoelastic properties of the milk protein at various interfaces. The aqueous phase (pH7; 25 °C) contained the compact globular β-lactoglobulin at a concentration of 11 mg l-1. Compared to lipid phase (dielectric constant=2), the use of apolar phase with a higher permittivity value (7.2) resulted in an increase in both the surface activity of β-lactoglobulin and viscoelastic parameters of the interfacial film. Moreover, the interfacial water organization would appear as determinant as dielectric constant value, in the increase in surface pressure due to increase in protein concentration at the interface. |
| Magazine |
Colloids and Surfaces A: Physicochem.Eng.Aspects279(2006)159–166 |
| Year |
2006 |
| Autors |
Eric Kolodziejczyka, Vera Petkovab, Jean-Jacques Benattarb, Martin E. Lesera and Martin Michela |
| Estb. |
a Nestlé Research Center Lausanne, Nestec Ltd., Vers-chez-les Blanc, CH-1000 Lausanne 26, Switzerland
b CEA-Saclay, DSM/DRECAM, Service de Physique de l’Etat Condens´e, F-91191 Gif sur Yvette, France |
| Abstract |
When using fluorescence microscopy for the investigation of β-lactoglobulin (BLG) stabilized thin liquid films and monolayers, it is necessary to label the protein sample with a fluorescent dye. In the present study, we discuss the effect of labeling β-lactoglobulin with either Rhodamine iso-thiocyanate (RITC) or Fluorescein iso-thiocyanate (FITC) on the BLG properties at the air–water interface and in thin films. RITC and FITC are the two most frequently used dyes in fluorescence microscopy. Two different Rhodamine concentrations were used, namely the concentration conventionally used in fluorescence microscopy, and a two times higher Rhodamine concentration. Interfacial tension and rheology measurements, and thin film investigations using X-ray reflectivity or the diminishing bubble method showed that the labeling procedure of the β-lactoglobulin using Rhodamine at the lowest concentration does not change the viscoelastic properties of the air–water interface, as well as the film thickness and gas permeability. However, when taking the higher Rhodamine concentration the films are thicker and more permeable for gas. Similarly, Fluorescein at a concentration equivalent to the highest concentration of Rhodamine induced also a modification of the protein film properties. However, the labeling did not influence the BLG monolayer viscoelastic characteristics.
Labeling β-lactoglobulin with Rhodamine allows nowusing confocal fluorescence microscopy (CSLM) for the elucidation of structure formation in thin films and at water–air surfaces. As an example, images from thin films as formed in the diminishing bubble experiment and stabilized with labeled BLG show that the formed BLG aggregates are highly surface active, i.e., enriched at the water–air interface. The obtained images reveal that the aggregates are also present in the film. In general, CSLM combined with the diminishing bubble method seems to be an excellent experimental set-up to visualize the distribution of labeled components throughout a thin film and its adjacent monolayers. This is not possible using the diminishing bubble method in combination with conventional microscopy. |
| Magazine |
Carbohydrate Polymers (2009) |
| Year |
2009 |
| Autors |
Adem Gharsallaouia, Kosuke Yamauchib, Odile Chambina, Eliane Casesa and Rémi Saurela |
| Estb. |
a Eau, Molécules Actives, Macromolécules, Activité (EMMA), ENSBANA, Université de Bourgogne, 1 Esplanade Erasme, 21000 Dijon, France
b Department of Biotechnology, Tottori University, 4-101, Minami, Koyama, Tottori 680-8552,Japan |
| Abstract |
The effect of the addition of high methoxyl pectin on the stability of pea protein isolate emulsions was investigated. Except for low pectin concentrations at acidic pHs where bridging flocculation occurred the addition of pectin improved emulsion stability to pH changes and depletion fluctuation induced by maltodextrin addition. The mechanism of pectin induced stability was probed by measuring protein-pectin complex formation in solution, zeta potential of the emulsions droplets and the change in surface viscoelasticity on pectin addition. The phase diagrams of pectin-pea protein isolate in solution and pectin-pea protein stabilized emulsions were established based on the obtained experimental results. These diagrams showed that under acidic conditions and at low pectin concentrations, electrostatic bridging phenomena leads to the formation of high size pectin-protein complexes causing an increase in turbidity in solution and oil droplet flocculation in emulsions. It was concluded that the pectin induced stability could be mainly assigned to steric repulsion and oil-water interfacial membrane rigidity improvement after pectin adsorption. In fact, the emulsions formed after pectin adsorption could consist of oil droplets surrounded by multilayer interfacial coatings, which are comprised of an inner interfacial protein film and an outer pectin layer. |
| Magazine |
Food Hydrocolloids 21 (2007) 813–822 |
| Year |
2007 |
| Autors |
Karina D. Martineza, Cecilio Carrera Sanchezb, Victor Pizones Ruiz-Henestrosab, Juan M. Rodriguez Patinob and Ana M.R. Pilosofa |
| Estb. |
Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428) Buenos Aires, TE 541145763377, Argentina
Departamento de Ingenieria Quımica, Facultad de Quımica, Universidad de Sevilla, C/Prof. Garcıa Gonzalez, 1, 41012 Seville, Spain |
| Abstract |
The objective of the work was to study the effect of limited hydrolysis of soy protein on the interactions with polysaccharides with and without surface activity at the air–water interface at neutral pH where a limited incompatibility between macromolecules can occur. The surface pressure and phase angle as a function of time were evaluated with a drop tensiometer at 20 °C, pH 7 and ionic strength 0.05 M.
Hydrolysates of 2% (H1) and 5.4% (H2) degree of hydrolysis (DH) with neutral protease from Aspergillus oryzae were obtained from a commercial soy protein isolate. The polysaccharides used were: hydroxypropylmethylcellulose (HPMC) as surface active polysaccharide; lambda carrageenan (λC) and locust bean gum (LB) as non-surface active polysaccharides.
It was found that increasing DH decreased the surface pressure and increased film viscoelasticity (determined as the phase angle, θ) of soy protein hydrolysates and the nature of protein–polysaccharide interactions was strongly affected by DH. The presence of polysaccharides led to an increase of surface pressure of H1 but when added to H2, HPMC and λC decreased the surface pressure.
The less hydrolyzed protein H1 gave rise to a higher surface pressure and film viscoelasticity in combination with the polysaccharides. This result points out that a limited protein hydrolysis was sufficient to improve the surface properties of soy proteins if used in combination with polysaccharides.
Polysaccharides used in admixture with hydrolyzed soy proteins could control and improve the stability of foams and emulsions not only by increasing bulk viscosity but also by improving film viscoelasticity. |
| Magazine |
Langmuir, 2006, 22 (18), pp 7812–7818 |
| Year |
2006 |
| Autors |
Alexandre I. Romoscanua and Raffaele Mezzengab |
| Estb. |
a Nestlé Research Center, Vers-Chez-Les-Blanc, CH-1000 Lausanne 26, Switzerland
b Department of Physics, University of Fribourg, Perolles, CH-1700 Fribourg, Switzerland |
| Abstract |
We have developed a new method allowing us to transform low-viscous apolar fluids into elastic solids with a shear elastic modulus of the order of 103-105 Pa. The elasticity of the elastic solid is provided by a percolating 3D network of proteins, which are originally adsorbed at the interface of an oil-in-water emulsion template. By cross-linking the protein films at the interface and upon removal of water, the template is driven into a structure resembling a dry foam where the protein interfaces constitute the walls of the foam and the air is replaced by oil confined within polyhedral, closely packed droplets. Depending on the density of the protein network, the final material consists of chemically unmodified oil in a proportion of 95 to 99.9%. The physical properties of the elastic solid obtained can be tuned by changing either the average diameter size of the emulsion template or the cross-linking process of the protein film. However, the original low-viscosity emulsion can be restored by simply rehydrating the solidified fluid. Therefore, the present procedure offers an appealing strategy to build up solid properties for hydrophobic liquids while preserving the low viscosity and ease of manufacturing. |
| Magazine |
Food Hydrocolloids 25 (2011) 694-706 |
| Year |
2011 |
| Autors |
K. Rade-Kukic a, C. Schmitta and H. M. Rawel b |
| Estb. |
a Department of Food Science and Technology, Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland
b Institute of Nutritional Science, University of Potsdam, Arthur-Scheunert-Allee 114-116, D-14558 Nuthetal, Germany
|
| Abstract |
Whey proteins are widely used food ingredients due to their nutritional and functional properties (gelling, emulsifying, foaming). Owning to their structure (free thiol group, lysine residues, hydrophobic pocket), they can also be used as carriers for bioactives. In this study, conjugates between b-lactoglobulin (b-lg), and a bioactive metabolite from Brassicaceae vegetables, allyl isothiocyanate (AITC) were formed. Heat aggregation behavior (85°C, 15 min), foaming and emulsifying properties of conjugates, at pH 4.0 and 7.1, were evaluated. Conjugates were formed by incubating b-lg (0.5 mM) with AITC (0.05e20 mM) in water at pH 8.5 and room temperature. AITC primarily reacted with b-lg’s free thiol group (KD 0.2 _ 0.1 mM) and thereafter with its amino groups (KD 10.8 _ 3.4 mM). AITC binding destabilized secondary and tertiary structure of b-lg at pH 7.1, whereas induced molten globule conformation at pH 4.0. Conjugation reduced the heat aggregation of b-lg at pH 7.1, while promoting it at pH 4.0. Conjugates adsorbed faster to air/water and oil/water interfaces at pH 4.0 than at pH 7.1. After 30 min, air/water surface tension was lower at pH 4.0 (47 mNm-1) than at pH 7.1 (57 mNm-1), while the surface tension of the oil/water interfacewas 8 mNm_1 at both pHs. Foams produced with b-lgeAITC conjugates at pH 4.0 exhibited higher volume and liquid stabilities compared to foams obtained at pH 7.1. Emulsions formed with conjugates at both pHs were destabilized by creaming due to flocculation, but coalescence was prevented. This study revealed that whey protein could potentially be used for the delivery of isothiocyanates in the formof foam or emulsionbased products. |
| Magazine |
International dairy jounal 16(2006) 275-284 |
| Year |
2006 |
| Autors |
Hakim Bouaouinaa, Anne Desrumauxa, Catherine Loisela and Jack Legrandb |
| Estb. |
a GEPEA-ENITIAA-UMR-CNRS 6144, Rue de la Géraudière, BP 82225, 44322 Nantes Cedex 03, France
b GEPEA-UMR-CNRS 6144, Université de Nantes, CRTT, BP 406, 44602 Saint-Nazaire Cedex, France |
| Abstract |
An ultra high-pressure homogenizer was used to treat whey protein isolate solutions (3%, w/w). The treated solutions (up to 300 MPa) were characterised for both physico-chemical properties (particle size distribution, surface hydrophobicity and structural conformation) and functional properties (solubility, foaming stability and interfacial rheology). Dynamic high-pressure treatment did not affect the conformation of the proteins (determined by micro-calorimetry, size-exclusion chromatography and electrophoretic technique). This treatment dissociated large protein aggregates leading to unmasking of the buried hydrophobic groups without affecting protein solubility. Interactions may then occur between these groups that enhance the viscoelasticity of airwater interfaces (assessed by drop tensiometry) and improve foam stability (evaluated by sparging method). Dynamic high-pressuretreated whey proteins showed better foaming and stabilising properties. |
| Magazine |
European Journal of Pharmaceutics and Biopharmaceutics 69 (2008) 835 – 843 |
| Year |
2008 |
| Autors |
Aurélie Malzert-Fréona, Jean-Pierre Benoîtb and Frank Bouryb |
| Estb. |
a CERMN, University of Caen, Caen, France
b Inserm U646, University of Angers, Angers, France |
| Abstract |
From adsorption kinetics and interfacial rheological studies performed by using a pendant-drop method, i.e. in conditions close to those of the primary emulsion of the water-in-oil-in-water emulsion-encapsulation technique, it was shown that adsorption of the hen egg-white lysozyme (HEWL) at the water/dichloromethane (DCM) interface can be efficiently slowed down by modulating some parameters. It was shown that a decrease of the ionic strength of the aqueous phase, and the optimization of the density of the poly(ethylene glycol) (PEG) adsorbed film by increasing the PEG concentration or by modulating the polymer chain length, can significantly decrease the rate of adsorption of HEWL at the water/DCM interface. Moreover, it was shown that the choice of the dissolution phase of PEG (DCM or water) clearly influences the results. |
| Magazine |
European Journal of Pharmaceutics and Biopharmaceutics (2009) |
| Year |
2009 |
| Autors |
Aurélie Malzert-Fréona, Jean-Pierre Benoîtb and Frank Bouryb |
| Estb. |
a CERMN, University of Caen, Caen, France
b Inserm U646, University of Angers, Angers, France |
| Abstract |
From microscopic observations, it was established that an oil-in-water emulsion with droplets of a size in the micrometer range can spontaneously form at room temperature without additional external stirring as soon as a solvent that is only partly miscible to water-like dichloromethane (DCM) is put in contact with an aqueous mixture of polyethylene glycol (PEG) and a protein. Experimental results show that emulsification only occurs if the system simultaneously includes PEG with middle chain, an organic solvent partly miscible to water and for which PEG affinity is sufficiently high, and a protein. From adsorption kinetics, it appears that this spontaneous emulsification process is related to the rapid diffusion of DCM towards water through the formation of interfacial turbulences, once the accumulation of PEG close to the DCM/water interface occurs. The oil droplets formed would be then stabilized by adsorbed protein molecules. Since the presence of polylactic acid in the organic phase did not prevent the emulsion formation, we studied the feasibility of formulating microparticles using this polymer. From results, it appears that microcapsules with a polymeric shell, with a homogeneous size of about 50 μm and able to encapsulate a model hydrophobic drug, such as amiodarone, can be obtained by using this spontaneous emulsification method. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 68 (2009) 39–47 |
| Year |
2009 |
| Autors |
María J. Martineza, Cecilio Carrera Sánchezb, Juan M. Rodríguez Patinob and Ana M.R. Pilosofa |
| Estb. |
a Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires, Argentina
b Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, C/Prof. García González, 1, (41012) Seville, Spain |
| Abstract |
The aim of thisworkwas to study the interactions and adsorption of caseinoglycomacropeptide (GMP) and GMP:β-lactoglobulin (β-lg) mixed system in the aqueous phase and at the air–water interface. The existence of associative interactions between GMP and β-lg in the aqueous phasewas investigated by dynamic light scattering, differential scanning calorimetry (DSC), fluorometry and native PAGE-electrophoresis. The surface pressure isotherm and the static and dynamic surface pressure were determined by tensiometry and surface dilatational properties. The results showed that GMP presented higher surface activity than β-lg at a concentration of 4% wt but β-lg showed higher film forming ability. In the mixed systems β-lg dominated the static and dynamic surface pressure and the rheological properties of interfacial films suggesting that β-lg hinders GMP adsorption because, in simple competition, GMP should dominate because of its higher surface activity. The surface predominance of β-lg can be attributed to binding of GMP to β-lg in the aqueous phase that prevents GMP adsorption on its own. |
| Magazine |
Food Hydrocolloids 23 (2009) 2149–2157 |
| Year |
2009 |
| Autors |
Karina D. Martineza, Cecilio Carrera Sanchezb, Juan M. Rodrıguez Patinob and Ana M.R. Pilosofa |
| Estb. |
a Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina
b Departamento de Ingenierıa Quı´mica, Facultad de Quımica, Universidad de Sevilla, C/Prof. Garcıa Gonzalez, 1, 41012 Seville, Spain |
| Abstract |
The objective of the work was to study the impact of soy protein hydrolysis on foaming and interfacial properties and to analyze the relationship between them. As starting material a sample of commercial soy protein isolate was used (SP) and hydrolysates were produced by an enzymatic reaction, giving hydrolysates from 0.4% to 5.35% degree of hydrolysis (DH).
In this contribution we have determined foam overrun (FO), stability against liquid drainage and foam collapse, and the apparent viscosity of foams produced by a whipping method. The surface properties determined were the adsorption isotherm and surface dilatational properties of two hydrolysates (2 and 5.35% DH, H1 and H2 respectively).
The hydrolysis of soy proteins increased the surface activity at bulk concentrations where SP adopts a condensed conformation at the monolayer. At concentrations where it adopts a more expanded conformation a very low degree of hydrolysis (H1) also promoted the enhancement of surface activity. However, at 5.35% degree of hydrolysis (H2) the surface activity decreased. Moreover, H2 presented lower surface activity than H1 at every bulk concentration.
The hydrolysis increased the elastic component of the dilatational modulus and decreased phase angle of films at bulk concentrations below that corresponding to the collapse of SP monolayer (2% bulk protein).
SP hydrolysis increased foamoverrun and the stability against drainage that could be related to increased surface activity of protein hydrolysates. However, the collapse of foams was promoted by hydrolysis and could be ascribed to a decrease of the relative viscoelasticity (higher phase angle) of surface films.
