Problems associated with the determination of heterocyclic amines in cooked foods and human exposure

Epidemiological studies have shown diet to be an important factor in the global variation of human cancer rates. The presence of mutagenic/carcinogenic heterocyclic aromatic amines (HAs) in cooked foods has attracted a great deal of interest for more than 20 years. Accurate assessment of the human exposure to HAs requires food questionnaires that address cooking methods and reliable methods for the analysis of HAs in cooked foods, and of biomarkers of exposure. The complex food matrix, the low amounts of HAs present (ng/g), and the need for several isolation steps make accurate quantification difficult. Food composition, for example the concentrations and relative amounts of naturally occurring precursors, such as creatine, free amino acids and sugars and also the presence of enhancing or inhibiting compounds are known to greatly influence the formation of HAs. Cooking temperature and time are other important factors that affect the yield of HAs. One of the most abundant HAs, PhIP (2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine), is found typically in amounts up to around 35 ng/g, but there are some reports on much higher levels of PhIP. The levels of other HAs such as MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) and IFP (2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine) generally range from not detectable up to 10 ng/g, and AalphaC (2-amino-9H-pyrido[2,3-b]indole) up to 20 ng/g. Among the factors that influence human exposure to HAs are the type of food, cooking method, portion size and intake frequency. The estimated daily intake of HAs in different studies ranges from 0 to around 15 microg per person per day.