Fermentation Temp Increase

[mn_brew]

I was interested in brewing a saison, but the temps in the northeast are not yet favorable for saison for those of us fermenting at ambient temps. So, I thought I'd experiment with what I had available to me. I brewed a 10 gallon batch of saison based on Stone's posted saison du BUFF recipe.

For those interested in specifics, I did an overnight mash to try and shorten my brew day, 75 min boil, 4L of WY3726 yeast starter (estimating a cell count of 230B - old yeast).

I fermented at a starting temperature of 75*. Here's the thing, I wanted to capture and monitor the temperature rise created by the metabolic activity of the yeast. I was not sure how much the increase would be, but figured saison was the perfect beer with which to experiment.

In order to contain the fermentation temperature increase, I fermented in a 50L Dewar flask. A dewar is intended for liquid nitrogen, is super insulated and made perfect sense for what I was trying to accomplish.

I pitched the yeast on Sunday at noon.

Sunday Noon Pitch: 75*
Sunday 8pm: 75*
Monday 6am: 81*
Monday 6pm: 88*
Tuesday 6am: 91*
Tuesday 5pm: 92*

I doubt that I will see much more increase in the temp at this point - but I find it fascinating that there was a 17* increase in temp. Perhaps I need to reconsider fermenting at ambient temps from now on.

A pic of the dewar is attached.








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[sketerbuck]

The increase is not surprising if the fermenter is insulated.

 

[BackAlley]

That's a wicked fast rise. Should be interesting to see how it tastes.


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[acidrain]

I'm not familiar with 3726.

 

[user 141939]

Neat. I'd be more interested in the temp increase in a regular fermentation vessel though since this would have more of a practical application for me.

I am currently fermenting a porter in a large water bath at 58 - 60 degrees. The temp on my stick on thermometer at the top of my carboy has read 60 for the first three days. I'm wondering if the stick on is not a good indicator or if the water bath is just doing a really good job at keeping the temp down.


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[jnacey]

I'm not familiar with 3726.

Allegedly it is Brasserie Blaugies' strain. No brett or bacteria.

Cool experiment. I recently did a saison with duponts strain that didn't get nearly as warm and conked out at the dreaded 1.020 spot. I might try to grab a pack of this and insulate a bit better.

 

[DSorenson]

If we assume perfect insulation and make some assumptions about the contents of the fermenting vessel, what you have there is a rough idea of the energy released into the wort during fermentation.

We can use those numbers to get an idea of the cooling that must take place throughout fermentation.

It would be helpful to know what the gravity and volume were in the fermenter

 

[mn_brew]

Sure.

OG of 1.061 and about 11.5g in the fermenter. I pulled a gravity sample at about 60 hours after pitching and it had dropped to approx. 1.016

I pulled 5 gallons off at that point to pitch some WL644 (Brett Brux Trois) on half to see how it plays with the WY3726.

The hydro sample tasted excellent. Very fruity and topical, still slightly sweet but not hot at all.

With 5 gallons pulled out my thermo doesn't reach the liquid anymore so I can't check for temps until tomorrow when a new probe thermometer arrives.


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[DSorenson]

so in about 53 hours, the delta T is 17 degrees F. About 7 hours later you noticed that the gravity had a change of 45 gravity units. We also have a mass of the initial wort which is the volume times the density, which can be found by taking the SG and multiplying times the density of water at room temp. There is something here, for sure.

if we assume wort has the specific heat of water and heat loss is negligible, we can start coming up with some equations for things!

 

[DSorenson]

So making some assumptions about the beer:
1) I'm going to consider the mass of the wort equal to the mass of an equivalent volume of water. I make this assumption because the density changes over time as fermentation occurs.
2) I am using the specific heat of water at 90 degrees F. Between freezing and ninety there is a change of (-0.01).
3) I am neglecting the energy lost to air inside the insulated fermenter: it's not a significant contributor of heat absorption.
4) The fermenter will be considered perfectly insulated.

Where x is the volume in gallons...

ΔH=CρVΔT=1.00 (btu/lbm∙R)×(62.2 (lbm/ft^3)×0.11368(x) (ft^3)×ΔT (R)= y (btu)

ΔH=7.07(x)(ΔT)=7.07(11.5)(17)= 1380 Btus

Those little beasties put out 1380 Btus into the wort. 1380 Btus!