EFFECT OF COOKING TIME AND TEMPERATURE ON THE HETEROCYCLIC AMINE CONTENT OF FRIED BEEF PATTIES

The mutagenic heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-f]qu inoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-ami no-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,4,8-tr imethylimidazo[4,5-f]quinoxaline (DiMeIQx) were measured in ground-bee f patties fried at 150, 190 and 230 degrees C for 2-10 min on each sid e. Heterocyclic amines were purified using solid-phase extraction and analysed by HPLC. Recovery-corrected amounts of each heterocyclic amin e were determined by the method of standard addition based on spiked s amples with recoveries ranging from 40 to 70%. Mutagenic activity meas ured by the Ames/Salmonella test was determined for each sample. The a mounts of MeIQx, PhIP, DiMeIQx and IQ increased with time and temperat ure of cooking. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-9H-pyri do[2,3-b]indole (A alpha C) were not detected in any sample. The mutag enic activity response measured for the meat extracts (TA98 revertants ) was similar to the mutagenic activity calculated from the mass of he terocyclic amines present. The rate of formation of PhIP in a model sy stem containing creatinine and phenylalanine heated in 80% diethylene glycol was compared with PhIP formation during meat frying. The appare nt heats of activation were 6.5 kcal/mol in the model system compared with 6.0 kcal/mol in the fried meat patties. The increase in PhIP and MeIQx formation fitted an exponential function over the range 0 to 11 min and from 150 to 230 degrees C. This report shows clearly that incr eases in cooking temperature and time can have a profound effect on th e amounts of heterocyclic amines generated and subsequently consumed i n the diet.