Regional differences in N-nitrosamine content of traditional Chinese foods

Traditional uncooked and cooked Chinese foods from six provinces with different cancer patterns were analysed for volatile N-nitrosamines (VNA) by gas chromatography-thermal energy analysis. Selected samples were also analysed for N-nitrosamino acids (NAA). N-Nitrosodiethylamine was the VNA found most often (in 91/108 samples; less than 0.2-17.5 micrograms/kg), followed by N-nitrosodimethylamine (in 75/108 samples; less than 0.2-17.3 micrograms/kg). N-Nitrosodipropylamine was detected in 11/108 samples (0.9-6.2 micrograms/g). Samples selected for analysis of NAA on the basis of their VNA content contained one or more NAA, including N-nitrosoproline and N-nitrosothiazolidine 4-carboxylic acid (range, 1.1-115 micrograms/kg; average, 35 micrograms/kg). Both the incidence and pattern of occurrence of VNA suggest that Chinese foods differ from western foods, which would not be expected to contain NAA as frequently nor to contain N-nitrosodipropylamine. The highest percentages of positive samples were from Zhejiang and Fujian provinces (89 and 91%, respectively), and they had the highest average VNA content. Beijing city and Sichuan province gave the lowest percentages of positive samples (75 and 56%, respectively) and the lowest average VNA content.