Hey homebrewers! How are your Robust Porters going?
Not too much has changed with my beer since yesterday. There's still a thick krausen on top, the airlock is bubbling away and the yeast are still chomping away on the sugar, just as they should be.
I stick a fermometer (a fermentor-thermometer) to the side of each of my carboys and fermenting buckets. These allow me to keep an eye on the temperature of beer during fermentation. I mentioned in previous posts that I've been keeping by fermenting beer in a closet that stays at around 66°F, and I don't really worry too much about it after that. Fermentation generates some heat, so the temperature of fermenting beer can be 4 or 5 degrees above the ambient room temperature. This is usually fine, since American Ale yeast that we're using is generally produces good flavors when the temperature is in the mid-to-high 60s.
However, I noticed something a little unusual when I checked in on the beer today.The weather caught me off guard. Spring started showing up here in Chicago, and the room that I ferment in got a lot warmer than usual. The robust porter is now fermenting at 73-74°F. This fermentation temperature is not ideal, but the beer is not ruined. The increased temperature will stimulate the yeast to produce chemical compounds known as esters. These chemicals create flavors and aromas that are often described as fruit-like, and can manifest as apple, pineapple or strawberry. Potentially, less desirable esters can also form and contribute aromas like acetone or strong glue.
In the end, this temperature will produce a few flavors that I wasn't anticipating, but the roasty flavors of the porter should do a good job of masking any problems that might come up. I'm going to try to keep the temperature down and let this beer finish fermenting.
Not much will change in the next few days, but we'll check in again next Tuesday for Day 9.