In view of the fact that perilla oil tends to be oxidized during storage, with soy protein isolate (SPI) or its blends with chitosan (CS) and sodium alginate (SA) as the emulsifier, electrostatic layer-by-layer self-assembly was used to encapsulate perilla oil to maintain its physical stability and for its sustained release. The microscopic morphology and stability of the perilla oil single-layer emulsion, double-layer emulsion and three-layer emulsion were investigated, and an in vitro simulated digestion model was established to determine changes in the fatty acid composition of the three emulsions before and after digestion by gas chromatography. The results showed that the three emulsions, prepared using a wall material composed of 1.0% SPI solution, 2.0% CS solution, and 1.5% SA solution, had small particle size, high potential, and good physical and chemical stability. Under acidic conditions, the multi-layer emulsions could better protect polyunsaturated fatty acids. As the number of layers increased, the oxidation rate of perilla oil became slower. The in vitro simulated digestion results showed that the three-layer emulsion had a better sustained-release effect than the single-layer and double-layer emulsions, and the multi-layer emulsion could ensure the effective release of fatty acids from the oil. These findings can guide the development of slow-release systems for oils.

In this paper, we explored the relationship between the conformational changes of soybean protein isolate (SPI) caused by charge density modification through succinylation and the improvement in emulsifying properties. Succinic anhydride was used to modify SPI. The conformational changes of SPI with different degrees of succinylation were analyzed by fluorescence spectroscopy, ultraviolet spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The effect of succinylation on the physiochemical properties of SPI was characterized by scanning electron microscopy, zeta potential, surface hydrophobicity, molecular flexibility and emulsification. The results showed through succinylation reaction, succinyl groups were successfully grafted onto SPI, so that the isoelectric point of SPI decreased and the electronegativity increased. Additionally, the microstructure was changed with small holes on the surface of the smooth and irregular sheet structure, and the the molecular mass was increased. The increase in charge density led to unfolding of the tertiary structure of SPI, exposure of tryptophan residues burying and tyrosine residues, and a red shift in the fluorescence and ultraviolet absorption spectra, which proved that succinylated SPI is located in a more hydrophilic environment. The reaction between free amino groups in SPI and succinyl groups transformed the N–H bond into C–N bond, resulting in changes in the amide Ⅲ band. The surface hydrophobicity of succinylated SPI was decreased, the molecular flexibility was increased, and the emulsification activity and emulsifon stability were improved compared to SPI. This study confirmed that the increase in the charge density of succinylated SPI can affect the spatial conformation of SPI and consequently improve the emulsifying properties significantly.

The present work was executed in order to investigate the influence of pasteurization on the oxidative stability of oil body emulsions from soybean, sunflower, peanut, sesame and walnut. The basic composition and fatty acid composition of the five oil bodies and the composition of their associated proteins were evaluated, and the influence of pasteurization at 85 ℃ for 10 min on the physical and oxidative stability of the oil body emulsions was investigated by dynamic laser scattering and confocal laser scanning microscopy. The results showed that the oil bodies revealed significant differences in their basic composition and fatty acid composition as well as the composition of their associated proteins. The oil body-associated proteins consisted of intrinsic and extrinsic membrane proteins. Unsaturated fatty acids were the major ones in oil bodies. Oleic acid, linoleic acid and α-linolenic acid were the predominant unsaturated acids. Of these five oil bodies, soybean oil bodies had the highest contents of protein and moisture, and the lowest oil content. Peanut oil bodies had the highest relative content of saturated fatty acids (21.27%), while walnut oil bodies had the highest relative content of unsaturated fatty acids (90.10%). Pasteurization is proven to improve the oxidative stability of oil body emulsions from soybean and peanut significantly. However, it can promote the oxidation of oil body emulsions from sunflower, sesame and walnut. These results provide evidence supporting the industrial application of oil bodies in salad, vegetable milk and other similar products.

The purpose of this study was to understand the stability of natural emulsions formed from soybean oil bodies (SOB) extracted at alkaline pH (8.0‒11.0) and their digestive properties in the gastrointestinal tract. The stability of SOB was evaluated in terms of its basic composition, particle size, zeta potential and rheology, and the digestive properties were evaluated in terms of fatty acid release from SOB and the microstructure of SOB. The results showed that with an increase in extraction pH, the water and protein contents of SOB decreased and the particle size decreased from (471.57 ± 8.53) nm to (424.77 ± 12.21) nm, while the lipid content increased. In addition, the oxidative stability of SOB showed a similar trend. Specifically, the peroxide value (POV) decreased with increasing extraction pH and the thiobarbituric acid reactive substances (TBARS) value increased with an increase in storage time. The apparent viscosity decreased with increasing shear rate. SOB emulsions showed shear thinning behavior with G’ being greater than G” for all samples, and the release percentage of free fatty acids from SOB significantly increased with increasing extraction pH (P < 0.05). This study provides theoretical support for the wide application of highly stable natural SOB.

