Effects of adding blueberry residue powder and extrusion processing on microstructure and in vitro digestibility of indica rice flour

Using crushed indica rice flour as the main raw material, after adding blueberry residue powder, the indica rice puffed powder containing blueberry residue (IREPBR) was obtained through extrusion and crushing. The effects of adding blueberry residue and extrusion processing on the microstructure and in vitro digestibility of indica rice flour were studied. The basic component analysis results showed that the fat and total starch content of indica rice powder significantly decreased after adding blueberry residue powder and extrusion puffing, while the total dietary fiber content significantly increased. The results of scanning electron microscope (SEM) showed that there were many pits and bubbles in the extruded indica rice flour after adding blueberry residue powder. Compared with indica rice flour (IRF), its Water Absorption Index (WAI) and Water Solubility Index (WSI) significantly increased, and its thermal properties also changed. XRD and FT-IR analysis showed that after extrusion, the crystalline morphology of indica rice starch changed from A-type to V-type, and the relative crystallinity also changed. In addition, the content of resistant starch (RS) in indica rice flour added with blueberry residue powder and processed by extrusion increased significantly, while the starch hydrolysis rate and estimated blood glucose index (eGI) decreased.