[Influence of nutritional composition and digestibility of different oat products on their glycemic index]

To investigate the nutrient component contents, in vitro digestive properties of different oat products, and their effects on the in vivo glycemic index(GI).

Four commercially available oat products(oat bran, rolled oats, thinly cut oats, and steel-cut oats) were selected for analysis. Their proximate nutritional composition-including moisture, ash, fat, dietary fiber, and protein content-was determined. An in vitro digestion simulation was conducted to assess starch digestion characteristics, namely the contents of rapidly digestible starch(RDS), slowly digestible starch(SDS), and resistant starch(RS). Additionally, the GI was measured via human trials following standardized protocols. Contribution analysis was performed to identify the principal factors influencing GI values.

Differences in the starch digestive properties of oats led to variations in GI values. Steamed oats had the highest content of RDS(58.93%) and the largest HI(0.70), resultsing in the highest GI value(69), which classified it as a medium-GI food. Rolled oats ranked second(GI=63). In contrast, steel-cut oats(GI=49) and oat bran(GI=45) were categorized as low-GI foods due to their higher RS contents(51.27% and 55.34%, respectively) and lower RDS contents. Correlation analysis showed that RDS was significantly positively correlated with GI(r=0.996), while RS was significantly negatively correlated with GI(r=-1.000). Further contribution degree analysis indicated that starch digestive properties(e. g. , RDS, RS, HI) contributed the most to GI variation(contribution degree index> 0.197), whereas the effects of nutrient components such as total dietary fiber and protein were relatively weaker.

The GI of oats is primarily determined by their starch digestibility, which is influenced by processing method. Specifically, the ratio of RDS to RS plays a critical role: a higher RDS content is associated with an elevated GI, whereas a higher RS content contributes to a lower GI. This study provides a theoretical foundation and practical guidance for the development of low-GI oat-based foods.