Do Microwaves Ovens Really Kill Bad Bacteria?

This morning while perusing the fridge in search of something to eat, I spied some chicken and rice that was in a Tupperware container. Problem was, how long had it been in there? I couldn’t remember. But, I thought, I’ll just make sure to ‘nuke’ it really well in the old microwave. That should kill any bad bugs that might lurk somewhere within. The trouble was, I was wrong.

One study, by researchers at the Centers for Disease Control and Prevention, was published in The American Journal of Epidemiology. It looked at a salmonella outbreak after a picnic where dozens of people ate reheated roast pork. Of 30 people studied, all 10 who used a microwave oven became sick, compared with none of the 20 who used a conventional oven or skillet.

Another study, in the journal Epidemiological Infections, looked at six people who contracted salmonella at a buffet after eating a dish consisting of chicken and vegetables. The scientists found that the food had been heated in a 500-watt microwave oven for five minutes before it was consumed — which apparently was not enough.

The problem, studies show, is that microwave users often ignore recommendations like stirring and rotating food for even cooking and checking its temperature once done. You have to hit somewhere between 160 to 170 degrees Fahrenheit to make sure that the bad guys have all bit the dust. (Note: Salmonella is one of the toughest to kill. The rate at which these bacteria are destroyed depends on temperature, species, acidity (pH), and humidity. Ten minutes at 65°C (150°F), or less than two minutes at 70°C (160°F), are both about as effective as an hour at 60°C (140°F). These times and temperatures are sufficient to kill 99.9999% of a particularly heat-resistant strain (S. senftenberg), in custard. At any given temperature, the proportion of surviving bacteria killed in a given time is constant: it takes one sixth of these times to destroy 90% of the bacteria; one third of the time to kill 99%; half the time to kill 99.9%, and so on. A lethal dose may be as few as 500,000 bacteria.)

So, the answer is no! If you have leftovers that you suspect may be a little old (more than a few days). Throw them out! But, if you do decide to take a chance… then at least make sure you reheat them over the stove and that you get them over the 160 to 170 mark.