Tasting Off

The proper glassware is something I always consider though, similar to the specific color of the beers I drink, I admittedly do not often think about off-flavors as I am drinking.  Now it is true that the beers you buy really shouldn’t taste off, but as a craft product that can be unfiltered, unpasteurized, or just plain old from sitting on the shelf too long off-flavors can be found in them from time to time.  In home brewing situations they are found far more frequently.

There are quite a few of these flavors that I could get into, but for today I really just want to focus on a handful of the more common (or perhaps popular) ones.  Primarily I referenced the BJCP website for this information (and to a lesser degree craftbeer.com), but I am hoping to simplify the facts based on what I think I know in an effort to keep this post shorter.

Getting to it now in alphabetical order . . .

• Acetaldehyde
• This gives a green apple-like aroma and/or flavor.  It can also bring a grass, green leaves, or even latex paint character, but I associated it with the apple.
• Usually this is reduced to ethanol (the primary alcohol in beer) in secondary fermentation and does not come into play much.
• Low levels of this are actually found in Budweiser because of the method they use to drop the yeast.
• Diacetyl
• Very simply put this is the stuff that gives beer a buttery or butterscotch or toffee-like character to the aroma and flavor.
• Can possible cause a slickness on the palate.
• A compound that some people can pick out easily even at low levels and one that others have a hard time identifying at all.  I have no idea where I fall on that scale.
• This can appropriately be found in low levels in some styles like English and Scottish Ale, Czech Pilsner, and Oktoberfest.
• DMS (dimethyl sulfide)
• This commonly produces a cooked vegetable flavor and/or aroma, but I have always associated it with a canned corn-like characteristic.  I guess in extreme cases it can even bring a shellfish quality, but I hope to never taste a beer with that problem.
• In most lighter lagers (such as Lite American Lager) and some pilsners a bit of this is expected, but too much would be problematic.  Ales really should not have this at all.
• Infection
• This is the one that I am least confident in providing a specific description since (I think) it depends on the beer that has been infected and specifically what it has been infected with.  With that said . . .
• Infected beer can lead to a beer being significantly over carbonated to the point of gushing from the bottle uncontrollably.  Over carbonated beer does not necessarily mean infection though (based mostly on some of my bottles of homebrew).
• Flavors resulting from infection can include sour/acidic (like vinegar), plastic (Band-Aid-like), rotting eggs (sulfur), or other unpleasant vegetal qualities like that of onions or asparagus.
• I am fairly certain that none of these things can really hurt you, but that doesn’t mean your stomach will enjoy it.
• Phenolic
• This also brings on a Band-Aid-like quality as well as possibly a disinfectant or bleach character.
• While those are never desirable qualities, phenols can also bring a clove-like, vanilla-like, or slightly smoky (perhaps from smoked malt) profile that is OK in German Wheat Beers and some Belgian styles.
• Trans-2-Nonenal
• This one may be the most straight forward as it is produced by oxidation and generally brings a papery or cardboard-like characteristic to the aroma and/or flavor.
• Oxidation can cause other flavors as well, such as wine or sherry-like.
• Generally an indication that the beer is old and much past its prime.

As you can see in a few of those off-flavors are not always a bad thing.  Some styles will have a certain level and it is OK, if not appropriate.  The key is then knowing if the flavor you are tasting belongs in the style of beer you are drinking.

Hopefully that is a good start to me hammering this info into my brain, though I really did not even get into the causes for many of these let alone start looking at the other dozen or more off-flavors I did not cover today.  If I missed something important or am off with any of this please let me know.  As I have said before, there is no reason to take up space in my head with inaccurate information.

Cheers!