Oxidation Degree-Dependent Precision Matching of Polyphenols with Rice Bran Protein: Structural Stabilization and Digestion Behavior

To alleviate the structural and nutritional deterioration of oxidized rice bran protein (RBP), this study proposes an oxidation degree-guided polyphenol matching strategy for improving the RBP structure and digestion behavior. Endogenous rice bran (RB) polyphenols were conjugated to RBP with different oxidation degrees under ultrasonic treatment to obtain RBP-polyphenol (RBP-PP) complexes. Caffeic acid (CA), gallic acid (GA), and chlorogenic acid (CGA) were identified as the optimal polyphenols for native, moderately oxidized, and excessively oxidized RBP, respectively. Optimal RBP-PP complexes exhibit enhanced structural stability, reduced protein oxidation markers, stronger antioxidant capacity, and higher digestibility. Molecular simulations reveal oxidation degree-dependent binding modes and conformational rearrangements. Peptidomic and metabolomic analyses show that polyphenol binding changes digestion behavior, increasing low-molecular-weight peptides and generating oxidation degree-dependent metabolites. This study establishes an oxidation degree-guided precision polyphenol matching strategy for the targeted regulation of oxidized RBP, providing a theoretical basis for the high-value utilization of oxidized RBP.