Changes in Colloidal Properties of Oil in Water Emulsions Stabilized with Sodium Caseinate Observed by Acoustic and Electroacoustic Spectroscopy

Sodium caseinate is a commonly used emulsifier in foods, as it adsorbs on the surface of oil droplets and stabilizes them via electrostatic and steric stabilization, forming a polyelectrolyte layer at the interface. Since the protein interface is affected by varying environmental conditions such as pH, ionic strength, concentration of unadsorbed polymers, these emulsions are prone to a variety of destabilization mechanisms. The objective of the present work was to observe the destabilization of sodium caseinate stabilized oil in water emulsions using electroacoustic spectroscopy. This technique can be utilized for the characterization of concentrated colloidal systems in situ, without dilution. The electroacoustic and ultrasonic properties of soy oil in water emulsions were determined for sodium caseinate stabilized emulsions under conditions known to cause destabilization. Ultrasonic attenuation and electrophoretic mobility (ζ-potential) could clearly follow the changes occurring in the emulsion droplets, under minimal sample disruption. This is critical for these systems in a very fragile, metastable state. The emulsions were stable to the addition of high methoxyl pectin (HMP) up to 0.1% HMP. Addition of free sodium caseinate induced depletion flocculation, causing a decrease in the attenuation and electrophoretic mobility measured. The presence of HMP limited depletion interactions. Acidification of the emulsion droplets resulted in a clear sol–gel transition, as shown by a steep increase in the particle size and a decrease in attenuation. Again, destabilization was limited by HMP addition. It was concluded that ultrasonics and electroacoustics are suitable techniques to understand the details of the destabilization processes occurring to food emulsions, measured in situ.     

Emulsification Capacity of Microgels Assembled from β-Lactoglobulin and Pectin

Microgels formed from beta-lactoglobulin were used to prepare oil-in-water emulsions in order to examine their emulsifying capacity. Corn oil emulsions prepared with microgels of pure beta-lactoglobulin at pH 5.8 were initially stable, but a fraction of the droplets quickly flocculated to form a creamed layer that could not be dispersed by shear, which was attributed to hydrophobic attractions between the microgels on adjoining droplets. Emulsions prepared from microgels of beta-lactoglobulin and pectin at pH 4.75 possessed greater droplet sizes at lower concentrations, yet all emulsions were relatively stable to irreversible flocculation. Increased stability of emulsions stabilized by BP-gels was attributed to the presence of pectin on the surface of microgels, which increased repulsions between adjoining droplets. Stable corn oil emulsions were still prepared from microgels that were previously dialyzed to remove non-aggregated protein, which verified that the microgels were responsible for stabilizing emulsion droplets. Equilibrium surface pressure of corn oil droplets was similar between microgels and the unheated beta-lactoglobulin and pectin, yet the dynamic surface pressure was reduced at intermediate times and indicated a slow relaxation and deformation of the microgels at the interface. Microgels formed with pectin stabilized emulsions containing 90 % limonene for up to 5 days of room temperature storage, demonstrating the capacity of such protein microgels to stabilize flavor oil emulsions.     

脉冲回波法研究微乳液体系的稳定性

本文主要以正庚炕（C71116）、水乳浊液（以span-80为表面活性剂）为模型体系,研究了脉冲回波法探测微乳体系结构稳定性的可能性,并进行了初步讨论。实验结果表明,超声衰减系数（a）与微乳体系配比、表面活性剂含量及微乳液制备时搅拌转速密切相关。微乳液体系在实验当中均出现了由油和水两相混合的状态到油和水分相的状态。微乳液体系的超声衰减系数在分相前后均保持着相对平稳的变化,但对应于不同条件下制备的溶液,分相时间都有所不同。且一般而言,当微乳液开始两相（水相和油相）分离时,超声衰减系数将发生明显变化。因此预计脉冲回波法有可能发展成为一种简单、可靠、非破环性的微乳体系稳定性检测新方法。     

Physical properties of emulsion-based hydroxypropyl methylcellulose films: Effect of their microstructure

