Polished rice for sake brewing is subjected to a rice storage period called "karashi" until soaking. Generally, just polished rice for sake brewing has a low moisture content, and the moisture content tends to increase during rice storage; however, the equilibrium moisture content (EMC) in adsorption has not yet been indicated. In this study, a major sake brewery rice variety 'Yamada-nishiki' was used as the sample and polished to 70% of the apparent polishing ratio, and the EMCs of 'Yamada-nishiki' were determined at various conditions of temperature and relative humidity. It was observed that the obtained EMCs fitted the Chen-Clayton equation well (R2＝0.997), and the calculated parameters were used to demonstrate the contour line shown by the moisture contents of 'Yamada-nishiki' (70% of the apparent polishing ratio), as affected by temperature and relative humidity. In addition to this, it was shown that the cracking ratio of 'Yamada-nishiki' (70% of the apparent polishing ratio) during soaking (15℃, 120min) increased with decreasing moisture content of polished 'Yamada-nishiki'. Our study indicates the fundamental knowledge on moisture control of polished rice for sake brewing during the rice storage period "karashi," which is one of important processes during sake brewing.
