Why and how does yeast produce heat when fermenting?

[Finlandbrews]

What is the reason that yeast makes the wort warmer during fermentation and what parameters define the value of increase in heat produced?

Is the increase of temperature from a specific yeast strain always the same? If I pitch at same rate with exact same vitality and viability of let's say safale 05 in identical worts, will the temperature increase in value and in time be the same whether I pitched the yeast at 15 celsius or at 20 celsius?

For example, if the specific yeast produces +2 degrees celsius for 30 hours during the second and third day when I pitched at 20 degrees celsius will the same yeast in same wort results in the same changes If I pitch it at 15 degrees?

I'm just trying to understand how to predict production of heat from fermentation to better control them.

Thanks

 

[didinho]

For example, if the specific yeast produces +2 degrees celsius for 30 hours during the second and third day when I pitched at 20 degrees celsius will the same yeast in same wort results in the same changes If I pitch it at 15 degrees?

I don't think so. temperature raise depends on yeast activity: at 15 degrees yeast is less active, so less reactions that determine a smaller temperature increase.
same wort with same pitch rate at a temperature of 20 instead of 15 degrees, will have faster chemical (enzimatic) reactions by the yeast, so a bigger temperature raise.
I expect something more like +1 degree at 15C, +2 degrees at 18C, +3 degrees at 20C
it could be interesting to test different temperatures

 

[ScrewyBrewer]

What is the reason that yeast makes the wort warmer during fermentation and what parameters define the value of increase in heat produced?

Is the increase of temperature from a specific yeast strain always the same? If I pitch at same rate with exact same vitality and viability of let's say safale 05 in identical worts, will the temperature increase in value and in time be the same whether I pitched the yeast at 15 celsius or at 20 celsius?

For example, if the specific yeast produces +2 degrees celsius for 30 hours during the second and third day when I pitched at 20 degrees celsius will the same yeast in same wort results in the same changes If I pitch it at 15 degrees?

I'm just trying to understand how to predict production of heat from fermentation to better control them.

Thanks

It's complicated. There are so many different variables that have an affect on fermentation, temperature, pitch rate, vitality of the yeast, etc. That's why brewers implement automated temperature control, to eliminate those variables and to achieve consistency in fermentation under all conditions.

 

[55x11]

I don't think so. temperature raise depends on yeast activity: at 15 degrees yeast is less active, so less reactions that determine a smaller temperature increase.
same wort with same pitch rate at a temperature of 20 instead of 15 degrees, will have faster chemical (enzimatic) reactions by the yeast, so a bigger temperature raise.
I expect something more like +1 degree at 15C, +2 degrees at 18C, +3 degrees at 20C
it could be interesting to test different temperatures

Agreed! The heat generated by the yeast is metabolic (the same reason you get hot and sweaty when you exercise). So the higher the level of their activity the more heat will be generated. Yeast will be more active at higher temperatures (generally, at some point when temperature gets into 70ies, most yeast reach the saturation of their activity, but then begin to experience heat shock that can damage their cell membranes and their activity may slow down instead).

 

[ajdelange]

C6H12O6 --> 2CO2 + 2CH3CH2OH + 72 kJ/mol

That's a constant. Each mole of glucose fermented will produce 72 kJ of heat. What happens with respect to temperature depends on
1)How fast a mole of glucose ferments
2)The thermal mass of the wort in which the yeast are suspended
3)The thermal resistance between the wort and the ambient
4)The temperature of the ambient.

1)Depends on yeast health, temperature, availability of glucose, ethanol concentration etc.
2)Depends essentially on the volume of the wort
3)Depends on how well the fermenter is insulated and whether it is just sitting in air, surrounded by cooling jackets etc.

Up to a point the warmer the wort the faster fermentation takes place which means more rapid evolution of heat which, if the fermenter is well insulated, means further rise in temperature which means faster fermentation etc. This is called thermal runaway which might be a problem in a huge commercial fermenter but if you think about it 72 kJ isn't a lot of energy spread out over several days. A mole of glucose 180 grams so 20L of 12 °P wort would contain about 1.05*20*0.12/0.18 = 14 mol and produce. With an RDF of 60% about 8.4 mol would ferment producing 8.4*72 = 604.8 kJ = 604800 J. IF fermentation took a day that would mean 604800/(24*60*60) = 7 watts. if it took 2 days 3.5 W and so on. That just isn't a lot of heat.

