Characterisation of fish oil emulsions stabilised by sodium caseinate

Fish oil emulsions varying in sodium caseinate concentration (25% w/w oil and 0.1–1.0% w/w protein, giving oil-to-protein ratios of 250–25) were investigated in terms of their creaming stability, rheological properties, the mobility of oil droplets and the oil/protein interaction at the interface. The presence of excessive protein in an emulsion (i.e., at 1% w/w) caused the aggregation of oil droplets through depletion flocculation, resulting in low creaming stability and high low-shear viscosity. At a lower protein concentration (0.1% w/w), when protein was limited, the emulsion droplets were stabilised by bridging flocculation and showed good stability to creaming. Shear-thinning behaviour was observed for both flocculated emulsions. A reduction in the low-shear viscosity and a Newtonian flow was obtained for the emulsion containing an intermediate concentration of protein (0.25% w/w). At this concentration, there was relatively little excess unadsorbed protein in the continuous phase; thus the emulsion was most stable to creaming. NMR was used to characterise these emulsion systems without dilution. Shorter T₂ values (by low-field ¹H NMR), for the emulsions containing both high (1% w/w) and low (0.1% w/w) amounts of protein, indicated increased restricted mobility of oils, caused by depletion or bridging flocculation. The line broadening in oil signals in the high-field NMR spectra (¹H, ¹³C) indicated increased interaction between oil molecules and proteins at the interface with increasing protein concentration in emulsions. In addition, ³¹P NMR spectra, which reflect the mobility of the casein component only, showed increased line broadening, with reduction in protein content due to the relatively higher proportion of the protein being adsorbed to the interface of the oil droplets, compared to that in the continuous phase (i.e., as the oil-to-protein ratio was increased). The T₂ values of resonances of the individual groups on oil molecules, obtained using high-field ¹H NMR, reflected their different environments within the oil droplet.     

Whey protein–carboxymethylcellulose interaction in solution and in oil-in-water emulsion systems. Effect on emulsion stability

Carboxymethylcellulose (CMC) was used as coagulation aid to precipitate the whey proteins from defatted milk serum and the ability of the resulting whey protein concentrate (WPC, protein content: 63.69%) to aid in the physicochemical stabilization of oil-in-water emulsions, during ageing or following the application of heat or freeze–thaw treatment, was investigated, along with the stability of emulsion systems prepared with a commercial whey protein isolate. The stability of WPC emulsions against droplet flocculation and creaming, and to a lesser extent against droplet coalescence, depended on the presence of the CMC molecules in the emulsion continuous phase and the extent of adsorbed protein–polysaccharide interactions as affected by the emulsion pH. Studies on whey protein–CMC interaction were conducted, both in biopolymer mixture solutions and emulsion systems, by applying zeta potential measurement and viscometry techniques. These results were combined with data on protein surface hydrophobicity and on methylene blue-binding ability of CMC molecules and indicated that whey protein–CMC interaction may take place in solution, both at neutral as well as at acidic environments, leading, depending on pH, to the formation of soluble or non-soluble amphiphilic conjugates. In emulsion systems, however, conjugate formation is observed only at relatively acidic pH environments, probably because at a neutral or at a slightly acidic pH whey protein adsorption to the emulsion droplet surface and molecular unfolding does not favour protein–polysaccharide interaction.     

Stability and rheology of egg-yolk-stabilized concentrated emulsions containing cereal β-glucans of varying molecular size

The effects of barley and oat β-glucans on rheological and creaming behaviour of concentrated egg-yolk-stabilized model emulsions were investigated. Four polysaccharide preparations were used, two from each cereal; one sample with high and one with low molecular weight, i.e. the molecular weights were alike in pairs (110×10³ and 40×10³, respectively). In order to elucidate the mechanism of action of β-glucans in emulsions, Tween 20-stabilized emulsions were also examined. Tween 20 enhances neither the continuous phase viscosity nor the interactions between the droplets, so the changes could be easily attributed to β-glucans. It appeared that the low Mw β-glucan samples stabilize emulsions against creaming by means of network formation in the continuous phase while their high molecular weight counterparts enhance the viscosity of the continuous phase. Comparison of dynamic rheological tests between a reference emulsion without β-glucans and emulsions containing β-glucans showed that the polysaccharides largely affects the viscoelastic behaviour of the emulsion. Ageing of β-glucan-containing emulsions did not affect significantly the viscoelastic properties except for the emulsions containing low Mw β-glucans extracted from oat. Interestingly, all emulsions containing β-glucans creamed approximately the same after 30 days of storage regardless which preparation was used. The egg yolk constituents seemed to play a dominant role on the viscoelastic and the creaming behaviour of the emulsions, i.e. the viscoelastic behaviour was further enhanced and this could not only be attributed to the presence of the β-glucans but also to the stronger interactions between the oil droplets. Ageing did not affect the viscoelastic properties of β-glucan-containing emulsions while the reference emulsion, prepared only with egg yolk, showed a decrease in the value of storage modulus. The former could be interpreted as a steady consistency of the product during storage independent of the creaming behaviour. The creaming behaviour varied among the samples with the high molecular weight β-glucans from oat showing the highest stability.     

