Microwave ovens in homes, offices and laboratories appear to harbor a wide range of microbes. This underscores the importance of cleaning this appliance regularly.
Microwave ovens are home to a wide range of bacteria. This is surprising, because the devices are used not only to heat food, but also to sterilize samples.
The radiation emitted by microwaves is non-ionizing. Biological molecules are not harmed by this. Microwaves heat things up by making water molecules vibrate. This can kill bacteria, but only if a high enough temperature is reached. However, it was thought that microwaves, through repeated heating and drying, provided a harsh environment for microorganisms.
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bacteria
spanish microbiologist Manuel Burkar From the University of Valencia and his colleagues took samples from thirty microwave ovens. Ten came from single-person households. Ten were in shared kitchens, such as companies, scientific institutes and cafeterias. The other ten were in biological laboratories for molecular biology and microbiology. The team published their findings in the scientific journal Frontiers in Microbiology.
In total, the researchers found 747 different bacterial species, from 25 bacterial strains. Diversity was lowest in household microwaves and highest in laboratory-based devices.
The same bacteria often occur in microwave ovens and shared microwaves in individual households. They were similar to bacteria commonly found on human hands and in other parts of the kitchen. This suggests that the microbes don’t need any special adaptations to survive in the microwave. That could be because food scraps protect them from radiation, Borkar says.
The bacteria in the lab, where food is not prepared, were different. They resembled microbes found in harsh, dry, hot, irradiated environments, such as solar panels.
health
Some bacteria have been found to live in home microwave ovens, such as: Klebsiella, Enterococci and AeromonasResearchers say this could pose a health risk. However, the microbial populations in microwave ovens are no more dangerous than those found elsewhere in the kitchen.
“Obviously, a microwave can’t be relied upon to provide a cleaner environment in terms of microorganisms than any other kitchen surface. It needs to be cleaned just like the rest of the kitchen,” says Borkar.
microbiologist Belinda Ferrari From the University of New South Wales in Australia, she wasn’t at all surprised that researchers found bacteria living in microwave ovens. “They can survive in almost any environment and they can adapt to anything,” she says.
Ferrari recommends cleaning microwaves regularly with disinfectant products. “Some microwaves at work are dirty and no one cleans them,” she says. She would like to see more information in the study about when the microwaves were last cleaned. “If I were to do this experiment, I would also want to study the microbiome before and after cleaning.”
