Pitching into Cold Starter Wort, or Why a Broken Thermometer is a Bad Thing

Hi everyone,

Very cold starter wort question. First though, the requisite story: earlier today, I made a starter for a Saison I'm brewing tomorrow evening. Everything went as planned, and even though those last few degrees of cooling were uncharacteristically difficult to reach, I finally pitched the yeast, hoping to get some nice fermentation going in anticipation of the brewday.

5 minutes later, I notice perspiration on the starter flask.

I feel the flask and it's stone cold. Long story short, after some examination, it turns out that my thermometer is somehow broken, stuck so that it will read no lower than about 76ish. In other words, I pitched tomorrow's yeast into a starter wort at (my guess) 30 degrees.

I'm posting this after searching around because I can't seem to find good info on this. First, is the yeast salvageable for tomorrow, say 6:00? If so, anybody got a good procedure for where to go from here? Is my best bet just getting a new vial of yeast? What I've done to try to correct this is let the starter flask come back to room temperature by wrapping it in a dish towel, and later, carefully placing it in a warm (90ish) water bath. Besides this, however, there is a somewhat scientific concern here: even if I was able to get the yeast up and fermenting the starter wort, is the benefit now negligible on account of these snags, and the relative short time before pitching it into the wort tomorrow?

At any rate, it's not all loss: I'd rather find out that the thermometer is broken today, than in the middle of brewing tomorrow...

Well, you didn't hurt the yeast any. They are just fine. You might have some temp shock going on, but the yeast will regain activity once the temp comes up. I know this because I freeze yeast. I bring up frozen yeast and brew with it all the time. Whether or not you have enought time to ferm out the starter before tomorrow is hard to say. Kind of depends on your yeast strain, how big the starter is and if you plan to pitch yeast slurry or the whole starter. If you plan to pitch the whole starter and not settle out the yeast first, I'd say you will probably be fine. If you want to pitch slurry, I don't know if that's enough time.

I have to believe cold shock is less harmful to yeast than heat shock. I'd warm your starter up to 85-90°F and check it in the morning to see if they wee yeasties have woken up and gone to work. With any luck the li'l bastids will get over your cruel and unusual treatment and be ready to ferment your brew

Cheers!

That's a bummer, but at least you see the upside of discovering it now. I'm definitely no yeast expert, but it seems like I always come across the warnings about generating "petite mutant" yeast when cold shocking the yeast. Apparently large numbers of petite mutants can lead to high amounts of diacetyl. I don't know how to gauge the severity of what you did. Might be best to just re-make your starter.

On a related note, I've recently started canning wort. It's a wonderful thing because you can effectively eliminate the whole cooling step.

Thanks, everyone. Lots of helpful information here. I think the take-away for me is that this isn't the end of the world--or the yeast--and that as far as this batch goes, it might be a game time decision. I'm going to sleep on this, and see what's going on in the flask tomorrow morning, fingers crossed that there's activity. Assuming there is, I'll pitch the lot of it and not worry about decanting and pitching only slurry.

Worst case scenario, this costs me another vial of yeast. That's not a bad price for learning something. Don't you feel though, that this hobby always has you making these types of rationalizations? Much to learn still...

Posting this update for anyone who might be interested later:

I pitched this starter after warming it up in bath (as I posted above), about 28 hours after I originally made the starter. The Saison I pitched this into had a starting gravity of 1.058 and began a vigorous ferment after about 10 hours, give or take. Not a terribly fast start, but the yeast is alive and active. With any luck, fermentation and flavor profile will be unaffected and fermentation won't stall out.

Thanks again to everyone who advised...