I made up 4 pints of washed yeast from a recent batch and put them in the beer fridge in the garage. Temps dropped and the pints froze. The beer in my picnic tap lines were frozen, too. I would assume that freezing yeast in water would squeeze them and kill them off. Uncertain how long the pints were frozen. Is it worth trying to salvage them?
Viability and vitality are both going to be low. I’d replace it with a new vial or pack, but if it’s a discontinued strain or you’re so inclined, I’d combine them, give them a no-stir starter at 1.020 for a week with plenty of nutrient, and then wash it again. There’s probably still live yeast, but for most people it’s not worth the trouble to revitalize it, nor the risk that it won’t perform well when you pitch it.
I’ve frozen smack packs in the back of the fridge before and the yeast was fine. As long as they’re not frozen for a long time then you will still be able to use the yeast. Just to be safe, I would give them a little wake up call with a small starter.
I turned the dial on the fridge down all the way last night and cracked the door open so that the light stays on. They are not frozen solid anymore, but they are still kind of chunky. I think tomorrow I will make a sacrificial starter from one of them just to see if it takes off. If it works, I can wash the yeast and put it back in the fridge.
This looks like a good idea, but I’m curious as to why a no stir starter would be preferred. A stir plate would give the yeast more oxygen which would keep them out of the fermentation stage longer which would build up more sterol reserves which is what is likely depleted. Sterols are crucial to building cell membranes, and allowing permeability.
I will be using my home made stir plate.
This looks like a good idea, but I’m curious as to why a no stir starter would be preferred. A stir plate would give the yeast more oxygen which would keep them out of the fermentation stage longer which would build up more sterol reserves which is what is likely depleted. Sterols are crucial to building cell membranes, and allowing permeability.[/quote]
I seem to recall Jamil saying in “Yeast” that a stirplate keeps yeast from taking up necessary nutrients they’ll need for dormancy or storage. I’ll check on that and try to post the quote.
Also, I wouldn’t want to encourage weak cells to reproduce too quickly, straining the cells through multiple buddings. My idea of a no-stir was to let them leisurely uptake the nutrients and sugars, reproduce a time or two, then uptake more stuff, and go dormant. I don’t have lab tests to back this up, it just seems like a nice way to treat yeast that’s had a tough life.
Freezing doesn’t usually have a negative impact on yeast, it’ll just defrost and go on like nothing happened.
