Fermenting beer at 80 degrees Fahrenheit is generally not recommended, as it can lead to a variety of issues that can negatively impact the final product. While it is true that a fermenting beer generates its own internal heat during fermentation, reaching temperatures of 85+ degrees can be detrimental to the overall quality of the beer.
One of the main concerns with fermenting at higher temperatures is the production of off flavors. Yeast, which is responsible for converting sugars into alcohol during fermentation, can produce certain compounds at elevated temperatures that can result in undesirable flavors in the beer. These off flavors can range from fruity esters to harsh and solvent-like flavors. In extreme cases, the beer can develop a finish that is often described as “unclean” or “astringent”.
Another issue that arises when fermenting at higher temperatures is the increased likelihood of fusel alcohols formation. Fusel alcohols are higher alcohols produced by yeast during fermentation, and they can contribute to a harsh and hot alcohol sensation in the finished beer. This can be particularly noticeable in styles that are meant to be clean and crisp, such as lagers or light ales.
Additionally, fermenting beer at high temperatures can also lead to incomplete attenuation, meaning that the yeast may not fully consume all the sugars in the wort. This can result in a sweeter final product with higher residual sweetness. It can also lead to a higher final gravity, which can affect the mouthfeel and body of the beer.
I have personally experienced the consequences of fermenting at higher temperatures. In one instance, I attempted to ferment a Belgian-style ale at around 80 degrees Fahrenheit due to a lack of temperature control options. The resulting beer had a strong banana-like ester character, which was not intended for that particular style. The beer also had a slightly solvent-like finish, which was off-putting to say the least. It was a valuable lesson in the importance of maintaining proper fermentation temperatures.
To mitigate these issues, it is generally recommended to ferment beer at the lower end of the yeast's recommended temperature range. This allows for a more controlled fermentation, where the yeast can produce a cleaner and more desirable flavor profile. Most ale yeasts perform well between 60-75 degrees Fahrenheit, while lager yeasts prefer temperatures in the 45-55 degree range.
In situations where temperature control is a challenge, there are a few options to consider. One is using a fermentation chamber or temperature-controlled environment, such as a dedicated fermentation fridge or a temperature-controlled fermentation vessel. These options allow for precise control over the fermentation temperature, ensuring optimal conditions for the yeast.
Another option is to use a yeast strain that is known to tolerate higher temperatures without producing excessive off flavors. Some yeast strains, such as certain Belgian ale yeasts, are more forgiving when it comes to temperature fluctuations. However, it is important to note that even these strains have their limits, and pushing the temperature too high can still result in undesirable flavors.
While a fermenting beer does generate its own internal heat, fermenting at 80 degrees Fahrenheit or higher is generally not recommended. The elevated temperatures can lead to the production of off flavors, harsh alcohol sensations, and incomplete attenuation. To produce the best quality beer, it is important to maintain proper fermentation temperatures within the yeast's recommended range.