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At least 19 recordsLinked to original sources

PubMed2000

Coalescence-Induced Coalescence of Inviscid Droplets in a Viscous Fluid.

A comprehensive simulation of the coarsening mechanism coalescence-induced coalescence (CIC) is developed to predictthe growth rate of inviscid droplets in a viscous matrix fluid. In CIC, the shape relaxations of coalescing droplets establish flow fields that drive other droplets into contact, thus creating a cascade of coalescence events. It is believed that CIC is responsible for droplet growth in some demixed polymer solutions, such as isotactic polypropylene (iPP) and diphenyl ether (DPE). A cascade of coalescence events is simulated using a three-dimensional molecular dynamics-like simulation of a dispersed two-phase isopycnic fluid system. The coalescence-induced flow is driven mostly by the strong gradients in curvature at the neck of a coalescing pair of droplets, and the flow is modeled analytically by approximating it as due to a ring of point forces. The resultant velocity of each droplet in the suspension is calculated by superimposing all of the coalescence-induced flow fields and applying Faxen's Law. The mean droplet size grows like t(xi), where t is the coarsening time and xi a growth exponent that increases with increasing minority phase volume fraction varphi. Good agreement with experimental values of xi (0.22 /=0.23. It is also shown that the droplet size distribution broadens for semidilute suspensions (varphi</=0.42) but remains relatively narrow for highly concentrated suspensions (varphi>/=0.54). A phenomenological kinetic theory of coalescence is proposed. It is believed that in nondilute emulsions, CIC can account for coarsening that has been attributed previously to more traditional coalescence mechanisms. Copyright 2000 Academic Press.

Journal Article↗

PubMed2005

Coalescence-induced coalescence and dimensional crossover during the phase separation in ternary surfactant/polymer/water mixtures.

We studied the separation process in the ternary mixtures of nonionic surfactant (C(12)E(6), hexaethylene glycol monododecyl ether), polymer (PEG = poly(ethylene glycol)), and water. The separation process of PEG/water rich domains from the surfactant rich matrix was observed by the optical microscopy. From the morphological analysis, we determined the size of the domains as a function of time. On this basis we identified a dominating mechanisms of domains growth, that is the coalescence-induced coalescence mechanism. The coalescence (collision) event of two droplets induces a flow or a change of concentration distribution around droplets which pushes other droplets together inducing further growth. We also observed the evaporation-condensation (Lifshitz-Slyozov) mechanism of growth, but it did not affect the growth of large domains appreciably. We determined two regimes of the coalescence-induced coalescence associated with the dimensionality of the system. When the domains were smaller or comparable in size to the sample thickness we observe a three-dimensional growth. When the domains became larger than the sample thickness, a two-dimensional growth was observed. In the first regime, the size of the domains, L(t), grew linearly with t, while in the second regime, L(t) approximately t(0.3). In the binary, surfactant/water system, water domains grew by the geometrical coalescence-induced coalescence as L(t) approximately t in three dimensions.

Journal Article↗

PubMed2004

Reflectivity-based evaluation of the coalescence of two condensing drops and shape evolution of the coalesced drop.

Image analyzing interferometry is used to study the details of the evolving shapes and coalescence of two condensing drops of 2-propanol on a quartz surface. The measured thickness profiles give fundamental insights into the transport processes within the drops before and after coalescence and the evolution of the coalesced drop from asymmetric to symmetric shape. The results indicate that the constant value of the adsorbed film thickness between the drops and profiles of the local thickness, slope angle, curvature, and curvature gradient govern the pressure fields in the coalescing drops. The shape evolution after coalescence is found to be driven by the capillary forces within the drop. Using the experimental data, we find that the calculations of the average shear stress for the fluid flow between the drops, the decrease in the interfacial excess energy, and the positions of the center of mass of the drops explain the physics of the coalescence phenomenon. However, the flow field is found to be complex because the pressure field indicates that there are complicated flows within the drop.

Journal Article↗

PubMed2006

The coalescence time of sampled genes in the structured coalescent model.

The aim of this article is to investigate the distribution of the coalescence time (T) for sampled genes in the structured coalescent. We obtain some exact solutions for small samples and approximate distributions for n sampled genes in strong and weak migration. We also conduct computer simulation to evaluate efficiencies of these approximations and show the dependency of the distribution of the coalescence time on the geographical structure and the intensity of migration. In a panmictic population, we prove that the conditional distribution of the coalescence time given the number of segregating sites (S) among sampled genes is given by the weighted mean of the convolution of gamma distributions. We also study the joint distribution of T and S in the structured coalescent model and show some exact solutions.

