In Vitro Starch Digestion of Cooked Rice Grain Following the Addition of Various Vegetable Oils

The present study aimed to investigate the in vitro starch digestion of cooked rice grain with added vegetable oils. Polished rice grain (400 g) was cooked with 500 mL of ultrapure water only or with one of six types of vegetable oils (cocoa butter [CB], coconut oil, corn oil [CO], olive oil [OO], palm oil, and rapeseed oil [RO]), and then was frozen and stored. The frozen grain was reheated using a microwave and used for texture analysis, in vitro gastro-small intestinal digestion, and microstructure observation. The cooked grain with added CB had significantly higher resistant starch content (0.70% d.b.) than the control (0.19% d.b.). Although the surface firmness and overall adhesiveness of the cooked grain were not significantly different between the samples, the overall firmness of the grain cooked in RO was significantly lower than that of all others. Cooked grain with added RO (70.35%) indicated a significant reduction in starch hydrolysis compared with the cooked grain with added OO (95.04%) and CO (83.94%) at 210 min of in vitro digestion. However, no difference was observed in tissue structure of the digested cooked grain between the samples.