Emulsifying properties and oil-water interface properties of succinylated soy protein isolate: Affected by conformational flexibility of the interfacial protein

This work aims to investigate the effect of succinylated modification of soy protein isolate (SPI) on its emulsifying and oil-water interfacial properties. The structure-effect mechanism was further analyzed between the emul-sifying properties and the interfacial protein conformational flexibility of SPI. After succinylation, the zeta-potential of emulsion droplets increased, the particle size decreased, the turbidity and flocculation index decreased, and their macroscopic stability improved. The interfacial protein adsorption increased and the interfacial tension decreased, reaching their optimum when the degree of succinylation (DS) was 89.71%. As the increase of DS, the content of beta-turn and random coil of interfacially adsorbed proteins increased to 16.27% and 25.15%, respec-tively, and the flexibility increased and the particle size decreased, while the opposite changes were observed for the unadsorbed proteins. Correlation analysis showed that the emulsifying and interfacial properties of SPI emulsions were closely related to the conformational flexibility of the interfacially adsorbed proteins, while the interfacial adsorption process was also affected by the zeta-potential and particle size of the unabsorbed proteins. This research could provide theoretical guidance on the regulation of protein-emulsifying properties by succi-nylation and reference data for the conformational characterization of interfacial proteins.