Reduction of Radiocesium in Internal- and Surface-Contaminated Komatsuna (Brassica rapa var. perviridis) during Washing and Processing.

Radiocesium dynamics data during food processing are required for the realistic estimation of internal radiation content in food. Radiocesium contamination of leafy vegetables can occur externally due to the adhesion of fallout and/or resuspension from the air, and internally from soil via the root transport. Information regarding the dynamics of both surface and internal radiocesium contamination during food processing is required; however, such information for leafy vegetables is limited compared to other major agricultural products. In this study, the effect of washing on the removal of surface radiocesium contamination by resuspended materials and that of cooking (grilling, boiling, and microwave heating) on internal radiocesium contamination were investigated using komatsuna (Brassica rapa var. perviridis), a leafy vegetable. The surface-contaminated samples were experimentally grown in a difficult-to-return area in Fukushima Prefecture, which has not yet been decontaminated. The internally contaminated komatsuna were obtained after experimental cultivation in a greenhouse with soil containing 137 Cs and no surface contamination. The concentration of 137 Cs in surface-contaminated komatsuna was reduced to approximately half (processing factor: 0.55) after washing with water. However, the annual processing factor ranged from 0.12 to 0.95, suggesting that the growing environment and climatic conditions may affect the removal rate of radiocesium by washing. Internal contamination of 137 Cs was removed by 23% and 14% by boiling and grilling, respectively, but no effect was observed for microwaving. Moreover, the concentration of 137 Cs decreased by 0.66-fold after boiling, while it increased by 1.19- and 1.20-fold after grilling and microwaving, respectively. Therefore, boiling was found to be preferable than grilling or microwaving for radiocesium removal.