Is a pressure cooker entirely necessary

[Cain Harland]

Is a pressure cooker entirely necessary for sterilizing slant vials etc? or does a pot with a false bottom boiling away get the job done. We are talking about single celled organisms that thrive at fermentation temp. My logic says that 100c for a sustained period should be plenty but maybe I'm wrong since there are bacteria around that can tolerate more.

[Steve Adkins]

No not 100% necessary.  Just boil for a while and maybe follow up with a good dose of starsan before use.

[Damon Colbert]

At the risk of sounding pedantic, it comes down to the difference between sanitising and sterilizing.  Sanitising means reducing unwanted organisms to a low level, sterilising means everything is killed.

Sanitising is generally sufficient for brewing, besides being safer and/or easier to conduct.  A long boil will kill most bacteria, some yeasts, and the vegetative state of molds - meaning your plates/slants will likely be contaminant free for 2-3 weeks.  But it will not destroy fungal spores - so you could find molds/wild yeasts cropping up after some time (even in the cold).

If you're aiming to keep plates/slants for long-term storage (which isn't really ideal anyway, a few months is probably the limit of usefulness), then a pressure cooker would be ideal.  If you really can't be bothered, a few cycles of boiling and cooling should get you an improvement over a long boil.

Hope that helps.

[Cain Harland]

So the difference between 100c in a pot and 120c in a pressure cooker makes the difference there? I will keep an eye out for an old pressure cooker, its just that I don't have one right now and I'm not going to fork out for a new one.

How about the microwave in a suitable pot with a cup of water? kind of like one of those baby bottle sterilizers. I quite like using the microwave for sanitising things like dry hop bags (which I put in a cup of water) or the water used for gelatin fining. I figure its boiling + a little extra, but the level of sanitisation needed for a hop bag is very low.

[Damon Colbert]

That's correct, the combination of pressure and temperature kills hardier things like spores.  That's the principle behind autoclaving, which medical and research institutions use to sterilise equipment.

Like I said, a few cycles of heating and cooling can improve the longevity of your media in the absence of pressure.

I can't speak for the killing power of a microwave, but I did work with someone who routinely used what they called 'microclaving'.  There seems to be some precedent for it killing bacteria and yeast, but again the hardier microbes remain resilient.  Boiling is boiling at the end of the day, all I can say for sure is don't microwave water in a flask, it will blow water everywhere :D

[Chuck]

An Oldie but I don't think much has changed.

http://www.morebeer.com/brewingtechniques/library/backissues/issue1...

Cheers-

Jim

[Cain Harland]

Thanks for the input guys I scored a pressure cooker for  $10 off trade me.

[martin w]

i see you have a pressure cooker now,but another method i used when i first started was tyndallisation,i used a baby bottle steriliser in the microwave,which you do at least 3 times over a period of time,the idea is everything you are trying to eliminate is weakened by the first heating and is killed in the next rounds,i never had a problem with infected slants however the agar mixture tends to boil over if your not careful and you end up with a bunch of empty test tubes,i now have a pressure cooker which is way easier!

[Peter Smith]

This is a good thread as well

http://www.homebrewtalk.com/showthread.php?t=35891

I tend to just buy a fresh batch every 6 months and do the big starter split thing,  I have always found repitching from under good tasting beer to be best,  I think 3 gens of lager probably starting to push your luck in the homebrew world....   but have the original split starter packs that are only 2 months old.