I was browsing the forums this morning and came across a question that I’ve seen a couple of times… “is my fermentation temperature too high?”
There are two times you will worry about your fermentation being too high… when you are out of the recommended range, and when the yeast character will give you more flavors than what you actually want even if you stay within range…
Even more important than fermenting too hot is keeping the temperature constant… one degree change in temperature is like a 10 or 15 degree change for us…
Most yeast manufacturers will give you a temperature range that is supposed to be good for the yeast… but that doesn’t mean that the temperature should fluctuate as long as it stays within the range…
The scenario I read about in the forum was that the brewer left his fermentor in a closet, and ambient temperature got up to 78 F or close to 80 F… which is definitely too hot for any yeast strain…
High temperatures will ferment beer faster, but it will also produce more esters, off flavors and possibly fusel alcohols… not good…
but what really concerned me was that the brewer decided to move the fermentor down to a basement where ambient temperature was about 62 F…
62 F is a good temperature to start off with… but when you make yeast drop in temperature you can send them into dormancy and could possibly lead to a stuck fermentation…
Most ale yeast strains will go up to 72 F… depending on the character of the yeast strain and the beer style you are brewing, this may or may not be too high… If you are using a yeast strain that is considered clean, then you could get away with minimum off flavors and slight esters in exchange for a bit faster fermentation.
If you are using a strain that is considered strong, then 72 F may be too high for your beer style if the yeast strain produces too many esters and overwhelms your beer. This takes a little bit of experience to see for yourself what exactly is considered clean or strong, but you can ask your local home brew supply store about the character of the yeast and make a decision until you can gain experience with the yeast.
The same applies for lager yeast strains, except you will be playing around temperatures ranging from 45 F and 55 F. Some lager yeast strains are actually good performers above 55 F, and they are used to brew hybrid beers, like California common beer (steam beer).
So always stay within the temperature range recommended by the manufacturer and keep your temperature constant during fermentation.