Analysis of Variance↗

PubMed1999

Coalescence of Lipid Emulsions in Floating and Freeze-Thawing Processes: Examination of the Coalescence Transition State Theory.

Lipid emulsions, triacylglycerol droplets covered with single surface monolayers of phospholipid in aqueous medium, were prepared by high-pressure emulsification and successive ultracentrifugation. Egg yolk phosphatidylethanolamine did not stabilize triolein (TO) droplets in aqueous medium. Phosphatidylcholine (PC) of various long fatty acyl chains dispersed TO and tricaprylin (TC) well in aqueous medium as emulsion droplets of 110 nm. After ultracentrifugation, however, oil separation was observed in the floating creamy layer of TO/dioleoyl-PC emulsions. Dioleoyl-PC contains two bulky unsaturated fatty acyl chains, as well as oleoyl chains, and it has a lower spontaneous curvature than egg PC. Egg PC and dipalmitoyl-PC gave stably dispersed emulsion droplets of TO even after the freeze-thawing (F-T) procedure. On the other hand, TO/egg PC emulsion droplets containing cholesterol of 83 mol% PC and TC/egg PC emulsion droplets coalesced after the F-T procedure. Cholesterol and a medium chain triacylglycerol, TC, were distributed into the surface PC monolayers and occupied an appreciable fraction of the surface area. These neutral lipids have small polar groups and thus decrease the mean spontaneous curvature of surface lipids. The relationship between the droplet coalescence and the spontaneous curvature was discussed on the basis of the coalescence transition state theory recently developed by Kabalnov et al. in 1996. In addition, effects of maltose on the emulsion coalescence in the freeze state were briefly discussed. Copyright 1999 Academic Press.

Journal Article↗

PubMed2002

Coalescence during emulsification. 3. Effect of gelatin on rupture and coalescence.

An oil-soluble fluorescent probe, undecyl pyrene (UDP), is used to measure the amount of coalescence that occurs during the emulsification of tri-2-ethylhexyl phosphate using a high-pressure homogenizer. From these measurements, the roles of anionic surfactant (SDS) and gelatin in stabilizing drops against coalescence and promoting drop rupture during emulsification are deduced. It is found that gelatin aids in reducing coalescence, whereas SDS aids in rupture of drops. The effect of variables such as gelatin MW, surfactant type, and pH on coalescence and final drop size is investigated.

Journal Article↗

PubMed1999

Coalescing into the 21st century: An overview and prospects of coalescent theory.

Coalescent theory represents the most significant progress in theoretical population genetics in the past two decades of this century. It is now widely recognized as a cornerstone for rigorous statistical analyses of molecular data from populations. In the future, challenges from the rapidly expanding body of molecular data will continue to inject fresh blood into the development of coalescent theory. As the 21st century looms, we review recent progress in coalescent theory and discuss some prospects for future developments, particularly with regard to human population genetics.

Algorithms↗

PubMed2006

Phase separation in binary polymer/liquid crystal mixtures: network breaking and domain growth by coalescence-induced coalescence.

A small-angle light scattering (SALS) technique together with optical microscopy observation are used to investigate phase separation kinetics in films of low molecular weight thermotropic liquid crystal (4-cyano-4'-n-octyl-biphenyl, 8CB) with flexible polymer (polystyrene, PS). The growth of domains is studied as a function of time, film thickness, and film composition. The light scattering results are correlated with the images obtained by optical microscopy observation. In this paper, we study the breaking of a bicontinuous network of polymer in liquid crystal into droplets and their further growth via the coalescence-induced coalescence mechanism. The appearance of droplets in the system leads to a strong scattering at small wave vectors, while the bicontinuous network gives a peak at a nonzero wave vector. Superposition of these scattering intensities leads to the appearance of a second peak in the full scattering intensity signal, when the bicontinuous network starts to break up into disjointed elongated domains. Finally, both peaks merge into a single peak, which moves quickly toward zero wave vectors, indicating a complete transformation of elongated domains into spherical droplets of variable size. We found that the separation process does not depend on the size of the system. Irrespective of the sample thickness, the network breaks into fragments always at the same time after temperature quench. On the basis of morphological analysis, we found that the average size of the droplets which formed from the network grows with time, t, as t(alpha), alpha = 0.9 +/- 0.1, in the isotropic phase and in the nematic phase.

