Diagnose your problem
This troubleshooting section is intended to touch on some of the more common off-flavors that you may encounter as a home brewer, homebrew judge, or just lover of beer. Please note, some of these “off-flavors” discussed may be appropriate in certain styles (diacetyl), while some are never appropriate (skunky).
Beer tasting is an art!
A common theme to help reduce your chance of off-flavors is that THOROUGH SANITATION IS OF THE UTMOST IMPORTANCE IF YOU WANT TO MAKE GREAT BEER!!! So go ahead and try your own beer taste test…
Acetaldehyde
Description: This flavor or aroma is reminiscent of the flavor or aroma of green apples.
Cause: It may be indicative of bacterial infection, but also may be a sign that the beer is too “young” and needs to age.
Remedy: Make sure good sanitation procedures are followed to avoid infection. Make sure your homebrew is not removed from the yeast too soon during fermentation.
Fusel Alcohol
Description: In excessive levels, this is sometimes referred to as “hotness” or “hot.” A sensation of warmth in the mouth that can contribute or detract from the beers overall character and complexity. Of course ethanol is produced during fermentation and is a necessary component in beer, however it can be harsh if the beer contains any longer chain alcohols (fusel alcohols). You want some alcoholic notes in a stronger beer style, however they should never be harsh or solvent-like.
Cause: Too high of a fermentation temperature, try to keep fermentation below 80F regardless of beer style or yeast strain. Also can be caused by yeast underpitching, and insufficient oxygen dissolved in solution before pitching.
Remedy: Keep fermentation temperatures at a reasonable temperature. Make sure to pitch a sufficient amount of yeast (always do a yeast starter with liquid yeast), and be sure to aerate your wort thoroughly before pitching your yeast.
Astringency
Description: Think of the sensation you get in your mouth when sucking on a teabag, or chewing on grape skins (Yeah, I know, not stuff you do every day). Sometimes confused with bitterness. Astringency is a dry mouth-puckering sensation, whereas bitterness is detected on the back of the tongue and is desired and assertively noticeable in certain styles, such India Pale Ale or American Pale Ale.
Cause: Several causes. Extract brewers sometimes have problems with astringency from steeping their steeping grains too long, or at too hot of a temperature. Overcrushing your grain, oversparging or sparging with boiling-hot or alkaline water, and bacterial infection. Excessive oxidation also produces a rather unpleasant astringency.
Remedy:Pay more attention to water temperature whether mashing, sparging, or steeping. Keep good sanitation practices. Make sure grain is crushed, not pulverized into powder. Try to minimize oxygen exposure after fermentation to decrease chance of severe oxidation
Cider Flavor
Description: Tastes, smells like apple cider.
Cause: Old, stale extract. Adding too much cane or corn sugar to your recipe (this is debatable in homebrew circles however, some claim sugar doesn’t cause the cideriness).
Remedy: Use fresh extract, limit sugar usage in your recipes.
Diacetyl
Description: Tastes, smells like butter or butterscotch. It can also manifest itself as a “slickness” on the tongue. Diacetyl is produced by yeast early in the fermentation stages, however it is later absorbed by the yeast towards the end. In moderation, it is acceptable and desirable in certain styles (English Ales and many other ales), however it is not acceptable in others (Munich Helles). I’ve tasted this stuff at both extremes, from the diacetyl that adds a subtle complexity and interesting nuances to the over-the-top-buttered popcorn that is downright nasty.
Cause: Removing your beer from the primary yeast before fermentation is complete, bacterial infection, insufficient aeration of wort before yeast is pitched.
Remedy: Make sure primary fermentation has run its course fully before racking to secondary or bottling, practice good sanitation, and be sure to adequately aerate wort before you pitch your yeast. Lager brewers sometimes employ a diacetyl rest, conditioning the beer at 50-55F for a few days.
Dimethyl Sulfide
Description: Tastes and smells of cooked vegetables/corn/cabbage or shellfish/seafood. Is acceptable in light lagers to a degree.
Cause: Bacterial infection can cause DMS, as well as covering up your brewpot during the boil. DMS is removed from the wort during the boil, so covering it up is obviously going to cause the DMS-laced condensation to fall back into your brewpot.
Remedy: Keep good sanitation procedures, and make sure to keep a rolling, uncovered boil when brewing. Do not cover your brewpot during the boil!
Esters
Description: This is the fruity character found in some ales. Certain yeasts will throw more esters than others. Acceptable in most ales, not acceptable in clean lagers. That banana aroma/flavor you get from a hefeweizen? That’s an example of ester(s).
Cause: Higher fermentation temperature will usually produce more esters, as will certain yeast strains. Poor aeration of wort before pitching can also jack up the esters in your brew.
Remedy: Make sure to ferment your beer at the correct temperature according to style and yeast strain. Do your research on whatever yeast strain you are using. Make sure to aerate wort thoroughly before pitching yeast.
Phenols
Description: “Band-Aid” like flavor or aroma, that can also present itself as medicine-like or clovey. Chlorophenols resemble the aforementioned taste descriptors combined with bleach. Phenols are usually part of the flavor profile in Belgians and Wheat beers however.
Cause: Bacterial Contamination can be responsible, or not rinsing your equipment thoroughly after sanitizing with bleach is another culprit. Also, phenols can be leached from the grain husks by overcrushing or oversparging your malt.
Remedy: Good sanitation once again is key. Make sure to always rinse your equipment thoroughly if you sanitize with bleach or a bleach-based sanitizer. Be more cognizant of grain crushing and sparging methods.
Oxidation / Stale
Description: Carboardy, papery flavor or aroma that is not acceptable in any beer style. Sherry-like is another way to describe an acceptable characteristic in many Barleywines, Old Ales, or Scotch Ales.
Cause: Poor wort handling.
Remedy: Do not introduce oxygen to wort after fermentation and avoid rough handling or splashing of hot wort.
Skunky
Description: Your beer smells like a skunk! Not acceptable in any style, even though some people want you to believe that skunkiness is appropriate in imported, green-bottled beer. Ahh no.
Cause: Reaction between UV light and hop compounds.
Remedy: Be sure to bottle your beer in brown glass bottles only as green or clear glass do not effectively filter out the UV rays.
Sour Beer
Description: Sourness registers on the sides of the tongue. Not acceptable in most beer styles, however it is part of the necessary flavor profile in brews like lambics and berliner weisse.
Cause: Bacterial Infection.
Remedy: Good sanitation!
Sulfur
Description: Flavor or aroma that resembles rotten eggs or sulfur.
Cause: Yeast autolysis (yeast cannibalism), bacterial infection.
Remedy: Do not let you homebrew sit on the primary yeast cake for a long period of time. Rack out of the primary when fermentation subsides, but be sure not to separate the wort off the primary yeast cake too soon also. Good sanitation also will reduce your chances of this off-flavor!
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