As seen in the Burlington Free Press January 8, 2016
With the craft beer boom in full swing, we often hear about how much incredible beer is out there. The quality bar has been set pretty high as microbrewers continue to innovate and refine brewing practices. But what we don’t hear very much about is how common bad beer is out in the market.
Let’s be clear: Bad beer is not the same thing as “beer I don’t like.” Not liking a beer is a matter of personal taste. When you judge a beer to be “bad,” you’re saying that it wasn’t brewed properly and it is exhibiting some fault. Faults can occur at any stage of the brewing process. They can be the result of poor quality ingredients, insufficiently sanitized brewing equipment, exposure to light, or any number of other factors.
The easiest fault for most people to pick up on is referred to as “skunking.” A skunked beer will have a pungent, skunk-like, or rubbery aroma. Skunking is the result of a chemical chain-reaction that occurs when light interacts with isohumulones, which are bittering compounds from hops. This chemical reaction can start in a matter of seconds and is most pronounced in hoppier beers. Once the reaction is in motion, there’s no stopping it. If you’re going to drink beer outside and don’t particularly enjoy the aroma of skunk, ditch the clear pint glass and stick to brown glass bottles or cans which can block light.
Not all “bad beer” is skunked, however. I hear this term get misused frequently as a general catch-all term to mean a beer has gone bad. The same misappropriation happens in the wine world, too, with the term “corked.” (Cork-tainted or corked wine is affected by trichloroanisole, which imparts a wet cardboard or musty basement aroma.) There are many other faults that beers can exhibit. Here’s a short list of the ones that consumers are most likely to encounter.
Dimethyl Sulfide (DMS): This fault can be produced during the boil. The result is an aroma akin to creamed corn, canned green vegetables or cabbage. In dark beers it can show up as a canned tomato aroma.
Diacetyl: Can result from stressed out yeasts during fermentation or contamination from poorly kept draught lines. It shows up as a buttery aroma, much like movie theater popcorn “butter.” In fact, that movie theater topping is flavored with this exact chemical compound. In large quantities it can smell like butterscotch.
Acetaldehyde: Formed during fermentation, acetaldehyde produces a green apple aroma similar to a Jolly Rancher candy. Acetaldehyde occurs naturally during fermentation. If a beer is conditioned properly, the yeast cells will re-uptake this chemical and convert it into ethanol.
Oxidation: This fault shows itself as Trans-2 Nonenal, which produces papery flavors and aromas similar to cardboard. Oxidation can be an issue during the brewing process if oxygen is introduced at the wrong times. It can also occur once the beer is packaged. It’s almost impossible to rid a bottle, can or keg of every molecule of oxygen before filling it, so all beer will oxidize eventually. In certain styles of beer, such as Barleywines and Imperial Stouts, oxidation can play a positive role in the evolution of flavor development as a beer ages. In most styles, however, oxidation is not a plus.
If you encounter any of these issues in a beer, you should alert the brewery or publican. Brewers generally want to know when there’s something wrong with their product. You’ll need to give them some specific information so that they can investigate the issue. The packaging date or bottling code is usually what they’ll ask for.
(Sidenote: Brewers, please put a packaging code on your products!) Or, if you had a bad beer at a bar, let the brewery know which bar and when you were there so they can contact the bar directly.
If you’d like to learn more about beer faults, I’d recommend picking up a copy of Randy Mosher’s “Tasting Beer.”
Jeff S. Baker II is the Curator of the Curriculum for Farrell Distributing. You can find him on Twitter and Instagram @aPhilosophyOf.