Minimization of Heterocyclic Amines and Thermal Inactivation of Escherichia coli in Fried Ground Beef

Abstract

Background: Heterocyclic amine carcinogens are formed during the cooking of a number of foods, especially well-done meats. Lower temperatures and shorter cooking times can minimize the formation of these carcinogens, yet a major food safety concern is that pathogens in the meat must be thermally inactivated. This study investigated cooking techniques that minimize heterocyclic amine formation while simultaneously destroying contaminating bacteria. Methods: Ground beef patties were inoculated with Escherichia coli K12 bacteria and fried to internal temperatures ranging from 35 °C to 70 °C in a skillet preheated to 160 °C, 180 °C, or 200 °C. Each patty was then analyzed for four common heterocyclic amines and for surviving bacteria. Additionally, the frequency of turning of the beef patty during cooking was varied (a single turn or multiple turns), length of time required for each patty to reach 70 °C was recorded, and heterocyclic amine levels were determined. An additional pan temperature of 250 °C was tested for its effect on heterocyclic amine formation but not on bacterial killing. Statistical tests were two-sided. Results: Colony-forming bacteria were reduced by five orders of magnitude at internal temperatures greater than 60 °C, regardless of cooking method, and were completely inactivated at 70 °C. For patties turned just once, heterocyclic amine levels increased as the cooking temperatures increased. However, levels of heterocyclic amines were statistically significantly lower with turning every minute. For each pan temperature, patties reached 70 °C internal temperature sooner when they were turned every minute than when they were turned just once during cooking. Conclusion: Lowering the pan temperature and turning the patties frequently can greatly reduce the formation of heterocyclic amines and can simultaneously achieve bacterial inactivation with little or no increase in cooking time, ensuring a product that is safe for human consumption.