Mechanism governing the rice glutelin fibrils on inhibition of in vitro wheat starch digestion

Our previous research found that rice glutelin fibril aggregates (RGFA) can mitigate in vitro starch digestion, while the mechanism is not well understood. Here the effects of RGFA on starch properties and activities of amylolytic enzymes were studied. The peak viscosity decreased significantly to 1041.0 ± 11.3 cP (mixture of 10 h fibril and starch) (p < 0.05). The short-range structural order of starch (R-value, calculated from the intensity ratio of the bands at 1047 and 1022 cm−1) changed from 0.73 ± 0.02 (pure wheat starch) to 0.86 ± 0.01 (mixture of 2 h fibril and starch), and 0.58 ± 0.01 (mixture of 10 h fibril and starch) (p < 0.05). The RGFA inhibited in vitro wheat starch digestion significantly (p < 0.05). And RGFA also displayed strong inhibitory effects on amylolytic enzymes. The residual activities of α-amylase, glucosidase and double enzymes were only 61.0 ± 3.2, 63.1 ± 2.5, and 60.5 ± 0.1%, respectively in the presence of 2 h fibril. The results indicated that RGFA with distinctly different fibril structures had different inhibitory mechanisms on starch digestion. The study provides new strategies for application of food protein fibrils and production of foods with reduced starch digestion.