Evaluation of the Starch Properties of Raw Rice and Enzymatic Digestibility of Steamed Rice Grains for Sake Production by Visual Observation of Swelling Behavior in Urea Solutions

ABSTRACT Background and Objectives The facile low‐cost evaluation of rice starch properties may help assess the suitability of rice for sake production and other applications. Herein, the starch gelatinization properties of raw rice and enzymatic digestibility of steamed rice were simply evaluated by observing the swelling of raw rice grains in urea solutions. Findings Polished rice grains were soaked in urea solutions of varying concentrations to determine the concentration at which the rice grains started swelling or completely absorbed the solution. The swelling‐onset concentration was strongly positively correlated with the DSC‐determined gelatinization temperature and rapid visco analysis–determined pasting temperature of raw rice and negatively correlated with the enzymatic digestibility of steamed rice ( R 2 = 0.81–0.94) while being only slightly affected by the rice polishing ratio and moisture content. Conclusions The starch gelatinization properties of raw rice and enzymatic digestibility of steamed rice could be simply evaluated using the urea swelling test. Significance and Novelty The developed simple method does not require apparatus and flouring and provides results that are not influenced by rice moisture content and polishing ratio, thus holding promise for analyzing rice used in sake production and starch‐containing food materials.