Synergistic modification of structural and functional characteristics of whey protein isolate by soybean isoflavones non-covalent binding and succinylation treatment: A focus on emulsion stability

This investigation explored the structural and functional characteristics of whey protein isolate (WPI) and succinylated whey protein isolate (SAn-WPI) modified by varying concentrations (0.25, 0.5, 1.0, 2.0 mg/mL) of soybean isoflavones (SI) through non-covalent interactions. The results of SDS-PAGE and total phenolic contents confirmed the formation of non-covalent complexes. Molecular docking techniques, Fourier-transform infrared spectroscopy, and thermodynamic parameters obtained from fluorescence spectra revealed that non-covalent binding to SI primarily occurs through hydrophobic interactions and hydrogen bonding. Additionally, multispectroscopic techniques demonstrated that succinylation treatment resulted in partial unfolding of the proteins. This led to increased protein flexibility, exposing more binding sites and facilitating the binding between the proteins and SI. Therefore, SAn-WPI/SI exhibits stronger fluorescence quenching ability, antioxidant activity, and emulsifying property compared to WPI/SI at the same SI concentration. The findings illustrate the synergistic effect of non-covalent binding to SI and succinylation treatment on the WPI molecules, thereby promoting the utilization of protein-polyphenol complexes in food emulsion systems.