The results point out that a low degree of hydrolysis (2–5%) would be enough to improve the surface activity of SP, decrease foam drainage and maintaining a considerable viscoelasticity of the surface films to retard foam collapse. |
| Magazine |
Journal of Physical Chemistry B 2007, 111, 2727-2735 |
| Year |
2007 |
| Autors |
J. Juareza, J. G. Galazb, L. Machia, M. Burboaa, L. E. Gutierrez-Millanc, F. M. Goycoolead and M. A. Valdeza |
| Estb. |
a Departamento de Investigacion en Polimeros y Materiales,Universidad de Sonora, Rosales y TransVersal, 83000 Hermosillo Sonora, Mexico
b Departamento de Fısica,Universidad de Sonora, Rosales y TransVersal, 83000 Hermosillo Sonora, Mexico
c Deparamento de Investigaciones Cientificas y Tecnologicas,Universidad de Sonora, Rosales y TransVersal, 83000 Hermosillo Sonora, Mexico
d Departamento de Farmacoloxia, Universidad de Santiago de Compostela,Campus UniVersitario Sur s/n Pabellon C, Santiago de Compostela, A Coruna 15782, Galicia, Espana |
| Abstract |
Interfacial properties of N-nitrosodiethylamine/bovine serum albumin (NDA/BSA) complexes were investigated at the air-water interface. The interfacial behavior at the chloroform-water interface of the interaction product of phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), dissolved in the chloroform phase, and NDA/BSA complex, in the aqueous phase, were also analyzed by using a drop tensiometer. The secondary structure changes of BSA with different NDA concentrations were monitored by circular dichroism spectroscopy at different pH and the NDA/BSA interaction was probed by fluorescence spectroscopy. Different NDA/ BSA mixtures were prepared from 0, 7.5 × 10-5, 2.2 × 10-4, 3.7 × 10-4, 5 × 10-4, 1.6 × 10-3, and 3.1 × 10-3 M NDA solutions in order to afford 0, 300/1, 900/1, 1 500/1, 2 000/1, 6 000/1, and 12 500/1 NDA/BSA molar ratios, respectively, in the aqueous solutions. Increments of BSA α-helix contents were obtained up to the 2 000/1 NDA/BSA molar ratio, but at ratios beyond this value, the α-helix content practically disappeared. These BSA structure changes produced an increment of the surface pressure at the air-water interface, as the α-helix content increased with the concentration of NDA. On the contrary, when α-helix content decreased, the surface pressure also appeared lower than the one obtained with pure BSA solutions. The interaction of DPPC with NDA/BSA molecules at the chloroform-water interface produced also a small, but measurable, pressure increment with the addition of NDA molecules. Dynamic light scattering measurements of the molecular sizes of NDA/BSA complex at pH 4.6, 7.1, and 8.4 indicated that the size of extended BSA molecules at pH 4.6 increased in a greater proportion with the increment in NDA concentration than at the other studied pH values. Diffusion coefficients calculated from dynamic surface tension values, using a short-term solution of the general adsorption model of Ward and Tordai, also showed differences with pH and the NDA concentration. Both, the storage and loss dilatational elastic modulus were obtained at the air-water and at the chloroform-water interfaces. The interaction of NDA/BSA with DPPC at the chloroform-water produced a less rigid monolayer than the one obtained with pure DPPC (1 × 10-5 M), indicating a significant penetration of NDA/BSA molecules at the interface. At short times and pH 4.6, the values of the storage elastic modulus were larger and more sensible to the NDA addition than the ones at pH 7.1 and 8.4, probably due to a gel-like network formation at the air-water interface. |
| Magazine |
Food Hydrocolloids 23 (2009) 1253–1262 |
| Year |
2009 |
| Autors |
Adrian A. Pereza, Carlos R. Carraraa, Cecilio Carrera Sanchezb, Liliana G. Santiagoa and Juan M. Rodrıguez Patinob |
| Estb. |
a Instituto de Tecnologıa de Alimentos, Facultad de Ingenierıa Quımica, Universidad Nacional del Litoral, Santa Fe, Argentina
b Departamento de Ingenierıa Quımica, Facultad de Quımica, Universidad de Sevilla, Sevilla 41012, España |
| Abstract |
The effect of two non-surface active polysaccharides (sodium alginate, SA, and l-carrageenan, λ-C) in the aqueous phase on the surface dynamic properties (dynamic surface pressure and surface dilatational properties) of a commercial milk whey protein concentrate (WPC) adsorbed film at the air–water interface has been studied. A whey protein isolate (WPI) was used as reference. The WPC and WPI concentration (at 1.0% wt), temperature (at 20 °C), pH (7), and ionic strength (at 0.05 M) were maintained constant, while the effect of polysaccharide (PS) was evaluated within the concentration range 0.0–1.0% wt. The surface dynamic properties of the adsorbed films were measured in an automatic pendant drop tensiometer. At short adsorption time and in the presence of PS, the rate of diffusion of WPC to the interface was affected by the interactions with PS in the aqueous phase, which could limit protein availability for the adsorption. On the other hand, at long-term adsorption, the magnitudes of the molecular penetration and configurational rearrangement rates of WPC in mixed systems (WPC/PS) reflected the viscoelastic characteristics of the adsorbed films. The attractive interactions between WPC and PS and/or the WPC aggregation in the presence of PS, which depend on the proper polysaccharide and its concentration in the aqueous phase, have an effect on the adsorption kinetic parameters, the amount of WPC adsorbed at the air–water interface, and the dilatational viscoelastic characteristics of WPC/PS mixed systems. |
| Magazine |
J. Agric. Food Chem. 2005, 53, 9089-9099 |
| Year |
2005 |
| Autors |
CHRISTOPHE SCHMITT a, CLAUDINE BOVAY a and PHILIPPE FROSSARD a |
| Estb. |
a Nestlé Research Center, Department of Food Science, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland
|
| Abstract |
The formation of conjugates between â-lactoglobulin and acacia gum based on electrostatic complexes formed at pH 4.2 was investigated upon dry-state incubation for up to 14 days at 60 °C and 79% relative humidity (RH). By means of SEC-HPLC and RP-HPLC, it was shown that the â-lactoglobulin incubated alone was able to form polymers with molecular masses higher than 200 kDa until 50% of the initial monomeric protein disappeared after 14 days. In the presence of acacia gum at initial protein to polysaccharide weight mixing ratios of 2:1 and 1:2, only 35% of the initial â-lactoglobulin monomers disappeared after 14 days. Using RP-HPLC, an apparent reaction order of 2 was found for the disappearance of monomeric â-lactoglobulin both in the presence or absence of acacia gum. However, the reaction rate was faster in the absence of acacia gum. SDS-PAGE electrophoresis with silver staining confirmed the formation of â-lactoglobulin/acacia gum conjugates. The solubility curves of the incubated â-lactoglobulin showed a minimum around pH 4-5. By contrast, the minimum of solubility of the â-lactoglobulin/acacia gum incubated mixtures shifted to lower pH values compared to initial mixtures. The conjugates exhibited higher foam capacity than the incubated protein as well as lower equilibrium air/water surface tension. Conjugation at ratio 1:2 led to increased interfacial viscosity (300 mN s m-1 at 0.01 Hz) compared to â-lactoglobulin alone (100 mN s m-1 at 0.01 Hz), but similar interfacial elasticity (30-40 mN m-1). The foam capacity of the conjugates was significantly higher than that of the incubated â-lactoglobulin as well as foam expansion and drainage time, especially at pH 5.3, i.e., higher than the pH of formation of the conjugates. |
| Magazine |
Langmuir, 2008, 24 (13), pp 6812–6819 |
| Year |
2008 |
| Autors |
P. Reisa,b, R. Millerc, J. Krägelc, M. Lesera, V. B. Fainermand, H. Watzkea and K. Holmbergb |
| Estb. |
a Nestlé Research Center, CH-1000 Lausanne 26, Switzerland
b Chalmers UniVersity of Technology, Department of Chemical and Biological Engineering, Applied Surface Chemistry, SE-412 96 Göteborg, Sweden
c Max-Planck-Institut fu¨r Kolloid- and Grenzfla¨chenforschung, Max-Planck-Campus, D-14476 Golm, Germany
d Medical Physicochemical Center, Donetsk Medical UniVersity, 16 Ilych AVenue, 83003 Donetsk, Ukraine |
| Abstract |
The adsorption behavior of two globular proteins, lipase from Rhizomucor miehei and β-lactoglobulin, at inert oil/water and air/water interfaces was studied by the pendant drop technique. The kinetics and adsorption isotherms were interpreted for both proteins in different environments. It was found that the adopted mathematical models well describe the adsorption behavior of the proteins at the studied interfaces. One of the main findings is that unique interfacial properties were observed for lipase as compared to the reference β-lactoglobulin. A folded drop with a “skinlike” film was formed for the two proteins after aging followed by compression. This behavior is normally associated with protein unfolding and covalent cross-linking at the interface. Despite this, the lipase activity was not suppressed. By highlighting the unique interfacial properties of lipases, we believe that the presented work contributes to a better understanding of lipase interfacial activation and the mechanisms regulating lipolysis. The results indicate that the understanding of the physical properties of lipases can lead to novel approaches to regulate their activity. |
| Magazine |
Colloids and Surfaces B: Biointerfaces |
| Year |
2010 |
| Autors |
Adrian A. Pereza, Cecilio Carrera Sanchezb, Juan M.Rodrıguez Patinob, Amelia C. Rubioloa and Liliana G. Santiagoa |
| Estb. |
a Grupo de Biocoloides, Instituto de Tecnología de Alimentos, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santa Fe, Argentina.
b Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, Sevilla, España. |
| Abstract |
In this contribution, we present experimental information about the effect of xanthan gum (XG) on the adsorption behaviour of two milk whey protein samples (MWP), β-lactoglobulin (β-LG) and whey protein concentrate (WPC), at the air-water interface. The MWP concentration studied corresponded to the protein bulk concentration which is able to saturate the air-water interface (1.0% wt). Temperature, pH and ionic strength of aqueous systems were kept constant at 20ºC, pH 7 and 0.05M, respectively, while the XG bulk concentration varied in the range 0.00-0.25% wt. Biopolymer interactions in solution were analyzed by extrinsic fluorescence spectroscopy using 1-anilino-8-naphtalene sulphonic acid (ANS) as a protein fluorescence probe. Interfacial biopolymer interactions were evaluated by dynamic tensiometry and surface dilatational rheology. Adsorption behaviour was discussed from a rheokinetic point of view in terms of molecular diffusion, penetration and conformational rearrangement of adsorbed protein residues at the air-water interface. Differences in the interaction magnitude, both in solution and at the interface vicinity, and in the adsorption rheokinetic parameters were observed in MWP/XG mixed systems depending on the protein type (β-LG or WPC) and biopolymer relative concentration. β-LG adsorption in XG presence could be promoted by mechanisms based on biopolymer segregative interactions and thermodynamic incompatibility in the interface vicinity, resulting in better surface and viscoelastic properties. The same mechanism could be responsible of WPC interfacial adsorption in the presence of XG. The interfacial functionality of WPC was improved by the synergistic interactions with XG, although WPC chemical complexity might complicate the elucidation of molecular events that govern adsorption dynamics of WPC/XG mixed systems at the air-water interface. |
| Magazine |
Colloids and SurfacesA:Physicochem.Eng.Aspects 331(2008)76–83 |
| Year |
2008 |
| Autors |
S. Mezdoura, A. Lepinea, P. Erazo-Majewiczb, F. Ducepta and C. Michona |
| Estb. |
a UMR GENIAL, AgroParisTech-CNAM-INRA-CEMAGREF, 1 avenue des Olympiades, F-91744 Massy Cedex, France
b HERCULES, Hercules Plaza, 1313 North Market Street, Wilmington, DE 19894-0001, United States |
| Abstract |
Hydroxypropyl cellulose (HPC) is a neutral branched polysaccharide derivatized from a wood substrate. Widely used in whipping vegetable creams, HPC is a thickening biopolymer having surface active properties both at air/water and oil/water interfaces.Myglyol/water interfacial rheologywas used to characterize the behavior of HPC at this interface in the presence or the absence of lecithin, an emulsifier classically used in combination with HPC. Addition of HPC in the aqueous phase leads to an increase of the surface pressure at the oil/water interface depending on the HPC concentration. The higher the HPC concentration, the shorter is the lag time before the surface pressure increase. The equilibrium surface pressure is about 13–16mN m−1 whatever the HPC concentration in the studied range. In order to understand the way the HPC positions itself at the interface, a viscoelastic characterization of the interface was performed during adsorption, in the presence and in the absence of lecithin. A comparison to the stability of emulsions containing HPC or HPC/lecithin is made and discussed using droplet size evolution and droplet displacement rate to an upper layer. |
| Magazine |
Food Hydrocolloids 21 (2007) 804–812 |
| Year |
2007 |
| Autors |
Karina D. Martineza, Cecilio Carrera Sanchezb, Victor Pizones Ruiz-Henestrosab, Juan M. Rodriguez Patinob and Ana M.R. Pilosofa |
| Estb. |
a Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina
b Departamento de Ingenierıa Quımica, Facultad de Quımica, Universidad de Sevilla, C/Prof. Garcıa Gonzalez, 1, 41012 Seville, Spain |
| Abstract |
This work studies the interfacial behavior of mixed soy protein (SP) + polysaccharide (PS) systems to gain knowledge on the interactions between these biopolymers at the air–water interface under dynamic conditions at neutral pH where a limited incompatibility between macromolecules can occur. The PSs used were: hydroxypropylmethylcellulose (HPMC) as surface-active PS; lambda carrageenan (λC) and locust bean (LB) gum as non-surface-active PSs. Protein and PS concentration in the mixed systems were 2% and 0.25%, respectively. The dynamic surface pressure and rheological properties of films were evaluated with a drop tensiometer at 20 °C, pH 7 and ionic strength 0.05 M.
The presence of HPMC and λC greatly increased the surface pressure, surface dilatational elasticity and relative viscoelasticity on the basis of different mechanisms. HPMC competed for the interface with SP, but due to its unusual strong surface activity it could dominate the surface pressure and improve film viscoelasticity. The modification of surface pressure and rheological properties of adsorbed SP films in the presence of λC necessarily suggests the participation of λC+ contaminants at the interface. Pure λC could influence the interface by a complexation mechanism, or indirectly by a depletion mechanism in the vicinity of the interface. In addition surface-active contaminant of λC if strongly bound to the PS could bring some PS molecules at the interface.
LB little affected the surface pressure and rheological properties of SP films even if surface-active contaminants were present in the commercial preparation. Differences in the interaction of λC and LB gum with the protein should be mainly ascribed to different degrees of incompatibility and to the fact that LB is not charged. |
| Magazine |
Journal of Food Engineering 78 (2007) 1001–1009 |
| Year |
2007 |
| Autors |
JoséMinones Condea and Juan M. Rodriguez Patinob |
| Estb. |
a Departamento de Ingenierıa Quımica, Facultad de Quımica, Universidad de Sevilla, C/Prof. Garcıa Gonza lez, 1, 41012 Sevilla, Spain
b Departamento de Quımica Fısica, Facultad de Farmacia, Universidad de Santiago de Compostela, Spain |
| Abstract |
The adsorption kinetic at the air–water interface of a sunflower protein isolate (SPI) and its hydrolysates at different degrees of hydrolysis (DH = 5.62%, 23.5% and 46.3%) adsorbed from aqueous solutions, was studied. Data are presented and analyzed for short adsorption time, taking into account the diffusion of the protein (SPI and its hydrolysates) from the bulk phase to the interface, and the long-term adsorption, taking into account the adsorption and penetration of the protein at the interface. The adsorption kinetics were determined by surface tension measurements as a function of time and protein concentration in the bulk phase (within the range of 1 and 1 × 10-5 %, w/w). The ionic strength (0.05 M) and the temperature (20 °C) were maintained constant. The adsorption of SPI and its hydrolysates to the interface increases with the protein concentration in the bulk phase, depending on the protein and, especially, on the degree of hydrolysis. The adsorption kinetic at short adsorption time is diffusion controlled. However, the mechanism that controls the adsorption at long-term adsorption is the penetration of the protein at the interface. The optimum functionality of SPI hydrolysates occurs at low degrees of hydrolysis and high protein concentrations in solution. |
| Magazine |
Food Hydrocolloids 20 (2006) 872–878 |
| Year |
2005 |
| Autors |
Renate A. Ganzevlesa,b, Martien A. Cohen Stuartb, Ton van Vlieta,c and Harmen H.J. de Jongha,d |
| Estb. |
a Wageningen Centre for Food Sciences, P.O. Box 557, Wageningen, 6700 AN, The Netherlands
b Lab.of Physical Chemistry and Colloid Science,Department of Agrotechnology and Food Sciences,Wageningen University,P.O.Box 8038, Wageningen,6700EK,The Netherlands
c Department of Agrotechnology and Food Sciences, Wageningen University, P.O. Box 8129, Wageningen, 6700 EV, The Netherlands
d TNO Quality of Life, P.O. Box 360, Zeist, 3700 AJ, The Netherlands |
| Abstract |
In order to understand foaming behaviour of mixed protein/anionic polysaccharide solutions, we investigated the effect of β-lactoglobulin/ pectin interaction in the bulk on β-lactoglobulin adsorption to the air–water interface. Adsorption kinetics were evaluated by following surface pressure development in time of several pure protein solutions and of mixed protein/polysaccharide solutions using an automated drop tensiometer (ADT). It was found that complexation of proteins with polysaccharides can slow down the kinetics of surface pressure development by at least a factor 100, and greatly diminish foam formation. In contrast, a five times acceleration in the increase of surface pressure was observed in other cases. We propose a mechanism for protein adsorption from mixed protein/polysaccharide solutions. Effects of ionic strength, pH and mixing ratio on this mechanism were studied for mixtures of β-lactoglobulin and low methoxyl pectin, whereas other proteins and anionic polysaccharides were used to explore the role of protein and polysaccharide charge density and distribution. Whereas the possibilities to change system parameters like ionic strength or pH are limited in food related systems, selecting a suitable combination of protein and polysaccharide offers a broad opportunity to control protein adsorption kinetics and with that foam formation. |
| Magazine |
International Dairy Journal 15 (2005) 1006–1016 |
| Year |
2005 |
| Autors |
G. Houzéa, E. Casesa, B. Colasa and P. Cayota |
| Estb. |
a IMSA-team, ENSBANA, University of Burgundy, 1 Esplanade Erasme, Dijon 21000, France |
| Abstract |
The viscoelastic properties of acid milk gels containing small amounts of different fats were investigated. Skim milk was reconstituted from ultra low-heat skim milk powder and emulsions made with 2% (v/v) sunflower oil, olive oil, groundnut oil, or anhydrous milk fat using a pressure homogenizer. Acidification at 20 °C for 14 h to pH ~4.6 was achieved by adding glucono-δ-lactone to the emulsion. Stress relaxation testing enabled determination of the firmness and the solid-like properties, i.e., elasticity. Regardless of the physical state of the fat, emulsion gels exhibited higher firmness than fat-free gels, despite the lowfat level used. The firmness of the gels containing this small quantity of fat was more sensitive to temperature than was the firmness of fat-free gels. The relaxation time was higher in the presence of fat crystals. Modifications in the rheological properties of gels containing fat were attributed to fat droplets acting as active filler particles. |
| Magazine |
Colloids and surfaces A:physicochem,Eng,Aspects 114(1996)245-254 |
| Year |
1996 |
| Autors |
A.Cagnaa, J.Benjaminsb and E.H.Lucassen-Reyndersb |
| Estb. |
a IT. Concept, Parc de Chancolan, 69770 Longessaigne, France
b Unilever research Laboratorium,olivier van Noortlaan 120,3133 AT Vlaardingen, The Netherlands |
| Abstract |
