Revealing the influence of oat β-glucan on the structural properties and digestive characteristics of rice starch: A perspective on different molecular weights.

Oat β-glucan (OBG) demonstrates several physiological benefits, including hypoglycemic and antioxidant properties, and is widely used in the food industry. The molecular weight of OBG is crucial in determining its ability to inhibit the digestion of rice starch. OBG with different molecular weights (36.5, 30.7, and 18.7 kDa) were prepared through gradient ethanol precipitation. The results indicated that OBG with different molecular weights affected rice starch digestion inhibition differently. Notably, the addition of 15 % low molecular weight OBG (L-OBG) had the most significant inhibitory effect, increasing the proportion of resistant starch (RS) in rice from 4.8 % to 28.0 %. L-OBG reduced rice starch gel's peak viscosity during pasting and inhibited amyloglucosidase and α-amylase activities by 28 % and 22 %, respectively. Based on these results, it is hypothesized that L-OBG forms hydrogen bonds with starch granules, protecting the granular structure of rice starch and hindering the interaction between amylase and starch. L-OBG may compete for the enzyme-starch binding site through non-covalent interactions, thereby reducing amylase activity and inhibiting starch digestion. These findings suggest that L-OBG is a promising ingredient for slowing rice starch digestion and could be used in the development of low-GI foods, hypoglycemic nutraceuticals, and gut probiotics.