Harnessing particle disintegration of cooked rice grains for predicting glycaemic index

This study investigated the particle disintegration of cooked milled rice during in vitro digestion to identify its potential for rapidly predicting glycaemic index (GI). Milled grains and flour of rice with varying GI were cooked, stirred and subjected to digestion followed by kinetics analyses. Despite variations in physicochemical parameters (typically amylose content), flours showed a single-phase-digestion rate (k, similar to 0.12 min(-1)) which did not vary significantly between varieties. In contrast, intact grains were disintegrated into small/intermediate (d < 30 mu m, 30 < d < 300 mu m) and large (d > 300 mu m) particles. The small/intermediate particles comprising 50-70 % starch were initially-digested (0 - 20 min) at a fast k-f (similar to 0.05 - 0.10 min(-1)), which enabled to differentiate rice digestibility; whereas the large was latter-digested (20-180 min) at a slow k-s (similar to 0.04 min(-1)). The sum-ratio of disintegrated-particle 0 -300 mu m (Q-300) correlated positively with clinical GI values, allowing for a digestibility prediction of intact milled rice grain.