SURVIVAL OF LISTERIA SPP. ON RAW WHOLE CHICKENS COOKED IN MICROWAVE-OVENS

The prevalence of microwave ovens in North American homes has increase d dramatically within the last decade. Although microwave ovens are pr imarily used for reheating of foods, they are now more commonly being applied to the cooking of raw foods. Although cooking of raw foods, ac cording to manufacturers' instructions targets an organoleptically acc eptable end product, the process does not address the microbiological safety of the cooked food. Seventeen microwave ovens from various comm ercial suppliers were used to cook naturally contaminated whole raw br oilers (less than or equal to 1.8 kg) and roasters (>1.8 kg) according to manufacturers' instructions. Temperature probes (six per chicken) were used to measure the temperature of chickens immediately after coo king and during the holding period. Of 81 Listeria-positive raw broile rs and 93 raw roasters, 1 (1.2%) and 9 (9.7%), respectively, yielded v iable Listeria spp. after microwave cooking. Of these, two were underc ooked (visual inspection), one was over the maximum weight stipulated by the oven manufacturer and another one was over the maximum weight a nd undercooked. A significantly greater proportion of contaminated coo ked birds was observed with roasters than with broilers, where for one of these contaminated roasters, the temperature at all six measured s ites was greater than or equal to 87 degrees C. Most of the postcook L isteria-positive birds were associated with 2 of the 17 microwave oven s. Factors such as wattage, cavity size, and the presence or absence o f a turntable seemingly did not play a significant role in the surviva l of Listeria spp. in microwave-cooked chicken. However, the general i nability of microwave ovens to uniformly heat chicken carcasses was no ted. In order to promote greater safety of microwave-cooked foods, gen eral recommendations for consumers are provided.