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Old 11-15-2012, 05:49 PM   #1
mgortel
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Been brewing for several years now....started All Grain last year.....and until now I haven't really thought much about this but.....here is my question:

When a recipe calls for a fermentation temperature.....or brewers talk about fermenting at a certain temperature......I have always done the following.

Lets suppose the recipe says to ferment at 68F....

To me that means cool my wort down to 68F....pitch my yeast....and stick my ale pail/carboy in a my fermenter with a setpoint temperature (ambient in fermenter) of 68F.

But....with the yeast activity the wort temp could be 3-4 degrees (even more) above ambient.....so if my starting wort temp = 68F....it will reach 71-72F maybe......so with this in mind should the ambent temp be 3-4 degrees below the fermentation temp recommended in the recipe, etc.....i.e. in this case set fermenter temp to 65F.

THis may not matter in most cases....but for some beers like a Hefeweizen where the fermentation temp can really effect the flavors (i.e. more banana or more clove...etc) this could be a big deal.

Any thoughts on this?


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Old 11-15-2012, 06:03 PM   #2
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Im in the same boat, been brewing for 2 years and just started to monitor ferm temps more closely. Just finished 2 seperate ferm rooms so we can have multiple beers fermenting, crashing, or aging at the same time. We used a previously installed exhaust fan in reverse to pull cool air in from a crawl space and a space heater to raise temps. Have a Nut Brown fermenting now we just ramped up from 65 to 68 degrees to get the yeast to clean up a bit before we keg/bottle. These rooms are both in the basement and insolated so it has been easy to keep temps steady. We made add an A/C unit to one for cold crashing in the warmer months.


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Old 11-15-2012, 06:04 PM   #3
ktraver97ss
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Im hoping this will result in more consistant quality beer.
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Old 11-15-2012, 06:09 PM   #4
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"Fermentation temperature" is always the temperature of the fermenting beer, not ambient temperatures. I've seen a very active fermentation be more than 10 degrees warmer than ambient temperatures, although 5 degrees is more common.

When a yeast strain lists "optimum fermentation" temperatures, that is always the fermentation temperature and not the room temperature. I normally go at the low end of the optimum range listed by the yeast manufacturer, so if the fermentation temperature range is 60-68, I almost always ferment at 60-62.
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Old 11-15-2012, 06:20 PM   #5
bobbrews
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I almost always ferment my American Ales in a 58-64 F room as well. The actual wort/beer temp. is most likely a few degrees higher during the first 5 days.

Something to think about is if your floors are made of concrete and the ground is actually a good deal colder than the air temp. This can skew fermometer temp readings a bit.

 
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Old 11-15-2012, 06:24 PM   #6

You are on the right track with your thinking. A couple of things I would note:

(1) I wouldn't pay too much attention to the "recipe" temperature; instead focus on the yeast strain being used and the flavour profile you are seeking. Your system/process will evolve to that point if you aren't there already.

(2) Yes, fermentation temperature will be higher than ambient. You have three choices: (a) ignore that fact [this is what lots of people do] (b) ballpark it by going a few degrees cooler on ambient than you want to ferment at (c) check your actual fermentation temperature with a probe or thermometer vs. ambient then adjust future batches accordingly.
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Old 11-15-2012, 06:47 PM   #7
mgortel
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I am definately going to monitor my chamber temperature versus the actual beer temperature on future brews.....to get a catalog of data on this for future adjustments....great idea.

Oh yeah....and what about pitching temperature? If I want to ferment at 68F....should I pitch at 65F if I expect temp to rise 3 degrees?? It seems obvious to me that the answer is yes.

Obviously once the initial fermentation is cvomplete....the temp of beer will drop to ambient......when the mild clean-up / fermentation is happening....so at this point is it necessary to increase chamber temp....??

So for example....lets say I want to ferment beer at 68F.....I set my chamber to 65F and lets assume during the first 3-4 days the beer temp is at 68 as planned (3 degrees higher due to yeast activity).......then when the yeast acivity decreases the temp of the beer will start to drop to ambient (i.e. 65F in this case)....at this point would I need to bring temp up in the chamber up to the 68F....or is it fine to let it go at lower temp since 90% or so of fermentation is done anyway....

I realize either way will be ok....but....is there a benefit to keeping the beer temp stable througout the primary.??
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Old 11-15-2012, 06:58 PM   #8
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Fermentation temperature is, to me, the single most important factor in making good beer. The listed temperature is going to always be the temp of your beer, and Yooper's right- fermentations can EASILY reach 10F warmer than ambient when active- that's bad news for your beer. You need to control fermentation temperatures in a way that you can keep them in the optimal range for the yeast you're using, and avoid changes in temp more than a degree or two.
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Old 11-15-2012, 08:27 PM   #9
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Does everyone feel comfortable that a carboy 'stick on' thermometer is within 1 or 2 degrees of the worts fermentation temp? How about the temperature reading from a digital controller? I rely on both of these devices to monitor fermentation temperature and not the ambient.

 
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Old 11-15-2012, 08:40 PM   #10
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There was much discussion about the accuracy of the fermometer. Some say it's fairly accurate to within a couple degrees, others do not agree. I assume it has a lot to do with how cold your floor is, if the carboy is surrounded by water, or if a cold draft is blowing directly on the carboy.

When I am not using a chest cooler, I just sit my carboy on a wooden floor away from the window. I'm not worried when it registers 58-62 F on the side of my plastic Better Bottles. I took a sample in the past directly from the carboy and the temp. on my very accurate wire digital thermometer read 65-66 F whereas the fermometer was showing the 58-62 F range.



 
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