3 Degree Temperature Fluctuations

So I bought a Johnson analog temperature controller and have used it my last couple batches. While my beer has improved, I have yet to find any sort of definitive answer to my question: What is produced by temperature fluctuations?

I know that fermenting in the higher ranges causes greater ester/fusel production, but I'm not sure what smaller (3*F) temperature fluctuation in the lower range of the yeast does. I have been fermenting my ales between 61 and 64. I'm starting to regret not purchasing the digital controller. I've heard some people claim that this controller is good enough, some claim 3*F is too wide of a swing. What do you think?

Also, I've heard there is a way to adjust the analog controller sensitivity. All I found was a screw within the controller that can slide along a rail, but doesn't connect to anything. Does anybody know how to adjust this?

Not much and whatever effects are minimal compared to ambient fermentations. I tend to think that having a little wider temperature range on a controller is better than having a tighter range. With a wider range (within limit), the compressor doesn't kick on and off all the time, extending its life.

IffyG said:

Not much. I tend to think that having a little wider temperature range on a controller is better than having a tighter range. With a wider range (within limit), the compressor doesn't kick on and off all the time, extending its life.

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+1 to this. Fluctuating between 61 and 64 shouldn't really cause anything in the way of noticeable effects to the beer. Not warm enough to create lots of ester or fusels, and not cold enough to start dropping stuff out of suspension.

That is what I was thinking.

My only concern was in the book Yeast (I do not claim to understand much of it yet) it mentions that 3*f is a significant temperature change for yeast, but does not mention what it does.

Krane said:

That is what I was thinking.

My only concern was in the book Yeast (I do not claim to understand much of it yet) it mentions that 3*f is a significant temperature change for yeast, but does not mention what it does.

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I think the yeast book, while a good read, is very much a "in perfectly ideal conditions" type of book rather than what happens in a persons house. Sure, we'd all love to have perfect climate control and dial things in the the nth degree. But in the real world for the homebrewer that, for the most part, isn't a reality.

As much as I respect Jamil for his contributions to the homebrewing community, I feel like he talks out of his ass sometimes and says stuff without either providing evidence or a thorough explanation of what he is saying. To be honest, I think his yeast book might be straying too close to professional brewing as he entered into his commercial endeavor. I know his work with Heretic has bled over into the Brewing Network to the point that I don't listen to as much stuff as I used to because I just don't want to learn about pro brewing on a homebrew podcast...

The only thing yeast know about temperature relates to metabolic pathways. Temperature and available nutrients determine which pathways(reactions) occur within the yeast cells. I doubt very much that 3F variation (if it's within the yeasts optimum range) have any significant impact on varying the pathways (and subsequently, flavors).

You could inquire at Wyeast or White and I'm sure they will give you a good answer.

helibrewer said:

You could inquire at Wyeast or White and I'm sure they will give you a good answer.

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Is there a link on the website? Never really considered this option before.

IffyG said:

As much as I respect Jamil for his contributions to the homebrewing community, I feel like he talks out of his ass sometimes and says stuff without either providing evidence or a thorough explanation of what he is saying. To be honest, I think his yeast book might be straying too close to professional brewing as he entered into his commercial endeavor. I know his work with Heretic has bled over into the Brewing Network to the point that I don't listen to as much stuff as I used to because I just don't want to learn about pro brewing on a homebrew podcast...

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I agree with this....I'd also be very surprised is they are able to control fermentation to within 3 degrees in a professional setting.

I have heard that A/B controls their fermentation temps within .1 degree....but they are trying to make the exact same product over and over.

Well provided the probe is 3 degrees AIR variation, I doubt it would affect your fermentation if at all. Maybe this swings the beer temps 1 degree? I see some people put the probe in the beer, or insulated contact with the fermenter. Then the beer will actually see that up and down temp variation.

I currently have a digital controller set to a 1 degree variation (in air). Honestly with good seals and good insulation for the small fridge, the compressor doesn't run all that much. But the comments above have me wondering if I should switch to a 2 degree differential.

Also agree with poster above that most pro's will have better temp control, not worse.

Is air the best measure though during the first few days? This is an issue of timing. I realize that it takes more energy to heat up liquid than air, which should make air the best measure...but since the beer is the source of heat, which reaches 64 first, beer or air?

Krane said:

Is air the best measure though during the first few days? This is an issue of timing. I realize that it takes more energy to heat up liquid than air, which should make air the best measure...but since the beer is the source of heat, which reaches 64 first, beer or air?

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Beer is the best temp to monitor and control.

i have mine set at 1° differential and my minifridge doesn't cycle very often (maybe once every 2-3 hours)

i'd set it as low as possible without causing frequent cycling

you def don't want your probe in the air - i have mine strapped to the side of the bucket with a gel ice pack and my measured wort temps are always within 1° of the temp controller readout

Plus, from what I've read, fast temperature changes are much more stressful to the yeast. I'd assume if yotou're fermenting in a fridge, the beer temp fluctuates less, and slower, than you think.

tgmartin000 said:

Plus, from what I've read, fast temperature changes are much more stressful to the yeast. I'd assume if yotou're fermenting in a fridge, the beer temp fluctuates less, and slower, than you think.

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That is one of the reason why I really like to ferment in a water bath with an aquarium heater. There is no way that I could get a "fast" temperature rise or fall.

Phunhog said:

That is one of the reason why I really like to ferment in a water bath with an aquarium heater. There is no way that I could get a "fast" temperature rise or fall.

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While I have heard of this, it gives me an idea: what about putting a tub of water in the fridge prior to fermentation (a few days) so it is at my ideal fermentation temperature, then placing the carboy in that. My thinking is that the beer would need to produce more heat to actually raise the temperature this way. I could even put a little bit of ice in if I notice the temperature is rising to help cool the water back to the original temperature which would essentially start the same process again. Sounds interesting...

Krane said:

While I have heard of this, it gives me an idea: what about putting a tub of water in the fridge prior to fermentation (a few days) so it is at my ideal fermentation temperature, then placing the carboy in that. My thinking is that the beer would need to produce more heat to actually raise the temperature this way. I could even put a little bit of ice in if I notice the temperature is rising to help cool the water back to the original temperature which would essentially start the same process again. Sounds interesting...

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Theoretically this is correct, but I think most people find (myself included) find that ferm temps are kept in check just fine without a tub of water.