Yeast generates its own heat

[nachov]

Hi everybody,


I've read that yeast generates its own heat during fermentation. And therefore, the temperature inside the fermenter can reach 7F degree higher than ambient temperature.

I've found a nice spot in my flat where I can brew at 65F degree.

The optimal temperature range of the yeast I'm using is 59-68F degree.

My concern is that the heat generated by yeast will increase my fermentation temperature to 72F.

Should I find a colder spot (around 60F), so that would make up for the heat generated by yeast? Or Am I just overthinking too much¿


Thank you for your hints.


Cheers.

 

[jeffjm]

You are correct...fermentation releases heat. Depending on the gravity of your beer, it may be much more than 7F.

So yes, finding a cooler spot is a good idea. Or, if you can place your fermentor in a tub of water, that water will absorb some of the heat and keep your temps more stable. You can freeze water in 2-liter soda bottles and put them in the tub for additional cooling. Or, put your fermentor in a tub of water and then wrap a towel around it. The towel will wick up water which will then evaporate, cooling the fermentor.

This last idea works best in dry climates.

 

[trogdor447]

I tell ya my first batch spiked 6 degrees overnight had me nervous i wrapped some cold towels around it and turned the fan on for a little it helped bring the temp down. I'll just start cranking the a/c up downstairs for the first few days of the ferment

 

[woozy]

That's *exactly* the type of thing you should be thinking about and that's exactly the type of conclusion you should reach.

The actually conclusion will vary on a case by case basis but nearly always cooler temps are a good idea.

freezing water bottles in a tub works miracles.

You *might* be able to get away with 72-75 degree fermenting depending on the type of beer and yeast but this is a risk and it's knowingly glossing over a known concern. Bad temp control is the number one cause of off-flavors and off-flavors are the number one disappointing non-successes. That's not to say you beer won't be good. But it's likely they will have a bit of an alcohol strident taste, probably very mild and ignorable but probably noticeable (especially when you look for it). My first beers which brewed in the high seventies were, I thought at the time, pretty darned good but "hmm, what's that rubbing alcohol taste every fourth sip or so?". I started tubbing in water with frozen bottles and got the ferementation to the low 70s and it made a world of difference. They'd probably be even better if I got them lower.

 

[nachov]

Thanks pals for all your comments.

I've found that interesting article: http://homebrew.stackexchange.com/q...-in-the-primary-due-to-fermentation/5564#5564

It shows a chart of the expected rise of temperature.

The actually conclusion will vary on a case by case basis but nearly always cooler temps are a good idea.

Indeed, I've read that there are many factors involved in the heat generation by yeast:
- volume of beer fermented
- type of yeast: how vigorous is the fermentation
...

I think I'll try the water tub with ice packs method.
That's the only feasible option in the place where I live.

And I monitor the temperature inside the fermenter with temperature strips.

That's good experiment and good fun anyway

 

[pjj2ba]

The room you ferment in can make a big difference in how much it warms up. If you ferment is a small room with no/poor air movement, the fermenter can heat up quite a bit. If you ferment in a open room with good air movement, it may only heat up a few degrees.

Placing it in a tub of water is a good idea as the heat generated is transferred/removed to water faster than it is to air and then there is bonus cooling via evaporation

 

[Wynne-R]

The link’s analysis is a little scary. I haven’t taken time to review the math, but a couple things jump out.

The first is that 21L is more like 5 ½ gallons. Not a biggie, but not a good way to start.

The other thing is that they left time out of the equation. The total energy is what would happen if the fermentation went off like a bomb, i.e. zero time. This is the heat you will be adding on days 2,3, and 4.

If you have control of your fermentation, it will happen in a few days, more or less depending on style, gravity, yada yada. If you go too slowly, you might not get the character of the yeast for the style, too ‘clean’. If you go too fast, lots of bad things can happen, fusels, phenols and so on.

What I’m getting at is that the heat of fermentation makes it tricky, it is not linear. The hotter it gets, the hotter it gets. There is a runaway point that the fermentation will run to completion before you can cool it. If you’re in water you can pull it back with ice before all the damage is done. If you’re in air, it takes FOREVER. Prevention is the key. Stay on top of it.

Make sure the wort is cool before you pitch. As the fermentation slows, you can let the temperature drift up. Yeast love to be warmed, they hate to be chilled.

 

[qmax]

This link above does not account for heat lost to the environment through the walls of the fermenter as well as heat carried out with CO2.
With these factors left out, it's impossible to accurately predict the temperature rise in the wort.

Now if you want to know the heating load to design a cooling system, that can be easier.

My sources:
Fermentation heat = 118 kJ mol−1 of glucose
http://en.citizendium.org/wiki/Fermentation_(biochemistry)

Peak yeast performance = 50-75 g glucose/L/day = 0.28-0.42 mol/L/day
https://books.google.ru/books?id=0a...nepage&q=yeast peak fermentation rate&f=false

Peak heating load = 118*0.42/24/60/60*1000 = 0.57 Watts/L
Total Energy = 6.55 kJ/°P/(kg of wort) = 0.00182 kW*h/°P/kg

[10 g of glucose in 990 g of water = 1°P
10/(180g/mol) = 0.0555 mol/°P/kg
0.0555*118 = 6.55 kJ/°P/kg]

I do not know for what conditions the peak yeast performance was given. I assume it really reflects the highest peak load possible.
If you let CO2 escape from your fermentation chamber before it cools, it may carry away some heat and reduce the cooling load.

 

[airbrett]

Because the temperature difference isn't super dramatic, maybe you will have luck with the method I just used (it's only my second brew so take this with a grain of salt). Rather than a full water path with a towel wicking water from the bottom, I just wrapped a wet bath towel around the fermenter. I also put a fan on low pointed at it.

The towel alone seemed to drop temps around 3-4 degrees and the combo with the fan closer to 5-6 degrees. I kept the towel wet each day, changing it every other day for the first 5 days or so when fermentation was active. After that, I removed the fan and towel. Of course you want a container like pictured to keep your floor getting wet. This is a Steralite storage container that Target sells for about $20. It's also great for storage and for conditioning bottles without worrying about floor damage if there are bottle bombs.

The other methods are probably better, but in my case this was the only place in the apartment to do this and access is difficult because its in an under-stairs cubby hole. I would not want to be dealing with a container filled with water so this was my quick and dirty solution.