Microwave ovens are commonly used to cook and reheat food; however, these appliances often provide non-uniform heating, which may produce hot and cold spots within food products being heated.
The uneven distribution of heat could lead to the survival of pathogens in contaminated food cooked in microwave ovens.
During the study, researchers evaluated different power and time combinations of microwave oven heating for inactivation of Listeria monocytogenes on inoculated and stored frankfurters.
The study showed that highest reductions of Listeria monocytogenes contamination were obtained when frankfurters were reheated at high power for 75 seconds.
Standing time after treatment may also play a role in obtaining a more uniform distribution of heat, by conduction, after the microwave power is off and can improve microbial destruction in food.
The hotdogs that were formulated with antimicrobials, which inhibited growth of the pathogen during product storage, displayed a decrease in Listeria monocytogenes counts after microwave treatments at high power for 60-75 seconds, regardless of storage time or packaging condition.
The effectiveness of the 75 second-high power treatment depended on the contamination level of the pathogen on the hotdogs, which in turn, was related to the length of product storage and packaging condition.
"Microwave oven reheating instructions must be designed specifically for each type of product and consider variations in microwave appliance power, amount of food to be reheated, age of the product and the presence of antimicrobial compounds in the formulation of the food," said Colorado State University researcher and IFT member expert Patricia Kendall.
The study appears in the Journal of Food Science.