EFFECT OF TEMPERATURE ON THE FORMATION OF MUTAGENS IN HEATED BEEF STOCK AND COOKED GROUND-BEEF

The microsome-activatable mutagens (chromatographically distinguishable from benzo[a]pyrene and from the mutagens produced from pyrolysed amino acids and proteins) previously found in beef extract and in bacterial nutrients which contain beef extract are produced when beef stock is heated. Reflux boiling of beef stock at 100°C results in a linear increase in mutagenic activity toward Salmonella strain TA1538. The rate of production of mutagenic activity at temperatures between 68°C and 98°C conforms closely to the Arrhenius equation, yielding an activation energy of 23 738 calories per mole. Extrapolation from these data predicts a sharp rise in the rate of mutagen formation between 140 and 180°C. This expectation is confirmed when ground beef patties (hamburgers) are prepared in various conventional electrically-heated appliances which operate at different cooking temperatures within this range. The mutagenic activity of hamburger cooked at high temperatures is limited to the surface layers; the temperature of the inside of the hamburger does not exceed 100°C during cooking. No mutagenic activity is found in comparable samples of uncooked meat. The results indicated that the mutagens may be formed as a result of the temperatures encountered in certain conventional cooking procedures. © 1979.