Effects of fermenting warm for 24, then cold?

[PLOVE]

Hi all,

Had a huge 30 gallon brewday on Sunday - 10 gal imperial red, 10 gal Nugget nectar clone (freshopped!), 5 gal oktoberfest lager, and 5 gal pumpkin ale. The problem is my fermentation chamber isn't big enough to hold everything at a single temp (two chamber set-up). So, some brews initially fermented at ~75° for between 24 to 48 hours before I was able to get everything down to 60. The good news is everything is holding nicely at 60 and fermentation is still very active.

So, my basic question is whether the off flavors/chemicals that are usually associated with high temperature fermentation (esters, isoamyl acetate, fusels, etc.) can be "cleaned" up by yeast if they are still actively fermenting at a lower temp. In other words, at what point have you gone too far down the warm path to fix the problem.

What's done is done, and wouldn't have been an issue if it we weren't suddenly smashing heat records (100+F) in the PNW, but I am curious how this will turn out.

Any thoughts? Predictions? Could be an interesting experiment, though tough to replicate
PLOVE

 

[brew_ny]

some brews initially fermented at ~75° for between 24 to 48 hours before I was able to get everything down to 60.

might not be a good thing with some yeast, from what I understand it is better to be cooler at first and warm up towards the end

all the best with your brews

S_M

 

[marvaden]

Ok, so from everything that I have read and my own experience, these few things tend to happen:

1. you will definitely get more esters. Whether they are the bad esters or not will be seen later on down the road when you taste it.

2. Hot alcohol does age out usually after a month or two if it did get in there.

3. Dropping the temperatures like that for some yeasts will knock them out of suspension and cause them to go to sleep. If you did a slow and steady cool down, that would be less likely to put the yeast to sleep, but you still run the risk.


Honestly, if I were you, I would go ahead and secondary the beers that this happened to after a month in primary. Let it ride in secondary for another month. Most of the flavors that can be gotten rid of during that should be gone. Do the secondary at a normal 70-75*F type temperature. Consider it almost like a diacetyl rest.

RDWHAHB. They will get good. Just don't bottle them until they are.

 

[Andrikos]

According to Chris White of White Labs, if you underpitch, starting warmer then cooling down shortly after is acceptable although probably not as good as pitching the right amount of yeast at a bit lower temp than the intended fermentation temp.

 

[duboman]

It is during the growth phase that stressed yeast begin to produce off flavors so pitching warm and staying warm through this phase is not ideal and is a precursor to off flavors, ester, fusels. As mentioned, dropping the temperature can further stress the yeast and possible cause them to stall until they acclimate and again, this is not ideal, yeast like stability

A perfect scenario is to pitch slightly colder and allow the yeast to self rise to the desired temperature and then hold. As fermentation slows it is sometimes beneficial to allow the temp to rise for certain strains to improve attenuation.

In the future you would be best to hold off pitching until the wort is at the proper temperature in a sealed sanitary environment and then pitch. You can try using a pre chiller, swam cooler setup with ice bottles if the fridge isn't capable of holding all the vessels.

As for predictions you will just have to taste your final gravity sample and determine if the beer needs additional time to condition and cleanup any unwanted flavors.

 

[IslandLizard]

You surely had a wild brew day there. For some of those beers a little heat is not the end of the world [pun intended] but I truly hope that lager wasn't the one suffering the brunt. There may be some fermentation byproducts on the ales, but I wouldn't sweat it. They're going to be unique, even if you need to condition them for a couple of months to wear off some of the fusels. Some yeasts are more aggressive creating them then others.

Ideally, I've learned, is to pitch coolish and let it rise a bit after the first fermentation stage is done. So, you need to give them time and the needed warmth later to clean up their act.

 

[PLOVE]

Thanks all. I'm in complete agreement with pretty much everything that has been said. The good news is the lager was the one beer that was always at 60. I realize this is fermenting a bit warm for a lager, but it was a compromise and I've done this in the past with decent luck. I will lager it at 40 once fermentation has finished and I've done a diacetyl rest. Second, I checked on the progress of the yeast post temp drop and everyone is still swimming in the pool and working away with vigor. Perhaps the drop in temp was slow enough for an adjustment.

Next time I'll do a better job of planning. Clearly my mistake was trying to throw in a small batch lager with 25 gal of ale!! Incidentally, the ale yeast was American Ale and a healthy pitch at that. I'm sure it will turn out ok.

P