Aggregation Of Oil Droplets Research Articles

Fabrication and characterization of mayonnaise based on xanthan gum/lysozyme nanoparticles and konjac glucomannan as egg yolk substitutes under different temperature stresses

High cholesterol levels in mayonnaise pose a potential health threat to consumers, and there is an urgent need to develop cholesterol-reduced mayonnaise to meet consumer demand. Therefore, the aim of this study was to prepare a cholesterol-reduced Pickering emulsion mayonnaise (PEM) by replacing egg yolk with xanthan gum/lysozyme nanoparticles (XG/Ly NPs) and konjac glucomannan (KGM). In addition, the decorated appearance, droplet size, centrifugal stability, microstructure, and rheological properties of PEM were determined at different temperature fields (ambient, pasteurized, and refrigerated). The results showed that KGM provided additional network structure for PEM when the yolk substitution rate was no more than 40%, limiting oil droplet aggregation, as evidenced by the enhanced centrifugal stability and significantly reduced droplet size (P < 0.05). Moreover, the PEM supplemented with 0.2% KGM at 40% yolk substitution showed good viscoelasticity and small particle size (12.4 ± 0.7 μm) after pasteurization (65 °C for 30 min) and 30 days of refrigeration. Overall, XG/Ly NPs and KGM can be used as potential egg yolk substitutes and provide a new theoretical reference for the food industry to develop highly stable cholesterol-reduced mayonnaise.

Wide pH, Adaptable High Internal Phase Pickering Emulsion Stabilized by a Crude Polysaccharide from Thesium chinense Turcz.

The ultrasound-assisted extraction conditions of Thesium chinense Turcz. crude polysaccharide (TTP) were optimized, and a TTP sample with a yield of 11.9% was obtained. TTP demonstrated the ability to stabilize high-internal-phase oil-in-water emulsions with an oil phase volume reaching up to 80%. Additionally, the emulsions stabilized by TTP were examined across different pH levels, ionic strengths, and temperatures. The results indicated that the emulsions stabilized by TTP exhibited stability over a wide pH range of 1-11. The emulsion remained stable under ionic strengths of 0-500 mM and temperatures of 4-55 °C. The microstructure of the emulsions was observed using confocal laser scanning microscopy, and the stabilization mechanism of the emulsion was hypothesized. Soluble polysaccharides formed a network structure in the continuous phase, and the insoluble polysaccharides dispersed in the continuous phase, acting as a bridge structure, which worked together to prevent oil droplet aggregation. This research was significant for developing a new food-grade emulsifier with a wide pH range of applicability.

Effect of protein oxidation on the structure and emulsifying properties of fish gelatin

This study aimed to investigate the effect of oxidation on fish gelatin and its emulsifying properties. Fish gelatin was oxidized with varying concentrations of H2O2 (0–30 mM). Increased concentrations of the oxidant led to a decrease in amino acids in the gelatin, including glycine, lysine, and arginine. Additionally, the relative content of ordered secondary structure and triple helix fractions decreased. Zeta potential decreased, while particle size, surface hydrophobicity, and water contact angle increased. Regarding emulsifying behavior, oxidation promoted the adsorption of gelatin to the oil–water interface and reduced interfacial tension. With increased degrees of oxidation, the zeta potential and size of the emulsion droplets decreased. The oxidized gelatin exhibited better emulsifying activity but worse emulsifying stability. Based on these results, a mechanism for how oxidation affects the emulsifying properties of gelatin was proposed: the increase in gelatin’s hydrophobicity and the decrease in triple helix structure induced by oxidation reduced the interfacial tension at the oil–water interface. This promoted protein adsorption at the oil–water interface, allowing the formation of smaller oil droplets and enhancing gelatin’s emulsifying activity. However, the decrease in electrostatic repulsion between emulsion droplets and the decrease in solution viscosity increased the flocculation and aggregation of oil droplets, ultimately weakening the emulsifying stability of gelatin.

(Non)linear Interfacial Rheology of Tween, Brij and Span Stabilized Oil-Water Interfaces: Impact of the Molecular Structure of the Surfactant on the Interfacial Layer Stability.

