Molecular mechanisms and functional implications of cyanidin-3-O-glucoside interactions with rice starch-protein binary matrix

Rice starch-protein interactions significantly influence techno-functional properties and phenolic binding. This study elucidated the molecular mechanisms governing cyanidin-3- O -glucoside (C3G) interactions with rice starch–protein matrices containing varying protein levels (0–15% w /w). Protein contents of 5% and 10% significantly enhanced C3G binding by 14.8% and 10.7%, respectively, whereas C3G bioaccessibility remained statistically unchanged upon starch digestion. Increasing protein levels reduced particle size, altered granule morphology, and reduced iodine affinity. FTIR analysis revealed strengthened hydrogen bonding, amide-I shifts, and modified starch chain organization, whereas XRD showed reduced crystallinity with attenuated V-type peaks. At 10% protein, C3G produced fine, uniform, pigment-loaded particles, whereas 15% protein induced reaggregation. These structural changes increased resistant starch, decreased slowly digestible starch, and shifted color from red-blue to red-yellow. Molecular docking confirmed that C3G intensified hydrogen bonding and hydrophobic interactions at the starch-protein interfaces. Overall, protein content can be tuned to engineer functional foods with targeted nutritional properties. • The ternary interactions of rice starch-protein-C3G were examined. • Protein levels regulated C3G binding and structural reorganization in rice starch. • C3G boost H-bonds, hydrophobic and non-covalent forces at starch-protein interface. • A 10% protein produced fine, uniform pigment-loaded stable ternary complex. • Functional outcomes included enhanced C3G retention and RS, with major color shift.