Ultrasonication-driven resveratrol modification of black rice starch: structural evolution regulating physicochemical behavior and in vitro digestibility.

This study focused on black rice starch as the research subject, constructing different ultrasonic power-based black rice starch-resveratrol (BRS-RE) composite systems to explore the correlation between structural changes, physicochemical properties, and in vitro digestion behavior. Ultrasound increased the complexation index (CI) to a maximum of 80.38 % at 400 W. Particle size initially increased and then decreased with ultrasonic power, indicating power-dependent molecular reorganization. FT-IR and Raman analyses indicated changes in the hydrogen-bonding environment and short-range order, while high-power ultrasound induced partial local reordering. Molecular docking suggested hydrogen-bonding and hydrophobic interactions between resveratrol and starch chains, with a potentially more favorable interaction with amylopectin than amylose. These structural changes improved hydration properties (maximum WAI, 2.61 g·g-1) and gel strength, accompanied by increases in bound water and immobile water content. Additionally, thermal and rheological properties were altered (maximum ΔH, 10.11 J/g), and setback values indicated a reduced retrogradation tendency. In vitro digestion results showed a decrease in RDS and an increase in RS (up to 26.87 %). Correlation analysis linked structural disorder and reorganization to changes in hydration, gel network reinforcement, and digestion resistance. Based on these observations, the BRS-RE system exhibited property-dependent responses to ultrasonic power, reflecting varying contributions of starch-chain disruption, resveratrol association, and molecular reorganization across different structural and functional attributes. This work offers mechanistic insights and theoretical support for designing starch-based functional foods with reduced digestibility and potential glycemic benefits.