While to you the microwave might be a trusty kitchen appliance, you might want to worry a little more about all the food residue and splatter you’re leaving behind after reheating last night’s leftovers.
Turns out, the trusty kitchen appliance is actually pretty disgusting, according to a new study. Researchers swabbed 30 microwaves in homes, offices, and microbiology laboratories and found 747 kinds of bacteria. Home microwaves contained mostly Staphylococcus, which can actually cause infections, as well as more microbes than other locations.
While you might be wondering why the heat doesn’t kill kill the bacteria entirely, there are a number of factors involved. For starters, a microwave heats things unevenly so not everything is getting zapped with the same temperature. According to Ahmed Yousef, Ph.D., a professor of food microbiology at The Ohio State University who spoke with Food & Wine, this causes food to splatter out, which may contain bacteria.
And the microorganisms actually get into the microwave from the food you put inside too. Your spaghetti sauce or dip splatter is probably landing on the walls, corners, or ceiling of your microwave, which are areas that aren’t designed to receive heat the same way. It allows the bacteria to survive for longer.
The water content in your food matters, too. “The drier the food, the less likely to be heated by microwave energy,” Yousef told the outlet. “Even popcorn has some water inside the kernels. Without that water, it would not pop in the microwave oven.”
He adds that the drier the particles become, the harder it is to kill them—even when you’re regularly firing up the microwave.
Do Dirty Microwaves Contaminate Our Food?
Here’s where you can breathe a sigh of relief. It’s rather unlikely that the bacteria will get into your food.
“Certainly, if a microorganism is sitting inside the oven cavity of a microwave, it’s very unlikely to be able to jump from there to get into food,” Donald Schaffner, Ph.D., a microbial risk assessment and cross contamination expert at Rutgers University, added.
Now, that’s if you’re properly plating your food in the process. You definitely don’t want to toss a slice of pizza directly on the turntable.
According to Yousef, you should worry about milk, soup, and stew the most because these types of “nutritious foods are also good for growing microorganisms.”
How Do We Prevent Bacterial Growth In Our Microwaves?
Properly covering your food is a start, so that it doesn’t explode all over your microwave in the first place. Even still, you’ll want to get into the habit of actually cleaning the appliance.
“Spills and explosions should be cleaned up immediately using warm soapy water and rinsed with clean water,” Janet L. Buffer, M.P.H., R.D., senior institute manager at the Institute for Food Safety and Nutrition Security at The George Washington University, told the outlet. “An antibacterial cleaner is an added benefit, but typically, the antimicrobial cleaner must be applied after the equipment is washed and then rinsed.”
Yousef added that by cleaning as soon as you spill and regularly checking for food residue, you should be fine.
Megan Schaltegger is an NYC-based writer. She loves strong coffee, eating her way through the Manhattan food scene, and her dog, Murray. She promises not to talk about herself in third person IRL.
