Acceptable temperature variation during fermentation

[Cloud Surfer]

Say you want to ferment at a constant temperature for the duration of primary. What effect would there be on the end product if the temperature constantly goes up and down around that target for a couple of weeks during fermentation. I guess my question is, what variation is acceptable? 1 degree, 2 degrees, 3 degrees before this starts affecting the beer.

 

[kadmium]

I would say within 2 degrees you are fine, unless you are running on the edge of the warm range. I ferment on the edge of warm, under pressure to help with this.

Gravity fermenting, your new system will settle in and be ******* light years ahead of what most people get.

 

[goatchop41]

Say you want to ferment at a constant temperature for the duration of primary. What effect would there be on the end product if the temperature constantly goes up and down around that target for a couple of weeks during fermentation. I guess my question is, what variation is acceptable? 1 degree, 2 degrees, 3 degrees before this starts affecting the beer.

I would say that 1 degree is preferable, but 2 is acceptable. I don't put heaps of weight in the findings from Brulosophy experiments, but they are worth considering - for what it's worth, they found that consistency/stability of temperature is much more important than the actual temp (eg. a tightly controlled lager fermentation at 18 or 20 was the same as one at 10 or 12, but they were very different when the temp was allowed to swing up and down during fermentation).

The other thing worth considering is that the majority of off-flavours are formed during the first few days of fermentation. I am taking this in to account soon when I will be getting 3 or 4 beers ready for the AFL grand final - instead of one beer taking up my fermentation chamber for a week or more, I'll control the temp for the first 3 days, then take it out and put the next one in. The initial beer will then be allowed to finish fermenting at room temp, but the temp swings won't affect it as much by that point.

 

[Cloud Surfer]

Gravity fermenting, your new system will settle in...

You must be a genius.

Yesterday, day 1 of the new Grainfather and the temps were up and down all over the place. I had 18C set and it was constantly cycling from 17C to 19C over a three hour period. Seemed like the fermenter was never resting, with either the heating or cooling running all the time. Not what I was expecting from this setup.

Today, day 2 and it’s all calm. It slowly rises to 18.5C over a couple of hours, then the cooling kicks in and brings it back to 18.0C in about two minutes. It’s excellent now, and obviously needed a day to settle in.

 

[Cloud Surfer]

I would say that 1 degree is preferable, but 2 is acceptable. I don't put heaps of weight in the findings from Brulosophy experiments, but they are worth considering - for what it's worth, they found that consistency/stability of temperature is much more important than the actual temp (eg. a tightly controlled lager fermentation at 18 or 20 was the same as one at 10 or 12, but they were very different when the temp was allowed to swing up and down during fermentation).

The other thing worth considering is that the majority of off-flavours are formed during the first few days of fermentation. I am taking this in to account soon when I will be getting 3 or 4 beers ready for the AFL grand final - instead of one beer taking up my fermentation chamber for a week or more, I'll control the temp for the first 3 days, then take it out and put the next one in. The initial beer will then be allowed to finish fermenting at room temp, but the temp swings won't affect it as much by that point.

Excellent. Well seems my new fermenter setup has sorted itself out after its day 1 behaviour. I’ve got it set so cooling and heating start when the temp drifts 0.5C away from my target. So hopefully going forward I will be able to stay inside that +/- 0.5C window.

Goodluck with the footy beers.

 

[kadmium]

Great to hear. Never been called a genius before haha. Its probably also to do with thermal mass, convection of the liquids inside and other factors. As the yeast rouse they naturally agitate the liquid, creating more efficient thermal regulation.

 

[Cloud Surfer]

Great to hear. Never been called a genius before haha. Its probably also to do with thermal mass, convection of the liquids inside and other factors. As the yeast rouse they naturally agitate the liquid, creating more efficient thermal regulation.

That makes sense.