During emulsification and further processing (e.g., pasteurizing), the oil-water interface is mechanically and thermally stressed, which can lead to oil droplet aggregation and coalescence, depending on the interfacial properties. Currently, there is a lack of insights into the impact of the molecular structure (headgroup and FA chain) of low molecular weight emulsifiers (LME) on the resulting interfacial properties. Additionally, the crystallization/melting of the oil/the emulsifier is often neglected within interfacial rheological experiments. Within this study, the stability of interfaces formed by Tween, Span or Brij was determined as a function of their molecular structure, taking crystallization effects of the LME into account. The headgroup was kept constant while varying the FA, or vice versa. The interfacial film properties (viscoelasticity) were investigated at different temperatures using dilatational and interfacial shear rheology. Both the headgroup and the FA chain impacted the interfacial properties. For the same FA composition, a rather small hydrophobic headgroup resulted in a higher packed interface. The interfacial elasticity increased with increased FA chain length (C12 to C18). This seemed to be particularly the case when the emulsifier crystallized on the interface among cooling. In the case of a densely packed interface, network formation due to chain crystallization of the LME's FA chains occurs during the cooling step. The resulting interface shows predominantly elastic behavior.

Investigating aggregation of heavy oil droplets: Effect of asphaltene anionic carboxylic

Understanding the impact of asphaltene molecules on heavy oil droplet aggregation is vital for oil field development. Here, the impact of terminal carboxyl groups in asphaltene molecules on heavy oil droplet aggregation was investigated. Results suggest that the anionic asphaltenes were more readily adsorbed onto the water–oil interface than normal asphaltenes. Stacking structures between asphaltene and resin involve predominant face-to-face and edge-to-face aggregation. The anionic asphaltene system boosts grid strength (Asp-Asp interaction) and interaction with water (Asp-water interaction) among oil droplet molecules. We hope these insights that can offer strategies for improving the efficiency and sustainability of heavy oil extraction.

Transglutaminase cross-linking ovalbumin-flaxseed oil emulsion gels: Properties, microstructure, and performance in oxidative stability

This study prepared emulsion gels by modifying ovalbumin (OVA)-flaxseed oil (FSO) emulsions with transglutaminase (TGase) and investigated their properties, structure and oxidative stability under different enzyme reaction times. Here, we found prolonged reaction times led to the transformation of α-helix and β-turn into β-sheet and random coil. The elasticity, hardness and water retention of the emulsion gels increased significantly, but the water-holding capacity decreased when the reaction time exceeded 4 h. Confocal laser scanning microscope (CLSM) indicated extended enzyme reaction time fostered oil droplet aggregation with proteins. Emulsion gel reduced FSO oxidation, especially after 4 h of the enzyme reaction, the peroxide value (PV) of the emulsion gel was reduced by 29.16% compared to the control. In summary, the enzyme reaction time of 4 h resulted in the formation of a dense gel structure and enhanced oxidative stability. This study provides the potential applications in functional foods and biomedical fields.

Construction and characterization of pickering emulsion gels stabilized by β-glucans microgel particles

Amidst the rising demand for protein and starch, polysaccharide-based microgel particles (MPs) offer a sustainable solution as Pickering emulsion gel (PEG) stabilizer. β-glucans, known for their resistance to rapid digestion, enable targeted ingredient delivery and intestinal health modulation. A novel PEG stabilizer was developed by incorporating non-gelatinous polysaccharide 1,3-α/β-D-glucan into gelatinous polysaccharide 1,3-β-D-glucan after thermally induced gelation and microgelation. Following the blending of these polysaccharides, the three-phase contact angle of the resulting composite β-glucans MPs was modified from 126.6° to 94.7°, achieving nearly neutral wettability. Moreover, the particle size was reduced from 6.64 to 2.74 μm, accompanied by a potential of −21.55 mV. These structural modifications facilitated improved adsorption properties of MPs at the oil-water interface, subsequently leading to complete coverage of the oil droplet surface. Consequently, this process resulted in the formation of small, uniformly distributed emulsion droplets. Confocal laser microscopy revealed that the β-glucans MPs either interconnected to create gel networks or coated with oil droplets. This phenomenon established a thick barrier that prevented oil droplet aggregation and conferred semi-solid physical properties of the PEG. It is worth noting that particle concentration and oil content significantly influenced droplet size, rheological properties, and the stability of PEGs. Specifically, PEGs with prolonged stability were successfully constructed at low MP concentrations (0.6–1.0 wt%) and low oil content (20–50 wt%). This research introduces an innovative approach for structuring liquid oil, with potential applications in fat replacement.

