Why does fermentation heat up?

[hotbeer]

Is it a certain point in the cycle of the yeast that they create a lot of heat? And is it population dependent?

I've been fairly use to yeast heating up the fermenter temperatures right about the time of the kraeusen, then temps dropping back down to roughly ambient air temps for the remainder of the time in the FV.

However this current batch never got hot at all. Pretty much mirrors the air temp swing in the house from 68°F to 71°F. I'm measuring SG and Temp with a Rapt Pill.

In 48 hours from pitch it's down to 1.022 from 1.058. I did over pitch this batch more so than I've done before. Just barely 2.5 US gallons and I used a full 11 gram packet of US-05.

So I'm sort of just curious about the whys.

 

[brewSJ]

It's just chemistry: converting sugar to alcohol gives off heat, and that causes the temperature to rise. The faster the yeast eat, the faster heat is produced.

In the fermenter, the liquid temperature is a balancing act. On the one hand, heat is released through the walls to the outside. On the other hand, yeast are producing more heat as they eat. If the yeast are producing heat faster, your liquid temperature will rise. If the fermenter is getting rid of it faster, your temperature will eventually fall back to room temperature.

 

[bracconiere]

It's just chemistry: converting sugar to alcohol gives off heat, and that causes the temperature to rise.

hmmm, i would have thought it was friction, and like rubbing your hands together when they're cold....

 

[day_trippr]

Related thread here: Why and how does yeast produce heat when fermenting?

Cheers!

 

[govner1]

Does anyone read Palmer or any other basic brewing books anymore???

 

[wepeeler]

Fermentation is an exothermic reaction ie it produces heat. The more vigorous the fermentation, the more heat given off.

 

[mattd2]

The more vigorous the fermentation, the more heat given off.

And the warmer it is the more vigorous the fermentation... which can sometimes lead to big temperature increases and big messes!

 

[BrewnWKopperKat]

Does anyone read Palmer or any other basic brewing books anymore???

I thought ChatGPT was doing the reading (and thinking and filtering) for us.

 

[mac_1103]

Fermentation is an exothermic reaction ie it produces heat. The more vigorous the fermentation, the more heat given off.

The more heat given off per unit time. For a given OG and FG, the amount of heat released is fixed. Just like the amount of CO2 and EtOH. What determines the temperature increase in the FV is how quickly the heat is released and dissipated. (Hmm, maybe I should put aluminum fins on my buckets.)

 

[VikeMan]

Does anyone read Palmer or any other basic brewing books anymore???

Here's what Palmer had to say about the heat arising from fermentation in the online edition of How To Brew:

"Furthermore, primary fermentation is an exothermic process. The internal temperature of the fermentor can be as much as 10F above ambient conditions, just due to yeast activity."

IOW, not much. @hotbeer's question, and the answers, particularly the older thread @day_tripper linked, were more in depth. Does Palmer go into more detail in the newer editions? I'd wager that none of the basic brewing books go to the level of detail of AJ Delange's posts.

I'm all for the "go read How to Brew" advice when warranted, but I'm pretty sure @hotbeer is beyond that stage.

 

[hotbeer]

IOW, not much. @hotbeer's question, and the answers, particularly the older thread @day_tripper linked, were more in depth. Does Palmer go into more detail in the newer editions? I'd wager that none of the basic brewing books go to the level of detail of AJ Delange's posts.

You hit that on the nail. Palmer doesn't get into the nitty gritty. And he shouldn't. His book is about how to brew, not an in depth lecture on why what happens when you brew. I'm looking for something in between the basic answer and the in depth science that will be over my head..

I thought the rate of SG falling might be something to do with it. However this current batch that shows no signs of heating up is fermenting at a slightly faster rate than the previous two beers.

This batch has fallen 30 points in 24 hours since it began falling. The previous brew fell only 28 points in 24 hours.

I am starting to wonder more if this is just more circumstance related to the heating and cooling in the small room where the FV is kept. I noticed that the register on the ceiling was open this time and previously I think it was closed. So maybe it was getting some air circulated around it to carry off the heat faster.

