Author Topic: Fermentation Temperature versus Ambient Temperature  (Read 5772 times)

Offline dhacker

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Fermentation Temperature versus Ambient Temperature
« on: December 11, 2009, 02:57:21 PM »
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.   
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Offline majorvices

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #1 on: December 11, 2009, 03:47:06 PM »
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.
« Last Edit: December 11, 2009, 03:55:55 PM by majorvices »
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Offline dhacker

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #2 on: December 11, 2009, 04:21:18 PM »
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.
Have you ever checked to see what temp your wort is during active fermentation?

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

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #3 on: December 11, 2009, 04:40:05 PM »
And big beers with more sugar, more yeast, and more oxygen can easily go over 10degF more than ambient.
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Offline skyler

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #4 on: December 11, 2009, 05:15:39 PM »
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.

Offline dhacker

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #5 on: December 11, 2009, 05:57:42 PM »
If indeed there is that much variation between active wort temp and ambient temp, then I just can't believe more isn't written about this in "How To" books. Or maybe I've just had my head up my . . . um . . in the sand all these years. It should be expressly stated that the fermenter should be placed in an area 4 - 6 degrees lower than the desired ferment temp. And when folks talk about how to construct fermenting chambers and coolers, they should specify that you REALLY need a thermowell to put the temperature probe into the middle of the wort. I know some folks have mentioned this casually in passing, almost as an afterthought, but this seems to be imperative and an essential element for SOP if you have any hope of controlling and maintaining desired temps throughout the course of fermentation..  :-\
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Offline babalu87

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #6 on: December 11, 2009, 06:40:17 PM »
If indeed there is that much variation between active wort temp and ambient temp, then I just can't believe more isn't written about this in "How To" books.................................................. Or maybe I've just had my head up my . . . um . . in the sand all these years.

How to books dont tell you EVERYTHING

The second sentence I might agree with and will if you continue to be ignorant to the fact that yeast, consuming sugars will generate heat.
Think of it on a GRAND scale
Yeast is the spark plug and the wort is the fuel/air mixture in a gasoline engine................... does that generate heat?

Some British ale yeasts, if left unchecked will reach temperatures of at least 6 degrees over ambient.

How to books tell you what temperature to ferment at, not how to get there.

I cant believe that someone with so much thought into this very subject hasnt at least done his homework????????????????????????????????

Jeff

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Offline dhacker

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #7 on: December 11, 2009, 06:57:21 PM »
How to books dont tell you EVERYTHING . . How to books tell you what temperature to ferment at, not how to get there.

And you think a noob has a chance of figuring it out on his own?? Something this important should at least be mentioned.  :)

I cant believe that someone with so much thought into this very subject hasnt at least done his homework????????????????????????????????

I know, I know . . Ben Franklin would be highly irritated.   ;)


*EDIT*

Well . . I picked up Palmer's book and I'll be darned if he doesn't talk about exothermic temps of active yeast. He mentioned the +10 over ambient. As many times as I've read that darn book, I can't believe I never saw it. I do feel silly and have decided I must stop drinking so much while reading!  :-[

And I WILL be getting a thermowell . . from this day forward, no fermenter shall enter the chamber without a probe in its bowels...
« Last Edit: December 11, 2009, 07:09:50 PM by dhacker »
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Offline babalu87

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #8 on: December 11, 2009, 07:37:46 PM »
How to books dont tell you EVERYTHING . . How to books tell you what temperature to ferment at, not how to get there.

And you think a noob has a chance of figuring it out on his own?? Something this important should at least be mentioned.  :)

I cant believe that someone with so much thought into this very subject hasnt at least done his homework????????????????????????????????

I know, I know . . Ben Franklin would be highly irritated.   ;)


*EDIT*

Well . . I picked up Palmer's book and I'll be darned if he doesn't talk about exothermic temps of active yeast. He mentioned the +10 over ambient. As many times as I've read that darn book, I can't believe I never saw it. I do feel silly and have decided I must stop drinking so much while reading!  :-[

And I WILL be getting a thermowell . . from this day forward, no fermenter shall enter the chamber without a probe in its bowels...

This is my boomstick

 
Jeff

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Offline pdbreen

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #9 on: December 11, 2009, 09:05:46 PM »
... enter the chamber without a probe in its bowels...
This is my boomstick

What forum is this again?
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Offline dhacker

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #10 on: December 12, 2009, 05:48:04 AM »
A couple of things still lurking in the gray cells that bother me.... Yes, Palmer addresses the exothermic action of fermenting beer, and says it can run as high as +10. Then in the same chapter he says pick a spot with an ambient temperature of 65-72 degrees to place your fermenter, which is exactly what I suspect the majority of folks do. To me that suggests a fermentation temp that could (theoretically) run from 75 to 82 degrees. Not too many beers will turn out as desired with those temps.

