Microwaves heat food, but they don’t necessarily kill bacteria.
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Microwaves in homes, offices, and laboratories are home to a surprising variety of bacteria.
Microwaves are widely used to heat food and sterilize samples, but the radiation they emit is non-ionizing radiation, meaning it does not damage biological molecules. Microwaves heat water molecules by vibrating them, but bacteria are killed only when they reach a high enough temperature.
Nonetheless, the repeated heating and drying cycles have led me to believe that microwave ovens are an environment in which it is difficult for microorganisms to survive.
Alba Iglesias Researchers at the University of Valencia in Spain took samples from 30 microwave ovens: 10 from single-family home kitchens, 10 from communal kitchens such as company centers, science labs, and cafeterias, and 10 from molecular biology and microbiology laboratories.
The researchers found 747 different bacterial genera across 25 bacterial phyla. Diversity was lowest in a single household microwave oven and highest in a laboratory device.
Many of the bacteria found in the shared and single-family home microwaves overlapped and were similar to bacteria often found on human hands and in other parts of the kitchen. But the bacteria in the uncooked lab were more distinct and resembled microbes found in other extreme dry, hot, and irradiated environments, such as solar panels.
Researchers have focused on some bacteria found in household microwave ovens. Klebsiella, Enterococcus and AeromonasIt may pose a risk to human health. However, they say the microbial communities found on microwave ovens do not present a unique or increased risk compared to other common kitchen surfaces. The researchers did not respond to requests for comment.
Belinda Ferrari A researcher at the University of New South Wales in Australia says she is not at all surprised that researchers have found bacteria that live in microwaves. “They can survive in almost any extreme exposure environment and can adapt to anything,” she says.
Ferrari recommends cleaning your microwave regularly with a disinfectant. “Some workplace microwaves are disgusting and no one cleans them,” she says.
She would like to see more information about the study on when the microwaves were last washed. “If I were to do this experiment, I would also like to study the biota before and after washing,” she says.
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