Mechanisms by which cooking processing and protein distribution synergistically affect the structural, physicochemical and digestive properties of black rice starch

This work investigated the impact of steaming and microwave processing on protein-starch interactions in black rice (RS), focusing on their effects on starch structure, physicochemical properties, and digestibility. Thermal treatment led to protein denaturation, reducing the α-helix/β-turn ratio and forming a protein barrier around starch granules, which increased their size. Both methods disrupted the ordered structures of starch and significantly decreased relative crystallinity. X-ray diffraction (XRD) showed that microwave processing preserved the A-type crystal pattern, while steaming transformed it into a V-type complex. Microwave treated samples formed weakly viscoelastic gels and demonstrated improved water binding capacity, unlike steamed samples. Additionally, microwave processing significantly reduced rapidly digestible starch (RDS) content and increased slowly digestible (SDS) and resistant (RS) starch fractions, whereas steaming encouraged RDS formation. Pearson correlation analysis revealed that changes in protein structure primarily influenced thermal and pasting properties, while starch structural disintegration predominantly reduced digestibility. These findings offer theoretical insights for the targeted regulation of black rice's functional properties through thermal processing.