Second, I've now convinced myself that placing a thermowell w/ controller probe in the fermenting beer is not such a good idea. Most controllers run with a 3 or 4 degree temperature offset, so the beer temp would be swinging up up and down. Plus, the lag time for the temp to reach the probe may cause the outer areas of the fermenter to be too cold before the controller shuts off. And trying to tighten the temp offset just makes the compressor work harder. I guess I'll just have to manually monitor the internal carboy temp and adjust the ferment chamber temp accordingly.

I'm glad we had this discussion!   :D
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Offline majorvices

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #11 on: December 12, 2009, 06:06:17 AM »
I use a Thermowell now and I have it set at a 1 degree differential - probably not thee best for my compressor. But honestly it doesn't seem to come on any more than before.

But for years I just set the ambient temp at about 4-6 degrees below my intended fermentation temp and watched the little stick on "Fermometer" and simply adjusted the temp that way. I never saw a variation on the temp strip due to the 6 degree differential of my old analog Johnson controller. It was an easy way to accurately control fermentation temps and it is a method I would feel comfortable recommending to anyone.

BTW I was pretty sure there wouldn't be too much debate on the subject. LOL!  :D ;)
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Offline majorvices

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #12 on: December 12, 2009, 06:27:34 AM »
BTW, I think you will also find that different peoples fermentation techniques will either exacerbate or reduce the exothermic action. The amount of yeast you pitch, how healthy that pitch is and how warm you pitch all make a difference. I have noticed when I pitch warmer the fermentation seems to go closer to the 6-8 degree mark. When I pitch cooler sometimes it only goes 2-4 degrees warmer. My lagers don't seem to be much more than 4 degrees over, ever. I pitch them at ~44 usually.

However, seeing how important fermentation control is it also surprised me how lacking the available literature is on the subject as well. Doesn't make sense to me that fermentation is easily the most important part of the brewing process - regardless how well you get you water chemistry, how well designed your recipe is, if your fermentation techniques are flawed your beer probably will be too. And yet, Palmer goes on and on and on about water Chemistry yet suggests to put your ale in an ambient room of 72 degrees.
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Offline dhacker

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #13 on: December 12, 2009, 07:24:51 AM »
However, seeing how important fermentation control is it also surprised me how lacking the available literature is on the subject as well. Doesn't make sense to me that fermentation is easily the most important part of the brewing process - regardless how well you get you water chemistry, how well designed your recipe is, if your fermentation techniques are flawed your beer probably will be too. And yet, Palmer goes on and on and on about water Chemistry yet suggests to put your ale in an ambient room of 72 degrees.

Thanks for confirming I'm not totally off my rocker! !    ;D
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Offline tom

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Re: Fermentation Temperature versus Ambient Temperature
« Reply #14 on: December 12, 2009, 08:56:50 AM »
Second, I've now convinced myself that placing a thermowell w/ controller probe in the fermenting beer is not such a good idea. Most controllers run with a 3 or 4 degree temperature offset, so the beer temp would be swinging up up and down. Plus, the lag time for the temp to reach the probe may cause the outer areas of the fermenter to be too cold before the controller shuts off. And trying to tighten the temp offset just makes the compressor work harder. I guess I'll just have to manually monitor the internal carboy temp and adjust the ferment chamber temp accordingly.

I'm glad we had this discussion!   :D
The stick on Fermometers are very accurate. Then you can be the controller. Which will work just fine with frequent checks. The first few days of fermentation are the more important time period. At first you'll need to adjust the temperature down to control the rising fermentation temeperature. As it settles down you'll need to increase the fridge temperature to prevent it from chilling too low. After that it is pretty stable. Unfortunately every beer will be different. Lagers change slowly, ales more quickly, and keep a very close eye on big beers.

As for a thermowell, it will have the least lag time of any type of measurement. I am not aware that the fermenting wort has different temperatures in different areas. I think the fact that fermentation is happening everywhere and the circulation of the wort will keep it pretty uniform. I will compare my thermowell and Fermometer next time.

Yes, some controllers have a 3-4 deg differential and they are best for just hanging in the air and controlling the fridge temperature. You don't want the beer to be changing 3-4 degrees.

Some digital controllers do have adjustable differentials. I set mine to 1degF and set the probe into a thermowell. Works well. I don't have to check it every few hours.

RDWHAHB
« Last Edit: December 12, 2009, 09:09:51 AM by tom »
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