Sudden temp drop 24 hours after pitching US-05

[Piggy Smalls]

Hi all,

I have just gotten back into brewing and have done a APA BIAB recipe over the weekend.

All went well and I pitched the yeast yesterday morning and put the fermenter in my temp controlled fridge set to 21 degrees Celsius.

This morning I noticed the wort temp had dropped to about 19 degrees so I plugged my fridge into the heat plug on my temp controller and went to work. Unfortunately it seems the heat setting doesn’t work on my fridge and the fridge has been in refrigeration mode all day. Temp in the fridge got down to 1 degree by the time I just checked but the wort in the fermenter is reading as 12 degrees Celsius. This temp drop has occurred over a six hour period.

I have just turned off the fridge and removed the fermenter to bring the temp back up closer to 20 degrees. Hydrometer reading shows that fermentation has begun as gravity has dropped from 1.048 to 1.038 since pitching the yeast 30 hours ago.

My questions are:

A) Will the drop to 12 degrees have killed the yeast and stalled fermentation? It looks to me like there is still a small amount of activity but I am no expert and haven’t brewed enough to deal with anything like this before.

B) Will the temp drop and subsequent rise have a significant effect on the overall product considering it has occurred just after fermentation really got going?

Any advice would be appreciated.

Cheers.

 

[beer gut]

The heat plug on your temp controller need a heating source plugged into it, like a heating belt or heating pad, normal fridges don’t have a heating function.

I don’t have enough experience to answer the rest of your questions with a lot of confidence but when it gets back up to 19° fermentation should kick back in but I’m not sure about any ill effects or off flavours from the yeast stress.

 

[Piggy Smalls]

Thanks BG. I probably should have read the instructions before plugging it in... I went back out to check this morning and the temp is at 17 degrees and fermentation is well and truly back on. Gravity has dropped to 1.030 now and the stuff in the hydrometer tasted great albeit still a bit sweet. Hopefully the yeast haven't been stressed enough to produce any off flavours (I couldn't detect any...) and I am thinking it is going to turn out fine. I will probably leave it at 18-19 degrees now until fermentation is complete just to be safe.

 

[FarsideOfCrazy]

That temp should only slow the yeast down. It's heat or freezing temps that can kill yeast.

Take another hydro 24hrs after that reading you already have to confirm.

 

[wide eyed and legless]

Only heat will kill yeast, freezing will keep it in suspended anticipation.