I consider fermentation to be the final frontier of homebrewing. Ingredients are pretty easy to pick out. Then you start worrying about things like quickly cooling your wort after brewing, but a wort chiller is a quick solution.
Once you go to all-grain, it’s mash temperatures and efficiency. You can even start to control the mineral content and pH of your water. That’s manageable.
Fermentation is probably the most impactful part of the process on the final character of the beer, yet it is the one part of the process that homebrewers often have the least control over.
I wanted to do an experiment to see how much difference fermentation temperature made on the beer. So I brewed 10 gallons of pale ale and split it into two five-gallon carboys. The original gravity was 1.064. For reference, the recipe is at the bottom of the post. I used nothing but malt, hops and yeast. No other additives.
I used the same yeast in each carboy: Wyeast 3522 Belgian Ardennes. One carboy was kept out at room temperature, around 68 degrees. The other went in my homemade cooler box along with a space heater set at 80 degrees.
The difference in the fermentation itself and the finished beer was remarkable. Temperature and had a much greater impact than I would have guessed. Here is the tale of two beers separated at birth.
The 68 Degree Fermentation
Primary fermentation finished in about 6 days. The final gravity I measured was 1.010, coming in at about 7.5% ABV.
The beer is a golden yellow with a frothy white head. The aroma is heavy with clove and spice. The flavor has cloves and dark fruit, like prunes or dates. It was very unexpected from such a lightly colored beer. That’s usually something I would expect from a dubbel or a darker Belgian.
The 80 Degree Fermentation
Primary for the 80 degree finished in about 3 days. It also finished drier than the 68 degree, at 1.006. (8.1% ABV). This isn’t unexpected, as warmer temperatures give the yeast more energy to work faster and harder.
The color is about the same as the 68 degree, but the head is much creamier with finely tight bubbles. The aroma and flavor is bright, with notes of bubble gum, banana and white pepper. It has a noticeably cleaner, drier finish than the 68 degree, which makes sense since its FG was a scant 1.006.
Like a parent choosing between their children, it’s hard for me to say which beer I like better. They are both good in their own way.
I had read about the importance of fermentation temperature in the production of esters and different character in beer, but I had no idea the effect would be this pronounced. These taste like two completely different beers, not born from the same wort. This will certainly be a part of brewing that I’ll pay more attention to going forward.
Untamed Belgian Pale Ale (10 gallons)
18 lbs Belgian Pils
2 lbs Belgian caravienne
1 lb Belgian aromatic
3.0 oz French Strisselspalt 2.9% AA (60 min)
3.0 oz French Strisselspalt (20 min)
1.0 oz French Strisselspalt (0 min)
4.0 oz French Strisselspalt (dry)
Wyeast 3522 Belgian Ardennes Yeast (4 packs)