A novel non-invasive technique is described for measuring the viscoelastic modulus in compression/dilation of surfactant-covered interfaces. The new setup is a dynamic drop tensiometer in which a droplet a few mm in diameter is subjected to sinusoidal fluctuations of its volume. The setup differs from the conventional barrier-and-plate technique in that the fluctuations in area and tension are measured on one and the same small interfacial area, that homogeneity of deformation of this area is far more easily ensured and, finally, that the response time of the tension probe is much shorter than that of a Wilhelmy plate. Also, the area fluctuations can be superimposed on the transient change in area of a growing drop from the early stages of its life onwards, enabling us to study interfacial dynamics over a wide range of surface ages. First results were obtained with three different proteins absorbed at a vegetable oil/water interface, and agreed within experimental error with conventionally measured moduli at the same interface. Up to quite high surface coverages, purely elastic behaviour was found. Moreover, results at different concentrations, frequencies and surface ages all coincided on a single modulus versus interfacial pressure curve characteristic for each individual protein at the given interface. In this range of surface coverages, reconformation phenomena within the protein layers occur so fast that a quasi-equilibrium state is reached in a time scale of 10 s. The characteristic curves at the oil/water interface were found to be distinctly different from those measured at the air/water interface. For example, bovine serum albumin moduli for oil/water were approximately half the values found for air/water at the same interfacial pressure, in the pressure range 0-10 mN m-1. At higher interfacial pressures, values for different concentrations and surface ages still more or less coincided. Results at different frequencies, however, started to diverge, indicating the onset of viscoelastic behaviour at higher surface coverages for all three proteins. |
| Magazine |
Langmuir, 2007, 23 (8), pp 4155–4166 |
| Year |
2007 |
| Autors |
Christophe Schmitta, Claudine Bovaya, Martine Rouveta, Sabrina Shojaei-Ramia and Eric Kolodziejczyka |
| Estb. |
a Department of Food Science and Department of Bioanalytical Science, Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland |
| Abstract |
Whey protein isolate was heat-treated at 85 °C for 15 min at pH ranging from 6.0 to 7.0 in the presence of NaCl in order to generate the highest possible amount of soluble aggregates before insolubility occurred. These whey protein soluble aggregates were characterized for composition, hydrodynamic diameter, apparent molecular weight, ζ-potential, surface hydrophobicity index, activated thiol group content, and microstructure. The adsorption kinetics and rheological properties (E′, ηd) of these soluble aggregates were probed at the air/water interface. In addition, the gas permeability of a single bubble stabilized by the whey protein soluble aggregates was determined. Finally, the foaming and foamstabilizing properties of these aggregates were measured. The amount of whey protein soluble aggregates after heat treatment was increased from 75% to 95% from pH 6.0 to pH 7.0 by addition of 5 mMto 120 mM NaCl, respectively. These soluble aggregates involved major whey protein fractions and exhibited a maximum of activated thiol group content at pH>6.6. The hydrodynamic radius and the surface hydrophobicity index of the soluble aggregates increased from pH 6.0 to 7.0, but the molecular weight and ζ-potential decreased. This loss of apparent density was clearly confirmed by microscopy as the soluble aggregates shifted from a spherical/compact structure at pH 6.0 to a more fibrillar/elongated structure at pH 7.0. Surface adsorption was faster for soluble aggregates formed at pH 6.8 and 7.0 in the presence of 100 and 120 mM NaCl, respectively. However, interfacial elasticity and viscosity measured at 0.01 Hz were similar from pH 6.0 to 7.0. Single bubble gas permeability significantly decreased for aggregates generated at pH > 6.6. Furthermore, these aggregates exhibited the highest foamability and foam liquid stability. Air bubble size within the foam was the lowest at pH 7.0. The coarsening exponent, α, fell within predicted values of ⅓ and ½, except for very dry foams where it was 1/5. |
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| Magazine |
Journal of Hazardous Materials, S0304-3894(09)01164-9 |
| Year |
2009 |
| Autors |
A. Alighardashia, D. Pandolfia, O. Potiera and M.N. Ponsb |
| Estb. |
a Water & Wastewater Engineering Department, Power and Water University, of Technology, Tehranpars, Hakimieh, P.O.Box : 16765-1719, Teheran, Iran
b Laboratoire des Sciences du Génie Chimique – CNRS, Nancy University, INPL, 1, rue Grandville, BP 20451, F-54001 Nancy cedex, France |
| Abstract |
The presence of antibiotics in water resources has been disturbing news for the stakeholders who are responsible for public health and the drinking water supply. In many cases, biological wastewater treatment plants are the final opportunity in the water cycle to trap these substances. The sensitivity of activated sludge bacteria to erythromycin, a macrolide widely used in human medicine was investigated in batch toxicity tests using a concentration range of 1 to 300 mg L-1. Erythromycin, a protein synthesis inhibitor, has been found to significantly inhibit ammonification, nitritation and nitratation at concentrations higher than 20 mg L-1. The degree of inhibition increased with greater concentrations of the antibiotic. Exposure to erythromycin also clearly affected heterotrophs, particularly filamentous bacteria, causing floc disintegration and breakage of filaments. Cell lysis was observed with the concomitant release of organic nitrogen (intracellular proteins) and soluble COD. Although erythromycin exhibits properties of a surfactant, this characteristic alone cannot explain the damage to heterotrophs: the effects from erythromycin were greater than those of Tween 80, a commonly used surfactant. Floc disruption can lead to the release of isolated bacteria, and possibly antibiotic resistance genes, into the environment. |
| Magazine |
Colloids and Surfaces A:Physicochem.Eng.Aspects353(2010)181-188 |
| Year |
2010 |
| Autors |
Xiaoqiang Donga, Jian Xua, Chengbo Caob, Dejun Suna and Xiren Jiangc |
| Estb. |
a Key Laboratory for Colloid & Interface Chemistry of Education Ministry, Shandong University, Shan Da South Road 27#, Jinan, Shandong 250100, PR China
b School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250061, PR China
c North China Sea Environmental Monitoring Center of State Oceanic Administration, Qingdao, Shandong 266033, PR China |
| Abstract |
The foamability and foam stability of hydrophilic silica particles (A200) and cationic surfactant cetyltrimethylammonium bromide (CTAB) dispersion in the presence and absence of liquid paraffin were evaluated by interface tension, zeta potential and dilatational rheology. At low surfactant concentration, both the foamability and foam stability of A200/CTAB dispersion in the presence of liquid paraffin are decreased, due to the low coverage degree of silica particles on the air/water interface of the foam films. At the intermediate surfactant concentration, in the absence of liquid paraffin, the foam stability is enhanced by the adsorption of silica particles on the air/water interface. In the presence of liquid paraffin, there is a synergistic stabilization by the adsorption of hydrophobically modified silica particles and oil droplets on the air/water monolayer of foam film. At the same surfactant concentration range, the foamability increases until a plateau value is reached. At high surfactant concentration, the surface of silica particles is hydrophilic and so the silica particles become to disperse in the aqueous phase again. In this case, both the air/water and oil/water interfaces are mainly covered by CTAB molecules, resulting in a slight decrease of foam stability. |
| Magazine |
Journal of Colloid and Interface Science 301 (2006) 274–281 |
| Year |
2006 |
| Autors |
Lok Kumar Shresthaa, Durga P. Acharyaa, Suraj Chandra Sharmaa, Kenji Aramakia, Hiroshi Asaokab, Keiichi Iharab, Takeshi Tsunehirob and Hironobu Kuniedaa |
| Estb. |
a Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan
b Food Research and Development Laboratory, Morinaga Milk Industry Co., Ltd., 1-83, 5-chome, Higashihara, Zama-city 228-8583, Kanagawa, Japan |
| Abstract |
Foaming properties of dilute aqueous solutions of pentaglycerol monostearate (C18G5) and pentaglycerol monooleate (C18:1G5) have been studied at 25 °C. The aqueous C18G5 system formed highly persistent foams, which did not rupture for several days. Foamability and foam stability were increased on increasing the surfactant concentration in both C18G5 and C18:1G5 systems. The C18:1G5/water system showed lower foam stability compared to the C18G5/water system. Aqueous phase behavior of the C18G5 and C18:1G5 systems showed the dispersion of α-solid and Lα phase respectively in water rich region at 25 °C. Stable foam in the C18G5/water system was mainly due to the finely dispersed small surfactant solid particles. The average particles diameter of α-solid and Lα dispersion is found less than 1 μm and it decreases with increasing surfactant concentration. There is no appreciable difference in the particle size of the α-solid and Lα dispersion; however, the foam stability differs largely. Foam stabilized by lamellar liquid crystal dispersion in C18:1G5/water system, is less stable compared to the foam stabilized by the surfactant solid dispersion in C18G5/water system. The foamability and foam stability of the surfactant systems show poor correlation with the dynamic surface tension properties. |
| Magazine |
Journal of Colloid and Interface Science (2009) |
| Year |
2009 |
| Autors |
Qian Liua, Lingyu Luana, Dejun Suna and Jian Xua |
| Estb. |
a Key Laboratory for Colloid and Interface Chemistry of the Education Ministry, Shandong University, Jinan, Shandong 250100, People’s Republic of China |
| Abstract |
The addition of salt promotes the adsorption of layered double hydroxide (LDH) particles onto the air– water interface, but stable foams cannot be prepared from LDH dispersions at all the concentration of NaCl or sodium acetate. We generated stable foams using positively charged plate-like LDH particles in the presence of sodium butyrate. The effects of adding sodium butyrate to LDH on the particle zeta potential, adsorption behavior and the adsorption of modified particles at the air–water interface were studied. At a fixed LDH particle concentration, adding of a trace amount of sodium butyrate maximizes flocculation of the aqueous particle dispersion. Foams prepared under this condition of particle dispersion are most stable to coalescence and halt completely disproportionation. Also, the size of the bubbles is the smallest. The bubbles are stable when drying at 80 °C with little change in size. Laser-induced fluorescent confocal micrographs and scanning electron microscopy observations clearly confirm the adsorption of LDH particles on the foam surfaces, and the bubbles are armored by an interfacial particle multilayer. |
| Magazine |
Langmuir, 2009, 25 (23), pp 13412–13418 |
| Year |
2009 |
| Autors |
Janine Emilea, Anniina Salonena, Benjamin Dolleta and Arnaud Saint-Jalmesa |
| Estb. |
a Institut de Physique de Rennes, CNRS UMR 6521, Universit de Rennes I, Rennes, France |
| Abstract |
Aqueous foams are often used under various flow regimes, and one of the biggest challenges is to create predictive models of their complex rheological properties. Previous theoretical and experimental studies have qualitatively characterized the wall slip of foams. We focus on this phenomenon in a 1D geometry, studying the friction force to move a train of foam films in a narrow channel. We perform, and correlate, 1D experiments and interfacial measurements of surface elasticity. We adapt existing models to correctly analyze and interpret 1D data, allowing for comparison with 3D foam slip results. Different mixtures of surfactants allow us to quantify the influence of interfacial properties. In particular, we show for 1D experiments that already with a low elasticity, of order 1mN m-1, we leave the regime where the interface can be considered as fluid, to enter a regime where dissipation depends only marginally on surface elasticity. |
| Magazine |
Langmuir, 2008, 24 (24), pp 13904–13911 |
| Year |
2008 |
| Autors |
N. Dietricha, S. Poncina, N. Midouxa and Huai Z. Lia |
| Estb. |
a Laboratoire des Sciences du Génie Chimique, Nancy-Université, CNRS 1 rue Grandville, BP 20451, 54000 Nancy Cedex, France |
| Abstract |
The aim of this study is to investigate three types of gas-liquid micromixer geometries, including a cross-shape and two converging shape channels for the bubble formation in different liquids. The bubble shape, size, and formation mechanism were investigated under various experimental conditions such as the flow rates of two phases, physical properties of the liquid, and mixer geometries. A micro particle image velocimetry technique and a high-speed camera were used to characterize and quantify gas-liquid flows. It was revealed that the bubble formation, in particular the bubble size, depends on the geometry of the mixing section between two phases. A correlation gathering numerous experimental data was elaborated for the estimation of the bubble size. The influence of different parameters such as the flow rate ratio between two phases, surface tension, and liquid viscosity is well taken into consideration on the basis of the understanding of the bubble formation mechanism at the microscale. This paper marks an original improvement in the domain where no flow field characterizations or correlations were established in flow-focusing devices. |
| Magazine |
Langmuir 2009, 25, 3396-3401 |
| Year |
2009 |
| Autors |
Maartje L. J. Steegmans a, Karin G. P. H. Schroën a and Remko M. Boom a |
| Estb. |
a Food Engineering Group, Department ATV, Wageningen UniVersity, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
|
| Abstract |
Microfluidic devices are a promising tool for controlled emulsification (i.e., the production of immiscible droplets of one phase in a continuous second phase). In contrast to other emulsification techniques such as high-pressure homogenizers, colloid mills, or membranes, in principle, droplet size and monodispersity can be controlled in microfluidic devices. The emulsification mechanism in microfluidic devices is, among others, determined by the geometric design. Regularly studied microfluidic geometries are, for example, microchannels using a so-called terrace system, Ψ junctions, and T junctions. In microfluidic devices with a terrace, droplets detach when the disperse phase changes from a flat to a spherical shape due to interfacial tension effects, while the disperse phase drops off a shallow terrace into a deep well.1,2 AtΨjunctions, droplets snap off when the nascent droplets are elongated by the surrounding continuous phase, which is known as flow-focusing or extensional flow.3,4 At T junctions, the shear force of the cross-flowing continuous phase snaps off the disperse droplets.5-7 For high-throughput applications, shear-driven microfluidic devices are interesting because of their relatively simple design and the fact that in principle many can be used in parallel.8 The most extensively studied shear-driven microfluidic geometry is the T junction.5,7,9,10 Droplets produced with T junctions are usually several to hundreds of micrometers in size with a polydispersity index (standard deviation to average droplet size ratio) of less than 5%.2 Typical applications include the production of microspheres6 or double emulsions.11,1 |
| Magazine |
Langmuir, 2009, 25 (17), pp 9721–9727 |
| Year |
2009 |
| Autors |
Mingqi Aoa, Guiying Xua, Jinyu Panga and Taotao Zhaoa |
| Estb. |
a Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Jinan 250100, P.R. China |
| Abstract |
The aggregation of ionic liquid-type imidazolium gemini surfactant [C12-4-C12im]Br2 on silicon wafer, which is compared with its monomer [C12mim]Br, have been studied.AFMmorphology images and contact angle measurements suggest that the aggregations of [C12-4-C12im]Br2 and [C12mim]Br on silicon wafer follow different mechanisms. Below the critical surface aggregation concentrations (CSAC), both surfactant molecules are adsorbed with their hydrophobic tails facing the air. But above the CSAC, [C12-4-C12im]Br2 molecules finally form a bilayer structure with hydrophilic head groups facing the air, whereas [C12mim]Br molecules form a multilayer structure, and with increasing its concentration, the layer numbers increase with the hydrophobic chains and hydrophilic head groups facing the air by turns. Besides, the watery wettability of [C12-4-C12im]Br2-treated silica surface is lower than that of [C12mim]Br at the concentration of 5.0 cmc, and the infrared spectroscopy suggests that the poorer watery wettability of [C12-4-C12im]Br2 may be relative to the less-ordered packing of methylene chains inside the aggregate. These different aggregation behaviors for the two surfactants ascribe to the different molecular structures and electrostatic interactions. This work would have certain theoretical guidance meaning on the modification of solid surface. |
| Magazine |
Langmuir, 2008, 24 (14), pp 7400–7407 |
| Year |
2007 |
| Autors |
Pedro Reisa,b, Krister Holmbergb, Reinhard Millerc, Jurgen Krâgec, Dmitri O. Grigorievc, Martin E. Lesera and Heribert J. Watzkea |
| Estb. |
a Nestlé Research Center, CH-1000 Lausanne 26, Switzerland
b Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, SE-412 96 Gôteborg, Sweden
c Max-Planck-Institut for Kolloid- and Grenzflâchenforschung, Max-Planck-Campus, D-14476 Golm, Germany |
| Abstract |
Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, β-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion. |
| Magazine |
Mendeleev, 2005, 15(5), 190–191 |
| Year |
2005 |
| Autors |
Valery G. Babaka and Jacques Desbrièresb |
| Estb. |
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
b Laboratoire de Physico-Chimie des Polymeres (LPCP), Université de Pau, 64053 Pau Cedex 09, France |
| Abstract |
The fluidity of adsorption layers of amphiphilic polyelectrolytes (chitosan derivatives) is characterised by the Deborah number defined as the ratio of the relaxation frequency of the material and the frequency of the applied deformation. |
| Magazine |
Journal of Supercritical Fluids 42 (2007) 69–79 |
| Year |
2007 |
| Autors |
Julien Galya, Kayo Sawadab, Bruno Fournela, Patrick Lacroix-Desmazesc, Serge Lagerged and Michel Persine |
| Estb. |
a CEA Valrhô DEN/DTCD/SPDE/Lab des Fluides Supercritiques et Membranes, BP 111, 26702 Pierrelatte Cedex, France
b EcoTopia Science Institute, Fuoro-cho, Chikusa-ku, Nagoya 464-8603, Japan
c Inst.C.G.-UMR5253 CNRS/UM2/ENSCM/UM1,Ingénierie et Architectures Macromoléculaires,Ecole Nationale Supérieure de Chimie de Montpellier,8r.de l'Ecole Normale,34296 Montp.,Fr
d Inst.Charles Gerhardt–UMR 5253 CNRS/UM2/ENSCM/UM1,Agrégats, Interfaces, Matériaux pour l'énergie,Université Montpellier II,Place Eugène Bataillon,CC015,34095 Montpellier,Fr
e Institut Européen des Membranes, UMR 5635 CNRS-ENSCM-UM2, Université Montpellier II, Place Eugène Bataillon, CC047,34095 Montpellier Cedex 5, France |
| Abstract |
The phase behavior of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers (PEO-PPO-PEO Pluronics) in liquid and supercritical carbon dioxide has been studied by cloud point measurements. It shows that such trade hydrocarbonated surfactants are fairly soluble (0.1 wt.%) in carbon dioxide in relatively mild conditions of temperature and pressure (T<65°C, P < 30MPa). An empirical model based on the molecular weight of the copolymer has been proposed to predict the pressure–temperature phase diagram for a series of Pluronics (10 wt.% of ethylene oxide). Furthermore, the water/CO2 interfacial tension has been measured to investigate the interactions between water and the polar moieties of the surfactants (PEO blocks and hydroxyl end-groups) as well as the interactions between CO2 and the “CO2-philic” moiety of the surfactants (PPO block). An interfacial saturation concentration was evidenced and it was shown to depend on the temperature at a given pressure. The cloud point curves and interfacial tension data are fully consistent with a change in the affinity of the surfactant for CO2 versus pressure and temperature. A correlation between CO2-philic characteristics and surface active properties of the copolymers is given. |
| Magazine |
Langmuir, 2007, 23 (18), pp 9213–9220 |
| Year |
2007 |
| Autors |
Nicolas Antona,b and Patrick Bouriatb |
| Estb. |
a Laboratoire des Fluides Complexes, UMR CNRS 5150, Université de Pau, BP 1155, 64013 Pau Cedex, France
b Inserm U646, Ingénierie de la Vectorisation Particulaire, Université d'Angers, Angers, F−49100 France |
| Abstract |
This paper deals with the different surface corrugations observable during the thinning of axisymmetric thin and large aqueous films, stabilized by saponin. The films are observed using a thin film balance under a constant driving pressure. This device allows measurement of the thicknesses of the film surface shapes arising all along the drainage, as well as the following-up of their evolution before equilibrium is attained. Depending on the electrolyte (NaCl) concentration, three different sorts of corrugation were originally observed in such suspended thin liquid films. At the lowest NaCl concentrations, corresponding to repulsive potential between film walls, only the hydrodynamic corrugations deformed the film surfaces. Regarding the higher NaCl concentrations, when van der Waals forces become predominant, and following the thickness of the first-established thin film, the experiments disclose either that the thinner films are broken up by spinodal decomposition, or that the thicker ones are broken by nucleation and growth of black film. In addition, an original aspect of these works appears in the fact that these observations of the spontaneous decomposition of suspended thin films are relatively similar to those usually described for dewetting experiments on solid substrates, and are well fitted by the existing theoretical models. |