Journal Article↗

PubMed2006

Exact coalescent for the Wright-Fisher model.

The Kingman coalescent, which has become the foundation for a wide range of theoretical as well as empirical studies, was derived as an approximation of the Wright-Fisher (WF) model. The approximation heavily relies on the assumption that population size is large and sample size is much smaller than the population size. Whether the sample size is too large compared to the population size is rarely questioned in practice when applying statistical methods based on the Kingman coalescent. Since WF model is the most widely used population genetics model for reproduction, it is desirable to develop a coalescent framework for the WF model, which can be used whenever there are concerns about the accuracy of the Kingman coalescent as an approximation. This paper described the exact coalescent theory for the WF model and develops a simulation algorithm, which is then used, together with an analytical approach, to study the properties of the exact coalescent as well as its differences to the Kingman coalescent. We show that the Kingman coalescent differs from the exact coalescent by: (1) shorter waiting time between successive coalescent events; (2) different probability of observing a topological relationship among sequences in a sample; and (3) slightly smaller tree length in the genealogy of a large sample. On the other hand, there is little difference in the age of the most recent common ancestor (MRCA) of the sample. The exact coalescent makes up the longer waiting time between successive coalescent events by having multiple coalescence at the same time. The most significant difference among various summary statistics of a coalescent examined is the sum of lengths of external branches, which can be more than 10% larger for exact coalescent than that for the Kingman coalescent. As a whole, the Kingman coalescent is a remarkably accurate approximation to the exact coalescent for sample and population sizes falling considerably outside the region that was originally anticipated.

Algorithms↗

PubMed2001

Experimental Investigation of the Orthokinetic Coalescence Efficiency of Droplets in Simple Shear Flow.

The coalescence efficiency of two droplets in simple shear flow was experimentally investigated. The effects of the radius of the colliding droplets, the viscosity of the continuous medium, and the radii ratio on the coalescence efficiency were studied. The coalescence efficiency was determined from the critical angle, alpha(crit), above which the droplets coalesce and below which no coalescence takes place. It was found that the coalescence efficiency decreases and then increases with the flow number. The theories of the drainage models and the trajectory analysis were unable to predict the experimental results. This was attributed to the inadequacy of the existing expression used for the critical film thickness. On the basis of the experimental data obtained a new expression for the critical film thickness was proposed. The new expression predicts a decrease followed by an increase in the critical film thickness. The increase in the critical film thickness is, perhaps, due to instabilities that take place at the interfaces. Implementing the proposed expression for the critical film thickness, the experimentally measured coalescence efficiency, the capture angle and the contact time were successfully predicted. The experimental investigation revealed that the coalescence efficiency does not depend on the radii ratio in the range 0.7 to 1. The experimental investigation also showed that the coalescence efficiency increases as the viscosity of the continuous phase decreases. Measuring the capture angle showed that coalescence can take place either in the compression or in the extensional quadrant of the shear plane. A variation in the capture angle and the contact time was observed for a given fixed set of conditions. The change of the angle alpha with time was measured. The measured values were compared to those calculated from an equation derived by R. S. Allan and S. G. Mason (J. Colloid Interface Sci. 17, pp. 383, 1962). A good agreement was obtained when the droplets were of equal radii and small in size. When the droplets were large in size and of different radii, the agreement was not satisfactory. Measuring the distance between the centers of the colliding droplets showed that the two droplets vibrated when they came close to each other. Copyright 2001 Academic Press.

Journal Article↗

PubMed2005

Coalescence in semiconcentrated emulsions in simple shear flow.

The coalescence frequency in emulsions containing droplets with a low viscosity (viscosity ratio approximately 0.005) in simple shear flow has been investigated experimentally at several volume fractions of the dispersed phase (2%-14%) and several values of the shear rate (0.1-10 s(-1)). The evolution of the size distribution was monitored to determine the average coalescence probability from the decay of the total number of droplets. Theoretically models for two-droplet coalescence are considered, where the probability is given by P(c)=exp(-tau(dr)tau(int)). Since the drainage time tau(dr) depends on the size of the two colliding droplets, and the collision time tau(int) depends on the initial orientation of the colliding droplets, the calculated coalescence probability was averaged over the initial orientation distribution and the experimental size distribution. This averaged probability was compared to the experimentally obtained coalescence frequency. The experimental results indicate that (1) to predict the average coalescence probability one has to take into account the full size distribution of the droplets; (2) the coalescence process is best described by the "partially mobile deformable interface" model or the "fully immobile deformable interface" model of Chesters [A. K. Chesters, Chem. Eng. Res. Des. 69, 259 (1991)]; and (3) independent of the models used it was concluded that the ratio tau(dr)tau(int) scales with the coalescence radius to a power (2+/-1) and with the rate of shear to a power (1.5+/-1). The critical coalescence radius R(o), above which hardly any coalescence occurs is about 10 microm.

