Designing emulsified systems with soybean oil body membrane protein aggregate: Insights into chain bead-like...

Soybean oil body membranes, which are high in amphiphilic proteins could serve as food emulsifiers. Due to the strong hydrophobicity of oil body membrane proteins, they tend to form aggregates. The hydrophobic residues within the proteins are concealed, leading to decreased interfacial performance, which further limits their application. This study innovatively constructed soybean oil body membrane protein aggregates (SOMA) through thermal treatment and pH modification, resulting in a chain-bead-like structure that effectively enhances their emulsification properties. The results indicated 24 kDa oleosin is the primary protein. As heat treatment time increased, the particle size of soybean oil body membrane protein aggregates increased, and electrostatic interactions were enhanced. Spectroscopic results and molecular dynamics simulations confirmed that at pH 6.5, heat treatment caused the unfolding of the T-type structure of oleosin, increasing its hydrophobicity. In contrast, at pH 8.5, the protein structure contracted due to electrostatic repulsion. Heat treatment resulted in β-sheet and intermolecular hydrogen bond contents exceeding 35% and 80%, respectively, which facilitated the structural assembly and the formation of chain-bead-like aggregates. Compared to pH 8.5, SOMA at pH 6.5 exhibited a larger bead distance, higher β-sheet content and flexibility. Under both pH conditions, the chain bead-like structure with 2 h heat treatment exhibited the lowest interfacial tension (13.27 mN/m, 15.84 mN/m) and highest rearrangement rates (67.42 s^-1, 58.12 s^-1), facilitating interfacial diffusion dominated by rearrangement. These findings provide new insights for developing novel food emulsifiers by utilizing the unique structural characteristics of soybean oil body membrane proteins.