| Magazine |
Acta Phys. Chim. December Sin., 2007, 23(12)：1881-1885 |
| Year |
2007 |
| Autors |
ZHANG Leia, WANG XiaoChuna, GONG QingTaoa, LUO Lana ZHANG Lua, ZHAO Suia and YU JiaYonga |
| Estb. |
a Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China |
| Abstract |
The dilational rheological properties of a pair of structural isomers: sodium 2-propyl-4,5-dihexyl benzene sulfonate (366) and sodium 2,5-dipropyl-4-nonyl benzene sulfonate(393) at the air/water and decane/water interfaces were investigated by drop shape analysis method. The influences of concentration on dilational modulus were expounded. The experimental results showed that the 5-alkyl played an important role in the surface dilational modulus, while the dimension of surfactant molecule dominated the interfacial dilatinal modulus. |
| Magazine |
Langmuir 2009, 25(17), 9751–9758 |
| Year |
2009 |
| Autors |
Maartje L. J. Steegmans a, Anja Warmerdam a, Karin G. P. H. Schroena and Remko M. Boom a |
| Estb. |
a Food Engineering Group, Department ATV, Wageningen University, P.O. Box 8129, 6700EV Wageningen, The Netherlands
|
| Abstract |
Emulsification in microdevices (microfluidic emulsification) involves micrometer-sized droplets and fast interface expansion rates. In addition, droplets are formed in less than milliseconds, and therefore traditional tensiometric techniques cannot be used to quantify the actual interfacial tension. In this paper, monodisperse droplets formed at flat microfluidic Y-junctions were used to quantify the apparent dynamic interfacial tension during (microfluidic) emulsification. Hexadecane droplets were formed in ethanol-water solutions with a range of static interfacial tensions to derive a calibration curve, which was subsequently used to access the dynamic interfacial tension of hexadecane droplets formed in surfactant solutions. For SDS and Synperonic PEF108, various continuous- and disperse-phase (hexadecane) flow rates were studied, and these conditions were linked to interfacial tension effects, which also allowed convective transport of surfactants to be investiagted. On the basis of these findings, various strategies for the formation of emulsion droplets can be followed and are discussed. |
| Magazine |
Langmuir 2011, 27(2), 538–545 |
| Year |
2011 |
| Autors |
Fang He a, Guiying Xu a, Jinyu Pang a, Mingqi Ao a, Tingting Han a and Houjian Gong a |
| Estb. |
a Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, P. R. China
|
| Abstract |
The aggregation behaviors of sodium deoxycholate (NaDC) at the air/water surface were investigated via surface tension and oscillating bubble measurements in the absence and presence of three alkaline amino acids, namely, L-Lysine (L-Lys), L-Arginine (L-Arg), and L-Histidine (L-His). The results of surface tension measurements show that NaDC has a lower ability to reduce the surface tension of water, becauseNaDCmolecules orient at the surface in an oblique direction and tend to aggregate together, which is approved by molecular dynamics (MD) simulation. L-Lys is the most efficient of the three amino acids in reducing the critical aggregation concentration (cac) of NaDC in aqueous solution. The influence of amino acids on the dilational rheological properties of NaDC was studied using the drop shape analysis method in the frequency range from 0.02 to 0.5 Hz. The results reveal that the absolute modulus passes through a maximum value with increasing NaDC concentration. The addition of amino acids increases the absolute modulus of NaDC, and the maximum value is observed at much lower concentration. From the perspective of structures of amino acids, the performance of L-Arg is similar to that of L-His, and both of them bring out a smaller effect on the absolute modulus than that of L-Lys. From the above results, it may be presumed that electrostatic and hydrophobic effects are important impetus during the interaction between amino acids and NaDC at the air/water surface. Hydrogen bonding is so ubiquitous in the system that the difference of hydrogen bonding between NaDC and amino acid is ignored. |
| Magazine |
Journal of Colloid and Interface Science 341 (2010) 101–108 |
| Year |
2010 |
| Autors |
Andrés L. Márqueza,b, Alejandra Medranoc, Luis A. Panizzoloc and Jorge R. Wagnerb |
| Estb. |
a Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA-CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 116,B1900AJJ La Plata, Buenos Aires, Argentina
b Departamento de Ciencia y Tecnología de Alimentos, Facultad de Química, Universidad de la República, General Flores 2124, 11800 Montevideo, Uruguay
c Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, B1876BXD Bernal, Buenos Aires, Argentina |
| Abstract |
The objective of this work was to obtain water-in-oil (w/o) emulsions with polyglycerol polyricinoleate (PGPR) as emulsifier and to study the effect of the addition of calcium in the dispersed aqueous phase on the stability of these systems. Emulsions were formulated with 0.2, 0.5 and 1.0% w/w PGPR and 10% w/w water containing calcium chloride at varied concentrations or other salts (calcium lactate or carbonate; sodium, magnesium or potassium chloride). The stability of these systems was studied with a vertical scan analyzer during 15 days; coalescence and sedimentation were observed as simultaneous destabilization processes. The increase of PGPR concentration and/or calcium chloride content gave more stable emulsions. The stabilizing effect of calcium salt was attributed to the diminution of the water droplets size, the decrease of the attractive force between water droplets and the increase of the adsorption density of the emulsifier. The viscoelastic parameters of the interfacial film were decreased with increasing calcium and PGPR concentrations. Calcium chloride produced a higher increase of stability than calcium salts with lower dissociation degree. The presence of any assayed salt in the aqueous phase also allowed the stabilization of w/o emulsions with higher water contents. |
| Magazine |
Langmuir, 2005, 21 (1), pp 149–159 |
| Year |
2005 |
| Autors |
Jan-willem benjaminsa, Krister Thuressona and Tommy Nylandera |
| Estb. |
a Department of Physical Chemistry 1, Lund University, P.O. Box 124, S-221 00 Lund, Sweden |
| Abstract |
In the presented studywehave developed and implemented a methodology for ellipsometry measurements at liquid interfaces that makes it possible to determine the amount adsorbed without assumptions of refractive index or thickness of the adsorbed layer. It was demonstrated that this is possible by combined measurements from different aqueous phases,H2O and D2O, which were shown to have sufficiently different refractive indices. The methodology was tested by studying adsorption of two types of nonionic poly- (ethylene glycol) alkyl ether surfactants, CnH2n+1(OC2H4)mOH or CnEm at the decane-aqueous interface, where C12E5< was adsorbed from the oil phase and C18E50 from the aqueous phase. The observed plateau values of the adsorbed amounts were 1.38 and 0.93 mg/m2 for C12E5 and C18E50, respectively, which is in agreement with the corresponding values of 1.49 and 1.15mg/m2 obtained from applying the Gibbs equation to interfacial tension data for the same systems. We will briefly discuss the adsorption behavior in relation to the molecular structure of the surfactant and the phase behavior of the oil-surfactant-aqueous systems in relation to our experimental results. |
| Magazine |
18ème Congrès Français de Mécanique |
| Year |
2007 |
| Autors |
N. DIETRICHa, C. ZHAOa, X. FRANKa, S. PONCINa, N. MIDOUXa and H. Z. LIa |
| Estb. |
a Lab. des Sciences du Génie Chimique, CNRS-ENSIC-INPL,1 rue Grandville, BP 20451, 54001 Nancy Cedex, France |
| Abstract |
In this work we present an investigation of the Weissenberg effect which happens at liquid-liquid interfaces obtained using Oil-newtonian as well as oil-non-newtonian liquid-liquid systems. The inverted Weissenberg effect has been confirmed for the Newtonian liquid-liquid system (water/oil). However, for the polymeric solution/oil system, an amplified vertical Weissenberg effect is obtained as the rise of the interface is much more pronounced than in absence of oil. A PIV-system (Particle Velocimetry Image) has been used to study the mechanisms responsible on the rod climbing heavy phase. However, this technique has been found to be not sufficient to obtain flow fields in small areas of few millimetres thickness. A micro-PIV system has thus been used to measure flow fields in the rod climbing zone using microscopic geometries which allow the visualization of horizontal as well as vertical micro-Weissenberg effects. These experiments contribute to further understanding of the Weissenberg effect mechanism. |
| Magazine |
Journal of Food Engineering 92 (2009) 86–99 |
| Year |
2009 |
| Autors |
Jean G, Detrya, Bo Boye Busk Jensenb, Marianne Sindica and Claude Deroannea |
| Estb. |
a Department of Food Technology, Gembloux Agricultural University, Passage des Déportés 2, B-5030 Gembloux, Belgium
b Food Process Technology Group, BioCentrum-DTU, Technical University of Denmark, Soltofts Plads, Build 227, 2800 Lyngby, Denmark |
| Abstract |
In the present work, a radial-flow cell was used to study the removal of starch particle aggregates from several solid substrates (glass, stainless steel, polystyrene and PTFE) in order to determine the critical wall shear stress value for each case. The particle aggregates were formed by aspersion of a water or ethanol suspension of starch granules on the surfaces. Depending on the substrate and on the suspending liquid, the aggregates differed in size and shape. Aggregate removal was studied at two flow rates. At the lower flow rate (Reinlet = 955), the values of critical wall shear stress for the different surfaces suggested that capillary forces were, for all of them, playing an important role in aggregate adhesion since aqueous based aggregates were always more difficult to remove. At the higher flow rate (Reinlet = 2016) the critical wall shear stress increased as a result of the change in the flow pattern in the vicinity of the aggregates and not because of changes in the type of particle adhesion. This raises the importance of the experimental conditions on assessing the critical wall shear stress since this parameter may not be always only directly related to the soil adhesion strength. |
| Magazine |
Colloids and Surfaces A: Physicochem.Eng.Aspects 186(2001)63-72 |
| Year |
2001 |
| Autors |
A. Cagnaa, E.H. Lucassen-Reyndersb and J. Lucassenb |
| Estb. |
a IT Concept, Parc de Chancolan, 69770 Longessaigne, France
b Mathenesselaan 11, 2343 HA Oegstgeest, The Netherlands |
| Abstract |
The surface dilational modulus, which is closely related to the Gibbs elasticity of thin liquid films, has been measured with different experimental methods. We report on new measurements of the modulus for C12E6, a surfactant of the ethylene oxide adduct type, with a dynamic drop tensiometer. In this method, the surface of a small drop or bubble in the surfactant solution is periodically compressed and expanded at a low amplitude and a constant frequency. The modulus follows from the periodic changes in surface tension obtained by axisymmetric drop size analysis. The results are shown to match earlier measurements on the same system with the traditional method employing a barrier oscillating in the surface and a Wilhelmy plate. Both the old and the new data cover the concentration range from zero to the critical micellar concentration (c.m.c). The time scale of the dynamic experiments, which is of the order of the inverse frequency, was varied between 1 and 100 s. We present a quantitative interpretation of these results in terms of the surface equation of state, coupled with diffusional relaxation. The surface equation of state and the adsorption isotherm were derived on the basis of a 2-D solution treatment applied to a Gibbs dividing surface defined so as to account for the presence of solvent. This phenomenological approach, which is independent of molecular size and structure in the surface region, describes both nonideal entropy and enthalpy of the surface mixture to first order. In the entire range of concentrations and frequencies considered, we found almost quantitative agreement between theory and experiment, for both dynamic and equilibrium data. The numerical values found for the equation of state parameters indicate a surface solution of surfactant molecules with a molecular area twice as large as the solvent, and a negative heat of interaction, in contrast to fatty acids where this heat is positive. Relaxation of the surface tension appeared to be purely diffusion-controlled. In no part of the concentration range, did we find any indication for the kinetics of the final adsorption step from sub-surface to surface being rate determining. |
| Magazine |
Applied Clay Science |
| Year |
2008 |
| Autors |
H. Nciria,b, M. Benna-Zayania, M. Stamboulic, V.N. Kbir-Ariguiba, M. Trabelsi-Ayadia, V. Rosiliob and J.-L. Grossiordb |
| Estb. |
a Laboratoire d’applications de la chimie aux ressources et substances naturelles et à l’environnement, Faculté des Sciences de Bizerte, 7021 Zarzouna, Bizerte, Tunisia
b Univ Paris-Sud 11, CNRS UMR 8612, Faculté de Pharmacie de Paris-Sud, 5 Rue Jean Baptiste Clément, 92296 Châtenay-Malabry Cedex, France
c Laboratoire de génie des procédés et matériaux, EA 4038, Ecole Centrale Paris, Grande voie des vignes, 92295 Châtenay-Malabry Cedex, France |
| Abstract |
The behaviour of olive oil-in-water emulsions (O/W) was studied in the presence of smectite particles. The distribution of these particles in the emulsions and the effect of their interaction with the surfactant on the stability of the emulsions were investigated. Whereas the variation of surfactant and/or clay content did not seem to affect the nature of the emulsion, it had a significant influence on emulsion stability. This observation led to two main assumptions on the distribution of clay particles within the emulsion, either exclusively in the continuous phase, or also at the oil-water interface.
In the absence of clay, the variation of surfactant concentration (from 0 to 17% (w/w)) allowed to distinguish 3 domains. In the first concentration domain (0 - 4.2%) emulsions stability increased with the content of surfactant. Within the second domain (4.2 - 8.5% (w/w)), a slight decrease in stability was observed due to flocculation by depletion. For surfactant concentrations equal or higher than 8.5% (3rd domain), emulsion stability increased sharply, probably due to the development of interactions between surfactant molecules as they came closer to their gelling concentration. The effect of clay addition to the aqueous phase (up to 10% (w/w)) on the physicochemical properties of the studied emulsions was assessed from stability, drop size, interfacial tension, rheological and acido-basic analyses. A model based on the location of clay particles either in the bulk or at the interface could be proposed, in which clay particles would interact with surfactant molecules in the bulk phase, and form a mechanical barrier around the oil droplets, thus increasing emulsion stability. |
| Magazine |
Langmuir, 2004, 20 (20), pp 8576–8581 |
| Year |
2004 |
| Autors |
F. Michauta, P. Perrina and P. Hébrauda |
| Estb. |
a L.P.M. ESPCI, UMR 7615, 10 rue Vauquelin, 75231 Paris Cedex 05, France |
| Abstract |
Wehave investigated the dynamic rheological properties of concentrated multiple emulsions to characterize their amphiphile composition at interfaces. Multiple emulsions (W1/O/W2) consist of water droplets (W1) dispersed into oil globules (O), which are redispersed in an external aqueous phase (W2). A small-molecule surfactant and an amphiphilic polymer were used to stabilize the inverse emulsion (W1 in oil globules) and the inverse emulsion (oil globules in W2), respectively. Rheological and interfacial tension measurements show that the polymeric surfactant adsorbed at the globule interface does not migrate to the droplet interfaces through the oil phase. This explains, at least partly, the stability improvement of multiple emulsions as polymeric surfactants are used instead of small-molecule surfactants. |
| Magazine |
Langmuir 2010, 26(13), 10663–10669 |
| Year |
2010 |
| Autors |
Antonio Stocco a, David Carriere b, Maximilien Cottat aand Dominique Langevin a |
| Estb. |
a Laboratoire de Physique des Solides, Universit e Paris-Sud, UMR CNRS 8502, B^atiment 510, 91405 Orsayy, Cedex, France
b Max Planck Institute of Colloids and Interface, 14476 Golm;Potsdam, Germany
|
| Abstract |
We report a dramatic increase in foam stability for catanionic mixtures (myristic acid and cetyl trimethylammonium bromide, CTABr) with respect to that of CTABr solutions. This increase was related to the low surface tension, high surface concentration, and high viscoelastic compression moduli, as measured with rising bubble experiments and ellipsometry. Dialysis of the catanionic mixtures has been used to decrease the concentration of free surfactant ions (CTA t ). The equilibrium surface tension is reached faster for nondialyzed samples because of the presence of these free ions. As a consequence, the foamability of the dialyzed solutions is lower. Foam coarsening has been studied using multiple light scattering: it is similar for dialyzed and nondialyzed samples and much slower than for pure CTABr foams. |
| Magazine |
Mendeleev conmmun, 2005,239-240 |
| Year |
2005 |
| Autors |
Valery G. Babaka,b, Rachel Auzelyb, Marguerite Rinaudob and Alexey R. Khokhlova |
| Estb. |
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation
b CERMAV–CNRS, BP53, 38041 Grenoble Cedex 9, France |
| Abstract |
The interpolyelectrolyte complex formation at the air–water interface has been studied by flow dilational rheometry. |
| Magazine |
Colloids and Surfaces A:Physicochem.Eng.Aspects 261(2005)25–28 |
| Year |
2005 |
| Autors |
A. Cagnaa, M.E. Leserb, S. Acquistapaceb, A.V. Makievskic and R. Millerd |
| Estb. |
a IT Concept, Longessaigne 69770, France
b Nestec Ltd., Nestlé Research Centre, CH-1000 Lausanne 26, Switzerland
c SINTERFACE Technologies, Berlin 12489, Germany
d MPI Kolloid- und Grenzfl¨achenforschung, Potsdam/Golm 14424, Germany |
| Abstract |
To determine the dilational rheology of surface layers, the profile analysis tensiometry can be used with oscillating drops or bubbles. The methodology limits for these oscillations depend on the liquids’ properties, such as density, viscosity and surface tension. For the most frequently studied water/air interface, the maximum oscillation frequency is of the order of 1 Hz, although much higher frequencies are technically feasible by the existing profile analysis tensiometers. For f > 1 Hz, deviations of the drops/bubbles from the Laplacian shape mimic non-zero dilational elasticities for the pure water/air and ethanol/air interface. For liquids of higher viscosity, the critical frequency is much lower. |
| Magazine |
Journal of Colloid and Interface Science 321 (2008) 177–185 |
| Year |
2008 |
| Autors |
Frédéric Marchala, Véronique Nardello-Rataja, Nelly Chaillouxa, Jean-Marie Aubrya and Gordon J.T. Tiddyb |
| Estb. |
a LCOM, Equipe Oxydation & Formulation, UMR CNRS 8009, Ecole Nationale Supérieure de Chimie de Lille, BP 90108, F-59652 Villeneuve d’Ascq Cedex, France
b School of Chemical Engineering & Analytical Science, University of Manchester, PO Box 88, Manchester, M60 1QD, UK |
| Abstract |
Azelaic acid was used as a starting material for the preparation of new monoester surfactants based on fragrance alcohols. Sodium monocitronellyl azelate (citroC9Na) and sodium monomenthyl azelate (menC9Na) were synthesized and their aqueous phase behaviour was studied. For comparison, monoesters derived from succinic anhydride, i.e. sodium monocitronellyl succinate (citroC4Na) and sodium monomenthyl succinate (menC4Na), were also prepared as well as sodium monodecyl succinate (C10C4Na) and sodium monodecyl azelate (C10C9Na) in order to study the effect of the position of the ester function inside the hydrophobic tail and of branching and unsaturation respectively. Liquid crystal structures were examined by optical polarising microscopy and schematic partial binary phase diagrams (surfactant + water, 0–100 wt%, 10–90 °C) of the surfactants were established. Succinate surfactants behave as longer alkyl chain surfactants than their azelate counterparts, meaning that these last ones probably adopt a more folded conformation, with the ester function more frequently present at the micelle surface. This conformation would result in a rougher micelle surface, making it slightly less easy for micelles to pack in liquid crystalline phases. It was also shown that the tendency to adopt a more folded conformation and to form smaller micelles is ranked in this order: monomenthyl > monocitronellyl > monodecyl. |
