How to Identify Off Flavors in Beer

Madison, Wisconsin

This week, we are talking a little more about off-flavors in beer!  As promised, we are getting into some of the less-common off flavors that have colloquial names that might leave you scratching your head or thinking back to a time if you ever had a beer that tasted similar to an animal.  Maybe some of these off-flavors were actually pleasant to you, but just didn’t belong in a particular style, or maybe it was just too much of something you thought should be there and overwhelms your palate.   Still others that come across as something in your medicine cabinet will be very obvious that they don’t belong.

Hops Growing in the Wild

Chlorophenol: Aroma - If you bring a beer to your nose and get the unpleasant aroma of a bandaid, adhesive tape, plastic, chlorine, or disinfectant, you might have this off-flavor in your beer.  As the name suggests, chlorophenol comes from chlorine or chloromine, sometimes found in water used to brew beer and reacts with phenols - organic compounds created during the brewing process - which gives some seriously unpleasant smells to your beer.

Goaty (Caprylic, Caproic, and Capric Acids): Aroma - Not to be confused with barnyard or brett, which is appropriate for those beers featuring brettomancyes (a type of yeast).  No, if you pick up your beer and notice an aroma of goats, animals, sweaty socks, or just general sweat (ew, David).  This is one that, in small amounts, may end up adding earthy characteristics to beer, but too high, and suddenly you’re eating some very undercooked lamb.

Banana Esters (Isoamyl Acetate): Aroma - Here is one that you’ve heard me talk about quite often when describing Hefeweizens.  In small amounts, this is an appropriate compound that gives some fruitiness, especially banana, to various beer aromas.  But the old adage is true, too much of a good thing can be a negative here.  In larger amounts it could be because you’re fermenting at too high a temperature or that the yeast was under stress.  At too high of levels, it starts to taste like nail polish.

Rancid (Butyric Acid): Aroma - Perhaps one of the worst, if you’re smelling rancid butter, baby vomit, putridness, or spoiled milk you may have found an acid that’s caused by infection of bacterial infection in sugar syrups, a sour mash, or other bacterial contamination in beer.  

Stale Hops (Beta Damascenone): Aroma - Another tricky one, as this aroma is never appropriate.  If you are smelling a hoppy beer that’s been sitting a little too long, crack it open and are picking up black currants, grape jelly, or grape soda you might be tasting the breakdown of carotenoid pigments in hops and that your beer is going stale.  Obviously, be wary of fruited sour ales that take on this characteristic. They don’t use a lot of hops to begin with and may intentionally be going for grape jelly in their flavor profile.

Mercaptan (Methanethiol, Ethanethiol): Aroma -  This one is one of the more obvious off-flavors - rotten, drainpipes, unwashed garbage can, rotten vegetables.  Mercaptan is what they put in propane to make it odorous, if you’re familiar with that smell.  This can be a sign of yeast autolysis or bacterial infection. 

Cheesy (Isovaleric Acid): Aroma -  Your beer shouldn’t smell like cheese, new or old, feet, or old socks.  Acids can form if you don’t store your hops properly.  This one can be confused somewhat with Caprylic acid (goaty) that we touched on earlier.   In very, very rare circumstances, a little bit of cheesiness has been said to be present in very highly hopped beers, but we have never come across it!

For the most part - you don’t have to be a beer connoisseur to notice some of the more glaring off-flavors in beer.  True, some of the trickier ones can take some practice to consistently identify them, and even more practice to tell when some of these flavors can be welcome in the correct amounts.  Just know that if you run into an off flavor, it doesn’t automatically make the brewery terrible - mistakes can happen even to the most practiced brewers.  However, if we run into glaring issues with consistent off flavors, we will be sure to let you know to maybe save you a trip until the next batch of beer is ready for release!

Until next time, keep on crusin’, don’t stop boozin!