Lagering and my wort temps have been too cold - is my yeast dead?

[bbshopplf]

Finally have a fridge just for fermenting, so I'm trying my first lager.

I have no data regarding my setup, e.g., when my set the temp controller to X, how cold does it really get inside, etc. I have an older temp controller, with a dial for the target temps and the fat probe.

After boil, I was able to chill my wort down to 70 deg in 45 minutes, but the cooling had slowed to a crawl so I put it in the fridge to finish the job (and prayed my sanitation practices had been spot-on so far).

The fridge cooled the wort to mid-50s in about three hours. It was warmer than where I wanted to pitch (I wanted to pitch at 48), but I grew paranoid about getting the yeast pitched.

Adding to complications, I hadn't aerated, which at that moment I immediately regret. My town had record-setting heat yesterday, and it was hot in my brew area. As I pulled the fermenter out to aerate, the glass carboy started to sweat and the temp began rising by the minute.

After aerating and pitching, when I put it back in the fridge the wort was back up to almost 70 degrees (at least the sticker thermometer on the side said so - internally I imagine that was not the case).

About five hours later, the fermenter was reading 48 degrees. I dialed back the temp controller until the fridge shut off.

But then over the next few hours I kept finding the fermenter cooler and cooler (into the mid-40s), so every hour when I went down to check it, I was dialing back the temp controller more and more.

And then I had to go to bed, which isn't good.

My concern is - the past 12 hours the wort has been around mid-40s. I've dialed back the TC yet again, and will resume hourly checks.

Can the yeast survive the super cold temps though?

 

[RPh_Guy]

A sticker thermometer is useless in this situation, remove it.

Tape the probe to the carboy and then tape or strap some insulation over it, like a sponge or foam or a small pillow or folded t-shirt.
Once the probe is getting accurate temps, the controller should do its job.

The yeast will be fine.

 

[micraftbeer]

I echo everything @RPh_Guy said. I'd add to it that if it did get too cold, it might take a bit longer to ferment, but it won't kill your yeast. Yeast is stored in homebrew shops in near-freezing temperature refrigerators after all.

Once you get to your 48 degrees and things seem stable/under control with your fridge, I'd give the fermentor some swirling action to get the yeast stirred up and back in solution. They may have dropped out when it got really cold.

 

[bbshopplf]

A sticker thermometer is useless in this situation, remove it.

Tape the probe to the carboy and then tape or strap some insulation over it, like a sponge or foam or a small pillow or folded t-shirt.
Once the probe is getting accurate temps, the controller should do its job.

The yeast will be fine.

Thanks man; I will do this.

 

[bbshopplf]

I echo everything @RPh_Guy said. I'd add to it that if it did get too cold, it might take a bit longer to ferment, but it won't kill your yeast. Yeast is stored in homebrew shops in near-freezing temperature refrigerators after all.

Once you get to your 48 degrees and things seem stable/under control with your fridge, I'd give the fermentor some swirling action to get the yeast stirred up and back in solution. They may have dropped out when it got really cold.

Thank you for the reply. It's been stable around 48 (I guess - still relying on the tape thermometer but will do as @RPh_Guy suggested), but no fermentation activity at all.

I'll attach the probe to the carboy, and give it a shake.

Thank you both again, very much.

 

[bbshopplf]

Temps seem to be stable, and there's definitely fermentation activity.

The activity is nothing like an ale, but I'm getting consistent bubbles in the airlock, every 8-10 seconds or so.

 

[bracconiere]

seems like this has been resolved, but just to chime in. i believe to 'kill' the yeast it would have to freeze solid, which is why you have to add glycerine to a freezer yeast bank.

and unless you pitch a lager at 70f, like the yeast people recommend then chill once active, in my experience they do take a couple days to take off...

And congrats on the new lager fridge! cold fermenting is fun!

 

[RPh_Guy]

Even freezing only kills a portion of the yeast.

The amount depends on various factors.
http://aem.asm.org/content/63/10/3818.full.pdf

 

[bracconiere]

Even freezing only kills a portion of the yeast.

The amount depends on various factors.
http://aem.asm.org/content/63/10/3818.full.pdf

interesting, at the end of that abstract it said hydrogen peroxide made them freeze tolerant too, i think...

i do know i keep my yeast from the last batch in the fridge, until i use it in my next batch, takes off fermenting fine after about an hour....maybe two...

think the OP just wasn't ready for the lag time pitching cold for lager....

 

[waldoar15]

Temps seem to be stable, and there's definitely fermentation activity.

The activity is nothing like an ale, but I'm getting consistent bubbles in the airlock, every 8-10 seconds or so.

That's a normal lager fermentation (when done at normal lager temps).