 

[Finlandbrews]

All what you are saying makes sense! Thanks for all these feedbacks!

I sometimes hear about how good it is to have an "active" fermentation or that the fermentation is "fast" but to me these terms are opposite of a fermentation with "control". What kind of effect could it have to cool the temperature very slowly during the active phase of the fermentation such as you pitch at 20 celsius and then you manage to lower the fermentation temperature for 0.5-1 celsius for the 3-4 days where the fermentation is active? Could it result in a cleaner taste?

Also what kind of materials release heat from fermentation the best? Is glass, stainless or PET better?

Is the fan in the kegerator for releasing heat of fermentation btw? Or for co2 to escape?

 

[k.emery.nbn]

C6H12O6 --> 2CO2 + 2CH3CH2OH + 72 kJ/mol
Each mole of glucose fermented will produce 72 kJ of heat.

I don't suppose you know the enthalapy of fermenting sucrose sugar? I cant seem to find this information anywhere.

 

[max.673]

The yeast is a living thing, it moves. The movement generates friction which generates heat. Don't believe me? take a bowl fill it with fruit peels whatever as long as it rots fast, mash it up loosely. Feel how hot it gets after a few weeks. It resembles a humans body heat. The bacterial are alive and moving which causes the heat.


In addition there could also be a chemical process happening where heat is a by product

 

[Vale71]

I don't suppose you know the enthalapy of fermenting sucrose sugar? I cant seem to find this information anywhere.

It's exactly the same. All sugars enter the glycolysis pathway as fructose. Any glucose or complex sugar is first broken down (in the case of polysaccharides) to its components which are then isomerized to fructose if needed by means of specific enzymes. In the case of sucrose it gets hydrolized do 1/2 fructose which will enter the pathway as-is and 1/2 glucose which will be first isomerized to fructose.
BTW the 72 kJ/mol are correct from a purely chemical standpoint but yeast has a yield that is <1 so you'll get a bit less in reality. This is partly due to incomplete reactions as yeast can leak intermediate products and partly to not 100% of the saccharides actually being used to produce ethanol but rather enterering alternate metabolic pathways.

 

[Vale71]

The yeast is a living thing, it moves. The movement generates friction which generates heat. Don't believe me? take a bowl fill it with fruit peels whatever as long as it rots fast, mash it up loosely. Feel how hot it gets after a few weeks. It resembles a humans body heat. The bacterial are alive and moving which causes the heat.


In addition there could also be a chemical process happening where heat is a by product

Such as ethanol fermentation, just to name one?

BTW yeast are not motile so the notion that they generate heat as a result of autonomous movement is just nonsense.

 

[max.673]

When cells reproduce they divide. Those calls are no longer in the same location they can't be as they'd be overlapping therefor they have to have moved. They aren't anywhere near as mobile as say a sperm cell which has a tail but yes they do in fact move when they reproduce. The bubbles from the co2 creation also increase this by agitating the fluid. One gram of yeast contains ~20billion cells so you can imagine theirs a lot of the above going on which would cause heat. Not necessarily all the heat but some.

Don't quote me on this part as it could be wrong. The yeast generates co2 from the yeast cell which means the cell pushes something out of it and therefor an equal and opposite 'motion' must be applied to the cell which is again moment, whilst its not a rocket ship its something. I'm not 100% sure on how the co2 is created e.g does it come from the cell directly or something else which is why i put the disclaimer at the start.

Hope this helps.

 

[Vale71]

Hope this helps.

It certainly doesn't. A good practice when one has no idea about something is to listen and try and learn as much as possible, but of course this is the Internet so apparently anything goes...

 

[max.673]

It certainly doesn't. A good practice when one has no idea about something is to listen and try and learn as much as possible, but of course this is the Internet so apparently anything goes...