Ability of flaxseed and soybean protein concentrates to stabilize oil-in-water emulsions

The ability of flaxseed protein concentrate (FPC) to stabilize soybean oil-in-water emulsion was compared with that of soybean protein concentrate (SPC). The stability of emulsions increased with increase in protein concentration. The FPC-stabilized emulsions had smaller droplet size and higher surface charge, but worse stability at the same protein concentration compared to SPC-stabilized emulsions. Oil-in-water emulsions stabilized by both proteins were diluted and compared at different pH values (3–7), ionic strength (0–200 mM NaCl) and thermal treatment regimes (25–95 °C for 20 min). Considerable emulsion droplet flocculation occurred around iso-electric point of both proteins: FPC (pH 4.2) and SPC (pH 4.5). FPC and SPC-stabilized emulsions remained relatively stable against droplet aggregation and creaming at NaCl concentration below 100 and 50 mM, respectively. The emulsions stabilized by both proteins were fairly stable within these thermal processing regimes. FPC appears to be less effective as an emulsifier compared to SPC due to its lower emulsion viscosity. Hence, FPC could be more effective in emulsions that are fairly viscous.     

Influence of chitosan concentration on the stability,microstructure and rheological properties of O/W emulsions formulated with high-oleic sunflower oil and potato protein

Relatively concentrated (40 wt%) O/W emulsions formulated with high-oleic sunflower oil as disperse phase, potato protein isolate as emulsifier and chitosan as stabiliser were prepared by rotor–stator/high-pressure valve/rotor–stator homogenization. The influence of chitosan concentration on the physical stability of emulsions was studied in (0.25–1) wt% range by visual inspection, rheological and microstructural techniques. Steady shear flow curves were sensitive to the occurrence of creaming upon the rise of zero-shear viscosity values. The effect of increasing concentration of chitosan on the zero-shear viscosity turned out to be dependent on emulsion ageing and always resulted in a stepwise increase of the critical shear rate for the onset of shear thinning flow. The critical oscillatory shear stress for the onset of non-linear viscoelastic behaviour was more sensitive than the critical shear rate to detect creaming in emulsions. Mechanical spectra are definitely demonstrated to be the most powerful tool to detect not only creaming but also oil droplet flocculation on account of changes in the plateau relaxation zone. CSLM micrographs supported the interpretation of dynamic viscoelastic results, especially when flocculation as well as coalescence took place. Cryo-SEM micrographs evidenced the formation of increasingly denser protein–polysaccharide networks with chitosan concentration and the fact that the latter governs the microstructure of the emulsion when reaches 1 wt% concentration promoting enhanced physical stability.     

Rheological properties and stability of model salad dressing emulsions prepared with a dry-heated soybean protein isolate–dextran mixture

The rheological characteristics of model salad dressing emulsions, incorporating a dry-heated soybean protein isolate (SPI)–dextran mixture as emulsifier, were investigated by applying dynamic rheometry tests in an attempt to probe the emulsion structure and to elucidate the mechanism of their stability against creaming. Both the viscoelastic properties and the creaming behaviour of the dressings were greatly influenced by the extent of protein–dextran conjugation and also by xanthan gum addition. The results are discussed in terms of emulsion droplet interactions which, depending on the extent of glyco-conjugation, may be dominated by depletion or ‘bridging’ flocculation effects and, thereby, influence the droplet network structure collapse during ageing.     

