General Category > Yeast and Fermentation

Fermentation Temperature versus Ambient Temperature

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I've heard a debate over the years on how fermenting wort generates heat and can be substantially warmer than ambient air. Another thread here said 4 to 6 degrees above ambient. Really?

I've also heard others say that there is no way with the agitation and mixing of the yeast and CO2 release that the core would that much warmer, if any over ambient.

I can see MAYBE in 150 bbl conicals where the temp MIGHT be a little warmer at the core, but in a carboy or bucket?? Really? Is there empirical evidence to prove this? I've never measured, but it seems 4 to 6 degrees is a little beyond the realm of reality.   

I have the fermentation chamber set to 60 and the wort reads 64-66. That empirical enough for ya?  ;) Have you ever checked to see what temp your wort is during active fermentation? If not, you need to. You might be surprised.

BTW: If there ever was a "debate" about wether fermentation is exothermic it was a short one. Pretty easy to check for yourself, pretty well known, not much of a debate. Batch sparge/fly sparge. Secondary/no secondary. Even starter/no starter - those are debated. The fact the fermentation is exothermic is not a debate.

Oh, don't misunderstand . . I'm not saying I don't believe there is some difference in temp. I know that living organisms at work generate heat. I'm just surprised the difference is in the 4-6 degree range. I would have guessed a degree or two at most, and less than that at the home brewer level.

--- Quote from: majorvices on December 11, 2009, 10:47:06 PM ---Have you ever checked to see what temp your wort is during active fermentation?

--- End quote ---

Ya know, I think I'll do just that!  ;D

And big beers with more sugar, more yeast, and more oxygen can easily go over 10degF more than ambient.

In my experience, the fermometer always reads 5 or more degrees above ambient when the beer is at high krausen. That's why I only ferment in ambient temp when ambient is likely to remain at least 5 degrees below the highest temp I am willing to ferment at. I just had too many funky beers, ESPECIALLY when using "American" style yeasts, which especially benefit from low fermentation temps.


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