A good practice for trying to disprove someones hypothesis is to submit a counter argument rather than simply saying 'you're wrong' which has 0 merit and displays a strong lack of understanding in itself. I took the time to listen to what you said and explain the reasoning as to why i believe my opinion to be the case you have simply said 'No' clearly you don't understand the process well enough to disprove me.

I'm more than happy to be proven wrong if you can demonstrate a method that disproves mine I will accept this, if correct.

 

[Pkrd]

Welcome to HBT Max. You're speculating over a question in four year old thread that was quite succinctly answered in the first 5 posts and then bumped by a new poster for ??? reasons. RDWHAHB

 

[max.673]

Welcome to HBT Max. You're speculating over a question in four year old thread that was quite succinctly answered in the first 5 posts and then bumped by a new poster for ??? reasons. RDWHAHB

Ahh, i'm waiting for it to ferment still should be good when its ready tho. Anyway, I'm a new member to the forum so ya know every post is like a new one to me so I decided to add my 2 cents to the thread. Only reason why i'm here is to increase my understanding of topic same as everyone else i'm sure. I simply want to understand why Vale71 disagrees with my statement which then increases my understanding of the topic you see. Didn't mean to come across as stressed.

 

[Jtvann]

I scrolled through the thread looking for one word and didnt see it. Exothermic. Not trying to get all scientific, but that is the reason fermentation produces heat. When any molecule breaks apart, the bonds holding atoms together release energy, or heat. When molecules are formed they absorb energy, which would be an endothermic reaction ... and would feel cooler to the touch.

Fermentation is exothermic. It's not the happy dancing of yeast causing friction. Good enough an explanation for why max is wrong and vale is right?

 

[max.673]

I scrolled through the thread looking for one word and didnt see it. Exothermic. Not trying to get all scientific, but that is the reason fermentation produces heat. When any molecule breaks apart, the bonds holding atoms together release energy, or heat. When molecules are formed they absorb energy, which would be an endothermic reaction ... and would feel cooler to the touch.

Fermentation is exothermic. It's not the happy dancing of yeast causing friction. Good enough an explanation for why max is wrong and vale is right?

Thanks you for the answer it is accurate! I was saying that friction from the cells also plays a part in the heat generated, its most certainly not the entire process. I did say this in my first comment. Anyway I've taken the time to locate an academic journal to validate my theory feel free to read through at your leisure, if you can be bothered. Basically the Biological Engineering Department @ Dalhousie University agrees that it is a factor.


https://www.researchgate.net/public..._invessel_composting_of_tomato_plant_residues

In short it says the following.
"The profiles of the average temperatures inside (Tv ) and on the outside surface (Ts ) of the bioreactor are presented in Fig. 5. The average bioreactors temperatures (Tv ) of the sterilized compost increased with time due to heat generated by particle friction reaching the steady state (constant temperature) after 3 h, at which time the heat generated by mixing was equivalent to the heat losses from the bioreactor. Since the experiment was run without aeration and sterilized material was used, the heat"

I'll just throw in the dancing cell replication video filmed under a microscope in as well. Despite the cell itself being very stable until it divides you can see whats happening inside is far from static.

 

[Jtvann]

Thanks you for the answer it is accurate! I was saying that friction from the cells also plays a part in the heat generated, its most certainly not the entire process. I did say this in my first comment. Anyway I've taken the time to locate an academic journal to validate my theory feel free to read through at your leisure, if you can be bothered. Basically the Biological Engineering Department @ Dalhousie University agrees that it is a factor.


https://www.researchgate.net/public..._invessel_composting_of_tomato_plant_residues

In short it says the following.
"The profiles of the average temperatures inside (Tv ) and on the outside surface (Ts ) of the bioreactor are presented in Fig. 5. The average bioreactors temperatures (Tv ) of the sterilized compost increased with time due to heat generated by particle friction reaching the steady state (constant temperature) after 3 h, at which time the heat generated by mixing was equivalent to the heat losses from the bioreactor. Since the experiment was run without aeration and sterilized material was used, the heat"

I'll just throw in the dancing cell replication video filmed under a microscope in as well. Despite the cell itself being very stable until it divides you can see whats happening inside is far from static.

Anyway ... welcome to the forums. You'll get to learn the personalities if you stick around long enough. It pained me to to say that Vail was right.