To examine how the cooking process affects the eating quality of cooked rice, changes in the contents of reducing sugar, amylase, and protein in rice grain were measured at a series of cooking stages. Rice grains of the Chiyonishiki, Nipponbare, and Koshihikari cultivars were employed in this study. The somogyi-nelson and simplified assay method were used for measurement of reducing sugar and amylose content, and BCA, combustion and SDS-PAGE method were for protein content, respectively.

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... g sugar content began to increase during the preliminary heating stage at 50 °C, whereas amylose content was relatively stable through the cooking process. Total protein content decreased with cooking, with the decrement becoming evident at 75 °C, though the decline process was different from its molecular weight. These results suggest that changes in compound contents were generated by enzymatic activity and/or a thermal denaturation during cooking.