Heterocyclic amine content in beef cooked by different methods to varying degrees of doneness and gravy made from meat drippings

Meats cooked at high temperatures sometimes contain heterocyclic amines (HCAs) that are known mutagens and animal carcinogens, but their carcinogenic potential in humans has not been established. To investigate the association between HCAs and cancer, sources of exposure to these compounds need to be determined. Beef is the most frequently consumed meat in the United States and for this study we determined HCA values in beef samples cooked in ways to represent US cooking practices, the results of which can be used in epidemiological studies to estimate HCA exposure from dietary questionnaires. We measured five HCAs [2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)] in different types of cooked beef using solid-phase extraction and HPLC. Steak and hamburger patties were pan-fried, oven-broiled, and grilled/barbecued to four levels of doneness (rare, medium, well done or very well done), while beef roasts were oven cooked to three levels of doneness (rare, medium or well done). The measured values of the specific HCAs varied with the cut of beef, cooking method, and doneness level. In general, MeIQx content increased with doneness under each cooking condition for steak and hamburger patties, up to 8.2 ng/g. PhIP was the predominant HCA produced in steak (1.9 to 30 ng/g), but was formed only in very well done fried or grilled hamburger. DiMeIQx was found in trace levels in pan-fried steaks only, while IQ and MeIQ were not detectable in any of the samples. Roast beef did not contain any of the HCAs, but the gravy made from the drippings from well done roasts had 2 ng/g of PhIP and 7 ng/g of MeIQx. Epidemiological studies need to consider the type of meat, cooking method and degree of doneness/surface browning in survey questions to adequately assess an individual's exposure to HCAs.