To investigate the targeted addition of Qiongbei red rice pigment into starch-based foods for modifying their nutritional and functional properties.

This study systematically examined the effects of red rice pigment on the physicochemical and digestive characteristics of starch using iodometry, scanning electron microscopy and rapid viscosity analysis.

Red rice pigment significantly influenced the physicochemical and digestive properties of starch (P<0.05). The addition of the pigment increased the pH of starch suspensions,reduced chroma, elevated a^* and b^*, and resulted in a reddish-brown appearance. It also significantly decreased the iodine blue value of wheat starch, altered the microstructure of starch granules, and increased granule size. In vitro digestion experiments showed that as pigment concentration increased from 0% to 1.0%, resistant starch content increased from 48.11% to 63.71%, while rapidly digestible starch decreased from 42.41% to 28.27%. Hydrolysis sensitivity values generally declined, and the predicted glycemic index of starch dropped from 94.40 to 73.81.

Red rice pigment reduces the iodine-binding capacity of starch in a dose-dependent manner. It interacts with starch through non-covalent bonds, affecting the spatial distribution and arrangement of starch chains, and disrupting the crystalline structure of starch granules. Consequently, the sensitivity of starch to hydrolytic enzymes decreases, leading to a reduced hydrolysis rate and inhibited in vitro digestibility.