How do bacteria fare in microwaves? Let’s say you’re heating up some leftovers which have the beginnings of some growth, would the microwaves affect them or would they just enjoy the warmth (presuming they had the capacity to enjoy anything)?
The microwaves will not kill the bacteria. The heat from the food getting hot will kill some of the bacteria, but you are more likely to become ill by heating up your leftovers in the microwave than you would be by heating them up on the stove top or in the oven. With conventional heating, your leftovers are heated fairly evenly, depending mostly on the rate of heat conduction through the materials involved. In a microwave, though, water, fats, and certain sugars and other materials heat significantly faster than other materials in the food, leaving colder spots where bacteria can more easily survive the heating process. Microwave ovens also naturally have hot and cold spots in them that don’t heat the food evenly.
I find that this isn’t a problem if I stir my food at regular intervals during heating, e.g. three minutes of heating with a stir at one-minute intervals.
For foods that can’t readily be stirred (e.g. lasagna), I cut the block of food into pieces about 1.5 inches on a side and spread them out across the plate to allow the microwaves to penetrate more evenly. Not because I’m particularly concerned about bacteria - I treat leftover food pretty carefully, refrigerating it ASAP after cooking the first time - but because I don’t like cold/lukewarm leftovers.
Microwave wet undies and the results are good on yeasts! Kills 'em dead in five minutes.
If you keep the microwave running long enough, it will kill just about any organism containing water.
Whether or not the food is still edible at that point is a seperate question.
Bacteria are mostly water & fats too. So they’ll heat as well or as poorly as the food. Some microwaves heat evenly, others don’t. Bacteria near the surface will get a bigger dose of heat than those at the center of the food.
A boiled bacteria is a dead bacteria. OTOH, one that was heated from fridge temp to a barely lukewarm 120 degrees is probably just fine. Or least fine enough to shake off the effects of the heat & get back to reproducing once it’s in your tummy.
Finally, a lot of food borne illness is not the direct result of bacteria. It’s the direct result of eating the toxic crap the bacteria have already emitted. Killing all the bacteria via a magic anti-bacterial death ray would do nothing about the toxins they left behind. Botulism is the classic example of this, but there are many others.
So microwaving the food will do nothing to solve this problem. Neither will heating it the old fashioned way.