Impact of the degree of cooking on starch digestibility of rice - An in vitro study

The impact of cooking degree on the starch digestibility of a non-waxy, cooked rice was examined through a simulated gastro-small intestinal in vitro digestion model. The starch hydrolysis of both non-homogenised and homogenised cooked rice samples during simulated digestion was also compared in order to examine the impact of grain structure on starch digestibility. Polished rice grains were cooked in boiling water for 10 min (partially cooked) and 20 min (fully cooked) to obtain samples of different cooking degree. No significant differences in the equilibrium starch hydrolysis (%) were observed among the partially and fully cooked grains, although significant differences were observed among the uncooked and cooked samples. The equilibrium starch hydrolysis (%) of homogenised rice was higher than its non-homogenised counterpart. These results showed that rice starch digestibility should not be affected by the cooking degrees related to starch gelatinisation, but was influenced by the modification/destruction of the grain structure during mechanical processing.