Effect of interfacial composition on the physical stability and co-oxidation of proteins and lipids in a soy protein isolate-(−)-epigallocatechin gallate conjugate emulsion

Fibrillation of soy protein isolate in the presence of metal ions: Structure and gelation behavior

The structure and functional properties of protein fibrils are closely related to environmental factors in fibrillation. Herein, soy protein isolate fibrils (SPIFs, 22 mg/mL) were prepared under acid-heating conditions in the presence of 100 mM metal ions (K+, Na+, Ca2+, Mg2+, and Fe3+). Except for Fe3+, fibrillation and subsequent larger fibril aggregates were promoted, ultimately leading to gel formation. Compared with K+ or Na+, the addition of Ca2+ or Mg2+ resulted in more organized SPIF structures with increased β-sheet contents and higher ThT fluorescence intensities. Furthermore, both of them resulted in longer fibrils with an average contour length of 700-800 nm, which significantly enhanced the storage modulus. However, the presence of Fe3+ accelerated protein hydrolysis and inhibited SPIF formation, resulting in samples consistently exhibited liquid behavior. These findings provide a foundation for understanding the influence of metal ions on regulating the fibrillation and gelling properties of SPIFs.

Comparison of the physical stability, microstructure and protein-lipid co-oxidation of O/W emulsions stabilized by l-arginine/l-lysine-modified soy protein hydrolysate

This work investigated the physical stability, microstructure, and oxidative stability of the emulsions prepared by soy protein hydrolysate (SPH) after modification with different concentrations of l-arginine and l-lysine. l-Arginine and l-lysine significantly increased the absolute zeta potential values, and decreased droplet sizes of the emulsions, thereby improving the physical stability of the emulsions. Meanwhile, l-arginine and l-lysine markedly decreased the apparent viscosity of the emulsions. The measurement of interfacial protein adsorption percentage showed that l-arginine (≤0.5 %) promoted the adsorption of SPH at the oil-water interface, whereas l-lysine (≤1%) reduced the adsorption of SPH at the oil-water interface. In addition, l-arginine and l-lysine (≤0.5 %) could retard lipid and protein oxidation. Correlation analysis indicated that the improvement in the physical stability of the emulsions by l-arginine and l-lysine also enhanced the oxidative stability of the emulsions. In summary, l-arginine and l-lysine could be effective modifiers for the protein-based emulsion systems.

The mechanism of resveratrol stabilization and degradation by synergistic interactions between constituent proteins of whey protein

Whey protein isolate (WPI) is mainly composed of β-lactoglobulin (β-LG), α-lactalbumin (α-LA) and bovine serum albumin (BSA). The aim of this study was to compare and analyze the influence of WPI and its three main constituent proteins, as well as proportionally reconstituted WPI (R-WPI) on resveratrol. It was found that the storage stability of resveratrol was protected by WPI, not affected by R-WPI, but reduced by individual whey proteins at 45°C for 30 days. The rank of accelerated degradation of resveratrol by individual whey proteins was BSA > α-LA > β-LG. The antioxidant activity, localization of resveratrol and oxidation of carrier proteins were determined by ABTS, H2O2 assay, synchronous fluorescence, carbonyl and circular dichroism. The non-covalent interactions and disulfide bonds between constituent proteins improved the antioxidant activity of the R-WPI-resveratrol complex, the oxidation stability of the carrier and the solvent shielding effect on resveratrol, which synergistically inhibited the degradation of resveratrol in R-WPI system. The results gave insight into elucidating the interaction mechanism of resveratrol with protein carriers.

Fabrication of soy protein-polyphenol covalent complex nanoparticles with improved wettability to stabilize high-oil-phase curcumin emulsions

BACKGROUND

Recent studies have shown that the wettability of protein-based emulsifiers is critical for emulsion stability. However, few studies have been conducted to investigate the effects of varying epigallocatechin gallate (EGCG) concentrations on the wettability of protein-based emulsifiers. Additionally, limited studies have examined the effectiveness of soy protein-EGCG covalent complex nanoparticles with improved wettability as emulsifiers for stabilizing high-oil-phase (≥ 30%) curcumin emulsions.

RESULTS

Soy protein isolate (SPI)-EGCG complex nanoparticles (SPIEn) with improved wettability were fabricated to stabilize high-oil-phase curcumin emulsions. The results showed that EGCG forms covalent bonds with SPI, which changes its secondary structure, enhances its surface charge, and improves its wettability. Moreover, SPIEn with 2.0 g L -1 EGCG (SPIEn-2.0) exhibited a better three-phase contact angle (56.8 ± 0.3o) and zeta potential (-27 mV) than SPI. SPIEn-2.0 also facilitated the development of curcumin emulsion gels at an oil volume fraction of 0.5. Specifically, the enhanced network between droplets as a result of the packing effects and SPIEn-2.0 with inherent antioxidant function was more effective at inhibiting curcumin degradation during long-term storage and ultraviolet light exposure.

