The Transfer Of Stable Cs-133 From Rice To Japanese Sake

Possible contamination by radioactive cesium (Cs), released by the Fukushima Daiichi Nuclear Plant Accident in Japan on March 2011, has been a matter of concern with respect to Japanese sake made from rice grains cultivated in affected fields. In this study, the behavior of stable (133)cs, which is a useful analogue for predicting the behavior of radioactive Cs, was investigated in the production of sake using rice grains harvested in Japan in 2010. The concentration of stable Cs-133 in the polished rice grains decreased gradually with decreasing milling ratios until a ratio of 70% was reached, and below that point, it did not change significantly. The Cs-133 concentration in the 70% polished rice was approximately 20% of that found in brown rice. The sake was brewed on a small scale using 70% polished rice, and the transfer of Cs-133 from rice to sake was examined. Approximately 30-40% of Cs-133 in the 70% polished rice was removed during the washing and the steeping of the rice grains, and approximately 40% of the Cs-133 in the 70% polished rice was transferred to the sake. If the radioactive Cs species behaves similarly, these results suggest that brown rice containing 100 Bq/kg radioactivity of Cs would generate 70% polished rice grains containing 20 Bq/kg and that the sake brewed from these grains would contain 3-5 Bq/kg. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.