The role of interfacial protein composition in the stability of soybean oil bodies: Elucidating the mechanism of protein-lipid co-oxidation under different extraction conditions.

Oil bodies (OBs), natural lipid-storage organelles, are typically co-extracted with storage proteins during aqueous processing, which significantly govern their stability. Different washing treatments (heating, GuHCl, urea, SDS) were used to prepare OBs with varied interfacial proteins for studying oxidation mechanisms at 40 °C/75 % RH. Physicochemical characterization revealed that GuHCl-treated OBs developed a three-peak particle size distribution and the lowest ζ-potential (-6.35 mV) after oxidation, while urea-treated OBs maintained greater colloidal stability. During the storage process, the sulfhydryl groups and intrinsic fluorescence intensity in all samples decreased, while the carbonyl content and Schiff base fluorescence intensity increased. Additionally, a strong correlation was observed between lipid and protein oxidation. SDS-PAGE confirmed endogenous Bd 30 K-mediated hydrolysis of membrane proteins in control, GuHCl, and SDS samples, compromising OB stability. In contrast, heating and urea treatments effectively removed Bd 30 K and other storage proteins, delaying protein-lipid co-oxidation. Correlation analysis showed that loose storage protein membranes provide inadequate oxidation barriers, accelerating OB degradation via particle growth and oxidation. These findings demonstrate that selective washing methods can modify OB interfacial composition by eliminating storage proteins and hydrolytic enzymes, thereby enhancing oxidative stability. This study provides a strategic approach to optimize OB extraction for improved shelf-life in food and industrial applications.