Using rice grains contaminated with radioactive cesium (134Cs and 137Cs) that was released by the Fukushima Daiichi
Nuclear Power Plant Accident in March of 2011, we investigated the behaviors of the radioactive cesium and potassium
(total K and 40K) during sake brewing. Cesiumis a congener of K, and yeast cells have the ability to take up Cs using
known K transporters. During rice polishing, the concentrations of radioactive Cs and K in the polished rice grains
decreased gradually until a milling ratio (polished rice weight/brown rice weight) of 70% was reached. No significant
changes were observed below this milling ratio. Sake was brewed on a small scale using the 70% polished rice. The
transfer ratio of radioactive Cs to sake and to the sake cake was significantly different than the ratio of K. Approximately
36% and 23% of radioactive Cs in the polished rice was transferred to the sake and sake cake, respectively; however, 40%
was removed by washing and steeping the rice grains. On the other hand, 25% and 40% of K in the polished rice was
recovered in the sake and sake cake, respectively, and 35% was removed by washing and steeping the rice grains. From
the present results, the concentration of radioactive Cs in sake would be 4 Bq/kg fresh weight, which is well below the
regulation values (100 Bq/kg), even using brown rice containing 100 Bq/kg of radioactive Cs