Further studies on the occurrence of volatile and non-volatile nitrosamines in foods

Approximately 250 samples of various foods, such as cured meat products, fried bacon, cooked-out bacon fats, baby foods containing meats, tomato products, cooked pizza, powdered and evaporated milk, mushrooms and different varieties of alcoholic beverages, were analysed by GLC-TEA for the presence of volatile nitrosamines. The levels detected in cured meat products (both cooked and uncooked) were very low, and both their incidence (at greater than 1 microgram/kg) and concentrations were much lower than those observed in a 1974 survey. The levels of N-nitrosopyrrolidine (NPYR) in fried bacon and cooked-out bacon fats were also somewhat lower than those observed at the end of 1976, but the decrease may not be significant. Traces (mean, 1.5 micrograms/kg) of N-nitrosodimethylamine (NDMA) were detected in 21 of 22 samples of beers and ales. Most of the remaining foods gave negative results, excepting the skim milk powders, which contained minute traces (mean, 0.4 micrograms/kg) of NDMA. An HPLC-TEA method was developed for the analysis of N-nitrosoproline (NPRO) and N-nitrososarcosine (NSAR) in raw and fried bacon. A study of the heat-induced decarboxylation of these nitrosamino acids suggests that these compounds are heat-labile and would not be expected to occur in fried foods at significant levels. Their presence, however, may lead to the formation of traces of NPYR and NDMA during frying at lower temperatures.