CONCLUSION

The results of the present study indicate that SPIEn with 2.0 g L -1 EGCG (SPIEn-2.0) comprises the optimum conditions for fabricating emulsifiers with improved wettability. Additionally, SPIEn-0.2 can improve the physicochemical stability of high-oil-phase curcumin emulsions, suggesting a novel strategy to design and fabricate high-oil-phase emulsion for encapsulating bioactive compounds. © 2024 Society of Chemical Industry.

The dispersibility of biphasic stabilized oil-in-water emulsions improved by the interaction between curdlan and soy protein isolate

Curdlan, a natural polysaccharide, exhibits emulsion-stabilizing and viscosity-modifying properties. However, when employed solely in the aqueous phase, curdlan's adhesive nature impedes droplet dispersion, resulting in a gel-like structure with limited applicability. This investigation formulated a biphasic stabilized oil-in-water emulsion by supplementing the oil phase with beeswax and the aqueous phase with curdlan and soy protein isolate (SPI). The addition of SPI transformed the structural characteristics from a gel-like to a mayonnaise-like structure. Maximal electrostatic repulsion was observed at an internal phase volume fraction of 30%, effectively precluding droplet aggregation owing to the absolute zeta potentials surpassing 40 mV. The emulsions displayed shear-thinning rheological behavior, with a higher storage modulus than the loss modulus, indicative of favorable elastic properties. Molecular docking revealed the predominant role of polar amino acids in facilitating hydrogen bond formation. This study provides a template for developing emulsions with biphasic stability and desirable dispersibility.

Lipid oxidation in emulsions: New insights from the past two decades

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products.

Effect of pectin concentration on emulsifying properties of black soldier fly (Hermetia illucens) larvae albumin modified by pH-shifting and ultrasonication

The effect of pectin concentration on the structural and emulsifying properties of black soldier fly larvae albumin (BSFLA) modified by pH-shifting (pH12) and ultrasound (US) was studied. The results (intrinsic fluorescence, surface hydrophobicity, Fourier transform infrared spectrum, and disulfide bonds) showed that modified BSFLA samples, especially pH12-US, were more likely to bind to pectin through hydrogen bonding, electrostatic interactions, and hydrophobic interactions due to the unfolding of BSFLA, the collapse of disulfide bonds and exposure of hydrophobic groups. Thus, a BSFLA-pectin complex with smaller particle size, more negative charges, and a relatively loose structure was formed. The emulsifying activity (EAI) and stability index (ESI) of pH12-US modified BSFLA were significantly enhanced by the addition of pectin, reaching the highest values (associated with 174.41 % and 643.22 % increase, respectively) at pectin concentration of 1.0 %. Furthermore, the interface modulus of the emulsion prepared by the modified BSFLA was mainly viscous, and had higher apparent viscosity, smaller particle size and droplet size, contributing to higher EAI and ESI. The study findings suggest the addition of pectin to pH12-US treated BSFLA could be used in industry to prepare BSFLA-pectin emulsion with exceptional/desirable properties.

Effect of heat treatment on the physical stability, interfacial composition and protein-lipid co-oxidation of whey protein isolate-stabilised O/W emulsions

This work aimed to investigate the effects of heat treatments at different temperatures (60, 70 and 90 °C, expressed as HT-60, HT-70 and HT-90) on interfacial composition and protein-lipid co-oxidation in whey protein isolate (WPI)-stabilised O/W emulsions during storage. Compared with control group, all heated emulsions exhibited weaker physical stability over 10 days of storage, which verified by the increased droplet size, as well as decreased adsorbed protein levels and absolute ζ-potential values. Moreover, proteins recovered from the HT-90 emulsion showed the highest fluorescence intensity and red-shift of the maximum emission wavelength, indicating partial unfolding of the protein structure. Meanwhile, severe changes in protein structure were also observed in the HT-70 and HT-90 emulsions, which clearly verified by the degradation of bovine serum albumin, α-lactalbumin and β-lactoglobulin. Furthermore, HT-70 and HT-90 emulsions showed lower levels of lipid hydroperoxides and thiobarbituric acid reactive substances. In contrast, the recovered proteins were subject to severe oxidative stress as indicated by carbonyl and N'-formyl-L-kynurenine. Hierarchical cluster and correlation analysis implied that the process of protein-lipid co-oxidation is inevitable, but it can be retarded by heat treatment. Our results clearly revealed the relevance among heat treatment, interfacial adsorption property, and the protein-lipid co-oxidation of O/W emulsions.

An overview of tea saponin as a surfactant in food applications

The residue of Camellia seeds after oil extraction contains many bioactive ingredients, including tea saponin. Tea saponin has many pharmacological effects and is an excellent nonionic surfactant. The development of natural surfactants has become a hot topic in food research. This review gathers the applications of tea saponin as a surfactant in food. It focuses on the application of tea saponin in emulsions, delivery systems, extraction and fermentation, as well as the challenges and development prospects in food applications. Tea saponin shows great potential as a surfactant in food applications, which can replace some synthetic surfactants. The full utilization of tea saponin improves the comprehensive utilization value of Camellia seed residue, contributes to the sustainable development of Camellia industry and avoids resource waste.