Journal Article↗

PubMed2004

Model for drop coalescence in a locally isotropic turbulent flow field.

The proposed model views drop coalescence in a turbulent flow field as a two-step process consisting of formation of a doublet due to drop collisions followed by coalescence of the individual droplets in a doublet due to the drainage of the intervening film of continuous phase under the action of colloidal (van der Waals and electrostatic) and random turbulent forces. The turbulent flow field was assumed to be locally isotropic. A first-passage-time analysis was employed for the random process of intervening continuous-phase film thickness between the two drops of a doublet in order to evaluate the first two moments of coalescence-time distribution of the doublet. The average drop coalescence time of the doublet was dependent on the barrier for coalescence due to the net repulsive force (net effect of colloidal repulsive and turbulent attractive forces). The predicted average drop coalescence time was found to be smaller for larger turbulent energy dissipation rates, smaller surface potentials, larger drop sizes, larger ionic strengths, and larger drop size ratios of unequal-sized drop pairs. The predicted average drop coalescence time was found to decrease whenever the ratio of average turbulent force to repulsive force barrier became larger. The calculated coalescence-time distribution was broader, with a higher standard deviation, at lower energy dissipation rates, higher surface potentials, smaller drop sizes, and smaller size ratios of unequal drop pairs. The model predictions of average coalescence-rate constants for tetradecane-in-water emulsions stabilized by sodium dodecyl sulfate (SDS) in a high-pressure homogenizer agreed fairly well with the inferred experimental values as reported by Narsimhan and Goel (J. Colloid Interface Sci. 238 (2001) 420-432) at different homogenizer pressures and SDS concentrations.

Colloids↗

PubMed2005

Film formation from monodisperse acrylic latices 5. Drying and ageing in coalescing agent containing latex films.

The influences of drying temperature, ageing time and ageing temperature on the film formation in coalescing agent containing latex films were investigated via turbidity measurements and atomic force microscopy. Coalescing agents used are 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TEX) and ethylene glycol monobutyl ether (EB). Latex films were dried at different temperatures. At a drying temperature of 40 degrees C, the differences in immersion patterns of neat and 1% coalescing agent containing latex films are too small to show significant improvement in film formation during 1 h of drying. Increase of the temperature from 40 to 50 degrees C, however, causes an improvement in film formation. At higher temperatures (95 degrees C), fast removal of the liquid phase cannot be prevented by the addition of 1% coalescing agent. Although addition of higher amounts of coalescing agent results in an increase of particle deformation and film surface smoothness, it intensifies also the water absorption of dried films. Ageing below the MFFT does not result in a significant improvement of film formation in the presence of 1% coalescing agent. Above the MFFT, coalescing agents act more efficiently and cause an improvement in film formation. By addition of higher amounts of coalescing agent the completion of the film formation process is delayed: for example, by the addition of 15% EB, nearly 1 year of ageing at room temperature is required for an efficient result.

Journal Article↗

PubMed2005

The effect of surface-active solutes on bubble coalescence in the presence of ultrasound.

The sonication of an aqueous solution generates cavitation bubbles, which may coalesce and produce larger bubbles. This paper examines the effect of surface-active solutes on such bubble coalescence in an ultrasonic field. A novel capillary system has been designed to measure the change in the total volume resulting from the sonication of aqueous solutions with 515 kHz ultrasound pulses. This volume change reflects the total volume of larger gas bubbles generated by the coalescence of cavitation bubbles during the sonication process. The total volume of bubbles generated is reduced when surface-active solutes are present. We have proposed that this decrease in the total bubble volume results from the inhibition of bubble coalescence brought about by the surface-active solutes. The observed results revealed similarities with bubble coalescence data reported in the literature in the absence of ultrasound. It was found that for uncharged and zwitterionic surface-active solutes, the extent of bubble coalescence is affected by the surface activity of the solutes. The addition of 0.1 M NaCl to such solutes had no effect on the extent of bubble coalescence. Conversely, for charged surface-active solutes, the extent of bubble coalescence appears to be dominated by electrostatic effects. The addition of 0.1 M NaCl to charged surfactant solutions was observed to increase the total bubble volume close to that of the zwitterionic surfactant. This suggests the involvement of electrostatic interactions between cavitation bubbles in the presence of charged surfactants in the solution.