| Magazine |
Journal of Membrane Science 243 (2004) 273–281 |
| Year |
2004 |
| Autors |
M. Bielskaa and J. Szymanowskia |
| Estb. |
a Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Sklodowskiej-Curie 2, 60-965 Poznan, Poland |
| Abstract |
The ultrafiltration of micellar solutions containing nitrobenzene and 4-nitrophenol using three types of polymeric membranes was studied. Hexadecyltrimethylammonium bromide (CTAB), oxyethylated coconut fatty acid methyl esters of an average oxyethylation degree equal to 10 (OMC-10) and oxyethylated nonylphenol of an average oxyethylation degree equal to 9 (ONP-9) were used as surfactants. It was found that the efficiency of the separation of nitrobenzene and 4-nitrophenol could be explained using the general linear solvation energy relationships proposed by Abraham. The efficiency of separation depended upon pollutant hydrophobicity, hydrogen bond acidity, surfactant and membrane. The use of binary mixtures of cationic and nonionic surfactants enhanced the recovery. Simultaneously, a strong synergistic effect in surface activity and micellization was observed for such mixtures. The use of hydrophilic membranes seemed to be preferred due to higher fluxes and often higher retention. Ultrafiltration experiments enabled the estimation of parameters characteristic for colloids and extraction studies. |
| Magazine |
Colloids and Surfaces A:Physicochem.Eng.Aspects282-283(2006)203-209 |
| Year |
2006 |
| Autors |
Alain Cagnaa, Hernan Ritaccob and Dominique Langevinb |
| Estb. |
a IT Concept, Longessaigne 69770, France
b Universite de Paris XI-Sud, Laboratoire de Physique des Solides, Batiment 510, 91405 Orsay, France |
| Abstract |
Mixed polyelectrolyte surfactant layers co-adsorbed at the surface of aqueous solutions have an unusual behavior. The adsorption is irreversible and the response to large compressions is highly nonlinear, as evidenced by Brewster angle microscopy. As a consequence, it is very difficult to measure equilibrium surface tension with bubble shape techniques, as soon as bubble volume is varied. These difficulties seem, however, specific to strongly viscoelastic layers. They are never found with surfactant solutions, and perhaps more surprisingly not seen either with more rigid layers such as those obtained with proteins. Long equilibration times are found, much longer than inWilhelmy plate experiments. Uncontrolled convective motions occurring with the plate technique might explain the observed differences. It is easier to obtain reliable compression viscoelastic moduli with the oscillating bubble technique. |
| Magazine |
Langmuir, 2010, 26 (8), pp 5397–5404 |
| Year |
2010 |
| Autors |
Jun Wanga, Fei Yangb, Junjun Tana, Guopeng Liuc, Jian Xua and Dejun Suna |
| Estb. |
a Key Laboratory for Colloid and Interface Chemistry of the Education Ministry, Shandong University, Jinan, Shandong 250100, P. R. China
b Department of Oil and Gas Storage and Transportation Engineering, China University of Petroleum, Qingdao, Shandong 266555, P. R. China
c Department of Chemistry, Shandong Institute of Education, Jinan, Shandong 250013, P. R. China |
| Abstract |
Liquid paraffin-water emulsions were prepared by homogenizing oil phases containing sorbitan oleate (Span 80) and aqueous phases containing layered double hydroxide (LDH) particles or Laponite particles. While water-in-oil (w/o) emulsions are obtained by combining LDH with Span 80, the emulsions stabilized by Laponite-Span 80 are always o/w types regardless of the Span 80 concentration. Laser-induced fluorescent confocal micrographs indicate that particles are absorbed on the emulsion surfaces, suggesting all the emulsions are stabilized by the particles. The difference of the particle-stabilized emulsion type may be explained by comparing particle contact angles and the oil-water interfacial tensions, indicating that more Span 80 molecules are adsorbed on the LDH particles than on Laponite. Apparently, the LDH particles are rendered more hydrophobic by Span 80, resulting in the formation of w/o emulsions. The long-term stability of the emulsions was also compared. Emulsions stabilized by Span 80 alone completely separate into two bulk phases of oil and water after 3 months. However, emulsion stability is greatly enhanced with the addition of LDH or Laponite particles. This synergism was accounted for by an increase of the dilational viscoelasticity modulus of the oil-water interface after particles were added to the aqueous phase. This increase indicates that the gel-like particle layer stays at the oil-water interface and resists emulsion coalescence. Scanning electron microscope (SEM) images display the presence of a firm layer surrounding the emulsion droplets and a three-dimensional particle network which extends into the bulk phase aiding emulsion stability. |
| Magazine |
Mendeleev Commun., 2008, 18, 193–195 |
| Year |
2008 |
| Autors |
Valery G. Babaka, Francis Barosb, Boris A. Izmailova, Dmitry I. Maltseva, Gali D. Markovaa, Viatcheslav N. Sokolovc and Valery A. Vasneva |
| Estb. |
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 499 135 5085; e-mail:
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
b Département de Chimie Physique des Réactions, CNRS UMR 7630, BP 451, 54001 Nancy Cédex, France
c Department of Geology, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation |
| Abstract |
Polycondensation in tetradecaethoxyhexasiloxane adsorption layers at the methylene chloride/water boundary under alkaline conditions has been studied by interfacial dilational rheometry in view of the formulation of hollow nano- and microcapsules. |
| Magazine |
Langmuir 2010 |
| Year |
2010 |
| Autors |
Cécile Monteuxa, Claire Marlièreb, Pauline Parisb, Nadège Pantoustierb, Nicolas Sansonb and Patrick Perrinb |
| Estb. |
a Laboratoire de Physico-Chimie des Polymères et Milieux Dispersés, UMR7615 UPMC-ESPCI-CNRS,
b Ecole Supérieure de Physique et de Chimie Industrielles ESPCI, 10 rue Vauquelin, 75231 Paris, Cedex 05, France |
| Abstract |
Highly monodisperse poly(N-isopropylacrylamide), PNiPAM, microgels were prepared by the conventional radical polymerization of NiPAM in the presence of dimethylamino ethyl methacrylate (DMAEMA) monomers at various concentrations. The effect of DMAEMA on the polymerization of PNiPAM microgels was examined at constant initiator (V50) and cross-linker (MBA) concentrations. The presence ofDMAEMAin the synthesis batch allows for the preparation of PNiPAM microgels with controlled size and a narrow size distribution. The oil(dodecane)/water interfacial properties of the model PNiPAM microgels were then investigated. The pendant drop technique was used to measure the interfacial tensions as a function of temperature. Over the whole range of temperature (20-45 °C), the interfacial tension remains low (on the order of 17 mN/m) and goes through a minimum (12 mN/m) at a temperature of about 34 °C, which well matches the volume phase transition temperature (VPTT) of PNiPAM microgels. Below the VPTT, the decrease in the interfacial tension with temperature is likely to be due to the adsorption of dense layers because of the decrease of the excluded volume interactions. Above the VPTT, we suggest that the increase in the interfacial tension with temperature comes from the adsorption of loosely packed PNiPAM microgels. We also studied the effect of temperature on the stability of emulsions. Dodecane in water emulsions, which form at ambient temperature, are destabilized as the temperature exceeds the VPTT. In light of the interfacial tension results, we suggest that emulsion destabilization arises from the adsorption of aggregates above the VPTT and not from an important desorption of microgels. Aggregate adsorption would bring a sufficiently high number of dodecane molecules into contact with water to induce coalescence without changing the interfacial tension very much. |
| Magazine |
|
| Year |
2010 |
| Autors |
Neha B. Raikara, Surita R. Bhatiaa, Michael F. Malonea, David Julian McClementsb, Cristhian Almeida-Riverac, Peter Bongersc and Michael A. Hensona |
| Estb. |
a Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003-9303, United States
b Department of Food Science, University of Massachusetts, Amherst, MA 01003-9303, United States
c Unilever R&D, 3133 AT Vlaardingen, The Netherlands |
| Abstract |
Most population balance equation (PBE) models of emulsion drop breakage are based on the assumption of binary drop breakage. We previously developed such a PBE model for high-pressure homogenizers with a daughter drop distribution function exhibiting a maximum probability for two equal sized drops. In this paper, we present a PBE model accounting for multiple drop breakage and show that the model provides superior distribution predictions reflected by decrease in least-squares objective function for an oil-in-water emulsion processed in a pilot-scale high-pressure homogenizer. Following our previous work, two distinct rate functions for drop breakage, one due to turbulent eddies and another due to turbulent shear were used to reproduce the measured bimodal distributions.Wefound that multiple drop breakage was satisfactorily modeled with a uniform daughter drop distribution function if the assumed number of daughter drops formed was chosen to be sufficiently large. The PBE model with multiple drop breakage was shown to provide superior distribution predictions compared to the analogous binary breakage PBE model when adjustable model parameters were determined by nonlinear optimization. The multiple breakage PBE model was shown to be extensible to different emulsion formulations by using these base case model parameters to predict the effects of oil concentration, surfactant concentration, oilto- surfactant ratio and emulsion premix distribution. Our experiments revealed that substantial breakage of the premix occurred during the first homogenization pass even under zero applied homogenization pressure operation, suggesting an unmodeled pressure independent breakage mechanism. |
| Magazine |
Colloids and Surfaces A: Physicochem. Eng. Aspects 288 (2006) 86–95 |
| Year |
2006 |
| Autors |
Véronique Nardelloa, Nelly Chaillouxa, Gilles Jolyb and Jean-Marie Aubrya |
| Estb. |
a LCOM, UMR CNRS 8009, Equipe “Oxydation et Formulation”,Cité Scientifique, ENSCL, BP 90108, F-59652 Villeneuve d’Ascq Cedex, France
b USTL, UMR CNRS 8024, “Laboratoire LDSMM, UMR 8024, Equipe Mati`ere Molle Moléculaire”, Cité Scientifique, USTL, F-59655 Villeneuve d’Ascq Cedex, France |
| Abstract |
New surfactants based on sodium monoalkyl α,ω-dicarboxylates H3C(CH2)n−1OC(O)(CH2)m−1CO2Na (CnCmCO2Na) with various chain lengths were prepared from succinic anhydride (m= 3), azelaic acid (m= 8) and dodecanedioic acid (m= 11). Their physico-chemical properties (Krafft point, critical micelle concentration and kinetics of hydrolysis) were measured and their lyotropic aqueous phase behaviour was investigated by polarized light optical microscopy. To assess the influence of the ester function inside the hydrocarbon chain, sodium monoalkyl azelates and monoalkyl succinates were compared with sodium soaps (m= 0) having a same carbon number. Insertion of an ester group within the surfactant alkyl chain considerably lowers the Krafft point and slightly delays the formation of the first mesophase. The methylene units localized between the ester and the carboxylate groups are equivalent to 0.5 methylene group in their effect on CMC. The rate of hydrolysis of those monoesters depends heavily on the pH and on the CMC. The kinetics is fast and pseudo-first order below the CMC and it is slow and pseudo-zeroth order above the CMC because the ester function is protected from hydrolysis when it is embedded within the micelle core. |
| Magazine |
Langmuir 2002, 18, 6458-6461 |
| Year |
2002 |
| Autors |
Anne Koeniga, Pascal Hébrauda and Patrick Perrina |
| Estb. |
a Lab.de Physico-Chimie Macromolé culaire,UMR 7615,Ecole Supérieure de Physique et Chimie de Paris,CNRS,Université Pierre et Marie Curie,10 rue Vauquelin, 75005 Paris, Fr. |
| Abstract |
|
| Magazine |
International Journal of Pharmaceutics 242 (2002) 167–170 |
| Year |
2002 |
| Autors |
B. Heurtaulta, P. Saulniera, B. Pecha, J.E. Prousta and J.P. Benoîta |
| Estb. |
a Inserm ERIT-M 0104, Ingénierie de la Vectorisation Particulaire, Immeuble IBT, 10, rue A. Boquel, 49100 Angers, France |
| Abstract |
This study proposed a method to understand the surfactant role in the first step of the formulation of a novel generation of lipidic nanocapsules. A dynamic rheological protocol was applied using a pendant drop tensiometer in order to determine the interfacial properties of the initial mixture implied in the first formulation step. The response, in terms of interfacial elasticities, described how this mixture led to monodisperse nanometer size range structures after a physico-chemical constraint. |
| Magazine |
WATER RESEARCH 40 (2006) 1027 – 1033 |
| Year |
2006 |
| Autors |
M. Bielskaa and J. Szymanowskia |
| Estb. |
a Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Sklodowskiej-Curie 2, 60-965 Poznan, Poland |
| Abstract |
Ultrafiltration of micellar solutions containing sodium dodecylsulfate (SDS) and oxyethylated coconut fatty acid methyl esters (OMC-10) and their binary mixtures were studied and used to recover methylene blue. This was achieved through solubilization in mixed negatively charged micelles. Under the experimental conditions used, no significant fouling of the membrane comprising of cellulose, polyethersulfone and polyvinylidene fluoride was observed, with no retardation of ultrafiltration. The introduction of a nonionic surfactant to SDS reduced the critical micelle concentration of mixed micelles and then the concentration of surfactants in the permeate, i.e., from 8.3 × 10-3M for SDS to 2.0 × 10-3M for the mixture of SDS:OMC-10 = 4:1. Such a tailored surfactant mixture enabled the authors to achieve 93–94% retention of methylene blue using a hydrophilic membrane made of cellulose.
Ultrafiltration of micellar solutions could also be considered a research method, helpful in determining important parameters such as micelle loading and the micelle binding constant used to characterize micellar solutions. Additionally the distribution coefficient employed in extraction studies can be resolved. |
| Magazine |
Langmuir, 2009, 25 (14), pp 7828–7835 |
| Year |
2009 |
| Autors |
G. Lecollineta, N. Delormeb, M. Edelyb, A. Gibaudb, J.-F. Bardeaub, F. Hindréc, F. Bouryc and D. Porteta |
| Estb. |
a SURFACTIS Technologies, 22 rue Roger Amsler, F-49100 Angers, France
b Laboratoire de Physique de l’Etat Condensé, Université du Maine, Avenue Olivier Messiaen, F- 72085 Le Mans Cedex 9, France
c INSERM U646, “Ingénierie de la Vectorisation Particulaire”, 10 rue A. Boquel, F-49100 Angers, France |
| Abstract |
Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms=0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle > 110° on stainless steel or titanium) and lipophobic (methylene iodide contact angle > 105° on titanium) properties are discussed in terms of industrial applications. |
| Magazine |
Langmuir, 2002, 18 (15), pp 5933–5938 |
| Year |
2002 |
| Autors |
Charles M. Kauscha, Jane E. Leisinga, Robert E. Medskera, Vernon M. Russella, Richard R. Thomasa and Aslam A. Malikb |
| Estb. |
a OMNOVA Solutions, Inc., 2990 Gilchrist Road, Akron, Ohio 44305-4489
b Aerojet Fine Chemicals, P.O. Box 1718, Rancho Cordova, California 95714 |
| Abstract |
A series of water-dispersible, surface-active poly(fluorinated oxetane)s was prepared by ring-opening polymerization of fluorinated oxetane monomers using Lewis acid catalysis. The fluorinated oxetane monomers are made by phase-transfer catalytic reaction of a fluorinated alcohol with 3-bromomethyl- 3-methyloxetane. Water dispersibility was introduced by conversion of the diol-terminated α,ω-(dihydroxy)- poly(fluorinated oxetanes) into diammonium salts of α,ω-sulfate esters. The poly(fluorinated oxetane) salts exhibit unusually low surface tensions for materials based on a pendant trifluoro- or pentafluoroalkyl group. At a critical micelle concentration of ~10-5 mol/L (~10-3 wt %), surface tensions of ~20-30 mN/m are obtained. The novel architecture of the poly(fluorinated oxetane) salts is thought to be responsible for the anomalous surface activity. |
| Magazine |
Carbohydrate Research 344 (2009) 136–139 |
| Year |
2009 |
| Autors |
Fabrice Goursauda and Thierry Benvegnua |
| Estb. |
a UMR CNRS 6226, Equipe Chimie Organique et Supramoléculaire, Ecole Nationale Supérieure de Chimie de Rennes, Université Européenne de Bretagne,Avenue du Général Leclerc, F-35700 Rennes, France |
| Abstract |
The synthesis of a novel long-chain cationic surfactant bearing a fructopyranoside polar head functionalized at the C-5 position by a natural glycine betaine residue through an amide linkage is described. |
| Magazine |
Carbohydrate Research |
| Year |
2010 |
| Autors |
Anas Allama, Jean-Bernard Behra, Laurent Duponta, Véronique Nardello-Ratajb and Richard Plantier-Royona |
| Estb. |
a Université de Reims Champagne-Ardenne, Institut de Chimie Moléculaire de Reims (ICMR), CNRS UMR 6229,UFR des Sciences Exactes et Naturelles, Bâtiment 18 Europol’Agro, BP 1039, F-51687 Reims Cedex 2, France.
b Université Lille 1, Sciences et Technologies, LCOM UMR 8009, Equipe Oxydation & Physico-chimie de la formulation, Bâtiment C6, F-59655 Villeneuve d’Ascq, France. |
| Abstract |
This paper describes a convenient and efficient synthesis of new complexing surfactants from D-galacturonic acid and n-octanol as renewable raw materials in a two-step sequence. In the first step, simultaneous O-glycosidation-esterification under Fischer conditions was achieved. The anomeric ratio of the products was studied based on the main experimental parameters and the activation mode (thermal or microwave). In the second step, aminolysis of the n-octyl ester was achieved with various functionalized primary amines under standard thermal or microwave activation. The physico-chemical properties of these new amphiphilic ligands were measured and these compounds were found to exhibit interesting surface properties. Complexing abilities of one uronamide ligand functionalized with a pyridine moiety towards Cu(II) ions was investigated in solution by EPR titrations. A solid compound was also synthesized and characterized, its relative structure was deduced from spectroscopic data. |
| Magazine |
Journal of Molecular Catalysis B: Enzymatic 62 (2010) 19–26 |
| Year |
2010 |
| Autors |
Ali Tiss a, Hans Lengsfeld band Robert Verger c |
| Estb. |
a The BioCentre, University of Reading, Whiteknights, PO Box 221, Reading RG6 6AS, UK
b Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland
c CNRS – University of Aix-Marseille, Enzymologie Interfaciale et Physiologie de la Lipolyse UPR 9025, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France
|
| Abstract |
The inhibitory effects of tetrahydrolipstatin (THL) on the hydrolytic activity of human pancreatic lipase (HPL) and T. lanuginosa lipase (TLL) on various lipidic substrates ‘poisoned’ with THL as previously described was studied, using either the pH-stat, monomolecular film or oil drop technique. Prior to adding lipase (method C), an ethanolic solution of THL was injected in a tributyrin (TC4) or a purified soybean oil (PSO) emulsion prepared in a pH-stat vessel. Under these conditions, THL was found to be a potent HPL inhibitor. After being dissolved in the pure triglyceride phase (method D), THL also strongly inhibited HPL. However, with TC4 as substrate TLL was efficiently inhibited by THL only when method C was used and not method D. The very different inhibitory effects on HPL and TLL recorded with method D and PSO as substrate were confirmed using the monomolecular film and oil drop techniques. With a monomolecular film of dicaprin (di-C10) as substrate, 1 molecule of THL embedded in 400 000 molecules of di-C10 sufficed to reduce the HPL activity to half of its initial value. HPL was therefore efficiently inhibited by THL with all the methods and substrates tested here. Paradoxically, TLL was inhibited by THL molecules transiently present in the aqueous phase and not by the THL molecules present at the triglyceride/water interface. It should therefore be stressed that the inhibitory effects of THL on each lipase depend strongly on the method and the substrate used. |
Top
Biochemistry
| Magazine |
Journal of Molecular Catalysis B: Enzymatic 62 (2010) 19–26 |
| Year |
2010 |
| Autors |
Ali Tissa,c, Hans Lengsfeldb and Robert Vergerc |
| Estb. |
a The BioCentre, University of Reading, Whiteknights, PO Box 221, Reading RG6 6AS, UK
b Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland
c CNRS – University of Aix-Marseille, Enzymologie Interfaciale et Physiologie de la Lipolyse UPR 9025, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France |
| Abstract |
The inhibitory effects of tetrahydrolipstatin (THL) on the hydrolytic activity of human pancreatic lipase (HPL) and T. lanuginosa lipase (TLL) on various lipidic substrates ‘poisoned’ with THL as previously described was studied, using either the pH-stat, monomolecular film or oil drop technique.