The initial characteristics of emulsions and the rearrangement of the oil droplets in the film matrix during film drying, which defines its microstructure, has an important role in the physical properties of the emulsion-based films. The objective of this work was to study the effect of the microstructure (two droplet size distributions) and stability (with or without surfactant) of HPMC oil-in-water emulsions over physical properties of HPMC emulsion-based edible films. HPMC was used to prepare sunflower oil-in-water emulsions containing 0.3 or 1.0% (w/w) of oil with or without SDS, as surfactant, using an ultrasonic homogenizer. Microstructure, rheological properties and stability of emulsions (creaming) were measured. In addition, microstructure, coalescence of oil droplets, surface free energy, optical and mechanical properties and water vapor transfer of HPMC films were evaluated. Image analysis did not show differences among droplet size distributions of emulsions prepared at different oil contents; however, by using SDS the droplet size distributions were shifted to lower values. Volume mean diameters were 3.79 and 3.77μm for emulsions containing 0.3 and 1.0% without surfactant, respectively, and 2.72 and 2.71μm for emulsions with SDS. Emulsions formulated with 1.0% of oil presented higher stability, with almost no change during 5 and 3 days of storage, for emulsions with and without SDS, respectively. Internal and surface microstructure of emulsion-based films was influenced by the degree of coalescence and creaming of the oil droplets. No effect of microstructure over the surface free energy of films was found. The incorporation of oil impaired the optical properties of films due to light scattering of light. Addition of oil and SDS decreased the stress at break of the emulsion-based films. The replace of HPMC by oil and SDS produce a lower "amount" of network structure in the films, leading to a weakening of their structure. The oil content and SDS addition had an effect over the microstructure and physical properties of HPMC-based emulsions which lead to different microstructures during film formation. The way that oil droplets were structured into the film had an enormous influence over the physical properties of HPMC films.     

Diffusing Wave and Ultrasonic Spectroscopy of Rennet-Induced Gelation of Milk in the Presence of High-Methoxyl Pectin

Rennet-induced aggregation was studied in milk systems containing high-methoxyl pectin (HMP) using ultrasonic and diffusing wave spectroscopy. These two techniques allow for in situ measurements of sol–gel transitions without the need for dilution. At low HMP concentrations, the casein micelles aggregation behavior was similar to that of skim milk, although changes could be noted in the microstructure of the renneted gels. At HMP concentrations between 0.1 and 0.15%, phase-separation kinetics were slower than the rennet-induced aggregation, and different microstructures formed caused by different dynamics of interactions between casein micelles present in HMP-depleted flocs. Higher amounts of HMP failed to create a continuous gel, as phase separation occurred at a faster rate than rennet aggregation. These results highlight the importance of non-invasive techniques in the study of concentration-dependent phase separating and aggregating systems, as only with observations in situ is it possible to determine new ways to control the structuring of protein–polysaccharide mixed systems.     

Evaluation of Electrostatic Interaction between Lysolecithin and Chitosan in Two-Layer Tuna Oil Emulsions by Nuclear Magnetic Resonance (NMR) Spectroscopy

The main objective of this work was to investigate the electrostatic interaction between lysolecithin and chitosan in two-layer tuna oil-in-water emulsions using nuclear magnetic resonance (NMR) spectroscopy. The influence of chitosan concentration on the stability and properties of these emulsions was also evaluated. The 5 wt% tuna oil one-layer emulsion (lysolecithin-stabilized oil droplets without chitosan) and two-layer emulsions (lysolecithin-chitosan stabilized oil droplets) containing 5 wt% tuna oil, 1 wt% lysolecithin and various chitosan concentrations (0.025–0.40 wt%) were prepared. The one-dimensional (1D) ³¹P and ¹H NMR spectra of emulsions were then recorded at 25 °C. The results showed that addition of chitosan affected the stability and properties of lysolecithin-stabilized one-layer emulsions. The ³¹P NMR peak of the choline head group on lysolecithin molecules disappeared when chitosan was added at concentrations above neutralization concentration (> 0.05 wt%). The ¹H NMR peak intensity monitoring free amino groups (?NH ₃ ⁺) of chitosan showed a strong positive linear relationship to the chitosan concentration with a high correlation coefficient (R² ≈ 0.99). This ¹H NMR peak in emulsions could not be detected for chitosan in emulsions lower than saturation concentration (< 0.15 wt%). These phenomena indicate an electrostatic interaction between lysolecithin and chitosan at droplet surface in emulsion and were consistent with the results from zeta-potential measurements. The T ₂* relaxation time of the choline head group (N-(CH ₃)₃) signal of lysolecithin also confirmed that lysolecithin-chitosan electrostatic interaction occurs at the surface of oil droplets in two-layer emulsions. The results suggest that NMR spectroscopy can be used as an alternative method for monitoring the electrostatic interaction between surfactant and oppositely charged electrolytes or biopolymers in two-layer emulsions.     

