Flours derived from rice varieties with different amylose content possess distinct physicochemical and
molecular properties. The aim of this study was to determine optimal processing conditions for preparing
rice flour-based foods with reduced starch digestibility. To do so, we evaluated the in vitro starch
digestibility of rice flours with five varieties. Reducing the amount of water (from 10-fold to 4-fold of rice
flour) used for cooking rice flour lowered its starch digestibility, and the magnitude of the decrease was
positively correlated with amylose content. When retrogradation of cooked rice flour proceeded for 7
days, the digestibility of high-amylose rice flours declined rapidly in the first 3 days, whereas the digestibility
of low-amylose rice flours declined continuously. Our analysis also demonstrated that the
chain length distribution of starch molecules and the final and setback viscosity pasting properties were
the most important parameters affecting the digestibility of rice flours. Based on our results, it appears
possible to reduce rice starch digestibility by establishing optimum processing conditions for different
varieties. We suggest a 7-fold addition of water and retrogradation for 1 day for high-amylose rice varieties
and a 4-fold addition of water with 3 days of retrogradation for low-amylose rice.