Protein-protein interactions elucidate the foaming behavior of soybean lipophilic protein: Insights from β-conglycinin, glycinin, and oil body protein-phosphatidylcholine complexes

Soybean lipophilic protein (LP) is composed of β-conglycinin (7S), glycinin (11S), and oil body protein-phosphatidylcholine (OBPs-PC), but the interactions among its components and their effects on foaming properties remain unclear. In this study, we reconstituted these components at the native LP ratio and systematically investigated the regulatory mechanism of protein-protein interactions on foaming properties. The results showed that the nature of component interactions determined foaming properties. 7S and 11S exhibited a synergistic effect: compared with the individual components, their combination underwent conformational rearrangement, characterized by decreased particle size, transition from β-sheet to random coil, increased free sulfhydryl content, reduced surface hydrophobicity, and fluorescence quenching. These changes enhanced interfacial adsorption and foam stability, making 7S + 11S exhibit the optimal foaming ability (136.44%) and stability (58.42%). In contrast, OBPs-PC, due to its strong hydrophobicity and large-sized aggregates, inhibited interfacial adsorption, causing a significant decrease in the foaming ability of OBPs-PC-containing complexes. Molecular interaction analysis indicated that hydrogen bonds and hydrophobic interactions were the main non-covalent forces driving complex formation. Rheological results confirmed that 7S + 11S foam had the highest storage modulus and the widest linear viscoelastic region. In conclusion, 7S and 11S achieved optimal foaming properties through conformational rearrangement and synergistic interfacial behavior, while the strong hydrophobicity and large-sized aggregates of OBPs-PC disrupted interfacial equilibrium and inhibited foaming. This study provides a theoretical basis for expanding the application of LP as efficient gas-water interface stabilizers and foaming agents.