Most home brewers, unfortunately, are familiar with the “alcoholic” off-flavor even if they do not realize it.
High alcohol content is desirable in some beer styles, such as barleywines, but it is problematic in many lighter beers.
This is a harsh, sharp, or spicy flavor that provides a “warming” sensation when consumed.
What Causes the Off-Flavor?
The alcoholic off-flavor is caused by the presence of fusel alcohols, as opposed to the ethanol alcohol that is usually found in beer. Fusel alcohols are produced by yeast when fermentation takes place at a temperature that is too high, usually over 80 degrees Fahrenheit.
There are other less-common causes of alcoholic off-flavors as well. Excessive amounts of yeast used in the fermentation can cause this flaw, as can leaving beer on the trub (the settled out proteins and debris) in the fermentor for too long.
Can This Off-Flavor Be Fixed?
Unfortunately there is no way to un-ferment the alcohols out of the beer. When the alcoholic off-flavor is present in a beer it is there to stay.
Can This Off-Flavor Be Prevented?
The alcoholic off-flavor is quite preventable. The most important factor to consider is the fermentation temperature.
Every yeast strain has a different ideal fermentation temperature range. It is the brewer’s job to know that range and to find a method to hold fermentation at a consistent temperature on the low end of that spectrum for the duration of the fermentation.
If the beer will be fermenting for an especially long period of time it may be beneficial to transfer it into a secondary fermentor after a couple of weeks. This will get the beer off of the trub after most of the fermentation is complete, and it will promote a finished beer with higher clarity.
Have you experienced the alcoholic off-flavor in your brewing? How did it affect the beer?