Exploring the regulation mechanism of digestibility of starch-polyphenol-protein ternary system by pH from multiple...

This study investigated pH-dependent modulation of starch digestibility in rice starch-quercetin-whey protein isolate system (RS-QUE-WPI). Results showed that the WPI-QUE binding affinity, starch-polyphenol interactions, and QUE degradation kinetics at different pH values collectively affected starch digestibility. Acidic conditions (pH 3) promoted hydrogen bond interactions between molecules and decreased WPI-QUE binding affinity, enhancing structural ordering in RS-QUE-WPI (R_1047/1022 = 1.109, RC = 23.49 %). This structural change improved thermal stability, and viscoelasticity of RS-QUE-WPI while reducing solubility and swelling power, ultimately lowering starch digestibility and increasing resistant starch content (49.25 %). In contrast, alkaline conditions (pH 9) strengthened the interaction between QUE and WPI, accelerated QUE degradation, and disrupted the structural ordering of RS-QUE-WPI, which collectively increased starch hydrolysis rates and decreased resistant starch content. Findings elucidate the mechanism of pH-driven modulation of starch digestion in complex food matrices, providing a potential strategy for designing functional foods with controlled glycemic response.