Monday, May 28, 2012

Microwaving Bacteria

I might have known that somebody would email me this question:

'Can you kill bacteria in a microwave?'

Without bothering to do any research or carry out an experiment (what else would you expect from me?) I'd say 'yes'. The microwaves used are at the right frequency to make water molecules vibrate, all living things have water in them and don't like being heated up for long. As long as the oven has enough power, then after a while they will croak.

How long you need to keep bacteria in the machine, I couldn't tell you.

9 comments:

Danielle Gohin said...
This comment has been removed by the author.
Anonymous said...

Yes and no. I believe ants can survive in microwaves because the wavelength is larger than the ant. Don't know why the microwave is able to hit a water molecule significantly smaller than an ant mind. However, bacteria contained within something wet will eventually be killed as the temperature of that water is raised by the microwaves.

Some confirmation of this may come from the fact that medical equipment is sterilised using small wavelength gamma rays and not microwaves.

Anonymous said...

Nothing personal Mr Chalk, but are some kind of leading bacteriologist? Why would someone randomly ask you?

Kimpatsu said...

Yes, microwaves are used to sterilize instruments in laboratories all the time. Note that this is sterilization and not cleaning, mind; if you put a used dinner plate in a microwave, you'll kill all the bacteria, but the plate still needs washing up.
I've never heard the ant story, but it's bollocks. Microwave lengths are nanometers, too small for the human eye to see; ants are macro and very large compared to microwaves.

Anonymous said...

Kimpatsu, ants can survive in a microwave- try it.

As long as you remove the rotating plate then they can walk around and find the cool spots (due to interference of the microwaves bouncing about I think)

I put ten in and six were still alive one minute later.

Anonymous said...

Yes they are killed but you can run into other difficulties.
http://news.bbc.co.uk/1/hi/6293735.stm

Anonymous said...

If the frequency of a domestic microwave is 2.45 Gigahertz, the speed of light is 300 million metress per second then the wavelength is about 12cm, which is a lot of nanometres and a lot bigger than an ant.

Anonymous said...

Kimpatsu: Physics FAIL. "Microwave lengths are nanometres"??? Have you never microwaved cheese to demonstrate how to measure the speed of light? Wavelength in a domestic oven is of the order of 10 CENTImetres. If it was nanometres, you wouldn't need a turntable to ensure even heating. Or did you never wonder why microwaves usually have turntables? Or if they don't, why they always require you to stir the food? It's because the heated zones are widely spaced.

I do find it funny when someone pronounces as "bollocks" something they themselves clearly don't even vaguely understand.

Anonymous said...

I thought t5hat microwaves w2ere ok ith killing germs but not so ok in killing spores.