Effect of microwave oven over the growth and survival of Escherichia coli O157:H7 inoculated in bovine minced meat samples

The use of microwave ovens in food industry is a growing trend. It is used for thawing, drying and cooking food, but the microorganism's inactivation that this treatment may exert or not is still a subject of worldwide discussion. At the same time. Escherichia coli O157:H7 now presents itself as an emerging pathogen, distributed worldwide and associated with food. Its resistance to adverse environments has been widely discussed. The purpose of this work was to determine the effect of different times of exposure and cooking intensities of microwave oven on the survival of this bacterium inoculated into minced meat samples. These were inoculated with a high (10(7)-10(9) CFU/mL) or low (10(7)-10(7) CFU/mL) population of E. coli O157:H7, frozen for 3 days at-4 degrees C and thawed in a Whirlpool microwave oven according to their weight. They were radiated at levels of 70%, 80%, 90% and 100% for periods of 30, 60, 90 and 120 seconds. In each sample the rate of survival of the bacteria was determined according to the methodology described by Vanderzant & Splittstoesser. The results obtained showed that the rate of destruction of the bacteria analyzed was significant (p < 0.005). The number of bacteria present in the meat samples diminished dramatically as the exposure time and temperature increased, even though, for the complete elimination of this microorganism, a prolonged exposure was necessary, even though it did cause undesirable organoleptic characteristics in the food samples.