Prior to adding lipase (method C), an ethanolic solution of THL was injected in a tributyrin (TC4) or a purified soybean oil (PSO) emulsion prepared in a pH-stat vessel. Under these conditions, THL was found to be a potent HPL inhibitor. After being dissolved in the pure triglyceride phase (method D), THL also strongly inhibited HPL. However, with TC4 as substrate TLL was efficiently inhibited by THL only when method C was used and not method D. The very different inhibitory effects on HPL and TLL recorded with method D and PSO as substrate were confirmed using the monomolecular film and oil drop techniques.
With a monomolecular film of dicaprin (di-C10) as substrate, 1 molecule of THL embedded in 400 000 molecules of di-C10 sufficed to reduce the HPL activity to half of its initial value.
HPL was therefore efficiently inhibited by THL with all the methods and substrates tested here. Paradoxically, TLL was inhibited by THL molecules transiently present in the aqueous phase and not by the THL molecules present at the triglyceride/water interface. It should therefore be stressed that the inhibitory effects of THL on each lipase depend strongly on the method and the substrate used. |
| Magazine |
Langmuir 2008, 24, 5781-5786 |
| Year |
2008 |
| Autors |
P. Reisa,d, R. Millerb, M. Lesera, H. Watzkea, V. B. Fainermanc and K. Holmbergd |
| Estb. |
a Nestlé Research Center, CH-1000 Lausanne 26, Switzerland
b Max-Planck-Institut für Kolloid- and Grenzflächenforschung, Max-Planck-Campus,D-14476 Golm, Germany
c Medical Physicochemical Center Donetsk Medical UniVersity, 16 Ilych AVenue, 83003 Donetsk, Ukraine
d Chalmers UniVersity of Technology, Department of Chemical and Biological Engineering, Applied Surface Chemistry, SE-412 96 Göteborg, Sweden |
| Abstract |
Dietary fat has long been recognized as an essential component in nutrition. However, most of the lipids present in food need to be converted into more bioavailable compounds. Lipases have a crucial role in converting triglycerides into more polar lipids with increased water solubility and a tendency to form micelles. However, the surface active molecules generated by lipolysis may have a detrimental effect on the interfacial biocatalysis. In the present work we evaluate the interfacial properties of lipase-generated molecules during fat digestion. By using the pendant drop technique we assessed the amphiphilic character of fatty acid salts, monoglycerides, and diglycerides as individual surfactants and mixtures. The experimental results are fitted with a mathematical model, which assists in the determination of the interfacial properties of the surfactants. Our results show that monoglycerides have considerably higher interfacial activity than fatty acid salts and diglycerides. Therefore, the interface will soon be dominated by monoglycerides. The pH dependency of the interfacial activity of fatty acids is also explored in the current work. We believe that our results can contribute to a better understanding of the complex interfacial phenomena occurring during fat digestion. |
| Magazine |
Colloids and surfaces A:physicochem,Eng,Aspects 243(2004) 33-42 |
| Year |
2004 |
| Autors |
Valery G.Babaka,b and Frank Bouryb |
| Estb. |
a A.N.Nesmeyanov institute of organoelement compounds, Russian academy of sciences,28,Vavilova Str,117813 Moscow,Russia
b INSERM Unité 646 "ingénierie de la vectorisation particulaire"Immeuble IBT,10,rue andré boquel, 49100 Angers, France |
| Abstract |
The kinetics of the adsorption of hydrophobic insoluble in water polymers (ammonio polymethylmethacrylates, known as Eudragits RL and RS) at the methylene chloride (MC)–water interface has been studied in function of their bulk concentration in the organic phase. These polymers, conventionally denoted as hydrophobic polysoaps, strongly adsorb at the oil–water interface by immersing their ionisable (trimethylammonium (TMA)) groups into the water phase. Unlike the hydrophilic polysoaps (the water-soluble hydrophobically modified polyelectrolytes) whose adsorption at the oil–water interface is controlled by the hydrophobic effect (the gain in entropy due to the destruction of the ordered layers of the water molecules around the adsorbed alkyl chains), the driving force for the adsorption of hydrophobic polysoaps is the gain in enthalpy due to the hydration of adsorbed hydrophilic groups of the polymer.
It has been shown that the dynamic interfacial tension curves γ(t) of hydrophobic polysoaps are characterized by several stages of adsorption with different characteristic relaxation times. During the lag-stage and the post lag-stage the adsorption is the diffusion-controlled process of macromolecules from the bulk of the organic solution to the interface. At the final stage, the adsorption is characterized by much lower rate due to the steric hindrance exerted by the yet formed adsorption layer with regard to newly adsorbing macromolecules. |
| Magazine |
Proceedings of the National Academy of sciences |
| Year |
2006 |
| Autors |
Libo Wanga, Mary T. Walsha and Donald M.Smalla |
| Estb. |
a Department of physiology and bilphysics, boston univesity school of medicine, boston, MA 02118 |
| Abstract |
Apolipoprotein B (apoB) is one of a unique group of proteins that form and bind to fat droplets, stabilize the emulsified fat, and direct their metabolism. ApoB, secreted on lipoproteins (emulsions), remains bound during lipid metabolism yet exhibits conformational flexibility. It has amphipathic β-strand (AβS)-rich domains and amphipathic α-helix (AαH)-rich domains. We showed that two consensus AβS peptides of apoB bound strongly to hydrophobic interfaces [triolein/water (TO/W) and dodecane/ water], were elastic, and were not pushed off the interface when the surface was compressed. In contrast, an AαH peptide modeling helical parts of apoB was forced off the TO/W interface by compression and readsorbed when the interface was expanded. In this report, the surface behavior of apoB-100 was studied at the TO/W interface. Solubilized apoB lowered the interfacial tension of TO/W in a concentration-dependent fashion. At equilibrium tension, if the surface was compressed, part of apoB was pushed off but quickly readsorbed when the surface was expanded. Even when the surface area was compressed by ≈55%, part of the apoB molecule remained bound. The maximum surface pressure that apoB could withstand without being partially ejected was 13 mN/m. ApoB showed high elasticity at the TO/W interface. Based on studies of the consensus AβS and AαH peptides, we suggest that AβSs anchor apoB and are its nonexchangeable motif, whereas its conformational flexibility arises from both the elastic nature of the AβS and the ability of AαH domains of the molecule to desorb and readsorb rapidly in response to surface pressure changes. |
| Magazine |
Langmuir, 2005, 21 (5), pp 1962–1971 |
| Year |
2005 |
| Autors |
Volkmar Heinricha and Wiesława Rawiczb |
| Estb. |
a Boston University, Department of Biomedical Engineering, 44 Cummington Street, Boston, Massachusetts 02215
b University of British Columbia, Department of Pathology, 2211 Wesbrook Mall, Vancouver, BC V6T2B5, Canada |
| Abstract |
|
| Magazine |
Langmuir, 2008, 24 (20), pp 11828–11833 |
| Year |
2008 |
| Autors |
Anita Swamia, Gabriel Espinosaa, Samuel Guillotb, Eric Raspauda, François Bouéc and Dominique Langevina |
| Estb. |
a Laboratoire de Physique des Solides, UMR 8502 UniVersité Paris-Sud, 91405 Orsay, France
b CRMD, UMR 6619 UniVersité d’Orléans, 45071 Orléans, France
c Laboratoire Leon Brillouin, CEA Saclay, France |
| Abstract |
The study of systems that allow DNA condensation in confined environments is an important task in producing cell-mimicking microreactors capable of biochemical activities. The water droplets formed in water-in-oil emulsions are potentially good candidates for such microcompartments. The anionic surfactant AOT was used here to stabilize the droplets. We have studied in detail the DNA distribution and the structural modifications of these microemulsion drops by varying the concentration and molecular weight of DNA and using various techniques such as light, X-ray, and neutron scattering, electrical conductivity, and surface tension. DNA induces the formation of large drops into which it is internalized. The size of these drops depends on the amount of DNA dissolved in water as well as on its molecular weight. The local DNA concentration is very high (>100 mg/mL). The large drops coexist with small empty drops (not containing DNA), similar to those found in the DNA-free microemulsion. |
| Magazine |
Research in Microbiology 159 (2008) 137e144 |
| Year |
2008 |
| Autors |
Benjamin Kleina, Vincent Grossib, Patrick Bouriatc, Philippe Goulasa and Régis Grimauda |
| Estb. |
a Institut Pluridisciplinaire de Recherche en Environnement et Matériaux, Equipe Environnement et Microbiologie UMR 5254 CNRS IBEAS, Université de Pau et des Pays de l’Adour, BP1155, 64013 Pau, France
b Paléoenvironnements & Paléobiosphère, UMR 5125 PEPS, CNRS France, Université Lyon 1, Campus de la Doua,Bâtiment Géode, 69622 Villeurbanne Cedex, France
c Laboratoire de Thermodynamique et Energétique des Fluides Complexes, UMR TOTAL CNRS 5150, Université de Pau et des Pays de l’Adour, BP1155, 64013 Pau, France |
| Abstract |
During growth on n-alkanes, the marine bacterium Marinobacter hydrocarbonoclasticus SP17 formed a biofilm at the alkaneewater interface. We showed that hexadecane degradation was correlated with biofilm development and that alkane uptake is localized in the biofilm but not in the bulk medium. Biofilms were observed in cultures on metabolizable n-alkanes (C8-C28) and n-alcohols (C12 and C16), but were formed neither on non-metabolizable alkanes (pristane, heptamethylnonane and n-C32) nor on inert substrata (glass, polystyrene and Permanox®). This substratum specificity indicates that biofilm formation is determined by the presence of an interface between an insoluble substrate and the aqueous phase. Simultaneously with biofilm growth, planktonic cells were released from the biofilm. Detached cells were in a non-growing state, implying that the growing population was exclusively located within the biofilm. Planktonic and sessile cells exhibited differences in their ultrastructure and lipid content. Biofilm cells contained a large amount of wax esters (0.47 mg/mg protein) in rounded or irregularly shaped cytoplasmic inclusions, whereas detached cells displayed rod-shaped inclusions and contained 5 times fewer wax esters (0.10 mg/mg protein) than their sessile counterparts. This study points out the inter-relationship between biofilm formation, insoluble substrate uptake and lipid storage. |
| Magazine |
Biomaterials 28 (2007) 4978-4990 |
| Year |
2007 |
| Autors |
Arnaud Béduneaua, Patrick Saulniera, François Hindrea, Anne Clavreulb, Jean-Christophe Lerouxc and Jean-Pierre Benoita |
| Estb. |
a Inserm, U646, Université d’Angers, Angers F-49100, France
b Département de Neurochirurgie CHU d’Angers, Angers, F-49033 France
c Canada Research Chair in Drug Delivery, Faculty of Pharmacy, C.P. 6128 Succ. Centre-ville, Montréal, Que. Canada H3C 3J7 |
| Abstract |
Immunonanocapsules were synthesized by conjugation to lipid nanocapsules (LNC) of whole OX26 monoclonal antibodies (OX26 MAb) directed against the transferrin receptor (TfR). The TfR is overexpressed on the cerebral endothelium and mediates the transcytosis mechanism. Fab’ fragments, known for their reduced interaction with the reticuloendothelial system, were also conjugated to LNC. This coupling was facilitated by the incorporation of lipid PEG2000 functionalized with reactive-sulfhydryl maleimide groups (DSPE–PEG2000–maleimide) into LNC shells by a post-insertion procedure, developed initially for liposome pegylation. An interfacial model using the dynamic rising drop technique helped determine the parameters influencing the DSPE–PEG2000–maleimide insertion and the quality of the anchorage. Heat was essential to promote both an important and stable adsorption of DSPE–PEG2000–maleimide onto LNC. OX26 MAb were thiolated to react with maleimide functions whereas thiol residues on Fab’ fragments were used directly. The number of ligands per nanocapsule was adjusted according to their initial quantity in the coupling reaction mixture, with densities from 16 to 183 whole antibodies and between 42 and 173 Fab’ fragments per LNC. The specific association of immunonanocapsules to cells overexpressing TfR was thus demonstrated, suggesting their ability to deliver drugs to the brain. |
| Magazine |
Polymer 46 (2005) 639–651 |
| Year |
2005 |
| Autors |
Fanny Lebouca, Isabelle Deza, Jacques Desbrièresb, Luc Pictonc and Pierre-Jean Madeca |
| Estb. |
a Laboratoire de Chimie Moléculaire et Thioorganique, UMR CNRS 6507, ENSICAEN, Université de Caen, 6 Boulevard du Maréchal Juin, 14050 Caen Cedex, France
b Laboratoire de Physico-Chimie des Polymères, UMR CNRS 5067, HelioParc Pau Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 09, France
c Laboratoire Polyme`res, Biopolymères et Membranes, UMR CNRS 6522, Université de Rouen, 76 821 Mont Saint Aignan Cedex, France |
| Abstract |
The grafting of poly(ethylene glycol) functionalized by ester groups (MeO-PEG-ester) onto chitosan was studied and optimized using different reaction conditions. In a first procedure, the grafting was made from 6-O-triphenylmethyl-chitosan after protection of primary hydroxyl groups and in a second one, it was made directly onto chitosan. NMR spectroscopy was an important tool to study these reactions and the grafting is unequivocally showed up. Moreover, for each procedure, the solubility and surface properties of the obtained copolymers were evaluated and compared. |
| Magazine |
Mendeleev commun.,2008,18,36-38 |
| Year |
2008 |
| Autors |
Valery G.Babaka,b, Francis Barosb, Frank Bouryc, Jacques Desbrièresd and Galina A. Vikhorevae |
| Estb. |
a A.N.Nesmeyanov institute of organoelement compounds, Russian academy of sciences,28,Vavilova Str,117813 Moscow,Russia
b Département de chimie physique des réactions, UMR 7630 CNRS-INPL,Groupe ENSIC, 54000 Nancy,France
c INSERM ERIT-M 0104 'Ingenierie de la Vectorisation Particulaire' Immeuble IBT,Angers,France
d Université de Pau et des pays de l'Adour, Pau, France
e A.N.Kosygin Moscow state textile academy, 117918 Moscow RUSSIAN Federation |
| Abstract |
The electrostatic interpolyelectrolyte complex formation between the hydrophobic cationic polyeletrolyte Eudragit RS and the anionic hydrophilic polyelectrolyte chitosan sulfate at the mehtylene chloride-water interface has been studied by dilational rheometry. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 65 (2008) 43–49 |
| Year |
2008 |
| Autors |
Valery G. Babaka,b, Francis Barosb, Frank Bouryc and Jacques Desbrièresd |
| Estb. |
a DCPR, CNRS UMR 7630, 1 rue Grandville, BP 451, 54001 Nancy Cedex, France
b INEOS RAS, Vavilova Street 28, Moscow 117813, Russian Federation
c INSERM Unité 646 “Ingénierie de la Vectorisation Particulaire” Immeuble IBT, 10 rue André Boquel, 49100 Angers, France
d Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2 av. Président Angot, 64053 Pau Cedex 09, France |
| Abstract |
Strongly adsorbing hydrophobic cationic polyelectrolyte, Eudragit RS, containing ~2.5 mol% of pendent hydrophilic trimethylammonium (TMA) groups irreversibly adsorbs from its methylene chloride (MCl) solution at the MCl/water interface and forms solid-like adsorption layers (ALs). Submitted to periodic dilational deformations with the standard radial frequency ω0 = 0.63 rad/s, these ALs exhibit relatively high dilational storage modulus E′ ~20mN/m and practically zero loss modulus E″ at the bulk concentration CEud =4×10−3 g/L. The frequency scanning of these ALs in the diapason ω= 0.01–0.63 rad/s and the approximation of the experimental dependences E′(ω) and E″(ω) by two relaxation times rheological model makes it possible to estimate the crossing frequency of these ALs determined from the condition E′(ωc) = E″(ωc) as ωc ~5×10−4 rad/s. Upon dissolving the hydrophilic anionic polyelectrolyte, chitosan sulfate (ChS), in the water phase (CChS =3×10−2 g/L) the electrostatic interpolyelectrolyte complexes form at the MCl/water interface. The elasticity moduli E′ and E″ of these mixed AL did not undergo remarkable variations, but the crossing frequency is sharply increased by ~10 times becoming equal to ωc ≅ 3×10−3 rad/s. The increase of ωc certifies for the liquefaction of mixed Eudragit RS/ChS adsorption layers. A remarkable decrease of the storage modulus down to E′ = 8mN/m and simultaneous increase of the crossing frequency up to ωc ≅ 10−2 rad/s occurs upon increasing the concentrations of both components, Eudragit RS and ChS, up to 0.1 g/L. The liquefaction effect in the mixed ALs of oppositely charged polyelectrolytes was explained on the basis of the proposed relaxation mechanism. The effect of the liquefaction of adsorption layers of strongly adsorbing hydrophobic polyelectrolytes by formation of interpolyelectrolyte complexes with hydrophilic polyelectrolytes must be taken into account in the production of nano-capsules and nano-fibers. |
| Magazine |
Journal of physical chemistry B 2005,109,1874-1881 |
| Year |
2005 |
| Autors |
Frederic Tewesa and Frank Bourya |
| Estb. |
a Ingeénierie de la Vectorisation Particulaire, INSERM U 646, Bat. IBT, 10 rue A. Boquel, 49100 Angers, France |
| Abstract |
We have studied the formation of water-CO2 interfaces in the presence of different concentrations of ovalbumin (OVA) by tensiometry and by means of interfacial rheological measurements to obtain some information on the capacity of protein film to stabilize H2O in CO2 emulsion. The formation of pure water-CO2 interface can be described as a two-step phenomenon. The CO2 molecules adsorb onto the water surface and then a reorganization of the interface creates a H2O-CO2 cluster network. This organization occurs at a temperature (40 °C) higher than the higher temperature limit (10 °C) allowing the formation of crystalline structure called CO2 clathrate. Our results show that ovalbumin adsorption from bulk concentrations higher than 0.0229 g/L inhibits the cluster formation for a CO2 pressure less than 80 bar. However, for lower concentrations, the more the CO2 pressure is close to 80 bar, the more OVA adsorption is reduced by the H2O-CO2 cluster network. Moreover, from a pressure of 90 bar, the affinity of OVA for the interface increases and mixed films made of protein molecules and clusters are obtained for the OVA concentrations lower than 1 g/L. |
| Magazine |
Colloids and Surfaces A: Physicochem.Eng.Aspects 293 (2007) 262-271 |
| Year |
2007 |
| Autors |
Lok Kumar Shresthaa, Emi Saitoa, Rekha Goswami Shresthaa, Hiroyuki Katob, Yoshihiko Takaseb and Kenji Aramakia |
| Estb. |
a Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan
b Interface Solution Division, Taiyo Kagaku Co. Ltd., Takara Machi 1-3, Yokkaichi, Mie 510-0844, Japan |
| Abstract |
Foaming properties of dilute aqueous systems of diglycerol fatty acid esters (Qn-D, n = 10, 12, and 14, where n represents the carbon number in the hydrocarbon chain length of the surfactant) has been studied at 25 °C. The aqueous Q14-D system formed highly stable foams, and the foams are stable for several days. The foam stability in the Q10-D and Q12-D systems are significantly low compared to the Q14-D system. However, unlike the foam stability, foamability of the aqueous Q14-D system is low compared to the short chain surfactants Q10-D and Q12-D/H2O systems. Both the foamability and the foam stability were increased on increasing the surfactant concentration in the studied systems. Phase behavior study of the Qn-Ds systems showed the dispersion of Lα in the Q10-D, and Q12-D systems and the dispersion of α-solid in the Q14-D system in water rich region at 25 °C. Stable foam in the Q14-D/H2O system was mainly caused by the finely dispersed small α-solid particles. The average particles diameter of the α-solid and the Lα dispersion from the laser diffraction technique is found less than 4.5 and 3 μm, respectively. The particles diameter of the dispersed phases showed the decreasing tendency with the surfactant concentration. Foam stabilized by the lamellar liquid crystal dispersion in the aqueous solutions of the Q10-D and Q12-D systems are less stable compared to the foam stabilized by the α-solid dispersion in the Q14-D system. Thus it can be said that α-solid dispersion can cause more stable foam compared to the Lα dispersion. The foaming properties of the present systems showed a good correlation with the dynamic interfacial properties such as dynamic surface tension and dynamic surface dilatational elasticity. |
| Magazine |
International Journal of Pharmaceutics 320 (2006) 157–164 |
| Year |
2006 |
| Autors |
A. Malzert-Fréona, S. Vrignauda, P. Saulnierb, V. Lisowskic, J.P. Benoîtb and S. Raulta |
| Estb. |
a Centre d’Etudes et de Recherche sur le Médicament de Normandie, UPRES EA 3915, Département de Pharmacie Galénique,5 rue Vaubénard, 14032 Caen cedex, France
b Inserm U646 Ingénierie de la Vectorisation Particulaire, 10 rue André Boquel, 49100 Angers, France
c Lab. des Aminoacides, Peptides et Protéines (UMR-CNRS 5810), Faculté de Pharmacie,15 Av charles Flahault, 34093 Montpellier cedex 5, France |
| Abstract |
The purpose of the present work is to develop nanoparticles of a new antitubulin agent of the family of tripentones by means of a phase inversion process. Dynamic light scattering, transmission electron microscopy and ζ-potential measurements were used to characterize tripentone loaded nanoparticles. From interfacial tension measurements and from the study of the rheological interfacial properties of the tripentone at the Labrafac®–Solutol® interface, the fraction of tripentone initially present in Labrafac® would stay in the oily core of nanocapsules. Moreover, the interpenetration of some tripentone molecules within the surfactant units helps to the stabilization of the formulated nanoparticles. The encapsulation efficiency was determined by high performance liquid chromatography (HPLC) and was found to be above 95%. In vitro release studies were carried out in blank nanoparticles containing phosphate buffer, pH 7.4, at 37 °C. The drug release kinetics was measured by HPLC. Antiproliferative activity studies on L1210 cells showed that the cytotoxic activity of tripentone was totally recovered after encapsulation of the antitubulin agent in lipid nanoparticles. This study shows that lipid nanocapsules could be a promising and effective carrier for tripentone delivery in the treatment of cancers. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 59 (2007) 194–207 |
| Year |
2007 |
| Autors |
Valery G. Babaka,b, Francis Barosb, Omar Boulanouarc, Frank Bouryd, Michel Frommc, Nathalie R. Kildeevae, Nathalie Ubrichf and Philippe Maincentf |
| Estb. |
a DCPR, CNRS UMR 7630, 1 rue Grandville, BP 451, 54001 Nancy Cedex, France
b INEOS RAS, Vavilova str. 28, Moscow 117813, Russian Federation
c LMN-AC, UMR CEA E4, Université de Franche-Comté, 16 route de Gray, 25030 Besancon, France
d INSERM Unité 646 “Ingénierie de la Vectorisation Particulaire” Immeuble IBT, 10 rue André Boquel, 49100 Angers, France
e MSTU, 1 M.Kaluzhskaya str., 117918 Moscow, Russian Federation
f Lab. de Pharmacie Galénique, Faculté de Pharmacie, Université Henri Poincaré, 54001 Nancy Cedex, France |
| Abstract |
The emulsifying and stabilizing ability of several hydrophobic (insoluble in water and soluble in volatile organic solvents) polymers, such as Eudragit RL, Eudragit RS, PLGA, PCL, and their mixtures, with regard to the methylene chloride (MC)-in-water mini-emulsions, has been compared to the viscosity of MC solutions and to the properties of adsorption and spread monolayers of these polymers.
