Freezing yeast Q:

[Ragde!]

OK, so I don’t think I quite got the discussion on “freezing” yeast I was looking for on Sunday. So for my first post, here I go!

I got this kit where you mix yeast slurry with glycerol (I think. It came with the Kit) and then put it in the freezer for storage. On the show the Whites said that you need to go much colder than a normal freezer to safely freeze yeast.

By adding the glycerol solution the water doesn’t freeze so the yeast walls won’t rupture. If the solution stays liquid in the freezer than I am not really freezing the yeast am I?

What I’m thinking is that the yeast stores longer at colder temp. So if I can bring them down past 32f (the lower the better) and hold them there (frost free freezer) without a thaw cycle, than they should have a longer storage life right?

The Whites mentioned something along the lines on a ten percent die off every thaw period, so as long as it doesn’t thaw I should be able to have enough viability to grow up a starter from the test tube right?

I want to be able to store yeast for a long time w/o having to re-culture and risk contamination each time.

[bub]

Only one way to find out... let us know!
BUB

[BrewerJeff]

OK, so I don’t think I quite got the discussion on “freezing” yeast I was looking for on Sunday. So for my first post, here I go!

I got this kit where you mix yeast slurry with glycerol (I think. It came with the Kit) and then put it in the freezer for storage. On the show the Whites said that you need to go much colder than a normal freezer to safely freeze yeast.

By adding the glycerol solution the water doesn’t freeze so the yeast walls won’t rupture. If the solution stays liquid in the freezer than I am not really freezing the yeast am I?

What I’m thinking is that the yeast stores longer at colder temp. So if I can bring them down past 32f (the lower the better) and hold them there (frost free freezer) without a thaw cycle, than they should have a longer storage life right?

The Whites mentioned something along the lines on a ten percent die off every thaw period, so as long as it doesn’t thaw I should be able to have enough viability to grow up a starter from the test tube right?

I want to be able to store yeast for a long time w/o having to re-culture and risk contamination each time.

I'm guessing here, but I think the reason that specific temperatures are mentioned (i.e. < -60) instead of "just below freezing" is that you want to stop as much activity as possible within the yeast cell, without actually freezing the yeast. You may still have changes or mutations within the cell, so they may not be as healthy as you think. If you are only storing the yeast for a few months, I would just simply use slants.

Worth a shot though!

[MTfarmboy]

my $.02

They also mentioned on the show that frost free freezer cycles can harm the frozen yeast. I have seem some people who store their frozen yeast with ice packs in a little cooler in the freezer, so when the freezer cycles the yeast don't notice. May people have had good luck with glycerol, so give it a try and let us know.

[yeast_slurry_speech]

What I’m thinking is that the yeast stores longer at colder temp. So if I can bring them down past 32f (the lower the better) and hold them there (frost free freezer) without a thaw cycle, than they should have a longer storage life right?

Actually the frost free freezers are the ones with heating elements in them (or let the cooling element heat up) and have thaw cycles. The old style that gathers big ole chunks of ice on it, don't have a thaw cycle.

[bergerandfries]

I have a "big ole chunks of ice" freezer and have kept my Duvel and Orval yeasts in there for almost a year. When I make my clones, I just pull one out, warm it up in a warm glass of water, pitch it in a starter, and make great beer. Now is the yeast 100%? Not a lab guy, so I don't know. I like the beer it makes, so I'll continue to do it, especially since that damn Orval yeast only comes out every OTHER year from White Labs....

[Thirsty Boy]

I asked that question when the whites were on the other week... didn't like their answer so I went ahead and did it anyway.

I suspect perhaps they thought I was asking about freezing a slurry (with glycerol) and expecting to be able to just pitch it when it was thawed...

not what I meant, nor why I think most people would try to freeze yeast. I am mixing 5ml of thick slurry, with 5ml of Glycerol and whacking that in my (not frost free) freezer at about -15C (5F).

As stated above, it doesn't really freeze properly, remaining quite liquid, just bloody cold.

I figure I'll warm it up, pitch it to a 50ml starter then step it up to the required level. Even if half of it turned up its toes... thats still a few million live cells to get me going.

Anyway, I'm doing it, so I'll let you know how it works.

Thirsty

[bergerandfries]

I asked that question when the whites were on the other week... didn't like their answer so I went ahead and did it anyway.

I suspect perhaps they thought I was asking about freezing a slurry (with glycerol) and expecting to be able to just pitch it when it was thawed...

not what I meant, nor why I think most people would try to freeze yeast. I am mixing 5ml or thick slurry, with 5ml of Glycerol and whacking that in my (not frost free) freezer at about -15C (5F).

As stated above, it doesn't really freeze properly, remaining quite liquid, just bloody cold.

I figure I'll warm it up, pitch it to a 50ml starter then step it up to the required level. Even if half of it turned up its toes... thats still a few million live cells to get me going.

Anyway, I'm doing it, so I'll let you know how it works.

Thirsty

I think that you'll be fine with that. It may not be the same as a fresh vial of yeast, but I wonder if you or I would have the pallet to tell a difference.