Removal of 137Cs in Japanese catfish during preparation for consumption

Japanese catfish contaminated by (137)Cs have been used to investigate how dressing and cooking methods affect the removal of radioactivity from the fish. During the dressing, 6.0% of the initial (137)Cs activity in live fish was removed by washing them, and a further 30.3% of this activity relative to the washed fish was removed by discarding the nonedible body parts (such as the skeleton, fins, visceral mass, liver, and kidney) and by washing the chopped edible remains. Fish curry was cooked with various spices, vegetable oil, and greens and other vegetables following a method commonly used in Southeast Asian and East Asian countries. The cooking process removed a further 61.6% of the (137)Cs activity relative to the activity in dressed fish. Taken together, this normal domestic fish dressing and culinary process removed 74.7% of the initial (137)Cs activity that had been present in the live fish. During the cooking, the radioactivity removed from the fish pieces was found to be distributed throughout the ingredients of the curry. The cooked pieces retained, on average, 38.5% of the radioactivity present in the raw dressed pieces. Among the ingredients, the gravy was found to contain an average of 34.8% of the activity of the dressed fish. The activity in greens and vegetables was found to vary from 4.0% (in cauliflower) to 7.2% (in potatoes). It may be concluded that normal home preparation and culinary processes removed much of the radioactivity from the fish.