Why microwaves do not kill harmful bacteria as well as boiling

boilingfood-safetymicrowave

Medical Biochemistry point of view

My biochemistry teacher said today that the problem with micros is that they do not kill all harmful bacteria. He proposed boiling food instead.

I think there are two reasons.
Water can emit heat to bacteria from many more different directions than microwaves can. The heat frequency is changing all the time to the bacteria, since water is moving.
Radio waves can be applied only from discrete directions. To make microwaves better, I think reflection and different materials on the walls should be considered

I am not sure which one is the stronger reason why micros cannot make good food:

  • sequentially different waves – probably not
  • or heating bacteria from different angles by mirror/reflection – I think this is the main reason why boiling and oven is better

There at least two types of micros – wide ones and more vertical ones. I have had an intuition that the vertical ones can be more effective. They can send signals more broadly from the bottom, while the wide micros can send them only from one direction – left or right. Also, the reflection technique is easier to apply to those vertical micros, since the roof can be circular, while in the other boxes it is not possible.

Medical Microbiology point of view

Murray's book, Medical Biochemistry, says for different diseases, like Listeria's epidemiology that "Disease can occur if the food is uncooked or inadequately cooked (e.g. microwaved beef and turkey franks) before consumption.

This suggests me that there is some point of view why microwaved food is called "soft-food".
I will add pieces of evidence here when I explore more.

Best Answer

There's an interesting article on The Straight Dope that tests the question of how well a microwave kills bacteria on pizza. Here's a few quotes:

If I take a piece of pizza that's been sitting on the table awhile and microwave it, would that kill the bacteria, or am I just eating nice hot bacteria?

Will a microwave kill microbes? Sure. Microwave ovens use electromagnetic radiation to heat water molecules in food. It's the heat, not the microwaves, that's lethal here; the hotter you make your food, the more likely you are to kill the bacteria in it. (Some contend microwave energy itself is fatal to bacteria, but that's unproven.) The key is making the food hot enough uniformly enough for long enough. If it heats unevenly, a common problem in microwaves, some bacteria may survive.

After running some real-world tests and examining their petri dishes, they concluded:

  1. Heating the pizza for 30 seconds was relatively ineffectual.

  2. Heating it for a full minute killed most of the bacteria but not all.

  3. We didn't go in for another round of testing, but suspect that at least two minutes of microwaving would be needed to ensure 100 percent bacteria eradication, at the possible cost of rendering the pizza inedible.

Checkout the full (quite entertaining) article here:
http://www.straightdope.com/columns/read/2947/do-microwave-ovens-kill-bacteria

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