Exploring the interfacial behavior and foam characteristics of various soy protein aggregates: Insights of morphology and conformational flexibility

This study investigates the morphology differences and structural flexibility of different soy protein aggregates, and examines their disparities in interfacial and foam characteristics at across pH levels. The results indicated substantial variations in the morphology of the aggregates, resulting in a notable alteration in their flexibility. The soy protein fibrils (SPF) demonstrated superior molecular flexibility relative to the other aggregates, demonstrating maximum flexibility (A_{280 nm} = 0.35) at pH 9. Soy protein fractal aggregates (SPA) exhibited a rigid structure at all pH levels because of the elevated presence of disulfide bonds, α-helixs, and β-sheets. The reduced particle size and elevated presence of irregular convolutions resulted in significantly greater molecular flexibility of the soy protein nanoparticles (SPN) in comparison to SPI. SPN exhibited the second highest flexibility following SPF, was distinguished by tiny particle size and homogenous dispersion, and demonstrated optimal flexibility at pH 9. Furthermore, SPF-9 displayed the lowest interfacial tension (39.29 mN/m), the best solubility (97.54 %), and the foaming ability (180.00 %). And SPN-9 demonstrated the best foam stability. It was ascertained that the interfacial properties and foaming ability of aggregates were positively correlated with their molecular flexibility and that alterations in the morphology and structure of aggregates could impact the flexibility of proteins and thereby enhance the interfacial functional properties. The outcomes of this study establish a theoretical foundation for the application of soy protein in foam-based meals.