Froze Starter by Accident...yeast dead?

Made a 2.5 quart starter I was going to step up tonight, and crash cooled last night. I set the keezer temp @ 37 and forgot to check on it last night and this morning before leaving for work. I called my wife this morning to check on it (thank god she was home) she said it was a little slushy and removed it from the keezer. Are all my yeast dead?

I am still planning on stepping it up tonight, so hopefully that gives them another boost for the lager pitch on sunday. Any input would be appreciated, thanks.

I would suspect that you at least killed a lot of the cells. You might try to step up but I would think that you will need to basically start over and it will take several days to propagate a sufficient cell count.

Starter bounced back fine, plenty of activity, i increased volume by .25 quart just to be sure.

mklojay said:

Starter bounced back fine, plenty of activity, i increased volume by .25 quart just to be sure.

Click to expand...

yeah, you said it was a lager yeast, right? lagers can handle much cooler temps than ale and unless it was frozen frozen, you probably didn't kill off the yeasts. good call on stepping it up to be sure.

yeah, WLP german lager...just a little slush on the surface.

Glad it worked out for you! Freezing Yeast is a viable way to save money and build a library of yeasts. Check out the Wiki Page for instructions on how to do it.

NordeastBrewer77 said:

yeah, you said it was a lager yeast, right? lagers can handle much cooler temps than ale and unless it was frozen frozen, you probably didn't kill off the yeasts. good call on stepping it up to be sure.

Click to expand...

I've heard that ale yeast can handle higher temp limits than lager yeast, but never heard about differences in low temp limit. Both can handle -80degF afaik. Without cryoprotectant, I would think both types of yeast are vulnerable to damage below 30degF or so, or wherever the solution solidifies.

StMarcos said:

Without cryoprotectant, I would think both types of yeast are vulnerable to damage below 30degF or so, or wherever the solution solidifies.

Click to expand...

of course. but seeing as lager yeast... and ale for that matter, handle near freezing temps (fridge is ~34 or so degrees) during storage the concern here would be the cell wall ruptures caused by freezing and by ice crystals. since the OP's yeast wasn't completely frozen in this case, some cells undoubtedly survived. my guess would be if his yeast completely froze, he wouldn't've had success building up a starter.