Understanding the digestibility of rice starch-gallic acid complexes formed by high pressure homogenization.

Rice starch-Gallic acid (GA) complex (RSP-GA) was prepared by high pressure homogenization (HPH), and the effect of GA on the digestibility and multi-structure of rice starch under HPH was investigated. The results showed that, after HPH, the digestibility of starch substantially changed in the reduced rapidly digestible starch (RDS) content, and increased resistant starch (RS) after interacting with GA. In particular, the RS content of RSP-GA ranged from 5.4% to 29.7%, which were much higher than that of rice starch (1.6%). Meanwhile, the results indicated that rice starch and GA were aggregated by hydrogen bonding and van der Waals forces to form a single helix V7 type complex during HPH processing. Moreover, with the increase addition of GA, the fractal structure of the RSP-GA is converted into a mass fractal structure, and the aggregate structure gradually became compact due to the enhancement of rearrangement and aggregation behavior of the degraded starch molecular chains. It thus reduced the accessibility of the starch molecules to digestive enzymes. These results demonstrated that HPH and GA complexation could be beneficial to control the digestion of starch products with desired digestibility.