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Off-Flavor Alert: Beer Tastes Sharp or Spicy, or “Warming”

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?

Off-Flavor Alert: Beer Tastes Like Green Apples or Pumpkin

The unintended flavor of green apples or fresh pumpkin in beer is common, especially early in one’s home brewing career when patience for the fermentation process might be lacking.

Green apple is not a desirable flavor in any beer, and pumpkin is only acceptable in a few styles.

What Causes the Off-Flavor?

This off-flavor in beer is caused by a natural byproduct in the fermentation process called Acetaldehyde.

Acetaldehyde is an intermediate stage between the sugar that the yeast begins fermenting and the final product, ethanol, given off by the yeast which provides the alcohol content of the beer.

Many off-flavors are caused by poor sanitation, but most often the green apple off-flavor exists because there simply was not enough time allowed for fermentation of the beer. The beer is still “green.”

In rare cases the green apple off-flavor might be caused by either oxidation of the beer or a bacterial infection. If an infection is the culprit, the essence of green apple can be especially intense.

Can This Off-Flavor Be Fixed?

Fortunately, the green apple or pumpkin off-flavor will usually go away with more time allowed for the beer on the yeast for fermentation.

Further fermentation will convert the acetaldehyde into ethanol, removing the green apple flavor. This process can take longer if the beer is strong, with a high specific gravity at the beginning of fermentation.

It can also take longer if the yeast being used is weak or not enough is pitched at the start of fermentation.

Can This Off-Flavor Be Prevented?

The simple way to prevent the flavor of green apples or fresh pumpkin in your beer is to be patient with the fermentation. Allow plenty of time for the yeast to do its work and the results will be improved.

Along the same lines, sufficient levels of strong yeast need to be pitched to encourage a strong fermentation. Determine the expected starting specific gravity of your beer and ensure that you have enough yeast to handle it. A calculator like the one over at MrMalty can be very useful for this.

Check the manufacture date of your yeast. Liquid yeast packs lose their viability quickly after a few months. A yeast starter may be required to build up the number of yeast before fermentation.

Finally, prevent the introduction of oxygen to the beer during transfers into a secondary fermentor or bottling bucket. Flush your fermentor with carbon dioxide and ensure that your transfer lines are secure to prevent oxygen from leaking in. This will prevent off-flavors due to oxidation.