Effects of bacteriostatic emulsifiers on stability of milk-based emulsions

For milk-based emulsion products such as canned coffee or tea, the addition of bacteriostatic emulsifiers is necessary to inhibiting the growth of heat-resistant sporeformers. Since bacteriostatic emulsifiers often cause the destabilization of emulsions, other type of emulsifiers, such as stability-enhancing ones, are necessary for the long-term stability of emulsions. Four milk-based emulsions were prepared from powdered milk combined with several types of emulsifiers. The long-term stability of emulsions, which was detected by the occurrence of a creaming layer after 3 months of storage, differed according to the composition of emulsifiers. To understand the reason for the differences in the stability of emulsions, particle size, distribution, ζ-potential, and the amount of proteins and phospholipids present in the cream layer (separated oil droplets) in the emulsions were measured. Only the amount of proteins adsorbed onto oil droplets was found to be closely related to the difference in emulsion stability, that is, the more proteins adsorbed, the higher the emulsion stability. SDS–PAGE analyses revealed that κ-casein and β-lactoglobulin play an important role in emulsion stability by adsorbing onto the oil droplet surface.     

Determination of stability of food emulsions Part 1. The influence of the type and concentration of protein on creaming stability determined by analytical ultracentrifugation

A centrifugal method is presented for the determination of emulsion stability against creaming (separation of continuous phase). It is based on the centrifugation to final values (equilibrium) for the separated continuous phase and cream. On this methodical basis two indices for the characterization of this kind of stability are obtained, the cream- or continuous phase-quotient. The influence of the type and concentration of protein on the emulsion stability has been investigated with O/W emulsions containing acetylated (AFBPI) and non-acetylated (FBPI) faba bean protein isolate in a concentration range of 0.1–4 %. The emulsions containing the two types of protein show a clear raise in stability with increasing AFBPI- and FBPI-concentration with the exception of that with 2 % AFBPI at a short storage period of the emulsion. The method is sensitive and indicates small changes in stability during storage, for example. It can be applied to emulsions which show different final values with stepwise increasing centrifugal fields. The method proposed is particularly interesting for preparation and characterization of high concentrated emulsions.     

Stabilization of acidic soy protein-based dispersions and emulsions by soy soluble polysaccharides

Soy soluble polysaccharides (SSPS) are shown to prevent destabilization of soy protein isolate (SPI) dispersions and SPI-based oil-in-water (O/W) emulsions under acidic conditions. Addition of SSPS above a critical concentration (0.25 wt%) increased the stability of 0.50 wt% SPI dispersions against aggregation and phase separation under conditions where SPI would normally precipitate (near its isoelectric point). Though SSPS neutralized SPI surface charge via electrostatic interaction, there was increased stability against aggregation due to steric repulsion. At acidic pH, addition of 1 wt% NaCl electrostatically screened protein–polysaccharide complexation which led to SPI precipitation and sedimentation. However, the order of salt addition had a significant impact on charge screening, with salt added before pH adjustment reducing SPI–SSPS complexation whereas it had less effect when added afterwards. Salt penetration efficacy diminished with decreasing pH. O/W emulsions (5 wt% oil) prepared with 0.50 wt% SPI destabilized at pH 4–5 due to protein aggregation, but addition of ≥0.25 wt% SSPS improved emulsion stability by inhibiting protein–protein interactions thus limiting increases in oil droplet diameter over time. Overall, both dispersion and emulsion stability greatly depended on pH, ionic strength and SSPS concentration. These results demonstrated that SSPS could effectively stabilize acidic SPI dispersions and that SPI–SSPS interactions may be used as a tool to improve the kinetic stability of SPI-based O/W emulsions.     

Oil-in-water emulsions stabilized by chitin nanocrystal particles

The aim of the present study was to investigate the oil-in-water emulsion stabilizing ability of chitin nanocrystals (colloidal rod-like particles) and the factors that may influence the properties of such systems. Chitin nanocrystal aqueous dispersions were prepared by acid hydrolysis of crude chitin from crab shells and oil-in-water emulsions were generated by homogenizing appropriate quantities of a chitin nanocrystal stock aqueous dispersion with corn oil, using an ultra-sonic homogenizer. The resulting emulsions were visually evaluated for their creaming behaviour upon storage. Additionally, the samples were studied with static light scattering, small deformation oscillatory rheometry and optical microscopy, under different conditions of nanocrystal concentration, ionic strength, pH and temperature. The chitin nanocrystals were proven quite effective in stabilizing o/w emulsions against coalescence, over a period of one month, as evidenced by static light experiments and microscopy, and this could be attributed to the adsorption of the nanocrystals at the oil–water interface. The rheological data provided evidence for network formation in the emulsions with increasing chitin nanocrystal concentration. Such a gel-like behaviour was attributed to an inter-droplet network structure and the formation of a chitin nanocrystal network in the continuous phase. The stability of the emulsions to creaming increased with an increase in nanocrystal concentration. Finally, by raising the temperature (20–74 °C), NaCl concentration (up to 200 mM) or pH (from 3.0 to 6.7) there was an enhancement of the emulsion elastic character and creaming stability.     

Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions

Flaxseed protein concentrate containing-mucilage (FPCCM) was used to stabilize soybean oil-in-water emulsions. The effects of FPCCM concentration (0.5, 1.0, 1.5% w/v) and oil-phase volume fraction (5, 10, 20% v/v) on emulsion stability and rheological properties of the soybean oil-in-water emulsions were investigated. Z-average diameter, zeta-potential, creaming index and rheological properties of emulsions were determined. The result showed that FPCCM concentration significantly affected zeta-potential, creaming rate and emulsion viscosity. The increasing of FPCCM concentration led to a more negative charged droplet and a lower creaming rate. Oil-phase volume fraction significantly affected Z-average diameter, rheological properties, creaming index and creaming rate. With the increase of oil-phase volume fraction, both Z-average diameter and emulsion viscosity increased, while creaming index and creaming rate decreased. The rheological curve suggested that the emulsions were shear-thinning non-Newtonian fluids.     

Influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions

Studies have been made of the changes in droplet sizes, surface coverage and creaming stability of emulsions formed with 30% (w/w) soya oil, and aqueous solution containing 1 or 3% (w/w) sodium caseinate and varying concentrations of xanthan gum. Addition of xanthan prior to homogenization had no significant effect on average emulsion droplet size and surface protein concentration in all emulsions studied. However, addition of low levels of xanthan (≤0.2 wt%) caused flocculation of droplets that resulted in a large decrease in creaming stability and visual phase separation. At higher xanthan concentrations, the creaming stability improved, apparently due to the formation of network of flocculated droplets. It was found that emulsions formed with 3% sodium caseinate in the absence of xanthan showed extensive flocculation that resulted in very low creaming stability. The presence of xanthan in these emulsions increased the creaming stability, although the emulsion droplets were still flocculated. It appears that creaming stability of emulsions made with mixtures of sodium caseinate and xanthan was more closely related to the structure and rheology of the emulsion itself rather than to the rheology of the aqueous phase.     

Application of multi-component biopolymer layers to improve the freeze–thaw stability of oil-in-water emulsions: β-Lactoglobulin–ι-carrageenan–gelatin

This study examines the influence of interfacial composition on the freeze–thaw stability of oil-in-water emulsions. Three 5% w/w oil-in-water emulsions (5 mM phosphate buffer, pH 6.0) were prepared using the layer-by-layer electrostatic deposition method that had different interfacial compositions: (i) primary emulsion (β-Lg); secondary emulsion (β-Lg–ι-carrageenan); (iii) tertiary emulsion (β-Lg–ι-carrageenan–gelatin). The primary, secondary and tertiary emulsions were subjected to from one to three freeze–thaw cycles (−20 °C for 22 h, +40 °C for 2 h) in the absence or presence of sucrose (10% w/w), and then their stability was assessed by ζ-potential, particle size, microstructure and creaming stability measurements. In the absence of sucrose, the primary and secondary emulsions were highly unstable to droplet aggregation and creaming after three freeze–thaw cycles, whereas the tertiary emulsion was stable, which was attributed to the relatively thick biopolymer layer surrounding the oil droplets. In the presence of 10% w/w sucrose, all of the emulsions were much more stable, which can be attributed to the ability of sucrose to increase the amount of non-frozen aqueous phase in the emulsions. The interfacial engineering technology used in the study could therefore lead to the creation of food emulsions with improved stability to freezing and thawing.     