Phycocyanin-chitosan complex stabilized emulsion: Preparation, characteristics, digestibility, and stability

Phycocyanin is a natural pigment protein with antioxidant, anti-tumor, and anti-inflammatory properties, but its relatively poor emulsibility limits its use in the food industry. In order to improve the emulsifying capacity of phycocyanin, a novel phycocyanin-chitosan complex was prepared, and the characteristics, digestibility, and stability of emulsion containing oil droplets stabilized by the complex were investigated. The results showed that the phycocyanin-chitosan complex had better stability and lower interfacial tension at pH 6.5 than phycocyanin, and it significantly improved the stability of emulsion and inhibited the aggregation of oil droplets. The phycocyanin-chitosan complex stabilized emulsion showed better physical stability, digestibility, and oxidation stability than the phycocyanin emulsion. The particle size of the phycocyanin-chitosan complex stabilized emulsion was very small (from 0.1 to 2 μm), and its absolute value of zeta potential was high. Overall, this study suggests that the phycocyanin-chitosan complex effectively improved the emulsifying capacity of phycocyanin.

Regulation mechanism of curcumin-loaded oil on the emulsification and gelation properties of myofibrillar protein: Emphasizing the dose-response of curcumin.

The regulation mechanism of curcumin (CUR) in the oil phase on the emulsification and gelation properties of myofibrillar protein (MP) was investigated. CUR enhanced the emulsifying activity index (EAI) of MP but decreased its turbiscan stability index (TSI) and surface hydrophobicity, which exacerbated oil droplet aggregation. Medium amounts (200mg/L) of CUR changed the 3D network architectures of emulsion gels from lamellar to reticular, improving the gels' water-holding capacity (WHC), storage modulus, springiness, and cohesiveness. Besides, the LF-NMR revealed that CUR had limited effects on the mobility of immobilized and free water. The α-helix of MP in gels with medium amounts of CUR decreased from 51% to 45%, but the β-sheet increased from 23% to 27% compared to those without CUR. Overall, CUR has the potential to become a novel structural modifier in emulsified meat products due to its dose-response.

H3O+…Cl− ion pairs on the surface of concentrated hydrochloric acid: Reverse mass transfer of dissociated hydronium and chloride ions and the effect on separation at interface

The separation process in hydrochloric acid environments is determined by the interfacial chemistry of the acid. However, the surface species of concentrated acids are complex. The effect of dominant species on the surface of concentrated acids and their dissociation behavior on interfacial separation has been the focus of academic debate. The extraction and separation of two typical anions, PdCl42− and PtCl62−, with different hydration characters on the surface of concentrated hydrochloric acid were investigated by thin layer extraction (TLX). A new phenomenon was discovered that the effect of hydrochloric acid concentration, extractant concentration, organic film thickness, and shear flow rate on the extraction of easily hydrated PdCl42− anions is greater than that of hardly hydrated PtCl62−. However, during the conventional SX process, the phenomenon cannot be observed due to the continuous dispersion and aggregation of oil droplets. It found that HCl molecules only dissociate into solvated H3O+…Cl− ion pairs on the surface of concentrated hydrochloric acid, but not H3O+ and Cl− ions respectively. The concentration of dissociated H3O+ ions at the interface is lower than that in the bulk phase. The protonation of the A336 molecule promotes the migration of dissociated H3O+ ions in the bulk phase towards the interface. Because the PdCl42− anions are more likely to be hydrated than PtCl62− anions and combine with H3O+ ions, the orderly migration of H3O+ ions in the laminar boundary layer towards the interface drives the mass transfer of easily hydrated PdCl42− anions. The anion exchange between PdCl42− and Cl− ions associated with the A336 molecules results in a higher concentration of Cl− ions enriched at the interface than that in the bulk phase. The migration of easily hydrated Cl− ions towards the bulk phase would drag the water molecules around PtCl62− anions and therefore inhibit the mass transfer of PtCl62− anions. The orderly reverse migration of H3O+ and Cl− ions enhances the separation between easily hydrated PtCl62− and hardly hydrated PdCl42− anions. This study offers a new perspective on the dissociation of species on the surface of concentrated hydrochloric acid and its impact on separation processes.