These last two brews were porters. Current brew in the FV started with an OG of 1.058 and the previous 1.052. The first porter didn't have near the heat increase that I have seen with other pale ales. It only climbed about 2 maybe 3 degrees over what the house temp would have been while my previous ales were usually 4 to 6 degrees higher than ambient during the initial and faster drop in SG.

 

[BrewnWKopperKat]

@hotbeer : what strains of yeast are you using with each batch?

For me, I find that US-05 ferments slower (less generated heat per unit of time); other strains ferment faster (more generated heat per unit of time).

 

[mac_1103]

I noticed that the register on the ceiling was open this time and previously I think it was closed. So maybe it was getting some air circulated around it to carry off the heat faster.

I think that would definitely make a difference. As would seasonal variation. Even if you keep your house at the same temperature all the time, the temperature and volume of the air your HVAC is moving to maintain that set point is going to change depending on the weather.

 

[hotbeer]

what strains of yeast are you using with each batch?

US-05 for the current in the FV. The previous was S-33. Though I might have mistakenly used S-04 in the previous and just wrote it down wrong.

 

[BrewnWKopperKat]

US-05 for the current in the FV. The previous was S-33. Though I might have mistakenly used S-04 in the previous and just wrote it down wrong.

Fermentis Tips & Tricks, p 28 has charts that show apparent attenuation over time. (FWIW, I see similar profiles with US-05 (frequent use) and S-33 (small number of uses)).

 

[hotbeer]

Fermentis Tips & Tricks, p 28 has charts that show apparent attenuation over time. (FWIW, I see similar profiles with US-05 (frequent use) and S-33 (small number of uses)).

When I look at their chart for the lower SG profile, the plot for S-33 and US-05 does sort of match these last few brews that I have that data for. Even the lag in starting with the US-05.

Makes me sort of wish next year will come quick so I'd have more data to compare. <grin> <not!>

 

[CascadesBrewer]

"Furthermore, primary fermentation is an exothermic process. The internal temperature of the fermentor can be as much as 10F above ambient conditions, just due to yeast activity."

I recently had a 2.5 gallon batch of a Dubbel that pushed itself up to 78F in a 68F ambient area. I was a little surprised given the smaller batch size. This was in my 3.5 gallon brew bucket with a thermowell.

I used to ferment in my "cool" lower level, mostly using the temperature strip stuck on the side of a glass carboy as a gauge. After I moved to temperature controlled ferments and away from using glass carboys, I am realizing how inaccurate my prior methods of judging beer temps were.

 

[bwible]

hmmm, i would have thought it was friction, and like rubbing your hands together when they're cold....

I thought it was the yeast doing work or working out. I know I heat up when I’m running around or working out

 

[hotbeer]

I guess the answer for the question I ask was more geared to curiosity if the heat was created by say friction or chemical or biological reactions/processes that are going on at that particular time of the ferment.

However I'm thinking now that it's that register on the ceiling being open for this ferment along with the fact that of the two porters I've done, they don't seem to heat up as much as the pale ales I've done. And many of those ales were done with US-05.

 

[mac_1103]

The biochemical conversion of glucose to ethanol and carbon dioxide is exothermic. That's why yeast can chew up the sugar for energy. Unfortunately (for the yeast, anyway) they can't convert all of the energy in the glucose to a usable form (ie, ATP). The remaining energy is released as heat. The temperature increase in your FV depends on how fast heat is generated and how fast it's dissipated. Different worts can ferment faster or slower with the same yeast, meaning more heat release per unit time. Moving more or less air around your FV will change the rate at which the heat is removed.

 

[bracconiere]

I thought it was the yeast doing work or working out. I know I heat up when I’m running around or working out

blood flow causes friction! that's what i said

 

[hotbeer]

The biochemical conversion of glucose to ethanol and carbon dioxide is exothermic. That's why yeast can chew up the sugar for energy. Unfortunately (for the yeast, anyway) they can't convert all of the energy in the glucose to a usable form (ie, ATP).

