Volatile N-Nitrosamines Detected in Commercial Fish Meals

Abstract

Volatile N-nitrosamines (VNA) in 32 commercial fish meal samples were analyzed by a gas chromatograph equipped with a thermal energy analyzer (GC-TEA), and three different VNA, N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR) and N-nitrosothiazolidine (NTHZ) were detected in these samples in common.
The VNA levels were apparently varied depending on the method of preparation, particularly on the drying system of meals. The VNA levels in fish meals which had been dried by blowing hot air exhausted from an oil burner (direct heating-drying type) were found to be much higher than those dried by a steam heating drier system (indirect drying type). The reason for high levels of VNA in the meals prepared by direct heating-drying system might be associated with the higher NO_X concentration in the heating air.
As to the components of VNA in fish meal samples, the quantities of NDMA were the highest, followed by those of NPYR and NTHZ. The NDMA contents in the direct heating-drying type of fish meals were fairly high, and the maximum value was as much as 1400μg/kg. The mean value of NDMA in this type of meals was about 40times higher than that of NPYR, and 80times that of NTHZ.
It was noted that carcinogenic N-nitrosomorpholine (NMOR) could he detected in two samples, although the migration route of morpholine, the precursor of NMOR, into these samples remained unclarified.