Comparative effects of micro vs. submicron emulsions on textural properties of myofibrillar protein composite gels

This study aimed to investigate the impact of emulsion particle size (micro vs. submicron) on the physicochemical and rheological properties of myofibrillar protein (MP) gels. MP-based oil-in-water micro-emulsions (∼2,091 nm) and submicron-emulsions (∼522 nm) were compared with each other and with lecithin-stabilized micro-emulsions (∼1,330 nm) and submicron-emulsions (∼543 nm). Emulsion particle size, ζ-potential, and morphological properties using transmission and confocal microscopies) were measured. Additionally, dynamic rheological behavior, mechanical strength, water-holding capacity (WHC), water mobility, and protein secondary structures of the emulsion gels containing 2.5% protein and 5% oil) were analyzed. The results showed that emulsion droplet size had no significant effect on gel strength and storage modulus, regardless of the surfactants used. However, the MP-coated submicron-emulsion exhibited a greater improvement in gel WHC (p < 0.05) compared to its micro-emulsion counterpart. Overall, emulsion gels displayed greater strength than oil-free control gels. MP-based emulsions proved more effective than lecithin-stabilized emulsions in modifying the gelling properties, primarily due to the formation of a visible interfacial protein film that prevented oil droplet aggregation. Based on these findings, protein-based emulsions were preferred over lecithin-based emulsions, with MP submicron-emulsions offering the advantage of enhanced moisture retention in cooked MP gels.

High inner phase emulsion of fish oil stabilized with rutin-grass carp (Ctenopharyngodon idella) myofibrillar protein: Application as a fat substitute in surimi gel

This study investigated the effect of rutin-grass carp myofibrillar protein (R-GMP) co-stable fish oil high internal phase emulsion on the quality of surimi gel compared with the direct addition of soybean oil. Combined with the stability, microstructure and rheological properties, R-GMP (GMP: 3.0%, rutin: 12%,/GMP, w/w) could form a stable O/W type high internal phase Pickering emulsion with an oil-water ratio of 0.75. The L*, a*, and b* values and whiteness of silver carp surimi gel were increased significantly (P < 0.05) after fish oil-based high internal phase emulsion was added as oil. Meanwhile, compared with the direct addition of soybean oil, the hardness, chewiness, gel strength and water-holding capacity of surimi gel were significantly enhanced (P < 0.05) after the addition of R-GMP high internal phase emulsion, and more free water was bound to the gel network. The microstructure showed that the R-GMP high internal phase emulsion could be evenly distributed in the dense and ordered protein network gel in the form of small oil droplets, while the direct addition of soybean oil would produce an aggregation of oil droplets and destroy the network structure of the gel. In conclusion, R-GMP stabilized fish oil high internal phase emulsion optimizes the gel quality of oil-enhanced surimi gel, providing new ideas for healthy fat replacement and the development of functional emulsified surimi products.

Studies on stabilized mechanism of high internal phase Pickering emulsions from the collaboration of low dose konjac glucomannan and myofibrillar protein

In this study, the effects of different concentrations (0%, 0.25%, 0.5%, 1%, 1.5%, w/v) of konjac glucomannan (KGM) on the structure and interfacial adsorption of myofibrillar protein (MP) and the mechanism of co-emulsification of high internal phase Pickering emulsions (Pickering HIPEs) by KGM and MP were investigated. The results showed that for interfacial MPs, KGM addition promoted MP structure unfolding and improved MP wettability with a three-phase contact angle from 73.69° (control) to 89.41° (0.5% KGM), thereby lowering the energy barriers to MP penetrating and rearranging at the interface. Furthermore, the adsorption kinetics and protein adsorption percentage (AP%) indicated that KGM (≤1%) facilitated the adsorption of MP from the aqueous phase to the oil-water interface. For MP in the aqueous phase, KGM induced a denser MP network structure by promoting “concentrated” MP and connecting MP through hydrogen bonding, which formed a stronger spatial site resistance and hindered oil droplet aggregation. KGM (≤1%, especially 0.5%) resulted in reduced droplet size, relaxation time (T2), lipid oxidation, and improved storage stability and energy storage modulus of Pickering HIPEs. However, the competitive adsorption of KGM (>1%) significantly decreased the interface MP, and the formation of continuous KGM hydrogel formed an unaggregated MP network structure, decreasing the emulsion performance further. Overall, KGM could modulate the physical properties of MP-stabilized Pickering HIPEs by altering the interfacial adsorption and network structure.

