Do microwaves kill nasties?

[spook100]

I have some small lab jars that I use for storing my yeast that I usually sterilise them in a pressure cooker before use. I was wondering whether I could just put a little water in the bottom of each and zap in the microwave for a minute instead. Will the critters be killed by the microwaves or are they like cockroaches? I'm not talking about boiling them to death in the microwave, but nuking them.

[oldbloke]

Googling around indicates that washing, leaving them wet, then nuking on high for about 3 mins will boil the remaining water, effectively sterilising. But some people like to have the jars about 1/8 full to generate more nice superhot sterlising steam.
The jars will be VERY HOT when you take them out.

[gregorach]

It's not going to be as good as pressure cooking them - you'd basically just be steaming them at atmospheric pressure. Nobody uses microwaves for sterilisation in commercial lab settings - they use gamma rays (and lots of them) for things that can't be sterilised by autoclaving. Stick with the pressure cooker, it's (more or less) what the pros use.

[EccentricDyslexic]

V. Interesting question! You would think that the waves would hit the bugs liquid internals and boil them pretty much imidiatly even if the jar was dry. Hmmm... Some experimentation needed! I recently got a microscope, will see if I can devise a test.....

Steve

[gregorach]

Microscope's not actually that much use for this sort of thing... What you want to do is prepare some sterile media plates and expose two sets, keeping a third set as negative controls. Of the two exposed sets, one gets zapped in the microwave, whilst the other is your positive control. I don't have a microwave, but having some idea of the level and duration of gamma ray exposure needed to sterilise something, I'd bet money that it won't really do the job.

There's a thread on the topic over here, which seems to mostly consist of people not understanding what the word "sterilise" really means... I'm very much of the opinion that yeast propagation equipment needs to be sterile, not merely disinfected - and the way that's done in labs all over the world is by autoclaving.

[spook100]

Thanks. I'll stick to the pressure cooker for now then.

[oldbloke]

There are thingies you put inside the microwave, for sterilising baby feeding gear. Looks like they basically keep the superheated steam the nuker makes in close contact with the stuff you want sterilised.

[gregorach]

There are thingies you put inside the microwave, for sterilising baby feeding gear. Looks like they basically keep the superheated steam the nuker makes in close contact with the stuff you want sterilised.

Yeah, but they still don't achieve pressure cooker temperatures. They "sterilise", rather than sterlise.

[Kev888]

IMHO a microwave is really just a way of heating water (molecules) in a high tech way; you can't guarantee that it'll affect 'nasties' directly, and without the pressurised environment the sanitising temperatures will be less than a pressure cooker. I'd not like to rely on it..

Also (I was saddened to hear), someone I knew in the past rather cruelly microwaved a bee for several minutes, and apparently it flew out alive - if a bit vaguely. If a bee can survive then...

Cheers
kev