Accidentally frosted my hybrid Oktoberfest

Following the suggestion of my LBS, I made an Oktoberfest using a hybrid yeast (Wyeast 2565) because I didn't have a lagering fridge set up yet--bought myself at least 2 weeks before needing to crash cool, and got a setup to chill in time. The problem is, when I did I accidentally chilled it a bit much--enough to make a layer of ice on the top (don't trust the thermometer enough for a reading to really matter).

I know that will obviously change the flavor (don't know how), but my concern is that the wyeast will not activate again for bottling. Since I can't provide the lowest temperature it hit, I know no answer is definitive, but what are the chances enough survived to bottle, and reasonably how cold can wyeast get before it won't reactivate--or is that dependent on the strain?

Topic crash-cool homebrew

Category Mac

1
answered at

As long as it was just a layer of ice on the top, the yeast should still be fine, since the rest of the water was still at or above freezing.

Yeast can withstand very low temperatures - I freeze them in glycerine solution at -36°C/-32°F, while commercial yeast banks freeze yeast at much lower temperatures - ca. -60°C/-80deg;F. What kills them when freezing in mostly water is ice crystals that form, which penetrate and rupture the cell. But in your case, since the ice was just on top, most of the water didn't hit freezing and some of the yeast has still probably survived.

If you want to be totally certain you get carbonation when you prime, you could add 1/2 tsp dried yeast at bottling time (to the whole batch.)

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