Formation and characterisation of concentrated emulsion gels stabilised by faba bean protein isolate and its applications for 3D food printing

Concentrated emulsions were prepared at a fixed oil concentration (50 wt%) using faba bean protein isolates (FPI) as an emulsifier and texturizer. Effects of FPI concentration (1, 3 and 5 wt%; at pH7), pH (pH 3, 5, 7, and 9; 3 wt%) and addition of salts (200 mM NaCl and 40 mM CaCl2; at 3 wt% FPI and pH 7) on the emulsion formation were studied. The oil droplet size and microstructural characteristics were examined by static light scattering and confocal laser scanning microscopy (CLSM), and the viscoelastic behaviours of emulsions were characterised by oscillatory rheology. At all different FPI concentrations, the emulsions formed viscoelastic gels with different gel strengths and stability due to network formation and interactions between jammed oil droplets and protein aggregates. The oil droplet size, rheological properties, and 3D printability of emulsions were not significantly changed by the presence of salts. The storage modulus G′ (1 Hz) values were higher at higher FPI concentrations, and higher pH values (i.e., pH 7 and 9) as the droplet size was smaller and the droplet packing was more compact, resulting in a better 3D printing performance. Furthermore, the heat treatment (90 °C for 30 min) remarkedly improved gel strength and the 3D printability because of protein denaturation and oil droplet aggregation. This finding demonstrated that the emulsion gel formed with FPI was tuneable for food 3D printing. Most of samples displayed high printing precision with great self-supporting capability, which may find potential applications in creating specialised diet.

Emulsion-Templated Liquid Oil Structuring with Egg White Protein Microgel- Xanthan Gum.

In this study, oleogels were prepared by the emulsion-template method using egg-white protein microgel as a gelator and xanthan gum (XG) as thickener. The physicochemical properties of the emulsion and oleogels were investigated. The adsorption of protein on the surface of the oil droplet reached saturation when the protein microgel concentration reached 2%. The excess protein combined with XG and accumulated on the outer layer of the oleogel, which prevented the emulsion from flocculation, enhanced the oil-holding capacity of the oleogel, and had a positive effect on preventing the oxidation of oil. When the concentration of XG was less than 0.4%, the EWP microgel, combined with the XG, stabilized the emulsion. As the concentration of XG was greater than 0.4%, excessive XG in the emulsion improved the viscosity and mechanical properties of the emulsion to prevent the aggregation of oil droplets. However, the change in XG concentration had no significant effect on the oxidation of the oil.

Structural properties of Phoenix Oolong tea polysaccharide conjugates and the interfacial stability in nanoemulsions.

Tea Polysaccharide conjugate (TPC) is a naturally occurring active substance that is extracted from tea. Due to its benefits in enhancing human immunity and antioxidant effects, TPC is widely used in culinary products. The binding mode of polysaccharides and proteins in TPC, however, hasn't been well studied, it may be closely related to their functional properties, especially emulsification. The molecular weights and monosaccharide compositions of TPC was determined by ion chromatography and high-performance gel permeation chromatography. Although the functional groups of polysaccharides and proteins were confirmed by infrared spectroscopy; the presence of proteins couldn't be detected by SDS-PAGE and UV spectroscopy. It was hypothesized that the hydrophobic groups of the proteins in TPC were wrapped by polysaccharide chains, thus making the proteins undetectable. The rheology and interfacial protein adsorption results show that TPC forms a viscoelastic film at the oil-water interface to prevent the aggregation of oil droplets, thereby enhancing the stability of the emulsion. Based on these structural and emulsifying properties of TPC, the binding mode of polysaccharides and proteins along with their phase behavior at the oil-water interface of the emulsion was speculated. In TPC, the hydrophilic groups of the proteins are linked to polysaccharides by covalent interactions, where the hydrophobic groups are wrapped with the polysaccharide chains with the help of hydrophobic forces to form a hydrophobic core. The unique binding of polysaccharides and proteins in TPC enhances its amphiphilic properties, which can be effectively distributed at the oil-water interface and form stable emulsions. This article is protected by copyright. All rights reserved.

Improvement of Oxidative Stability of Fish Oil-in-Water Emulsions through Partitioning of Sesamol at the Interface

The susceptibility of polyunsaturated fatty acids to oxidation severely limits their application in functional emulsified foods. In this study, the effect of sesamol concentration on the physicochemical properties of WPI-stabilized fish oil emulsions was investigated, focusing on the relationship between sesamol-WPI interactions and interfacial behavior. The results relating to particle size, zeta-potential, microstructure, and appearance showed that 0.09% (w/v) sesamol promoted the formation of small oil droplets and inhibited oil droplet aggregation. Furthermore, the addition of sesamol significantly reduced the formation of hydrogen peroxide, generation of secondary reaction products during storage, and degree of protein oxidation in the emulsions. Molecular docking and isothermal titration calorimetry showed that the interaction between sesamol and β-LG was mainly mediated by hydrogen bonds and hydrophobic interactions. Our results show that sesamol binds to interfacial proteins mainly through hydrogen bonding, and increasing the interfacial sesamol content reduces the interfacial tension and improves the physical and oxidative stability of the emulsion.