Eudragits RS and RL contain ~2.5 and ~5 mol% of pendent cationic trimethylammonium (TMA) groups per ~164 g/mol segments, whereas PLGA and PCL contain 1 and 2 polar carbonyl groups per 130 and 114 g/mol, respectively. The electrostatic attraction between the dipoles, formed by TMA groups and the condensed counter ions in the MC solutions, leads to the contraction of macromolecular coils of Eudragits, whereas the PLGA and PCL macromolecules, interacting by low polar carbonyl groups (with dipole moment μ= 2.7 D) retain more extended conformation in MC. This explains why the characteristic viscosities [η] of MC solutions are much lower for the former polymers (~0.1 dL/g) with regard to PLGA and PCL solutions whose [η] is equal to 0.3 and 0.6 dL/g, respectively.
The ionization of TMA groups in contact with the water phase leads to the irreversible adsorption of Eudragits at the MC/water interface and to high decrease of the interfacial tension γ (down to 4 mN/m for the 5% MC solutions). Whereas PLGA and PCL possessing low polar carbonyl groups adsorb poorly at the MC/water interface exhibiting γ ≅ 28 mN/m. Higher stability of spread monolayers of Eudragits (π* ~40 mN/m) with regard to PLGA and PCL (π* < 20 mN/m) correlates well with higher interfacial activity of the former with regard to the later. The higher surface potential ΔV of Eudragits (0.9 V) with regard to PLGA (0.3 V) and PCL (0.4 V) is explained by the formation of electric double layer (DL) by the former, whereas the later contribute to the ΔV only by cumulative dipole moments of carbonyl groups. The experimental values of surface potentials correlate well with the Gouy–Chapman model of the DL and the Helmholtz model of the monolayer.
The ensemble of experimental results leads to the conclusion that higher emulsifying and stabilizing ability of Eudragits with regard to PLGA and PCL is due to higher adsorption activity of the former which form the corona of polymeric chains with ionized TMA groups around the droplets. It can be postulated that Eudragit polymers have good surface active properties which may allow manufacturing of biocompatible nanoparticles by emulsification–solvent evaporation method without surfactants. |
| Magazine |
International Journal of Pharmaceutics 242 (2002) 405–409 |
| Year |
2002 |
| Autors |
A. Malzerta, F. Bourya, D. Renardb, P. Robertb, J.E. Prousta and J.P. Benoîta |
| Estb. |
a ERIT-M 0104 Ingénierie de la Vectorisation Particulaire, Immeuble IBT, 10, rue André Boquel, 49100 Angers, France
b Unité de Physico-Chimie des Macromolécules, INRA, BP 71627, 44316 Nantes Cedex 3, France |
| Abstract |
According to our results concerning the behavior of lysozyme at interfaces, its secondary structure and its enzymatic activity, successful protein encapsulation would need to maintain a pH value far from the enzyme isoelectric point value during the formulation to reduce, in particular, the adsorption of lysozyme molecules at the created interfaces. Moreover, buffers or salt solution must be used in order to keep intact the native secondary conformation of lysozyme, and preserve its enzymatic activity. |
| Magazine |
Journal of Colloid and Interface Science 259 (2003) 398–407 |
| Year |
2003 |
| Autors |
A. Malzerta, F. Bourya, P. Saulniera, Tz. Ivanovab, I. Panaïotovb, J.P. Benoîta and J.E. Prousta |
| Estb. |
a INSERM ERIT-M 0104 “Ingénierie de la Vectorisation Particulaire” Immeuble IBT, 10, rue André Boquel, 49100 Angers, France
b Biophysical Chemistry Laboratory, University of Sofia, James Bourchier str. 1, 1123 Sofia, Bulgaria |
| Abstract |
Adsorption kinetics of films of poly(ethylene glycol) (PEG2000) studied by the dynamic pendant drop method showed that PEG2000 was more tensioactive at the dichloromethane (DCM)–water interface than at the air–water interface. When initially solubilized into DCM, PEG2000 segments would form an adsorbed layer with hydrophobic segments buried into the polymer chains turned toward the organic phase. Compression of this layer, accompanied by viscoelastic effects, led to expulsion of some hydrophilic tails toward the water phase. When initially dissolved in water, adsorption of PEG2000 segments led to an elastic PEG2000 layer organized on both sides of the interface. Results showed that when the PEG2000–PLA50 (poly(D,L-lactide)) copolymer film was adsorbed at the DCM–water interface, it resulted in a mixed layer exclusively turned toward DCM and its rheological properties were governed by PLA50. When adsorption at the DCM– water interface resulted from a physical mixture of PEG2000 and PLA50, rheological properties of the film were influenced by the initial localization of PEG2000 in the bulk phases. In the case of a mixed film formed by the adsorption of PLA50 from DCM and PEG2000 from water, results showed that PEG2000 segments totally pushed those of PLA50 away from the interface and exclusively influenced the behavior of the mixed film. |
| Magazine |
Langmuir, 2009, 25 (4), pp 2322–2330 |
| Year |
2009 |
| Autors |
Matthew A. Mitschea, Libo Wanga, Z. Gordon Jianga, C. James McKnighta and Donald M. Smalla |
| Estb. |
a Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118 |
| Abstract |
ApolipoproteinB (ApoB) is a lipid binding protein that is a nonexchangeable component of chylomicrons, VLDL, and LDL. In the liver and intestinal cells ApoB recruits lipid to form nascent triacylglycerol rich particles cotranslationally in the endoplasmic reticulum membrane which are then processed and secreted to form plasma lipoproteins. The N-terminal domain, which comprises the first 22% of apoB, recruits lipid in a controlled manner. The first 6% (residues 1-291) of the N-terminus does not bind lipid. The first lipid binding domain, including residues 292-782 (B6-17), forms a lipid binding pocket which is predicted to consist of 17 α-helices and 6 β-strands. A structural model based on the X-ray structure of the homologues protein lipovitellin suggests that the N-terminal 6-8 helices and the β-sheet interact with lipid while the C-terminal helices form a structural unit stabilizing the β-sheet. Using isothermal drop tensiometry we showed that ApoB6.4-17 is surface active and binds to a triolein/water interface and exerts 16-19 mN/m of pressure (Π) on that surface. The protein initially adsorbs slowly from aqueous solution to the surface but following compression and re-expansion it reaches equilibrium much faster. When Π exceeds 16.9 mN/m part of the protein is ejected from the surface, but when compressed to high Π the protein is never completely ejected indicating that part of the peptide is irreversibly anchored to the interface. The surface dilation modulus (ε) varies between 25-38 mN/m, and is predominantly elastic with a small viscous component. When compressed at an air/water interface ApoB6.4-17 has a limiting area of ~11 Å2 per amino acid at lift off and only ~7 Å2 per amino acid at the collapse Π (28 mN/m). These values are about half the anticipated values if all the residues are at the surface. This suggests that ApoB6.4-17 retains some globular structure at an interface and does not completely denature at the surface, as many other globular proteins do. We suggest that while bound to the surface ApoB6.4-17 exhibits properties of both α and β structure giving it unique and versatile characteristics at a hydrophobic interface. |
| Magazine |
Journal of Lipid Research, Volume 45,2004 |
| Year |
2004 |
| Autors |
Libo Wanga and Donald M. Smalla |
| Estb. |
a Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118 |
| Abstract |
The region between residues 968 and 1882 of apolipoprotein B (apoB-21 to apoB-41) is rich in amphipathic βstrands (AβSs) and promotes the assembly of primordial triacylglyceride (TAG)-rich lipoproteins. To understand the importance of AβS in recruiting TAG, the interfacial properties of two AβS consensus peptides, P12 and P27, were studied at dodecane/water (DD/W) and triolein/ water (TO/W) interfaces. P12 (acetyl-LSLSLNADLRLK-amide) and P27 (acetyl-LSLSLNADLRLKNGNLSLSLNADLRLK-amide), when added into the aqueous phase surrounding a suspended oil drop (dodecane or triolein), decreased the interfacial tension (γ) in a concentrationdependent manner. At the DD/W interface, 1 × 10-5 M P12 decreased γ to ~ 20 mN/m and 6.6 × 10-6 M P27 decreased γ to ~ 13 mN/m. At the TO/W interface, 1.5 × 10-5 M P12 decreased γ to ~ 14 mN/m and 9.0 × 10-6 M P27 decreased γ to ~ 12 mN/m. The surface area of both peptides was between 11.2 and 15.1 Å2 per residue, consistent with β sheets lying flat on DD/W and TO/W interfaces. P12 and P27 are almost purely elastic on DD/W, TO/W, and air/water interfaces. When P12 and P27 were compressed beyond the equilibrium γ to as low as 4 mN/m, they could not be readily desorbed from either interface. These properties probably help in assembling nascent TAG-rich lipoproteins, and AβS may anchor apoB to β lipoproteins. |
| Magazine |
Journal of biological chemistry,Vol.278, No.39, 2003 |
| Year |
2003 |
| Autors |
Libo Wanga, David Atkinsona and Donald M. Smalla |
| Estb. |
a Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118 |
| Abstract |
Amphipathic α-helices are the main structure and the major lipid binding motif of exchangeable apolipoproteins. To understand how these apolipoproteins behave at an hydrophobic lipoprotein interface, the interfacial properties of a consensus sequence peptide (CSP) derived from three exchangeable apolipoproteins (A-I, A-IV, and E) were studied using an oil drop tensiometer at air/water (A/W) and dodecane/water (DD/W) interfaces. CSP ((PLAEELRARLRAQLEELRERLG)2-NH2) contains two 22-amino acid tandem repeat sequences that form amphipathic α-helices. CSP, when added into the aqueous phase, lowered the interfacial tension (γ) of A/W and DD/W in a concentration-dependant fashion. The γA/W was lowered ~24 mN/m, and γDD/W ~31 mN/m, indicating a greater affinity of CSP for DD/W. Using the Gibbs equation for surface, the surface area per CSP molecule was estimated at ~702 Å2 (~16 Å2/amino acid) on A/W and ~622 Å2 on DD/W (~14 Å2/amino acid) suggesting that adsorbed CSP lies flat with α-helices in the plane of both interfaces. At equilibrium γ, CSP desorbed from the interface when compressed and re-adsorbed when expanded. The adsorption rate was concentrationdependant, but the desorption rate was not. Less CSP desorbed from DD/W than A/W indicating that CSP has higher affinity for DD/W. Dynamic analysis of elasticity shows that the faster the oscillation period (4, 8 s) and the lower the oscillation amplitude the more elastic the surfaces. CSP can be compressed 6–12% while remaining on the surface, but large increases in pressure eject it from the surface. We suggest that surface pressuremediated desorption and readsorption of amphipathic α-helices provide lipoprotein stability during remodeling reactions in plasma. |
| Magazine |
Journal of biological chemistry |
| Year |
|
| Autors |
Libo Wanga, David Atkinsona and Donald M. Smalla |
| Estb. |
a Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118 |
| Abstract |
Amphipathic α-helices are the main structure and the major lipid binding motif of exchangeable apolipoproteins. To understand how these apolipoproteins behave at an hydrophobic lipoprotein interface, the interfacial properties of a consensus sequence peptide (CSP) derived from 3 HDL exchangeable apolipoproteins (A-I, A-IV and E) were studied using an oil drop tensiometer at air/water (A/W) and dodecane/water (DD/W) interfaces. CSP ((PLAEELRARLRAQLEELRERLG)2-NH2) contains two 22 a.a. tandem repeat sequences that form amphipathic α-helices. CSP when added into the aqueous phase, lowered the interfacial tension (γ) of A/W and DD/W in a concentration dependant fashion. The γA/W was lowered ~ 24mN/m and γDD/W ~ 31mN/m indicating a greater affinity of CSP for DD/W. Using the Gibbs equation for surface, the surface area per CSP molecule was estimated ~702Å2 (~16 Å2 /a.a.) on A/W and ~622Å2 on DD/W (~14 Å2 /a.a.) suggesting that adsorbed CSP lies flat with α helices in the plane of both interfaces. At equilibrium γ, CSP desorbed from the interface when compressed and re-adsorbed when expanded. The adsorption rate was concentration dependant but the desorption rate was not. Less CSP desorbed from DD/W than A/W indicating that CSP has higher affinity for DD/W. Dynamic analysis of elasticity shows that the faster the oscillation period (4, 8sec) and the lower the oscillation amplitude the more elastic the surfaces. CSP can be compressed 6-12% while remaining on the surface but large increases in pressure eject it from the surface. We suggest that surface pressure mediated desorption and readsorption of amphipathic alpha helices provide lipoprotein stability during remodeling reactions in plasma. |
| Magazine |
Colloids and Surfaces B: Biointerfaces 80 (2010) 125–132 |
| Year |
2010 |
| Autors |
Magali Deleua, Guadalupe Vaca-Medinab, Jean-François Fabreb, Julie Roïza, Romain Valentinb and Zéphirin Moulounguib |
| Estb. |
a Unité de Chimie biologique industrielle, Gembloux Agro-Bio Tech, Université de Liège, 2 Passage des Déportés, B-5030 Gembloux, Belgium
b Université de Toulouse - UMR1010 Chimie Agro-industrielle, ENSIACET, INPT, INRA, 4, allée Emile Monso – BP 44362, F-31432 Toulouse Cedex 4, France |
| Abstract |
Oleosins are plant proteins associated with phospholipids in seed oil bodies. The ability of oleosins to aid in the emulsification and stabilization of oil bodies is well known, but little information is available on their interaction with phospholipids at the interface between oil bodies and aqueous medium. Oil body reconstitution at various phospholipid/oleosin ratios was carried out to observe how rapeseed oleosins of 20 kDa and rapeseed phospholipids affect oil body stability. Phospholipids are needed to stabilize oil droplets, but oleosins are mandatory to avoid coalescence. We thus characterized how phospholipids affect the interfacial properties of oleosins at pHs 5.5 and 8.5, by analyzing the adsorption kinetics and interfacial dilational rheology. We observed a synergic effect between oleosins and phospholipids in increasing surface pressure at both pHs. This kind of effect was also observed for the dilational modulus at pH 5.5. A thermodynamic approach highlights these synergic interactions between oleosins and phospholipids through a positive deviation from ideality. |
| Magazine |
J Incl Phenom Macrocycl Chem |
| Year |
2010 |
| Autors |
Anca Laza-Knoerra, Nicolas Huanga, Jean-Louis Grossiorda, Patrick Couvreura and Ruxandra Grefa |
| Estb. |
a UMR CNRS 8612, Chatenay-Malabry, France |
| Abstract |
The aim of this work is to characterize rheologically the interfacial properties of oil/water interfaces stabilized with β-cyclodextrin (CD)-based inclusion complexes. Interfacial experiments were conducted using two different hydrophobic oils: Parsol MCX and Squalene. Dilatational interfacial rheology was performed with a dynamic drop tensiometer, allowing the determination of the interfacial tension from the drop profile, and the calculation of rheological values (phase angle, elastic and viscous moduli) from the correlation between the drop area and the interfacial tension sinusoidal variations. Practically, an oil drop was formed in the aqueous phase containing the CD-derivative. With Parsol MCX, no correlation was observed, indicating that surfactants were not adsorbed at the interface. With Squalene, two β-CD-derivatives were used: monomers and polymers. With monomers, a solid membrane was created, impeding any rheological measurements. This is consistent with the crystallization of the system and the impossibility to formulate an emulsion with monomers. With polymers, an effective correlation of the drop area with the interfacial tension variation demonstrated the adsorption of the CDcomplex at the interface. Rheological values clearly indicated the formation of an elastic interface, preventing droplets coalescence: an emulsion formulated with β-CD polymers results in a better stabilization. |
| Magazine |
|
| Year |
2009 |
| Autors |
I. MINKOVa, TZ. IVANOVAa, I. PANAIOTOVa, J. E. PROUSTb and P. SAULNIERb |
| Estb. |
a Biophysical Chemistry Laboratory, University of Sofia, James Bourchier Str. 1, 1164 Sofia, Bulgaria
b INSERM U 646 “Ingenierie de la Vectorisation Particulaire” Université d’Angers, Immeuble IBT, 10 rue A.Boquel, 49100 Angers, France |
| Abstract |
For the first time, a positive effect of permanent magnetic field on the alternating copolymerization (AC) of maleic anhydride (MA) with styrena (S), vinyl acetate (VA) and 2, 2, 4-trimethylheptane acid vinyl ester (VH) has been established. The application of a magnetic field not only accelerates AC, but also increases the tendency to alternation of the copolymers obtained. The curves describing the acceleration as a function of the magnetic induction (B) have a maximum. The experimental dependences are explained by the specific effect of B on the spin evolution of covalently bonded radical pairs (RPs), formed according to the scheme for bond-forming initiation of AC proposed by Hall. This specific effect is expressed by an induced-resonance exchange interaction between RPs and the donor-acceptor complexes according to the Förster mechanism. The latter makes possible the transformation of RPs into biradicals capable to participate in the growth and completion of the copolymer chain. In this way, the results obtained confirm the Hall’s scheme and also broaden the contribution of the formed RPs not only to the initiation, but also to the completion of the copolymer chain. These possibilities are experimentally proved and theoretically discussed in the present paper. |
