Madison, Wisconsin
This week, we are bringing part 1 in an educational series on off-flavors in beer. There are quite a few, distinct off flavors that you may have come across in beer and perhaps just chalked it up to being “not the beer for you” or simply a bad beer.
We used to be the same way. So come along with us to learn some terms, definitions, and flavors of things you shouldn’t be picking up when you taste beer. Some of them can be subtle, some are right in your face, and others are appropriate here and there, but not always. That’s why it’s important to us that we state the style of beer we are tasting in our reviews as each style has flavors that should be there and others that should not be there. Using this guide, we will try to stay more consistent with naming off flavors in our reviews and now you too, can get a better grasp on what we are talking about when we mention the below terms.
It’s important to remember that just because a beer may have an off flavor (especially if lightstruck) that doesn’t mean a brewery is bad or they don’t know how to make beer. Mistakes happen and some of these off flavors are not easy to pick up on to the untrained nose or tongue. However, if you’re seeing consistent flaws throughout your tasting, then you might want to make note of that when thinking of future visits!
Lightstruck (3-Methyl-2-Butene-1-Thiol or 3MBT): Aroma - Perhaps the one you are most familiar with and the one that I think we may come across the most. The technical term is: Lightstruck. This happens when sunlight and hop bittering compounds react with each other and can happen in as short of a matter of seconds. This off flavor presents itself as a skunky, sulphury, or even rubbery smell. It’s most likely to happen in beer bottles without tint, but can also happen in brown-tinted bottles - although the tint has been shown to help keep it at bay, and we would think, a can most likely prevents this. Knowing that it can happen that fast is definitely something that Hannah and I will keep in mind in the future, as so often we enjoy some brews outside in the summer.
DMS (2,3-butanedione): Aroma - Another big one, DMS is definitely one that you don’t want to find in your beer and is fairly stand-out - creamed corn, cabbage, green beans, canned asparagus and generally canned vegetables. It’s a fairly unique aroma that can be somewhat tricky to nail down as some beers have corn in them, corn flaked malt, and some lagers can even have this aroma appropriate at low levels. DMS is caused when S-methylmethionine (SMM) which is a byproduct of germinating barley and is usually driven away during later steps in the brewing process. Since the threshold of human detection is relatively low (30 to 50 part per billion) even a little bit of this off flavor can throw a beer out of whack.
Oxidization (Trans-2-Nonenal): Aroma/Flavor - This is an aroma or flavor that shows up as cardboard, papery, stale, or what an old box smells like and should never be present in beer and comes from the oxidation of fats released from the malt during the brewing process.
Diacetyl (2.3-butanedione): Aroma/Flavor - Diacetyl is something that is produced by yeast during the brewing process. Yeast will eventually reabsorb diacetyl during the conditioning part of beer - called a “diacetyl rest”. Fun fact, Diacetyl was once used to flavor movie popcorn until it was found to have adverse health effects. Fittingly, Diacetyl smells of butter and tastes of it as well, in large amounts it can take on a butterscotch or even caramel at high enough levels and can cause a slick sensation on the tongue. It isn’t always an off-flavor though as English-style ales, bitters, and some scotch ales benefit from it.
Acetaldehyde: Aroma - This is one of those things you should never pick up when smelling a beer - green or overripe apples, green leaves, latex paint, avocado - that means you’ve got acetaldehyde which is formed during the yeast getting rid of carbon dioxide (remember they’re alive little guys). This can happen in young beer and it’s usually eventually absorbed back up by the yeast and converted to ethanol. Oxygen in the package may cause this, extended wood aging, not oxygenating the wort fully, or not letting beer rest on yeast long. We’ve definitely come up against this unpleasant aroma at least once in our travels.
Metallic (ferrous sulphate): Taste/Aroma - If you sip or smell blood, metal, iron, copper or associated metallic bitterness you’ve found this off-flavor which is usually from the water sourced used in the brewing process, old brewing equipment, or even oxidation of fats that are catalyzed by metallic ions. A neat trick to tell is to rub a little of the beer on the back of your hand which is going to amplify the metallic aroma when it dries.
Musty (2,4,6-tricholoroanisole, “TCA”): Aroma - You don’t want your beer smelling of mold, basement, a wet wine cork, mushroom-like, beet-like, root cellar, or anything else you’re storing in your Grandma’s basement. TCA is never appropriate when smelling beer and it can happen when beer turns stale, and can also be a strong indicator of mold/fungus contamination either with the raw materials or improperly sanitized beer equipment or storage.
Keep an eye out for Part 2 where we will delve into some of the more fun off-flavors, that’s right, some fruits, acids, and cats, and perhaps surprisingly, goats, aren’t things you should be picking up in your beer.
Until next time, keep on crusin’, don’t stop boozin’!
Sources
Tasting Beer 2nd Edition by Randy Mosher
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