Importance of Fermentation Temperature Control
Why use fermentation temperature control?
According to Dr. Chris White (president of White Labs) and Jamil Zainasheff (Heretic Brewing), authors of Yeast: The Practical Guide to Beer Fermentation, “One of the greatest things a brewer can do to improve his beer is manage the fermentation temperature. This is far more important than using fancy fermentors or even all-grain brewing.”
White Labs conducted a study in which two of the exact same ales were brewed, except one was fermented at 66°F (19°C) and one at 75°F (24°C). They then tested for the difference in flavors. “Most of the flavors that we’d consider “off-flavors” showed a moderate increase, but what was really startling was the increase in acetaldehyde, which gives beer that green apple flavor. Its concentration was 8ppm in the 66°F (19°C) beer, but 152ppm in the 77°F (24°C) beer. So a 9 (5°C) degree increase in temperature, but the acetaldehyde was 19x higher!!”
Putting the bucket/carboy in the spare room/shed and praying isn’t going work. Even if your house stays at a cool 19°C, during the height of fermentation your beer can easily go up those 5°C because of the exothermic reactions. And 24°C is going to do the damage that will rob your beer of it’s clean taste.
The good news is that these flavours are mainly produced during the first 72 hours of fermentation, so you don’t need to maintain the cooler temperatures the entire time the beer is in the fermenter. In fact, it is beneficial to let the temperature rise after fermentation so they yeast can fully attenuate and clean up some of those flavours produced during the height of activity.
As those initial 72 hours are the critical time, and you need to make sure that the correct temperatures is maintained.
What tools do we have to achieve temperature control?