Frozen Yeast Vials

A while back I moved into a new apartment. I intentionally packed all of my beer brewing stuff last, so nothing would be lost in boxes. Anyway, I forgot that I had a vial of liquid yeast (London Ale) in the trunk. It has been consistently below freezing here for over a month.

A few days ago I made a starter out of this yeast that has been frozen solid for a few weeks. It took about 2 days before there was any activity. But it is now bubbling away (for a day and a half now).

My concern is that it never formed a Krausen. It got very cloudy, and you could see visible CO2 bubble going to the surface, but no foam at the top. Does anyone think that it is possible that there were a few Lager yeast cells mixed in, and they were able to survive the freeze? Only the strongest survive, and they were subjected to some pretty harsh conditions (Down to -20F at one point).

You probably had a few yeast survive the freeze thaw. The vials of yeast are pretty thick with cells so there's more protection for the yeast from ice crystals during a freeze. High concentrations of protein or cells do the same thing as glycerin. You probably lost 90% of your yeast to the freeze, but the 10 that survived are fine. I'd give the starter at least a day or two longer than you'd usually give it to reach pitchable numbers.

Cheers

mlee0000 said:

Does anyone think that it is possible that there were a few Lager yeast cells mixed in, and they were able to survive the freeze? Only the strongest survive, and they were subjected to some pretty harsh conditions (Down to -20F at one point).

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what kind of yeast did you use? What makes you think this?
Your yeast did not die when it froze it just went to sleep, a very deep sleep. When thawed and pitched into wort the yeast are re-energized and the yeast start to metabolize carbohydrates

so concerning your yeast survival question, the answer is no.

The starter was extremely active for about a day and a half, but it is slowing down now. What I'm saying is that it never formed a Krausen (no foam on the top) and I'm concerned that possibly there were a few lager yeast cells in the vials. I'm wondering if these took off instead of the ale yeast (as it looks like they are fermenting off the bottom). The original yeast I pitched was White Labs London Ale - WLP013.

What makes you think that there may be lager strains in your London Ale vial?

I rarely see a krausen on my starters.

All of the batches, and starters for that matter, have had krausen. I just thought it was odd that this one did not.