Air↗

PubMed2004

Nanoparticles of varying hydrophobicity at the emulsion droplet-water interface: adsorption and coalescence stability.

The coalescence stability of poly(dimethylsiloxane) emulsion droplets in the presence of silica nanoparticles ( approximately 50 nm) of varying contact angles has been investigated. Nanoparticle adsorption isotherms were determined by depletion from solution. The coalescence kinetics (determined under coagulation conditions at high salt concentration) and the physical structure of coalesced droplets were determined from optical microscopy. Fully hydrated silica nanoparticles adsorb with low affinity, reaching a maximum surface coverage that corresponds to a close packed monolayer, based on the effective particle radius and controlled by the salt concentration. Adsorbed layers of hydrophilic nanoparticles introduce a barrier to coalescence of approximately 1 kT, only slightly reduce the coalescence kinetics, and form kinetically unstable networks at high salt concentrations. Chemically hydrophobized silica nanoparticles, over a wide range of contact angles (25 to >90 degrees ), adsorb at the droplet interface with high affinity and to coverages equivalent to close-packed multilayers. Adsorption isotherms are independent of the contact angle, suggesting that hydrophobic attraction overcomes electrostatic repulsion in all cases. The highly structured and rigid adsorbed layers significantly reduce coalescence kinetics: at or above monolayer surface coverage, stable flocculated networks of droplets form and, regardless of their wettability, particles are not detached from the interface during coalescence. At sub-monolayer nanoparticle coverages, limited coalescence is observed and interfacial saturation restricts the droplet size increase. When the nanoparticle interfacial coverage is >0.7 and <1.0, mesophase-like microstructures have been noted, the physical form and stability of which depends on the contact angle. Adsorbed nanoparticle layers at monolayer coverage and composed of a mixture of nanoparticles with different hydrophobisation levels form stable networks of droplets, whereas mixtures of hydrophobized and hydrophilic nanoparticles do not effectively stabilize emulsion droplets.

Adsorption↗

PubMed2025

Parallel algorithms for phylogenetic inference under a structured coalescent approximation.

While advances in molecular epidemiology and computational modeling have enhanced our capacity to track pathogen evolution, the accurate reconstruction of spatiotemporal transmission dynamics remains essential for developing epidemic preparedness frameworks and implementing outbreak response measures. Structured coalescent models offer a phylogeographic framework by restricting lineage coalescence events to geographically proximate host populations. Although the Bayesian structured coalescent approximation (BASTA) provides a tractable approach, contemporary phylogeographic analyses involving dozens of geographic localities and hundreds to thousands of viral genomes substantially exceed the computational capacity of existing implementations. The BASTA likelihood scales cubically with deme count and quadratically with sequence count due to matrix exponentiation and pairwise coalescent probability calculations. Here, we introduce a comprehensive algorithmic restructuring of the structured coalescent likelihood that eliminates redundancies, optimizes memory access, and exposes parallelization opportunities. Our approach reorganizes computations along three dimensions: (i) independent calculation of deme-transition probability matrices across time intervals; (ii) simultaneous evaluation of partial likelihood vectors within temporal slices; and (iii) concurrent aggregation of coalescent probabilities. Algorithmic restructuring cuts average coalescent likelihood computation by 7-8 fold, and parallelization further boosts performance to 10-26 fold, enabling joint phylogeographic analyses of dengue virus across 10 South American countries and H5N1 avian influenza across 20 Eurasian regions to finish in a fraction of prior time. This computational efficiency also enables comparison between backward-in-time structured coalescent approximations and forward-in-time phylogeographic methods, revealing that the former provides appropriately conservative posterior estimates, particularly at intermediate phylogenetic depths. We integrate our implementation into the popular BEAST X and BEAGLE software packages, with an accompanying interface in BEAUti X to easily set up the analyses, providing researchers with an accessible and scalable tool for real-time phylogeographic surveillance of rapidly evolving pathogens.

Journal Article↗

PubMed2006

Coalescence of bubbles translating through a tube.