YdfH Identified as a Repressor of rspA by the Use of Reduced Genome Escherichia coli MGF-01

The effects of carnauba wax addition on the physical state of palm kernel oil-in-water emulsions were investigated. The oil-in-water emulsion (40 wt% oil + 60 wt% aqueous phase) kept the liquid state at 25°C irrespective of the presence or absence of carnauba wax in the oil phase. The emulsion containing the wax transformed from the liquid state to the solid state by shearing after storage for 20 h at 4°C, although the liquid-solid transition was not observed for the emulsion not containing the wax upon the same treatment. The viscoelasticity of the solid emulsions was demonstrated by small-deformation mechanical testing. Analysis of flow behavior of the emulsions showed that the change in physical properties of the emulsion containing the wax at 4°C was caused by the shearing at a low shear rate, around 50 s^?1–100 s^?1. According to the transition from the liquid state to the solid state of the emulsion containing the wax, the aggregation of oil droplets was found to occur to a large extent. The results of differential scanning calorimetry and surface pressure–surface area isotherms suggested that triglyceride molecules of palm kernel oil were more oriented at the oil–water interfaces in the emulsions after the wax addition. Based on these results, it is thought that carnauba wax is important in destabilization of palm kernel oil-in-water emulsions by modifying the physical state of the oil triglyceride molecules at the interfaces.     

Impact of Heat and Laccase on the pH and Freeze-Thaw Stability of Oil-in-Water Emulsions Stabilized by Adsorbed Biopolymer Nanoparticles

The enzymatic cross-linking of adsorbed biopolymer nanoparticles formed between whey protein isolate (WPI) and sugar beet pectin using the complex coacervation method was investigated. A sequential electrostatic depositioning process was used to prepare emulsions containing oil droplets stabilized by WPI – nanoparticle – membranes. Firstly, a finely dispersed primary emulsion (10 % w/w miglyol oil, 1 % w/w WPI, 10 mM acetate buffer at pH 4) was produced using a high-pressure homogenizer. Secondly, a series of biopolymer particles were formed by mixing WPI (0.5 % w/w) and pectin (0.25 % w/w) solutions with subsequent heating above the thermal denaturation temperature (85 °C, 20 min) to prepare dispersions containing particles in the submicron range. Thirdly, nanoparticle-covered emulsions were formed by diluting the primary emulsion into coacervate solutions (0–0.675 % w/w) to coat the droplets. Oil droplets of stable emulsions with different interfacial membrane compositions were subjected to enzymatic cross-linking. We used cross-linked multilayered emulsions as a comparison. The pH stability of primary emulsions, biopolymer complexes and nanoparticle-coated base emulsions, as well as multilayered emulsions, was determined before and after enzyme addition. Freeze-thaw stability (?9 °C for 22 h, 25 °C for 2 h) of nanoparticle-coated emulsions was not affected by laccase. Results indicated that cross-linking occurred exclusively in the multilamellar layers and not between adsorbed biopolymer nanoparticles. Results suggest that the accessibility of distinct structures may play a key role for biopolymer-cross-linking enzymes.     

Immunotherapy of a guinea pig hepatoma with ultrasonically prepared mycobacterial vaccines

Summary Oil-in-water emulsions containing either mycobacterial cell walls (CW) or killed whole cells attached to the oil droplets were prepared by ultrasonication and by a modified grinding procedure. The immunotherapeutic potency of the ultrasonically prepared vaccines was at least as great as that of similar vaccines prepared by emulsification in a tissue grinder. Among the advantages of ultrasonication over grinding for the preparation of mycobacterial cell and cell wall vaccines are simplicity and the ease with which sterility may be maintained. Both the ultrasonic and modified grinding methods are less time-consuming than published procedures for preparing mycobacterial vaccines.     