Oxidized high-amylose starch as pickering stabilizer for oil-in-water emulsion and delivery of bioactive compound

Polysaccharide based emulsions have received considerable attention due to their biodegradability, biocompatibility and food-safety. In this study, oxidized high-amylose starch (OHAS) is adopted for stabilization of oil-in-water (O/W) emulsion. Results showed that OHAS with oxidation degree of 90% (DO90-OHAS) exhibited higher wettability with three-phase contact angle of 70.6°. The obtained emulsion was stable within a wide range of different solution condition, with pH ranging from 3 to 7, salt concentration as high as 1.0 M and temperature ranging from -25 to 80 ℃. The gel-like network structure of DO90-OHAS effectively stabilized the emulsion and prevented the aggregation of oil droplets under different pH, as evidenced by confocal laser scanning microscopy (CLSM) observation. Furthermore, DO90-OHAS based emulsion prepared at different pH showed satisfactory long-term storage stability (up to 30 days). The fabricated emulsion was utilized for encapsulation of hydrophobic bioactive substances, with ∼72.5% encapsulation efficiency for β-carotene. The DO90-OHAS based emulsion enabled the controlled-release of β-carotene in vitro, with antioxidant activity maintained ∼50% of initial activity when exposed to elevated temperature (80°C). This research may provide a new avenue for OHAS based Pickering emulsions preparation and bioactive components delivery.

Improving freeze-thaw stability and 3D printing performance of soy protein isolate emulsion gel inks by guar & xanthan gums

Frozen storage of 3D printing inks could increase their shelf life. We improved freeze-thaw stability and 3D printing performance of soy protein isolate (SPI) emulsion gel inks by guar (GG) and xanthan gums (XG). Freeze-thawed inks led to higher storage modulus (G′), lower water holding capability (WHC) and poor printing performance compared to initial inks. An increase in gums content decreased oil droplet aggregation and protein flocculation in all freeze-thawed inks, hence reducing syneresis in the gel structure and preventing solid-liquid separation during 3D printing. The freeze-thaw stability of SPI-XG inks was consistently greater than that of SPI-GG inks at the same concentrations, resulting in superior 3D printing performance. The hardness of cylinders printed with SPI-XG0.5 freeze-thawed inks was lower than that of the cylinders printed by initial inks, in contrast to the results of G'. At the maximum strain amplitude (500%), Lissajous analysis indicated that the SPI-XG0.5 freeze-thawed inks retained less energy than the initial inks, resulting in a weaker gel. Overall, this study demonstrated that freeze-thaw treatment negatively affected the 3D printing performance of SPI emulsion gel inks, but that the 3D printing performance of freeze-thaw inks could be reinforced by modifying the formulation.

Effects of different pH conditions on interfacial composition and protein-lipid co-oxidation of whey protein isolate-stabilised O/W emulsions

The physical stability, interfacial composition and protein-lipid co-oxidation of O/W emulsions stabilised by whey protein isolate under different pH conditions (3.0, 5.0, 7.0 and 9.0) with fixed storage times were assessed in the present study. The results revealed that different pH conditions had distinct effects on the physical stability of the emulsions, as verified by the droplet size, ζ-potential and interfacial composition. Acidic conditions had an unnoticeable impact on protein-lipid co-oxidation. Remarkable physical barrier-like protection of the lipid core provided by adsorbed proteins (AP) was observed in the O/W emulsions under neutral conditions. However, alkaline conditions (pH 9.0) could induce the most severe protein-lipid co-oxidation when the storage time was extended, as indicated by the highest levels of protein and lipid oxidation products (carbonyl, N′-formyl-l-kynurenine, lipid hydroperoxides, thiobarbituric acid-reactive substances and volatile lipid oxidation products), in addition to the obvious molecular changes in unadsorbed proteins (UAP) or AP. Free radicals and metal ions could more easily react with highly unfolded and negatively charged AP under strong alkaline conditions. Our findings clearly revealed that the co-oxidation phenomenon of O/W emulsion systems were closely related to the synergistic effects between the transformation of interfacial composition and aggregation of oil droplets that occurred under different pH conditions.