Characterisation of emulsion properties and of interface composition in O/W emulsions prepared with hen egg yolk, plasma and granules

Comprehension of hen egg yolk emulsifying properties remains incomplete because competition between its various emulsifiers (proteins and lipoproteins containing phospholipids) has not been clearly elucidated and colloidal interactions between yolk-stabilised oil droplets have not been documented. Recent studies emphasised the interest of the fractionation of yolk into plasma and granules to improve this comprehension. In the present study, we characterised, concurrently, emulsion properties (oil droplet size and stability against creaming) and interface attributes (interfacial concentrations of proteins and phospholipids, SDS-PAGE profiles of adsorbed proteins and zeta potential) in oil-in-water (O/W) emulsions prepared with yolk, plasma and granules. We observed these features at four physicochemical conditions (pH 3.0 or 7.0 and at 0.15 or 0.55 M NaCl). Emulsion properties in emulsions made with yolk or plasma varied similarly as a function of pH and NaCl concentration whereas granules emulsions exhibited distinct properties. Therefore the main contributors to yolk emulsifying properties are to be sought for among plasma constituents (proteinaceous or phospholipids). Since, in plasma emulsions, variations of emulsion stability against creaming correlated exclusively to variations of protein interfacial concentration, a driving contribution of the proteinaceous part of plasma, namely apo-LDL, was hypothesised. In the pH and ionic strength ranges studied, zeta potentials of the interfaces were low, excluding extended electrostatic repulsion between oil droplets. We deduced that steric repulsion is the main interaction opposing to droplet aggregation in food emulsions made with yolk.     

Freeze–thaw stability of mayonnaise type oil-in-water emulsions

In this paper, the freeze–thaw stability of mayonnaise type oil-in-water emulsions is studied. The emphasis of the experiments have been on the properties of the dispersed oil phase as only small, or no effects, were observed from initial experiments on changing the properties of the aqueous phase within the investigated ranges. Different vegetable oils are investigated in order to relate the composition of the oil phase to the stability of the corresponding emulsion. The crystallization behaviour of the oils is studied with differential scanning calorimetry (DSC) and by freeze–thaw experiments in bulk systems. The amounts of triacylglycerides in the oils that theoretically crystallize at different temperatures are also calculated. Moreover, the impact of the freezing rate on the stability of emulsions is investigated. Large differences in freeze–thaw stability of emulsion prepared with different oils are observed. By principal component analysis (PCA) the stability of the emulsion could be correlated with the composition and crystallization behaviour of the oils. Small/no effects of the addition of different substances (for example polyglycerol esters and trehalose) to both oil and water phase are observed. Moreover, the experiments on the freezing conditions show that alteration of the freezing rate have a large impact on the freeze–thaw stability.     

Effect of processing conditions and composition on sodium caseinate emulsions stability

Many food products such as ice cream, yoghurt, and mayonnaise are some examples of emulsion-based food. The physicochemical properties of emulsions play an important role in food systems as they directly contribute to texture, sensory and nutritional properties of food. One of the main properties is stability which refers to the ability of an emulsion to resist physical changes over time. The aim of the present work was to analyze the effect of processing conditions and composition on sodium caseinate (NaCas) emulsions stability. The main destabilization mechanisms were identified and quantified. The relationship between them and the factors that influence them were also investigated. Emulsions stabilized with NaCas were prepared using an ultrasound liquid processor or a high pressure homogenizer. Stability of emulsions was followed by a Turbiscan (TMA 2000) which allows the optical characterization of any type of dispersion. The physical evolution of this process is followed without disturbing the original system and with good accuracy and reproducibility. To further describe systems, droplet size distribution was analyzed with light scattering equipment. The main mechanism of destabilization in a given formulation depended on different factors such as NaCas concentration, droplet size or processing conditions. The rate of destabilization was markedly lower with addition of sugar or a hydrocolloid to the aqueous phase. Xanthan (XG) and locust bean (LBG) gums produced an increase in viscosity of the continuous phase and structural changes in emulsions such as gelation. Sugars interacted with the protein decreasing particle size and increasing emulsion stability. The stability of caseinate emulsions was strongly affected not only by the oil-to-protein ratio but also by processing conditions and composition of aqueous phase. The structure of the protein and the interactions protein–sugar or the presence of a hydrocolloid played a key role in creaming and flocculation processes of these emulsions.     

