Ethanol-pretreated aqueous extraction soy protein isolate: Effects of molecular flexibility and interfacial adsorption behaviour on aerated emulsion properties

This is the authors' abstract. We don't add key points for this paper.

Developing plant proteins with superior interfacial properties is crucial for enhancing the quality of aerated emulsion-based foods. Conventional alkaline extraction-acid precipitation yields soy protein isolate (A-SPI) with a compact structure and low flexibility. This limits its performance as an interfacial stabilizer. This study compared ethanol-pretreated aqueous extraction SPI (E-SPI) with A-SPI in terms of subunit composition, molecular conformation, interfacial behavior, and functionality. The study also elucidated the underlying stabilization mechanisms. E-SPI exhibited selective enrichment of the 7S globulin fraction and impaired 11S globulin integrity. This resulted in weakened intermolecular forces, exposed hydrophobic groups, and a looser, porous morphology. In contrast, A-SPI maintained a compact globular structure. Functionally, E-SPI demonstrated superior foaming and emulsifying properties. Its advantages arose from a synergistic effect: high surface charge delayed initial adsorption. Strong hydrophobicity drove film formation, while high flexibility facilitated interfacial unfolding. These features allowed E-SPI to construct a highly viscoelastic interfacial film. The electrostatic repulsion generated by surface charges inhibited droplet coalescence. Although A-SPI showed faster adsorption and lower interfacial tension, its rigid conformation limited interfacial spreading and yielded mechanically weak films. This study elucidates the structure-function relationship of SPI. It provides a clean-label protein ingredient tailored for interface-dominated food systems.