This study aimed to explore the binding mechanism of soybean β-conglycinin (7S)/glycinin (11S) with baicalein, and to investigate the changes in the conformational and functional properties of the complexes. Fourier transform infrared (FT-IR) spectroscopy indicated that baicalein could induce the transformation of β-sheets into α-helices and random coils. Intrinsic fluorescence spectra confirmed that the addition of baicalein made the structure of 7S and 11S more compact. The reaction of baicalein with the proteins took place spontaneously and quenched the protein fluorescence in a static manner. The 7S and 11S proteins bound to baicalein by hydrogen bonds and hydrophobic interactions, respectively. Molecular docking results showed that the affinity of baicalein to 11S was higher than that to 7S. Scanning electron microscopy (SEM) showed microstructure differences between 7S and 11S and their complexes. In addition, the surface hydrophobicity of 7S and 11S was decreased and the functional properties such as thermal stability were improved after combining with baicalein.

A curcumin delivery system was prepared by using the pH-shift method to load curcumin into the oil phase core of soybean oil body, which has a natural oil-in-water structure. The encapsulation characteristics of the emulsion were studied in terms of its encapsulation efficiency, particle size, zeta potential, and microstructure. The structural changes were analyzed by endogenous fluorescence spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the storage stability, pH stability and oxidation stability were evaluated. The results showed that curcumin was successfully encapsulated with soybean oil body by the pH-shift method. At pH 1.0, the highest encapsulation efficiency of 65.55% was observed, and the lipid droplets were regular in shape and uniform in size, with an average particle size of 590.5 nm. The oxidative stability was good, but the storage stability and pH stability were poor. Protein structure was not changed significantly compared to untreated oil body. This study may provide a reference for future research on natural oil body to carry lipophilic polyphenols such as curcumin.

In this study, natural soybean oil body emulsion and pectin were combined by electrostatic deposition for the preparation of soybean oil body-pectin composite oleogel by emulsion template method. The macro- and micro-structures of soybean oil body-pectin composite oleogel were studied, and the average particle size, zeta potential, oil binding capacity, re-dissolution stability, rheological properties, texture properties and oxidative stability were analyzed. The results showed that the average particle size and zeta potential of the composite emulsion containing 1.0% of pectin (m/m) were both smallest and were 423.13 nm and −23.23 mV, respectively. Cryoscanning electron microscopy (Cryo-SEM) showed that with an increase in pectin concentration, the structure of the sample was more compact, the hardness of the freeze-dried sample increased, and the gel strength of the oleogel increased; it showed shear thinning and good thixotropy. In addition, the addition of pectin could significantly improve the oxidative stability of oleogels. Notably, the oleogel containing 1.0% or more of pectin had good re-dissolution stability, and the average particle size and zeta potential of the obtained emulsion were not significantly different from those of the initial emulsion. The three-dimensional network structure was restored to its initial state after dilution and shearing with the same mass of distilled water, and this process was reversible. Therefore, the new stable oleogel prepared with soybean oil body is a potential alternative to artificial solid fat.

This study aimed to explore the effect of ultrasound-assisted pH shift on the structural and functional properties of soybean lipophilic proteins (SLP). SLP were modified under ultrasound (240 W, 20 min) and extreme pH (pH 1 or 12)conditions. The primary, secondary and tertiary structures of native and modified SLP were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), free sulfhydryl content, Fourier transform infrared(FTIR) spectroscopy, and fluorescence spectroscopy, and their functional properties were analyzed. The results showed that ultrasound-assisted alkaline pH shift resulted in the greatest changes in the structural and functional properties of SLP. The average particle size of SLP decreased from 5245.33 to 447.13 nm, the ζ-potential value decreased from -5.95 to -18.53 mV, the free sulfhydryl content decreased, the α-helix content increased, and the fluorescence spectrum exhibited a blue shift and a decrease in fluorescence intensity. In addition, the solubility increased from 9.84% to 92.04%, and the emulsifying and foaming properties increased. Therefore, ultrasound and pH shift treatments have a synergistic effect on the structural and functional properties of SLP, and they are closely correlated with each other.