Molecular Mechanisms and Applications of Polyphenol-Protein Complexes with Antioxidant Properties: A Review

Proteins have been extensively studied for their outstanding functional properties, while polyphenols have been shown to possess biological activities such as antioxidant properties. There is increasing clarity about the enhanced functional properties as well as the potential application prospects for the polyphenol-protein complexes with antioxidant properties. It is both a means of protein modification to provide enhanced antioxidant capacity and a way to deliver or protect polyphenols from degradation. This review shows that polyphenol-protein complexes could be formed via non-covalent or covalent interactions. The methods to assess the complex's antioxidant capacity, including scavenging free radicals and preventing lipid peroxidation, are summarized. The combination mode, the type of protein or polyphenol, and the external conditions will be the factors affecting the antioxidant properties of the complexes. There are several food systems that can benefit from the enhanced antioxidant properties of polyphenol-protein complexes, including emulsions, gels, packaging films, and bioactive substance delivery systems. Further validation of the cellular and in vivo safety of the complexes and further expansion of the types and sources of proteins and polyphenols for forming complexes are urgently needed to be addressed. The review will provide effective information for expanding applications of proteins and polyphenols in the food industry.

Molecular mechanisms affecting the stability of high internal phase emulsions of zein-soy isoflavone complexes fabricated with ultrasound-assisted dynamic high-pressure microfluidization

In this study, zein-soy isoflavone complex (ZSI) emulsifiers were fabricated using ultrasound-assisted dynamic high-pressure micro fluidization to stabilise highinternal phase pickering emulsions. Ultrasound-assisted dynamic high-pressure micro-fluidization enhanced surface hydrophobicity, zeta potential, and soy isoflavone binding capacity, while it decreased particle size, especially during ultrasound and subsequent microfluidization. The treated ZSI could produce small droplet clusters and gel-like structures, with excellent viscoelasticity, thixotropy and creaming stability owing to their neutral contact angles. Ultrasound and subsequent micro fluidization treatment of the ZSI complexes were highly effective in preventing droplet flocculation and coalescence after long-term storage or centrifugation due to their higher surface load, thicker multi-layer interfacial structure, and stronger electronic repulsion between the oil droplets. This study provides insights and extends our current knowledge of how non-thermal technology affects the interfacial distribution of plant based particles and the physical stability of emulsions.

Targeting Interfacial Location of Phenolic Antioxidants in Emulsions: Strategies and Benefits

It is important to have larger proportions of health-beneficial polyunsaturated lipids in foods, but these nutrients are particularly sensitive to oxidation, and dedicated strategies must be developed to prevent this deleterious reaction. In food oil-in-water emulsions, the oil-water interface is a crucial area when it comes to the initiation of lipid oxidation. Unfortunately, most available natural antioxidants, such as phenolic antioxidants, do not spontaneously position at this specific locus. Achieving such a strategic positioning has therefore been an active research area, and various routes have been proposed: lipophilizing phenolic acids to confer them with an amphiphilic character; functionalizing biopolymer emulsifiers through covalent or noncovalent interactions with phenolics; or loading Pickering particles with natural phenolic compounds to yield interfacial antioxidant reservoirs. We herein review the principles and efficiency of these approaches to counteract lipid oxidation in emulsions as well as their advantages and limitations.

Effects of sous vide cooking combined with ultrasound pretreatment on physicochemical properties and microbial communities of Russian sturgeon meat (Acipenser gueldenstaedti)

BACKGROUND

The production of Russian sturgeon is expanding rapidly in China but it is necessary to adopt measures to extend the shelf life of sturgeon meat. Previous studies found that sous vide cooking (SVC) at 60 °C increased the protein and lipid oxidation. The addition of antioxidant substances reduced the acceptance of the product. The effect of combination SVC and ultrasound pretreatment was therefore investigated.

RESULTS

Results showed that SVC at 50 °C combined with ultrasound effectively restrained the growth of total viable counts (TVC) in samples. Meanwhile, the main dominant genera changed from Pseudomonas to Carnobacterium and the number of microbial species decreased. The odor profile of Russian sturgeon meat was more stable and the lipoxygenase (LOX) activity decreased more rapidly after treating with SVC and ultrasound. Importantly, more stable protein aggregates were formed in samples treated by SVC 50 °C together with ultrasound pretreatment, so the protein and lipid oxidation were slowed during storage. Higher springiness values were obtained and the color of sturgeon meat was lighter under these conditions.

CONCLUSION

The combination of SVC 50 °C and ultrasound pretreatment effectively inhibited the microbial growth of Russian sturgeon meat at lower oxidation levels. These findings theoretically support the preservation and development of sturgeon meat, and the application of SVC technology. © 2022 Society of Chemical Industry.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.