Influence of pH and ionic strength on formation and stability of emulsions containing oil droplets coated by beta-lactoglobulin-alginate interfaces

Emulsions of 0.1 wt % corn oil-in-water containing oil droplets coated by beta-lactoglobulin (0.009 wt % beta-Lg, 5 mM phosphate buffer, pH 7.0) were prepared in the absence and presence of sodium alginate (0 or 0.004 wt %). The pH (3-7) and ionic strength (0-250 mM NaCl) of these emulsions were adjusted, and the particle charge, particle size, and creaming stability were measured. Alginate adsorbed to the beta-Lg-coated droplets from pH 3 to 6, which was attributed to electrostatic attraction between the anionic polymer and cationic patches on the droplet surfaces. Droplets coated by beta-Lg-alginate had better stability to flocculation than those coated by beta-Lg alone, especially around the isoelectric point of the adsorbed proteins and at low ionic strengths (< 100 mM NaCl). At pH 5, alginate molecules desorbed from the droplet surfaces at high salt concentrations due to weakening of the electrostatic attraction.     

Whey Protein/Polysaccharide-Stabilized Emulsions: Effect of Polymer Type and pH on Release and Topical Delivery of Salicylic Acid

Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industries. They are thermodynamically unstable and require emulsifiers for stabilization. Studies have indicated that emulsifiers could affect topical delivery of actives, and this study was therefore designed to investigate the effects of different polymers, applied as emulsifiers, as well as the effects of pH on the release and topical delivery of the active. O/w emulsions were prepared by the layer-by-layer technique, with whey protein forming the first layer around the oil droplets, while either chitosan or carrageenan was subsequently adsorbed to the protein at the interface. Additionally, the emulsions were prepared at three different pH values to introduce different charges to the polymers. The active ingredient, salicylic acid, was incorporated into the oil phase of the emulsions. Physical characterization of the resulting formulations, i.e., droplet size, zeta potential, stability, and turbidity in the water phase, was performed. Release studies were conducted, after which skin absorption studies were performed on the five most stable emulsions, by using Franz type diffusion cells and utilizing human, abdominal skin membranes. It was found that an increase in emulsion droplet charge could negatively affect the release of salicylic acid from these formulations. Contrary, positively charged emulsion droplets were found to enhance dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect its release, whereas electrostatic interaction between the emulsion droplets and skin could influence dermal/transdermal delivery of the active.     

Factors Affecting Foamed Emulsions Prepared with an Extract from <Emphasis Type="Italic">Quillaja saponaria</Emphasis> Molina: Oil Droplet Size,pH and Presence of Beta-Lactoglobulin

Oil is well-known to act as antifoam and to destabilize foam lamellae by bridging between two adjacent foam bubbles. It was hypothesized that an optimal oil droplet size exists with respect to the stability of a foamed emulsions, where the oil droplets are sufficiently small to postpone bridging and the amount of free surfactant is sufficient to stabilize the oil/water-interface and the air/water-interface. Emulsions with 0.3% Quillaja saponin and a median oil drop-let size between 0.2 and 2.0 μm were prepared under varying homogenization conditions and characterized in a dynamic foam analyzer. Results confirmed the above mentioned hypothesis. Stability of the foamed emulsions considerably increased with increasing pH, which was attributed to electrostatic repulsion between oil droplets and the effect on the balance between disjoining pressure and capillary pressure. In a binary system containing proteins and saponins, stability of foamed emulsions can be further increased when emulsifiers are added sequentially. When the emulsion is stabilized by β-LG and QS is added after emulsification stability of the foamed emulsion is distinctly higher compared to systems, where QS and β-LG are added prior to emulsification. Future studies should deepen our understanding of these complex dispersed systems by investigating the molecular interactions including other proteins and additional food constituents.     

Emulsions Based on the Interactions Between Lactoferrin and Chitosans

In this work, purification of lactoferrin from whey was performed with high recovery rate. Lactoferrin was then exploited in the preparation of food emulsions. Two tertiary emulsions, formed by olive oil, lecithin, chitosan, and lactoferrin, were compared: both the emulsions showed similar turbidity and stability. In the secondary emulsion formed by oil/lecithin/chitosan, the pH was increased to 9 before addition of lactoferrin. Then, lactoferrin was added, and the pH was stabilized above pH 9. Lactoferrin was found in amounts of 1 to 2.5 mg/ml in the multiple experiments. A fraction of the added lactoferrin was also present in a milky layer above the emulsion layer. This was, to our knowledge, the first study of emulsions made exploiting the interactions between lactoferrin and chitosan. It was noted that chitosan droplets remained soluble, although the hydrocolloid solubility occurs at pH lower than 5.9. These results showed the feasibility of manufacturing lactoferrin-based emulsions as functional foods.     

