Can yeast survive freezing?

So yesterday I was in a huge hurry when I finished brewing my belgian quad and put it in my temp controlled freezer to ferment.. I went down to check on it today, and found that I had left the temp control outside the freezer, and my beer was frozen!

How likely is it that these yeast will survive? Should I repitch after it thaws?

I'd thaw it and bring it up to fermentation temperature....slowly. Wait 2 days and check for activity. If none, I'd repitch.

It is highly unlikely enough yeast will have survived to ferment your beer. I would bring up to temp and repitch.

I bought a Costco sized package of yeast to make bread about 5 years ago and it has been in storage in my freezer ever since. It expired last year. I continue to use it successfully to make bread. So no, its not dead, but one could reasonably assume its viability has been compromised a bit. Your results may vary, of course, this stuff was about $4 for a lb.

Your bread yeast was dehydrated. Freezing live or reconstituted yeast cells causes the cell wall to burst, killing the yeast.

Sounds like I need to try and pitch frozen yeast to see the truth in this. I have some harvested yeast I am going to freeze.

Dunerunner said:

Your bread yeast was dehydrated. Freezing live or reconstituted yeast cells causes the cell wall to burst, killing the yeast.

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+1 This is exactly the problem. Freezing the beer will fracture the majority of your yeast cells. The issue here is that whatever yeast manage to survive will likely not be enough to successfully regrow a large quantity of yeast to ferment your beer without off flavours.

likwidbliss said:

Sounds like I need to try and pitch frozen yeast to see the truth in this. I have some harvested yeast I am going to freeze.

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I guarantee you this is true, I did cell culture in the lab for many years. Unless there is DMSO or glycerol in the freezing medium, your cells are ****ed.

Well, it's back up to 60* now, and I'm seeing some activity. There's not more than 1/2" krausen, but at this point maybe it's just the temp and the defoamer I used during the brew process (first time using it, so I don't know how much it reduces the foam). I'll give it until tomorrow morning to decide, and pitch again if it doesn't seem to be taking off. I don't want to spend more money on this cursed batch if I can avoid it.. I missed my temps, burned the LME because I forgot to stir, and froze the beer. I think it might be a sign from the beer gods that I should just let this one go.

Dunerunner said:

I'd thaw it and bring it up to fermentation temperature....slowly. Wait 2 days and check for activity. If none, I'd repitch.

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+1 that. I've heard of this happening before with some people not having any issues, others had to repitch. It'll likely change the flavor profile of the end product but you've by no means ruined anything. It just make take an extra step or two to get where you're going in the end. No biggie.

I accidentally froze a Wyeast smack pack a couple of months ago. I thawed it, smacked it, and it swelled fine. I'm not recommending freezing yeast, but I also doubt all hope is gone.

spiffcow said:

Well, it's back up to 60* now, and I'm seeing some activity. There's not more than 1/2" krausen, but at this point maybe it's just the temp and the defoamer I used during the brew process (first time using it, so I don't know how much it reduces the foam). I'll give it until tomorrow morning to decide, and pitch again if it doesn't seem to be taking off. I don't want to spend more money on this cursed batch if I can avoid it.. I missed my temps, burned the LME because I forgot to stir, and froze the beer. I think it might be a sign from the beer gods that I should just let this one go.

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What was the outcome? I just did the same thing. Thermostat programming error on my temp-controlled freezer. Fermenter was nearly frozen for about 24 hours. Need advice.

I freeze pizza dough all the time and it doesn't seem to effect the yeast any.

I knitted some yeast sweaters.

I just made a cider from Nottingham yeast that I froze in a vial with glycerin. Worked out well.

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Holy thread revival! Was the beer good? Do I need to replicate this burnt sugar frozen yeast experiment to produce the greatest fermented beverage of all time?

old thread, but I just had the same thermostat malfunction and got my cali common partially frozen. I plan to repitch once it warms to 60. Anyone there to report on flavor following a beer slurpy?

Alphahorn said:

old thread, but I just had the same thermostat malfunction and got my cali common partially frozen. I plan to repitch once it warms to 60. Anyone there to report on flavor following a beer slurpy?

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Depending on the yeast used, I would think the bigger issue could be that much of the yeast would floc out. Unless the wort had not fermented and froze solid, probably a non issue. Just be sure to rouse the yeast back into suspension once your back to fermentation temps.
If it was slushy, not solid, the yeast were most likely in the non frozen liquid(sugar and alcohol). That would, in theory, keep their cell walls from rupturing, not unlike glycerin. While it surely killed some of the population, the other portion just went to sleep.
You could always pull a yeasty sample and put it in some sugar water to check viability.
Or even grab a few once of yeast off the bottom and make a vitality starter and pitch it.

Alphahorn said:

old thread, but I just had the same thermostat malfunction and got my cali common partially frozen. I plan to repitch once it warms to 60. Anyone there to report on flavor following a beer slurpy?

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Hi. I have a yeast bank and normally freeze yeast in glycerin to hold it, so it might be fine. Was your yeast in a smack pack/pure pitch pack when it froze or in a jar as slurry? If it wasn't totally hard frozen, you should be okay. Yeast can be incredibly tough little critters. It probably wouldn't hurt to proof it in about 500ml (~2 cups) of 1.035-37 starter for a few hours (6-8) just to increase it's vitality. Good luck to you. Ed


ETA: +1 what @Jwin said.

RedlegEd said:

Hi. I have a yeast bank and normally freeze yeast in glycerin to hold it, so it might be fine. Was your yeast in a smack pack/pure pitch pack when it froze or in a jar as slurry? If it wasn't totally hard frozen, you should be okay. Yeast can be incredibly tough little critters. It probably wouldn't hurt to proof it in about 500ml (~2 cups) of 1.035-37 starter for a few hours (6-8) just to increase it's vitality. Good luck to you. Ed


ETA: +1 what @Jwin said.

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thanks for the two responses. it wasn't totally frozen, just some slush on the top. I made a yeast starter from San Francisco Lager Yeast.

Day later, and we have fermentation