Harnessing particle disintegration of cooked rice grains for predicting glycaemic index

Abstract

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, ∼0.12 min−1) which did not vary significantly between varieties. In contrast, intact grains were disintegrated into small/intermediate (d < 30 μm, 30 < d < 300 μm) and large (d > 300 μm) particles. The small/intermediate particles comprising 50–70 % starch were initially-digested (0−20 min) at a fast k-f (∼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 (∼0.04 min−1). The sum-ratio of disintegrated-particle 0−300 μm (Q-300) correlated positively with clinical GI values, allowing for a digestibility prediction of intact milled rice grain.