Modulation of pH Sensitivity of Surface Charge and Aggregation Stability of Protein-Coated Lipid Droplets by Chitosan Addition

The impact of a cationic polyelectrolyte on the pH sensitivity of the electrical charge and aggregation stability of protein-coated lipid droplets was examined. One percent (w/w) corn oil-in-water emulsions containing lipid droplets coated by β-lactoglobulin [0.05% (w/w) β-Lg, 10 mM acetate buffer, pH 3] were prepared in the absence (“primary” emulsions) and presence (“secondary” emulsions) of chitosan (0 to 0.05 wt%). The pH (3 to 8) of these emulsions was adjusted, and the particle charge, particle size, creaming stability, and microstructure were measured. Chitosan adsorbed to the β-Lg-coated droplets from pH 4.5 to 7.5, which was attributed to electrostatic attraction between the cationic polyelectrolyte and anionic patches on the droplet surfaces. Droplets coated by β-Lg–chitosan had better stability to flocculation than those coated by β-Lg alone around the isoelectric point of the adsorbed proteins (pH 4.5 to 5.5), which was attributed to increased electrostatic and steric repulsion between the droplets. We have shown that chitosan may be used to modulate the electrical characteristics and stability of protein-coated lipid droplets, which may be useful in the design and formation of delivery systems for use in the food, pharmaceutical, and other industries.     

Stability Assessment of Injectable Castor Oil-Based Nano-sized Emulsion Containing Cationic Droplets Stabilized by Poloxamer–Chitosan Emulsifier Films

The objectives of the present work were to prepare castor oil-based nano-sized emulsion containing cationic droplets stabilized by poloxamer–chitosan emulgator film and to assess the kinetic stability of the prepared cationic emulsion after subjecting it to thermal processing and freeze–thaw cycling. Presence of cryoprotectants (5%, w/w, sucrose +5%, w/w, sorbitol) improved the stability of emulsions to droplet aggregation during freeze–thaw cycling. After storing the emulsion at 4°C, 25°C, and 37°C over a period of up to 6 months, no significant change was noted in mean diameter of the dispersed oil droplets. However, the emulsion stored at the highest temperature did show a progressive decrease in the pH and zeta potential values, whereas the emulsion kept at the lowest temperatures did not. This indicates that at 37°C, free fatty acids were formed from the castor oil, and consequently, the liberated free fatty acids were responsible for the reduction in the emulsion pH and zeta potential values. Thus, the injectable castor oil-based nano-sized emulsion could be useful for incorporating various active pharmaceutical ingredients that are in size from small molecular drugs to large macromolecules such as oligonucleotides.     

Influence of processing factors on the stability of model mayonnaise with whole egg during long-term storage

Mayonnaise-like oil-in-water emulsions with different stabilities—evaluated from the degree of macroscopic defects, e.g., syneresis—were prepared by different formulations and processing conditions (egg yolk weight, homogenizer speed, and vegetable oil temperature). Emulsions prepared with lower egg yolk content were destabilized for shorter periods. The long-term stability of emulsions was weakly related to initial properties, e.g., oil droplet distribution and protein coverage at the interface. Protein aggregation between oil droplets was observed and would be responsible for the instability of emulsions exhibited by the appearance defects. SDS-PAGE results for adsorbed and unadsorbed proteins at the O/W interface suggested that predominant constituents adsorbed onto the interface were egg white proteins as compared with egg yolk components when the amount of added egg yolk was low. In present condition, egg white proteins adsorbed at the O/W interface could be a bridge of neighboring oil droplets thereby causing flocculation in emulsions.     

Emulsifying behaviour of gum arabic. Part 1: Effect of the nature of the oil phase on the emulsion droplet-size distribution

The influence of the nature of the oil phase on the emulsifying behaviour of gum arabic has been investigated at neutral pH. Time-dependent droplet-size distributions are reported for oil-in-water emulsions (1% wt gum, 10% vol. oil) made with n-hexadecane, -limonene and orange oil. Three different gum samples of known analytical composition have been compared, and it is found that the gum giving the most rapid lowering of the tension at the n-hexadecane-water interface also gives the most stable n-hexadecane-in-water emulsions as well as the smallest droplets with all three oils. On the other hand, the same gum gives the poorest stability of the -limonene-in-water and orange oil-in-water emulsions.     