| Magazine |
European Journal of Lipid Science and Technology 2000, 133-153 |
| Year |
2000 |
| Autors |
Frédéric Beissona, Ali Tissa, Claude Rivièrea and Robert Vergera |
| Estb. |
a Lab. de Lipolyse Enzymamatique(UPR9025 du CNRS),inst.de biologiestructurate et microbiologie(IFR1 du CNRS et d'Université méditerranée),31ch.Joseph-aiguier,13402 Mar.Fr. |
| Abstract |
|
| Magazine |
Methods in Enzymology, Vol 286,1997 |
| Year |
1997 |
| Autors |
A.Cagnaa, G.Espositoa, S.Labourdenne, B.Delorme, R.Verger and C.Riviere |
| Estb. |
a IT Concept, Longessaigne 69770, France |
| Abstract |
|
| Magazine |
Langmuir, Vol 17, No.26,2001 |
| Year |
2001 |
| Autors |
A.Cagnaa, P.Saulnierb, F.Bouryb, A.Malzertb, B.Heurtaultb, Tz.Ivanovac, I.Panaïotovc and J.E.Proustb |
| Estb. |
a IT Concept, Longessaigne 69770, France
b Ingénierie de la Vectorisation Particulaire, INSERM ERIT-M No.0104,Bat.IBT,10 rue A. Boquel, 49100 Angers, France
c Biophysical chemistry labo, university of sofia, James bourchier str,1,1123 Sofia,Bulgaria |
| Abstract |
The dilational properties of monolayers are analyzed using the classical linear approximation. In most cases, the observed interfacial behavior can be approached by a model corresponding to a two-dimensional viscoelastic solid. The monolayer is characterized by two dilational elasticity terms (Ee, equilibrium elasticity, and Ene, nonequilibrium elasticity) and by one relaxation time (r). These three physical constants are obtained from the responses of a ramp type perturbation, or from the responses (as a function of the frequancies) after sinusoidal area variations. Using axisymmetric drop shape analysis experiments, a dipalmitoyl phosphatidylcholine (DPPC) layer at the dichloromethane/water interface is characterized. Measurements of the surface pressure variations as the response to linear or sinusoidal variations of surface area are performed. Identical rhelogical physical constants (equilibrium elasticity, nonequilibrium elasticity, and relaxation time) are obtained using both methods. Dilational behavior of DPPC monolayer can be attributed to the molecular diffusion between the DPPC layer and the adjacent phases. |
| Magazine |
Langmuir 2002, 18, 10248-10254 |
| Year |
2002 |
| Autors |
A. Malzerta, F. Bourya, P. Saulniera, J. P. Benoîta and J. E. Prousta |
| Estb. |
a Ingénierie de la Vectorisation Particulaire, INSERM ERIT-M No.0104,Bat.IBT,10 rue A. Boquel, 49100 Angers, France |
| Abstract |
The dilational rheological properties of interfacial films of poly(ethylene glycol) (PEG2000) and hen egg-white lysozyme (HEWL) were studied respectively at the dichloromethane (DCM)-water and airwater interfaces by means of the pendant drop method. In both cases, the observed interfacial behaviors were approached by a model corresponding to a two-dimensional viscoelastic solid. The interfacial layers were characterized by three physical constants: Ee, the equilibrium elasticity, Ene, the nonequilibrium elasticity, and τ, the relaxation time. Because the interfacial dilational properties of the films were studied by using a ramp type perturbation approach or a sinusoidal variations approach, identical rheological physical constants values were obtained for PEG2000 and HEWL. From these studies, the interactions within the interfacial layer and those between the interfacial film and adjacent phases can be indirectly accessed and estimated. |
| Magazine |
Rheol Acta |
| Year |
2010 |
| Autors |
Hammadi Nciria, Nicolas Huanga, Véronique Rosilioa, Malika Trabelsi-Ayadib, Mémia Benna-Zayanib and Jean-Louis Grossiordb |
| Estb. |
a Faculté de Pharmacie, Univ Paris-Sud 11, UMR 8612, 5 Rue Jean Baptiste-Clément, 92296 Châtenay-Malabry Cedex, France
b Faculté des Sciences de Bizerte, Laboratoire d’Applications de la Chimie aux Ressources et Substances Naturelles et à l'Environnement |
| Abstract |
The rheological behavior and interfacial properties of olive oil–water emulsions stabilized by surfactant and clay particles (smectite) were studied to evaluate the effect of particles and surfactant distribution both in the bulk phase and at the oil–water interface. The temperature sweep of surfactant solutions and emulsions with and without clay particles showed the critical effect of the solid particles on the viscosity change. The mechanism of adsorption of surfactant molecules onto clay particles has a direct impact on the micellization and gelling temperatures. Indeed, the presence of clay particles caused a slight decrease in the micellization temperature and a total cancellation of the gelling phenomenon. Dynamic interfacial tension values demonstrated that clay particles would not compete with the surfactant for adsorption at the interface. However, the significant increase in the elastic properties of the interface that was observed accounts for their accumulation in the vicinity of the interface, probably at the level of surfactant polar head groups. Thus, the clay particles would form a mechanical barrier, preventing coalescence of emulsion droplets. |
| Magazine |
Journal of bilbogical chemistry Vol.280, No.46,pp.38576-38582, 2005 |
| Year |
2005 |
| Autors |
Kevin Pearsona, Matthew R. Tubba, Masafumi Tanakab, Xiu Qi Zhangc, Patrick Tsoa, Richard B. Weinbergd and W. Sean Davidsona |
| Estb. |
a Department of Pathology and Laboratory Medicine, The University of Cincinnati, Cincinnati, Ohio 45237
b Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
c Department of Chemistry, University of Illinois , Chicago, Illinois 60607
d Departments of Internal Medicine and Physiology and Pharmacology,Wake Forest University, Winston-Salem, North Carolina 27157 |
| Abstract |
Apolipoprotein (apoA-IV) is a 376-residue exchangeable apolipoprotein that may play a number of important roles in lipid metabolism, including chylomicron assembly, reverse cholesterol transport, and appetite regulation. In vivo, apoA-IV exists in both lipidpoor and lipid-associated forms, and the balance between these states may determine its function. We examined the structural elements that modulate apoA-IV lipid binding by producing a series of deletion mutants and determining their ability to interact with phospholipid liposomes. We found that the deletion of residues 333–343 strongly increased the lipid association rate versus native apoA-IV. Additional mutagenesis revealed that two phenylalanine residues at positions 334 and 335 mediated this lipid binding inhibitory effect.Wealso observed that residues 11–20 in theNterminus were required for the enhanced lipid affinity induced by deletion of the C-terminal sequence. We propose a structural model in which these sequences can modulate the conformation and lipid affinity of apoA-IV. |
| Magazine |
Journal of lipid research |
| Year |
2008 |
| Autors |
Aubrey S. Ledforda, Victoria A. Cooka, Gregory S. Shelnessa and Richard B. Weinberga |
| Estb. |
a Departments of Pathology, Internal Medicine, and Physiology & Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157 |
| Abstract |
To better understand the earliest steps in the assembly of triglyceride-rich lipoproteins, we compared the biophysical and interfacial properties of two closely related apolipoprotein B (apoB) truncation mutants, one of which contains the complete lipoprotein initiating domain (apoB20.1; residues 1-912), and one of which, by virtue of a 50 amino acid C-terminal truncation, is incapable of forming nascent lipoproteins (apoB19; residues 1-862). Spectroscopic studies detected no major differences in secondary structure, and only minor differences in conformation and thermodynamic stability between the two truncation mutants. Monolayer studies revealed that both proteins bound to and penetrated egg phosphatidylcholine monolayers; however, the interfacial exclusion pressure of apoB20.1 was higher than apoB19 (25.1 mN/m vs. 22.8 mN/m). Oil drop tensiometry demonstrated that both proteins bound rapidly to the hydrophobic triolein/water interface, reducing interfacial tension by ~20 mN/m. However, when triolein drops were first coated with phospholipid, apoB20.1 bound with faster kinetics than apoB19 and displayed greater interfacial elasticity (26.9 ± 0.8 mN/m vs. 22.9 ± 0.8 mN/m). These data establish that the transition to assembly competence by apoB is accompanied by increases in surface activity and elasticity, but not by significant changes in global structure. |
| Magazine |
Journal of bilbogical chemistry Vol.278, No.36,pp.34438-34444, 2003 |
| Year |
2003 |
| Autors |
Richard B. Weinberga, Victoria R. Cooka, Jennifer A. Becksteada, Dale D. O. Martina, James W. Gallaghera, Gregory S. Shelnessa and Robert O. Ryana |
| Estb. |
a Departments of Internal Medicine, Physiology and Pharmacology, and Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157 and Children’s Hospital Oakland Research Institute, Oakland, California 94609 |
| Abstract |
Apolipoprotein A-V (apoA-V), the newest member of the plasma apolipoprotein family, was recently discovered by comparison of the mouse and human genomes. Studies in rodents and population surveys of human apoA-V polymorphisms have noted a strong effect of apoA-V on plasma triglyceride levels. Toward the elucidation of the biologic function of apoA-V, we used spectroscopic and surface chemistry techniques to probe its structure and interfacial activity. Computer-assisted sequence analysis of apoA-V predicts that it is very hydrophobic, contains a significant amount of α-helical secondary structure, and probably is composed of discrete structural regions with varying degrees of lipid affinity. Fluorescence spectroscopy of recombinant human apoA-V provided evidence of tertiary folding, and light scattering studies indicated that apoA-V transforms dimyristoylphosphatidylcholine vesicles into discoidal complexes with an efficiency similar to that of apoA-I. Surface chemistry techniques revealed that apoA-V displays high affinity, low elasticity, and slow binding kinetics at hydrophobic interfaces, properties we propose may retard triglyceride-rich particle assembly. Metabolic labeling and immunofluorescence studies of COS-1 cells transfected with human apoA-V demonstrated that apoA-V is poorly secreted, remains associated with the endoplasmic reticulum, and does not traffic to the Golgi. Given that overexpression of the apoA-V gene lowers plasma triglycerides in mice, these data together suggest that apoA-V may function intracellularly to modulate hepatic VLDL synthesis and/or secretion. |
| Magazine |
Journal of Microbiological Methods 70 (2007) 503–510 |
| Year |
2007 |
| Autors |
Chien-Yen Chena, Simon C. Bakerb and Richard C. Dartonc |
| Estb. |
a Department of Earth and Environmental Sciences, National Chung Cheng University, 168 University Road, Min-hsiung, Chia-yi 621, Taiwan
b School of Life Sciences, Oxford Brookes University, Gypsy Lane, Oxford OX3 0BP, UK
c Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK |
| Abstract |
The presence of biosurfactants in growth media can be evaluated by a variety of methods, none of which are suitable for high throughput studies. The method described here is based on the effect of meniscus shape on the image of a grid viewed through the wells of a 96-well plate. The efficacy of the method was demonstrated by the selection of a bacterium (producing a biosurfactant able to reduce the surface tension of pure water from 72 to 28.75 mN m−1) from a culture collection isolated from aviation fuel-contaminated land. The assay was found to be more sensitive, rapid and easy to perform than other published methods. It does not need specialised equipment or chemicals and excludes the bias which results from the surfactant properties of medium used for bacterial growth. |
| Magazine |
Chemistry and Physics of Lipids 150 (2007) 167–175 |
| Year |
2007 |
| Autors |
Nicolas Antona,b, Patrick Saulniera,b, Frank Bourya,b, Françoise Foussardc, Jean-Pierre Benoita,b,d and Jacques E. Prousta,b |
| Estb. |
a Inserm U646, Ingénierie de la Vectorisation Particulaire, 10 rue A. Boquel, F-49100 Angers, France
b University of Angers, F-49100 Angers, France
c Lab. de Biochimie, Faculté de Pharmacie, 16 bd Daviers, F-49100 Angers, France
d Ecole Pratique des Hautes Etudes (EPHE), 12 rue Cuvier, F-75005 Paris, France |
| Abstract |
This paper compares six phospholipidic monolayers at the water/chloroform interface by performing dilational rheological measurements with a drop tensiometer apparatus. The chosen lipids differ both in their headgroup structure and fatty acyl chain saturation or symmetry. The study concentrated on monolayers formed with DPPC, DPPE, DOPC, DOPE, POPC and POPE. Using a generalized Maxwell rheological model, transposed at the interface, the intimate intermolecular interactions between amphiphilic molecules are studied on and off the monolayer plane. The equilibrium and nonequilibrium phenomena are analyzed and, respectively, correlated with monolayer cohesion and with monolayer/sub-surface interactions. The purpose of this work is to gain further insights into the influences (as slight as they are) of the weak changes in phospholipid structure and on the behavior of the monolayers. The results, widely described, provide further details on nuances existing between very similar molecules, and likewise, on the synergies created between the different effects. |
| Magazine |
Journal of bilbogical chemistry Vol.280, No.6,pp.4154-4165, 2005 |
| Year |
2005 |
| Autors |
Libo Wanga, David Atkinsona and Donald M. Smalla |
| Estb. |
a Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118 |
| Abstract |
Apolipoprotein A-I (apoA-I) is the major protein in high density lipoprotein (HDL). During lipid metabolism, apoA-I moves among HDL and triacylglycerol-rich lipoproteins. The main structure and the major lipid binding motif of apoA-I is the amphipathic α-helix. To understand how apoA-I behaves at hydrophobic lipoprotein interfaces, the interfacial properties of apoA-I and an amphipathic α-helical consensus sequence peptide (CSP) were studied at the triolein/water (TO/W) interface. CSP ((PLAEELRARLRAQLEELRERLG)2-NH2) contains two 22-residue tandem repeat sequences that form amphipathic α-helices modeling the central part of apoA-I. ApoA-I or CSP added into the aqueous phase surrounding a triolein drop lowered the interfacial tension (γ) of TO/W in a concentration- and time-dependent fashion. The γTO/W was lowered ~16 millinewtons (mN)/m by apoA-I at 1.4 × 10-6 M and ~15 mN/m by CSP at 2.6 × 10-6 M. At equilibrium γ, both apoA-I and CSP desorbed from the interface when compressed and readsorbed when expanded. The maximum surface pressure CSP could withstand without being ejected (ΠMAX) was 16 mN/m. The ΠMAX of apoA-I was only 14.8 mN/m, but re-adsorption kinetics suggested that only part of the apoA-I desorbed at Π between 14.8 and 19 mN/m. However, above ~19 mN/m (ΠOFF) the entire apoA-I molecule desorbed into the water. ApoA-I was more flexible at the TO/W interface than CSP and showed more elasticity at oscillation periods 4–128 s even at high compression, whereas CSP was elastic only at faster periods (4 and 8 s) and moderate compression. Flexibility and surface pressure-mediated desorption and re-adsorption of apoA-I probably provides lipoprotein stability during metabolic-remodeling reactions in plasma. |
| Magazine |
Journal of Physical Chemistry B |
| Year |
2003 |
| Autors |
Frédéric Tewesa and Frank Bourya |
| Estb. |
a Ingénierie de la Vectorisation Particulaire, INSERM ERIT-M No.0104,Bat.IBT,10 rue A. Boquel, 49100 Angers, France |
| Abstract |
We have measured the interfacial tension (γ) between H2O and CO2 with a drop tensiometer that permitted us to regulate the drop area and to perform elasticity measurements. We observed that γ decreased with time and with the CO2 pressure. We first analyzed the adsorption of CO2 onto surface water by plotting the initial interfacial tension (γ0) versus CO2 fugacity and applied Gibbs and then Langmuir-Freundlich equations. We have calculated the interfacial area occupied by CO2 molecules onto H2O as well as the equilibrium constant and the thermodynamics parameters of adsorption. This permitted us to understand that the CO2 was adsorbed onto the surface water by formation of a one-to-one H-type complex with H2O. Second, we attributed the kinetics phenomena to the formation of interfacial clusters between water and CO2, which gave interfacial quasi-crystalline structure as shown by compression of the drop area at the end of the adsorption kinetics. We studied this interfacial organization by measuring the apparent elasticity versus time and CO2 pressure. This measurement allowed us to propose an interfacial organization based on the formation of small blocks, which grow to fill the interface, as already observed by Teng and al. Then we determined the filling of the clusters cavities by analyzing the difference between γ0 and γeq (Δγ) by means of the Hill equation. This permitted us to determine that this filling depended on temperature and was cooperative. |
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