Elimination of N-nitrosamines and their precusors in some foods by 60Co γ-ray irradiation

N-Dimethylnitrosamine (NDMA) in some marine foods, such as dried shrimp, fish meal and salted fish, was drastically reduced by γ-ray irradiation with 60Co. The shrimp contained 54.6 ppb NDMA, but only 29.3, 8.8, 11.4, and 1.9 ppb were detected after irradiation with doses of 5, 10, 15 and 20 kGy. The corresponding reduction was 46.3%, 83.9%, 79.1%, and 96.6%, respectively. Similar results were also obtained in other two kinds of foods. NDMA could be completely eliminated by the irradiation in aqueous solution, which was much more markable than that in food samples. The major irradiated products of NDMA were dimethylamine and nitrous acid, but no re-formation of nitrosamines took place. 60Co irradiation also significantly decreased the content of nitrite in salted fish and in aqueous solution. No effect on nitrate could be observed