Microstructure of indica and japonica rice influences their starch digestibility: A study using a human digestion simulator

Abstract

The aim of this study was to monitor the release of glucose and structural changes in Brazilian indica and Thai japonica rice during digestion in a human digestion simulator capable of simulating both mechanical and chemical food digestion. Chemical composition, cooking time, hardness, thermal properties and morphology of the grains were also investigated. The oral and gastro-small intestinal digestion led to the creation of open structures in the cooked rice endosperm due to hydrolysis by digestive enzymes and subsequent leaching of digested components. Indica cooked rice maintained its compact microstructure until the mid-small intestinal digestion phase, which agrees well with its slower starch hydrolysis. However, both types of rice had similar starch hydrolysis (%) at the end of the digestion period. Higher levels of amylose-lipid complexation and protein content in indica rice may have played a role in slowing down the release of glucose during digestion. The slower release of glucose during digestion of indica rice may reflect prolongation of satiety or the feeling of fullness after its consumption.