Okay, I can somewhat work with that to satisfy my curiosity. ATP sort of got me more into the process of what you are talking about. But I'm at the extreme edges of my education about such, so I probably can't discuss it correctly.

So things are going on similar to the synthesis of glycogen in the krebs cycle part of this chart at the bottom?

(The chart I had from some other stuff I was dealing with and it's not really geared for our discussion of yeast. Just something similar... I think.)

I notice that is an aerobic phase too where I assume the yeast are also using up any of the O2 in the wort.

I wonder if the fact I use dry yeast and don't aerate has a bearing on the temp it reaches too, since there'd be less O2 in the wort for the yeast to use. Though I understand for the first pitch of dry yeast, aeration of the wort is unnecessary.

 

[VikeMan]

I notice that is an aerobic phase too where I assume the yeast are also using up any of the O2 in the wort.

My old eyes can't really read that chart, but in beer wort, yeast does little or no aerobic respiration (production of water and CO2, and no ethanol) because of the Crabtree effect, which drives it to fermentation (even in the presence of O2) instead.

The yeast does assimilate O2 and uses it to make sterols, which are used to build up cell walls, allowing budding to happen. But that's different from respiration.

 

[hotbeer]

My old eyes can't really read that chart, but in beer wort, yeast does little or no aerobic respiration (production of water and CO2, and no ethanol) because of the Crabtree effect, which drives it to fermentation (even in the presence of O2) instead.

The yeast does assimilate O2 and uses it to make sterols, which are used to build up cell walls, allowing budding to happen. But that's different from respiration.

So it'd be totally wrong to make any assertion the amount of O2 in the wort might have an impact on the temps it reaches?

I really need to get motivated to looking at the cycles yeast go through during fermentation. But this is a good start to move me to do so!

 

[VikeMan]

So it'd be totally wrong to make any assertion the amount of O2 in the wort might have an impact on the temps it reaches?

I don't know that it would be totally wrong. When yeast cells bud (making more yeast cells), there are then more cells available to do fermentation, so fermentation can go faster, increasing the temperature more (for a while) than if there had been less cells. I think that's logical, but it's not based on any fermentation temperature data that I know of.

 

[mac_1103]

The yeast does assimilate O2 and uses it to make sterols, which are used to build up cell walls, allowing budding to happen.

Which is why oxygenating the wort is optional with an adequate pitch of dry yeast. The yeast were grown aerobically to build up their sterol reserves before being dried. They can reproduce enough to ferment your wort without needing much oxygen.

 

[mac_1103]

So things are going on similar to the synthesis of glycogen in the krebs cycle part of this chart at the bottom?

Glycolysis is the only part of that chart that's really relevant here. Pyruvate is converted to lactic acid in muscle cells when you go anaerobic. In yeast, it's converted to ethanol and CO2 instead. The Krebs cycle requires the electron transport chain to function, which requires oxygen.

 

[CascadesBrewer]

Which is why oxygenating the wort is optional with an adequate pitch of dry yeast. The yeast were grown aerobically to build up their sterol reserves before being dried. They can reproduce enough to ferment your wort without needing much oxygen.

Based on my limited understanding of propagating yeast, I am not sure this is correct. I think it is common for liquid yeast companies to grow their yeast in a constantly fed and aerated medium where the amount of sugar present is kept below the crabtree threshold. This encourages yeast growth. At least this is how it is done at a local yeast lab.

It is my understanding that dry yeast are intentionally stressed and then fermentation is interrupted. As I recall, a reserve of trehalose is important for dry yeast survival and yeasts that cannot be forced to produce trehalose are often not good candidates for drying. Where I believe liquid yeast finish fermentation and don't have as complete of cell wall structure as dry yeast.

Somebody with first hand knowledge of this area is free to correct me.

 

[mac_1103]

Based on my limited understanding of propagating yeast, I am not sure this is correct.

It is my understanding that dry yeast are intentionally stress

I believe that both are true. The yeast are grown under optimal conditions to build up sterol reserves and then stressed to induce trehalose expression to protect them during the drying process. Of course, I'm just taking Fermentis' word for this.