Yeast banking at home

[Evan B]

So I recently purchased a kit including 5 small vials, freeze shield (glycerin most likely), and an eye dropper. I froze up a few vials of White Labs Edinburgh, and going to do some Cal Ale as well.

After the thaw, I'm expecting to have to make a very low gravity starter, and most likely have it take a bit longer than normal. Has anyone else done this? Just seeing what anyone else has to say on the topic

[Bah]

I'd say that a starter between 1.030 and 1.040 would be ideal.

So what sort of freezer are you storing them in?

[Evan B]

just my standard kitchen freezer. i did some research and found out you can freeze yeast in a freeze shield (glycerin), and freeze them for quite a while and still get good viability. I heard it was best to bring them back to life in a 1.020-1.030 wort to ease them in to things then step up.

just wanted to see if anyone else had tried this. i haven't thawed any yet, so before i did i just wanted to get any last minute info that i could.

[Bah]

Well I've only done it before with yeast that's been frozen with a glycerin based product to protect cell walls, frozen at -80 F, which is so f'ing cold, it burns a bit to touch it with your bare hands. Anyways that was done in wort in that 1.030-1.040 range. Now that I think about it though, I'm not sure I fully know the science behind the -80F temp, but I can say I've seen it in other non yeast cell-culture labs too.

but either way, big props for giving it a shot, that's something I'd like to do again in the future myself.

[Evan B]

I'll update on how it works out for me. I'm just repitching right now, but when it comes time for some fresh yeast, I'll bust out a frozen vial.

I think the science behind the lower temps is to prevent freezing and re-freezing. In a lot of home frost free freezers, the temp gets up to a point where there are ice crystals forming and reforming at microscopic levels that break the cell walls of the yeast. You can minimize this by insulating the container you keep your vials in, and keeping it in the back of the freezer.

[Spidey]

I've had terrible success using this method in my home freezer because the freeze/thaw cycles to keep the freezer frost-free kill the yeast. It will work for short periods of time, but then you might as well just store them at 4C. This glycerin method works great if you have access to a -80C, which is what I do now.

[animaldoc]

One tip I've heard to deal with the freeze-thaw cycles in home freezers is to keep the frozen yeast samples in a small styrofoam cooler with ice packs inside. The rest of the freezer will go thru it's "frost-free" cycle but the temperature inside the cooler won't shift enough to damage the yeast cells.

I think the -80 thing has to do with RAPID freezing so ice crystals don't form and rupture cell membranes.

Where did you find this yeast-freezing kit??? Are these slants or large samples you are freezing?

-- Animaldoc

[Evan B]

For now I'm just using this kit from country wines and following their instructions. I still haven't needed to thaw one as I'm just repitching. I'll probably just pull one out here and throw it in a starter just to see how it works out with no intention of actually using it.

http://www.countrywines.com/products.asp?category=150