I brewed an amber ale kit on Sunday (my second time brewing at all). Using white labs wlp008. I left the carboy upstairs and the fermentation was very rapid and extremely active for two days reaching temps of 75F+.

I moved the carboy to my basement thinking that this was to hot and now am at 68F. My question is

A) should I have moved it at all? looking at this previous question "Temperature swing of 10+ degrees during fermentation" makes my wonder if those high fermentation temps going to affect diacetyl levels (referring to Brandons answer) or if the cooling drop moving it to the basement is going to produce acetaldehyde's (referring to Bakas answer) I know that was about a porter but maybe it still applies. And B) should I leave it at the current 68F or move it back up to the higher temp?

Also what kind of off flavors might I expect to see due to these temps (I am still trying to figure out exactly what these "off flavors" taste like).

  • UPDATE: My carboy has been at the lower temp now for 3 days, the first day at the lower temp it was still bubbling pretty steady at about 68F. Now the bubbling has slowed to about 10 per minute and is at 65F. Still has about a half inch of krausen on top so I am now wondering A) Will the krausen be gone before I should take a gravity reading? B) Is it still ok to leave at this temp (65F)? I assume it may go down a little once fermentation stops and is that lower temp going to be ok to let sit a few extra days?
    – Bullet86
    Jan 22 '11 at 15:17
  • Just popped a tester (a little early I know) but it would seem that any off flavors that may have occured were undetectable. Thanks for the great advice on this one!!!
    – Bullet86
    Feb 10 '11 at 12:46

It was definitely a good idea to move it. Leave it where it is. Personally, I would have moved it to someplace even cooler. I prefer to ferment generally ion the 62-65F range. The best thing to do is chill your wort to just below the temp you want to ferment. The heat of fermentation will bring it up into range. The temp you started at might have produced some harsh fusel alcohols. If so, they will eventually age out to some degree. As long as the yeast is still active, it will consume diacetyl and acetaldehyde and those shouldn't be a problem. Here's a good description of some common off flavors from How to Brew off flavors

  • Should I go even cooler by moving it to the unfinished portion of my basement (maybe as much as 10 degrees cooler) or keep it where it is since it is still fermenting (about 14 bubbles out of the airlock per minute) in hopes that the active yeast will drive out off flavors?
    – Bullet86
    Jan 20 '11 at 16:34
  • 2
    After the first couple of days, the activity of fermentation won't create nearly as much heat. So leaving it in the 68-degree room now is likely fine. If you go too cold, the yeast will stop working before eating up diacetyl & acetaldehyde.
    – Hopwise
    Jan 20 '11 at 16:39
  • up vote for the very informative off flavor link, I had not found one this descriptive yet. I will keep you posted on the tasting results
    – Bullet86
    Jan 20 '11 at 16:40
  • accidentally double clicked the up vote and now it wont let me do it again.
    – Bullet86
    Jan 20 '11 at 16:51

I would personally leave is at the lower temperature which is probably where it should have been all along. If the yeast is still active at the lower temperature you shouldn't get any more off flavors from the temperature change. Although the damage may have already been done at the 75+ fermentation temps. You will get lots of phenol production like medicinal and band-aid flavors along with some higher alcohols. It is possible that the yeast may reabsorb some of the flavors but it may need to age.

  • How long would it be good to let it sit? I have no problem leaving it as long as necessary but is there any benefit to leaving it in primary once I have reached FG as to avoid soapy flavors (just read about this off flavor for the first time thanks to Denny Conn's link)
    – Bullet86
    Jan 20 '11 at 16:36
  • After fermentation activity stops, it's good to leave the beer at fermentation temps for at least 2 more days. During that time the yeast will clean up some of the off-tasting chemicals that they created during fermentation -- like diacetyl.
    – Hopwise
    Jan 20 '11 at 16:41
  • 1
    There's no problem at all with leaving your beer in primary for 3-4 weeks. Autolysis does npot set in as quickly as had been previously thought. In fact, one of the worst things you can do is xfer your beer too early. In most brews, there is no need at all for a secondary fermenter. You can go 3-4 weeks in primary, then bottle or keg.
    – Denny Conn
    Jan 20 '11 at 18:15
  • Piggybacking on Denny's comment again: For a vast majority of my ales, I ferment for 3-4 weeks in primary and never transfer to secondary. It produces great results and I've never had off-flavors from leaving it in primary for that time range (in fact, the only time I ever have was when I left it for 2+ months). Jan 21 '11 at 13:53

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