Flow cytometry: a promising technique for the study of silicone oil-induced particulate formation in protein formulations

Subvisible particles in formulations intended for parenteral administration are of concern in the biopharmaceutical industry. However, monitoring and control of subvisible particulates can be complicated by formulation components, such as the silicone oil used for the lubrication of prefilled syringes, and it is difficult to differentiate microdroplets of silicone oil from particles formed by aggregated protein. In this study, we demonstrate the ability of flow cytometry to resolve mixtures comprising subvisible bovine serum albumin (BSA) aggregate particles and silicone oil emulsion droplets with adsorbed BSA. Flow cytometry was also used to investigate the effects of silicone oil emulsions on the stability of BSA, lysozyme, abatacept, and trastuzumab formulations containing surfactant, sodium chloride, or sucrose. To aid in particle characterization, the fluorescence detection capabilities of flow cytometry were exploited by staining silicone oil with BODIPY 493/503 and model proteins with Alexa Fluor 647. Flow cytometric analyses revealed that silicone oil emulsions induced the loss of soluble protein via protein adsorption onto the silicone oil droplet surface. The addition of surfactant prevented protein from adsorbing onto the surface of silicone oil droplets. There was minimal formation of homogeneous protein aggregates due to exposure to silicone oil droplets, although oil droplets with surface-adsorbed trastuzumab exhibited flocculation. The results of this study demonstrate the utility of flow cytometry as an analytical tool for monitoring the effects of subvisible silicone oil droplets on the stability of protein formulations.     

Use of coagulants in treatment of olive oil wastewater model solutions by induced air flotation

Natural polyelectrolytes are suitable coagulants for the treatment of industrial and minicipal wastewaters because they are safe and have environmental benefits. Chitosan, a natural cationic polyelectrolyte, and other similar coagulants were used in the treatment of an olive oil water suspension as a model for the processing wastewater. The effect of chitosan, starch, alum and ferric chloride on the coagulation of oil droplets were determined by the jar test apparatus and turbidometric measurements. Olive oil emulsion samples were prepared by the use of surface active agents and other agents that could form stable oil water emulsions. The effect of parameters such as pH, ionic strength and optimum dosage of the coagulants were determined in the jar test experiments. Following the jar experiments, with the optimum concentration of the suitable coagulant, the emulsions were placed in an induced air flotation (IAF) cell to separate the coagulated oil droplets from solution. In the air flotation experiments, the effect of temperature, surfactant concentration and air flowrate were determined on the decrease of turbidity and COD of the emulsion samples. In the jar experiments, chitosan and alum used together at concentrations of 15 and 25 ppm, respectively, at pH 6 produced the lowest turbidity values. In the air flotation experiments, a concentration of 100 ppm of chitosan, an air flowrate of 3 l/min, aeration time of 45 s, temperature of 20 degrees C and pH 6 produced optimum levels. At optimum conditions of coagulation and flotation stages, the COD of the olive oil emulsion could be reduced by 95%.     

Influence of Ionic Surfactants on the Microstructure of Heat-Set β-Lactoglobulin-Stabilized Emulsion Gels

Using confocal microscopy, we studied the effect of heating (up to 85°C) on the microstructure of β-lactoglobulin-stabilized emulsions (20 vol% oil, pH 6.8) containing excess protein (total protein content 13.2%). Two different fluorescent dyes were used to separately visualize the oil droplets and the protein. In overlay micrographs, their location with respect to each other could then be determined. In the presence of a low salt concentration, flocculation of the emulsion without surfactant was inhibited, by a mechanism analogous to the “salting-in” of aqueous protein solutions. Addition of the anionic surfactant sodium dodecyl sulfate (SDS) caused weak flocculation, probably as a result of the formation of protein−SDS complexes. The final heat-set emulsion contained distinct pores for a surfactant/protein ratio of R = 1, but no pores for R = 2. Addition of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) caused strong aggregation, as indicated by microscopic observation of the concentrated emulsion and light scattering of the diluted emulsion. For R = 1 with CTAB, there were aggregates consisting of oil droplets and excess protein. At R = 2, almost all the excess protein was aggregated into separate protein flakes. In the final emulsion gels containing CTAB, the protein was more spread out. Differing structural behavior with anionic and cationic surfactants has been interpreted in terms of different protein−surfactant interactions in aqueous solution and at the oil−water interface, both before and after protein denaturation.