Do Microwaves Kill Bacteria That Cause Food Poisoning?

It’s important to heat leftovers to high enough temperatures to destroy any bacteria that cause food poisoning. Is it safe to use a microwave oven to do this? Does a microwave kill germs?

Few people want to experience a bad case of food poisoning. Sure, it could give you a few days off from work, but who wants to spend it on the toilet? The solution? Keep food poisoning at bay by practicing safe food handling. Some people turn to their microwave to do this, assuming that a microwave oven zaps food hard enough to destroy the bacteria that cause food poisoning. Is this true? Does a microwave kill bacteria?

Does a Microwave Kill Bacteria: How Do Microwaves Work?

Microwaves use electromagnetic radiation, similar to very high frequency radio waves, to alter the charge of molecules, which causes them to move and rotate. This movement generates heat which warms up the food or water. As you might expect the longer the food or liquid remains in the microwave oven, the more it will heat up.

Can Microwaves Kill Germs: An Informal Experiment

An informal experiment was carried out on The Straight Dope website using pizza samples and Petri dishes to grow bacteria. Pizza samples were allowed to set out in the open air where they were exposed to bacteria for four hours. Samples from the pizza were then plated on Petri dishes after they had been microwaved for various periods of time.

The results? In this case, thirty minutes in the microwave didn’t kill a significant number of the bacteria, whereas sixty seconds killed most – but not all – of the bacteria that had landed on the pizza. Their informal conclusion? It takes at least two minutes in the microwave to kill germs. There are downsides. Two minutes in a microwave could destroy the flavor and texture of some foods.

Does a Microwave Kill Bacteria: Another Perspective

According to research published in The American Journal of Epidemiology and discussed in the New York Times, even five minutes in the microwave may not be enough to kill bacteria that cause food poisoning. At a buffet, six people came down with a bad case of foodborne illness after eating a mixture of chicken and vegetables that had been placed in the microwave for a five full minutes. Apparently, this wasn’t enough.

The problem is this. Microwave ovens don’t raise the temperature of foods uniformly – and they often leave under-heated areas where bacteria can grow and produce toxins. This spells bad news for the person unfortunate enough to bite into one of those “cold pockets” teeming with bacteria.

The Bottom Line?

Don’t count on your microwave to kill bacteria that could cause a nasty case of food poisoning. You could end up disappointed – and ill.


New York Times. “The Claim: Microwave Ovens Kill Bacteria in Food”

The Straight Dope. “Do Microwave Ovens Kill Bacteria?”

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  1. Another great one…..Keep going.

  2. Another Very nice post, thanks for sharing

  3. “In this case, thirty minutes in the microwave didn’t kill a significant number of the bacteria, whereas sixty seconds killed most – but not all…”

    I’m confused. Should this say thirty *seconds*?

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