Safe Microwave Heating of Refrigerated and Frozen Foods

June 9, 2009



Safe Microwave Heating of Refrigerated and Frozen Foods

Anaheim, CA -- Food borne illness in the news brings to light the importance of safe food preparation and handling. And while surveys indicate that consumers feel confident in their ability to safely prepare foods, a disconnect exists between this confidence and actual practice. Adherence to practices such as using different cutting boards for raw and cooked product is low, as is using a food thermometer, for example.

Consumers often do not check their microwave wattage before cooking, allow for enough standing time or use a food thermometer. Presenters noted that microwave heating can be spotty and non-uniform, which can lead to unpredictable results and implications for food quality and safety. Allowing the food to stand a few minutes before eating helps even out cooking results.

Dielectric properties (how an electric field behaves inside a material) changes drastically as frozen food thaws, which changes the absorption of microwaves, explained Ashim K. Datta, Ph.D., professor in the Department of Biological and Environmental Engineering at Cornell University. "This can lead to unpredictable results that have quality and safety implications," says Datta.

Frozen meat and poultry products that appear ready-to-eat (RTE) are most likely to be undercooked by consumers, according to Daniel Engeljohn, Ph.D., adjunct assistant professor of nutrition the graduate faculty at Howard University. Char-marked burger patties, for example, may appear RTE but are not. "Stuffed poultry products that appear RTE are most at risk," said Dr. Engeljohn. "The raw product often looks cooked. Plus, both RTE and not-ready-to-eat (NRTE) products are both available, which adds to the confusion." The Food Safety and Inspection Service (FSIS) is working on new information to help guide consumers, including clearer and more effective labeling.

The advantages and disadvantages of microwave cooking were similar to that found in traditional cooking methods, according to John Roberts, Ph.D., engineer in the R&D department at Rich Products Corporation. "Microwave cooking shows less destruction of water soluble vitamins (i.e. folate, vitamin C) than traditional cooking methods," said Roberts. "In addition, microwave cooking retained the antioxidant activity of foods.

The short cooking time required for meats showed a reduced risk of cancer-causing agents such as nitrosamines when cooked in a microwave. The effect of microwave cooking on lipids and carbohydrates requires further research, although legumes cooked in a microwave showed similar digestibility to pressure-cooked legumes.

Ashim K. Datta, Ph.D
Cornell University

John Roberts, Ph.D
Rich Products Corporation


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