Regulation of composite particle structure by soy isolate protein-citrus pectin mass ratio and its mechanism of influence on interfacial activity and stabilizing properties.

Abstract

Despite the advantageous functional properties of soybean protein isolate (SPI), its inherent conformation is susceptible to environmental influences, thereby limiting its utility in food systems. This work investigated the effect of mass ratio between soybean protein isolate (SPI) and citrus pectin (CP) on the structure and functionality of composite particles. Results showed that a 1:1 SPI-to-CP ratio produced the smallest particle size (280.13 nm) and the best dispersion stability. This ratio also significantly improved emulsifying activity (EAI: 54.80 m2/g) and emulsion stability (ESI: 105.91%), while enhancing the adsorption capacity of interfacial proteins. The composite particles were driven by hydrogen bonding, hydrophobic interactions, and electrostatic forces. These interactions promoted the conformational unfolding of SPI, increasing surface hydrophobicity and facilitating a structural transition from α-helix to β-sheet. This work provides fundamental insights for designing food-grade particles with enhanced interfacial activity and stability.