Model system studies on N-nitrosamine formation in relation to cured meat: the non-polar phase and S-nitroso peptides.

In view of recent findings that N-nitrosamine formation occurs principally in the adipose tissue of frying bacon, an heterogeneous protein-based model system has been developed which incorporates a 20% decane phase. The N-nitrosation reactions of a series of secondary amines, of varying lipophilicity, have been studied at 37 degrees C, pH 5.25, in the model system, formulated with and without the non-polar phase. In the presence of decane, a 20-fold enhancement in the formation of N-nitrosodihexylamine was observed, whereas no increase was found for N-nitrosopyrrolidine. Ascorbic acid enhanced the N-nitrosation of lipophilic amines in the presence of decane, but did not affect the yield of N-nitrosopyrrolidine under the same conditions. Ascorbyl palmitate had little influence on the N-nitrosation reactions in the presence or absence of decane. The results are discussed in relation to N-nitrosamine formation in the lean and adipose components of fried bacon. The degree of N-nitrosation afforded by S-nitroso amino acids and peptides has been investigated as a function of the size of the 'peptide' molecule in aqueous solution. The reactions of N-methylaniline with sodium nitrite, S-nitrosocysteine, S-nitrosoglutathione and S-nitrosoglutathione bound to a polysaccharide gel have been examined at 37 degrees C, pH 5.5. The rates of N-nitrosamine formation were found to be higher for S-nitrosocysteine than for the peptide systems, although the rate for the polysaccharide model system was dependent upon the local S-nitroso concentration on the gel. The results are discussed in relation to N-nitrosamine formation in cured meats and in the digestive tract.