The results of an experimental study of the interaction and coalescence of two air bubbles translating in a cylindrical tube are presented. Both pressure- and buoyancy-driven motion of the two bubbles in a Newtonian suspending fluid within the tube are considered. The close approach of the two bubbles is examined using image analysis, and measurements of the coalescence time are reported for various bubble size ratios and capillary numbers. For pressure-driven motion of bubbles, coalescence is found to occur in an axisymmetric configuration for all bubble size ratios considered in the experiments. For buoyancy-driven motion, on the other hand, the disturbance flow behind the leading bubble causes the trailing bubble to move radially out toward the tube wall when the trailing bubble size becomes very small compared to the size of the leading bubble. In that case, coalescence occurs in a nonaxisymmetric configuration, with a time scale for coalescence that is substantially larger than that for coalescence in the axisymmetric configuration. When the imposed flow is in the direction of the buoyancy force, coalescence time is independent of bubble size ratio, and decreases as the capillary number increases. Experimental measurements of the radius of the thin liquid film separating the two bubbles are used in conjunction with a simple film drainage model to predict the dependence of the coalescence time on the bubble size ratio.

Journal Article↗

PubMed2006

Coalescence stability of emulsions containing globular milk proteins.

This review summarizes a large set of related experimental results about protein adsorption and drop coalescence in emulsions, stabilized by globular milk proteins, beta-lactoglobulin (BLG) or whey protein concentrate (WPC). First, we consider the effect of drop coalescence on the mean drop size, d32, during emulsification. Two regimes of emulsification, surfactant-rich (negligible drop coalescence) and surfactant-poor (significant drop coalescence) are observed in all systems studied. In the surfactant-rich regime, d32 does not depend on emulsifier concentration and is determined mainly by the interfacial tension and the power dissipation density in the emulsification chamber, epsilon. In the surfactant-poor regime and suppressed electrostatic repulsion, d32 is a linear function of the inverse initial emulsifier concentration, 1/C(INI), which allows one to determine the threshold emulsifier adsorption needed to stabilize the oil drops during emulsification, Gamma* (the latter depends neither on oil volume fraction nor on epsilon). Second, we study how the BLG adsorption on drop surface changes while varying the protein and electrolyte concentrations, and pH of the aqueous phase. At low electrolyte concentrations, the protein adsorbs in a monolayer. If the pH is away from the isoelectric point (IEP), the electrostatic repulsion keeps the adsorbed BLG molecules separated from each other, which precludes the formation of strong intermolecular bonds during shelf-storage as well as after heating of the emulsion. At higher electrolyte concentration, the adsorption Gamma increases, as a result of suppressed electrostatic repulsion between the protein molecules; monolayer or multilayer is formed, depending on protein concentration and pH. The adsorption passes through a maximum (around the protein IEP) as a function of pH. Third, the effect of various factors on the coalescence stability of "fresh" emulsions (up to several hours after preparation) was studied. Important conclusion from this part of the study is the establishment of three different cases of emulsion stabilization: (1) electrostatically-stabilized emulsions with monolayer adsorption, whose stability is described by the DLVO theory; (2) emulsions stabilized by steric repulsion, created by protein adsorption multilayers - a simple model was adapted to describe the stability of these emulsions; and (3) emulsions stabilized by steric repulsion, created by adsorption monolayers. Fourth, we studied how the emulsion stability changes with storage time and after heating. At high electrolyte concentrations, we find a significant decrease of the coalescence stability of BLG-emulsions after one day of shelf-storage (aging effect). The results suggest that aging is related to conformational changes in the protein adsorption layer, which lead to formation of extensive lateral non-covalent bonds (H-bonds and hydrophobic interactions) between the adsorbed molecules. The heating of BLG emulsions at high electrolyte concentration leads to strong increase of emulsion stability and to disappearance of the aging effect, which is explained by the formation of disulfide bonds between the adsorbed molecules. The emulsion heating at low electrolyte concentration does not affect emulsion stability - this result is explained with the electrostatic repulsion between the adsorbed molecules, which keeps them separated so that no intermolecular disulfide bonds are formed. Parallel experiments with WPC-stabilized emulsions show that these emulsions are less sensitive to variations of pH and thermal treatment; no aging effect is detected up to 30 days of storage. The observed differences between BLG and WPC are explained with the different procedures of preparation of these protein samples (freeze-drying and thermally enhanced spray-drying, respectively). Our data for emulsion coalescence stability are compared with literature results about the flocculation stability of BLG emulsions, and the observed similarities/differences are explained by considering the structure of the protein adsorption layers.

Computer Simulation↗