Did I kill my yeast?

[phillip_h]

Ok, here's the situation. I have had a beer fermenting for about 10 days now in a temp-controlled conical fermenter. I have the SS brewtech 7 gallon with the integrated chiller coil with a Johnson controller and a submersible pump.

It has been colder than expected lately, so I haven't really bothered with changing the ice packs in my cooler. Apparently, the fermenter got to 70ºF and the pump kicked on and started cycling warm water through the coils.

I don't know how it happened, but when I got home from work a few minutes ago the temperature was reading 97º. It was like 68-69º when I was home on my lunch break.

I changed the ice packs and the temperature is going down, but what negative results am I looking at? It was probably at that temperature for 2-3 hours.

Did I probably kill my yeast (White Labs WLP051)? I know that I can keep checking the gravity over the next couple of days to know for sure. If so, can I just pitch more yeast? It's currently at 1.040, so it still has a way to go.

 

[Kent88]

I don't think you killed them, it was below 100F so they should be alive. You probably stressed the yeast and might get some off flavors.

 

[kh54s10]

At that temperature the yeast were probably loving life.. Too warm is great for the yeast but bad for the beer, but with the short time you are talking about I doubt you will notice any off flavors.

What I don't understand is where the warm water came from. Does the system use both the ice water and hot water and select one depending on temperature?

 

[bleme]

Yeast love the temp in the 90's. They just start chugging so fast, they make a lot of flavors that we don't want (unless it's a Belgian). They've likely all got hangovers now from partying too hard but they will eventually get their act together. You might benefit from an extra week in the fermentor so they can clean up some of their mess.

 

[phillip_h]

What I don't understand is where the warm water came from. Does the system use both the ice water and hot water and select one depending on temperature?

I only use the water for cooling, but we had a little cold front in south Texas (temps in the 50-60s), so the pump never came on. During that time I didn't change the ice packs and the temperature of the water rose to ambient levels.

I don't completely understand how the water got as hot as it did. I mean, it's only 76º outside right now. It's not like a Texas summer. My best guess is that the pump got hot from running constantly for 2-3 hours, heated up the water, and the contents of my fermenter in the process.

You were right about the yeast loving that temperature - the blowoff tube was bubbling like crazy. Maybe that woke them up enough to finally finish this beer. This yeast is pretty slow.

 

[phillip_h]

2 days later, and the refractometer is still showing the exact same reading. I have some US-05 that I'm planning to rehydrate and pitch tomorrow if there's still no change.

 

[Pkrd]

Your beer was done after 10 days anyway. You shouldn't use a refractometer for FG as the alcohol alters the reading.

 

[phillip_h]

Your beer was done after 10 days anyway. You shouldn't use a refractometer for FG as the alcohol alters the reading.

Dude, I had no idea that alcohol messes with the refractometer reading. I just took a reading with a hydrometer and it's right at 1.018. It's still higher than I'd like, but definitely better than 1.040.

 

[phillip_h]

I put the dry hops in last night, so it still has about a week to go. Hopefully it'll creep down closer to 1.015.