How does heat affect yeast after primary?

[grrickar]

Well it happened, my temp fridge probe detached from the carboy and fell out of the fridge, so the STC1000+ I had controlling fermentation switched to heat mode and pretty much baked my batch of cream ale.

So I brewed it last Friday, and fermentation had slowed considerably. No krausen, yeast was White Labs Cream Ale yeast. Best I can tell the incident occurred last night, so it spent about 12 hours increasing the temp from 68F to 94F!.

I reattached the probe, put the carboy back in the fridge and it is cooling now, but not sure if the batch is lost or not. I am going to let it push through and sample before I bottle, and hope that it is ok.

I'm dropping the temp back down to 68F.

I'm sure I am not the only one to have had this luck - anyone have any experiences to share?

Oh, and to make things more fun, I had 5 bombers of various things in the fridge with it, so they got nice and steamy too.

 

[trentm]

My guess is you are OK. I think temps that high are rarely good for beer but after most of the fermentation is over and for only a short period the effects should be only subtle or none at all. Do be careful bringing the temp back down. Remember warm liquids hold less gass than cold liquids. So as you beer warmed up it off gassed a lot of CO2 and as it cools it will want that gas back. So if the fermentation cannot supply it, the air will.

 

[grrickar]

Best I can tell at this point it way over attenuated, to the point the beer seems 'watery'. I suspect the net result was that the yeast were reactivated by the heat, and cleaned up more than they should have. I plan to try another sample, and then decide whether to bottle or to toss it.

 

[ncbrewer]

I've never had the temp get that high for half a day, but I wouldn't have expected it to cause super attenuation. What was your OG and FG?

 

[JimmyC-BYOB]

That's pretty high temp for saccharomyces cerevisiae. The mortality rate changes drastically over minutes let alone hours. This all depends on the what the gravity of your beer was when it happened. If it was high the shock would have been minimal as yeast has a safety mechanism and take up glucose and go dormant. If the OG was low there may not have been enough resorces for the yeast to react. There most certainly were survivors though. Your bigger problem is with flavonoids and proteins. Even if the yeast survived your flavor will be off. Drinkable? maybe but not what you were shooting for.
If you want to geek out on the effect of temp on yeast I have attached a white paper that was written about this. (Not my paper. Just one that I knew about)

JMO
Jimmy

http://www.microbiologyresearch.org...est&checksum=E3FE157BE962D85C8E4391B92DFA5C90

 

[ncbrewer]

When I try your link, I get this message: The page you have requested is not available. Is there a work-around?

 

[ACbrewer]

The yeast will live in to the 110 range. it will make good beer only as high as about 70 (well maybe 80 if it is Belgian in style). And since the pathways for the chemical reactions are temperature sensitive, yeah, you could have it do more clean up than normal, or other reactions may have occurred. This is why we function at about 99F, so that our chemical reactions work. Lower and they stop, higher and there are other related problems. Same thing for yeast - although being less complex, it's survival temps are much better than ours.

IF it tastes ok, then bottle and drink. If it tastes bad, then don't bottle, you will not drink it, and end up dumping. Skip the bottling step.