The effect of chitosan on the properties of emulsions stabilized by whey proteins

The influence of the cationic amino polysaccharide chitosan content (0–0.5%) on particle size distribution, creaming stability, apparent viscosity, and microstructure of oil-in-water emulsions (40% of rapeseed oil) containing whey protein isolate (WPI) (4%) at pH 3 was investigated. The emulsifying properties, apparent viscosity and phase separation behaviour of aqueous WPI/chitosan mixture at pH 3 were also studied. The interface tension data showed that WPI/chitosan mixture had a slightly higher emulsifying activity than had whey protein alone. An increase in chitosan content resulted in a decreased average particle size, higher viscosity and increased creaming stability of emulsions. The microstructure analysis indicated that increasing concentration of chitosan resulted in the formation of a flocculated droplet network. This behaviour of acidic model emulsions containing WPI and chitosan was explained by a flocculation phenomenon.     

Oil-in-water emulsions stabilized by sodium caseinate: Influence of pH,high-pressure homogenization and locust bean gum addition

The effect of pH, addition of a thickening agent (locust bean gum) or high-pressure homogenization on the stability of oil-in-water emulsions added by sodium caseinate (Na-CN) was evaluated. For this purpose, emulsions were characterized by visual analysis, microstructure and rheological measurements. Most of the systems were not stable, showing phase separation a few minutes after emulsion preparation. However, creaming behavior was largely affected by the pH, homogenization pressure or locust bean gum (LBG) concentration. The most stable systems were obtained for emulsions homogenized at high pressure, containing an increased amount of LBG or with pH values close to the isoelectric point (pI) of sodium caseinate, which was attributed to the size reduction of the droplets, the higher viscosity of continuous phase and the emulsion gelation (elastic network formation), respectively. All the studied mechanisms were efficient to decrease the molecular mobility, which slowed down the phase separation of the emulsions. In addition, the use of sodium caseinate was also essential to stabilize the emulsions, since it promoted the electrostatic repulsive interactions between droplets.     

Stability of Whey Protein Concentrate/Sunflower Oil Emulsions as Affected by Sucrose and Xanthan Gum

The effect of the addition of sucrose and xanthan gum, protein concentration, and processing method on the stability and destabilization mechanism type of emulsions formulated with two commercial whey protein concentrate powders was described and quantified following system changes with a Turbiscan TMA 2000, a light scattering equipment and a confocal laser scanning microscope. Two different processing methods that gave particle sizes with different orders of magnitude were compared: homogenization by ULTRA-TURRAX (UT) and by ultrasound (US). The addition of sucrose to the aqueous phase of emulsions significantly diminished volume-weighted mean diameter (D _4,3) and improved stability. When the aqueous phase contained xanthan gum, the main destabilization mechanism for UT emulsions changed from creaming to flocculation. For US emulsions, although some aggregation was detected by confocal laser scanning microscopy, it was not great enough to modify the backscattering average (BS_av) in the middle zone of the tube (20–50 mm). At low protein concentrations, the profiles corresponded to destabilization of small aggregates. In those conditions, creaming was markedly enhanced as evident from creaming rate values. Independently of aqueous phase composition, US emulsions stabilized by protein concentrations higher than 5 wt% were stable, indicating that whey proteins were good emulsion stabilizers at pH close to 7. This study shows the relevance of protein type on stability and describes for the first time a behavior for whey proteins different from the one reported for caseins in literature.     

Effects of protein concentration and oil-phase volume fraction on the stability and rheology of menhaden oil-in-water emulsions stabilized by whey protein isolate with xanthan gum

The influences of protein concentration (0.2, 1, 2 wt%) and oil-phase volume fraction (5%, 20%, 40% v/v) on emulsion stability and rheological properties were investigated in whey protein isolate (WPI)-stabilized oil-in-water emulsions containing 0.2 wt% xanthan gum (XG). The data of droplet size, surface charge, creaming index, oxidative stability, and emulsion rheology were obtained. The results showed that increasing WPI concentration significantly affected droplet size, surface charge, and oxidative stability, but had little effect on creaming stability and emulsion rheology. At 0.2 wt% WPI, increasing oil-phase volume fraction greatly increased droplet size but no significant effect on surface charge. At 1 or 2 wt% WPI, increasing oil-phase volume fraction had less influence on droplet size but led to surface charge more negative. Increasing oil-phase volume fraction facilitated the inhibition of lipid oxidation. Meanwhile, oil-phase volume fraction played a dominant role in creaming stability and emulsion viscosity. The rheological data indicated the emulsions may undergo a behavior transition from an entropic polymer gel to an enthalpic particle gel when oil-phase volume fraction increased from 20% to 40% v/v.