Fabrication and physicochemical characterization of SPI-gallic acid-guar gum ternary complexes: Insights into...

This study aimed to fabricate soy protein isolate (SPI)-gallic acid (GA)-guar gum (GG) ternary conjugates and to investigate relationship between covalent modification and SPI conformational, microstructural, and physicochemical changes. In SPI-GA binary system, reaction time and GA concentration were optimized; 4 h at 5 mg/mL GA yielded the highest grafting degree and antioxidant capacity, whereas grafting efficiency partially decoupled at higher GA levels, likely due to quinone self-polymerization that lowers electrophilicity and increases steric hindrance. In SPI-GA-GG ternary system, heating cycles were varied to optimize extent of glycation and browning index. Multiscale analyses (SDS-PAGE, FTIR, CD, intrinsic fluorescence, SEM) revealed a covalent network without backbone cleavage, decreased α-helix with increased β-sheet/random coil, and a shift of tryptophan microenvironments toward hydrophilicity. Functionally, solubility increased to 43.56%, while the surface hydrophobicity index decreased by 68.88% relative to native SPI; GG mitigated GA-induced thermal instability, yielding a tunable, process-stable ingredient for functional foods.