Factors affecting the formation and yield of heterocyclic amines

The main food mutagens found in cooked meat products are heterocyclic amines. The formation of these heterocyclic amines has been shown to require three classes of precursors: (i) creatine/creatinine, (ii) free amino acids or dipeptides, and (iii) sugar. The mutagen forming reactions were investigated in model systems and several heterocyclic amines (IQx, MeIQx, DiMeIQx, TriMeIQx and PhIP) were identified and quantified. A number of mutagenic fractions produced in the model system are not yet identified, among them one having a mass number of 217. A participation of the Maillard reaction in the formation of the heterocyclic amines was proposed ten years ago. Since then, the support for this route has increased, especially in a recent study in which carbon atoms from 14C-labelled glucose were shown to be incorporated into MeIQx and DiMeIQx. Other studies have shown sugar to either enhance or inhibit the yield of mutagenic activity depending on its molar ratio relative to the other reactants. Thus, the Maillard reaction can be utilized both to enhance and inhibit the formation of the heterocyclic amines. Olive oil and corn oil were found to almost double the yield of MeIQx in the model system after heating for 30 minutes at 180 degrees C. When adding deep-fat frying oil of different oxidation status in the model system, the yield of MeIQx was not affected by oxidation status or presence of vitamin E, but the lipids enhanced the formation of MeIQx by 30% after heating at 180 degrees C for 30 minutes. Artificial production of free radical reactions by adding FeSO4, hydrogen peroxide and oxygen to the model system doubled the yield of MeIQx.