I am a craft-beer lover who doesn’t just like hazy IPAs or pastry-inspired stouts, so I revel in being introduced to new flavors and flavor combinations when I can. However, this has both good and bad consequences.
Every so often, I try a beer that transcends all of its flavors and becomes a kind of liquid symphony. Then there are times when I can’t believe the brewery allowed the beer I’m tasting to ever leave its doors.
I need to be careful here and state the obvious: If you love a beer, that’s great. Continue doing so, and don’t let anything I say—or anything anyone says—rob you of that love. You might like it because of its flaws, or perhaps you didn’t perceive them as such.
However, if you would like to train your palate to be a more-reliable detector of off-flavors in beer, follow me, and see what you can pick up next time you’re at your local brewery. I’ll break down some common off-flavors by their descriptors and then explain why it might be there. I will attempt to do this without being too dry or pedantic. Wish me luck!
Butterscotch or buttered popcorn: This is my old nemesis diacetyl. This is a byproduct of fermentation initially before it goes into a secondary phase where the yeast cleans it up. Certain English styles allow for low levels of this, and it can sometimes be pleasant (or so I’m told—I despise this off-flavor wherever I come across it), but for the most part, it means a full, healthy fermentation did not occur. Occasionally, this flavor can arise alongside a vinegar-like flavor to indicate a possible infection in the beer line. When at high levels, diacetyl will also cause the beer to have a slicker mouthfeel. As much as I dislike this flavor when I encounter it in beer, I have seen it put to good use in a beer by Southern Tier Brewing Company called Creme Brulee. This beer is a great example of the sum being more than the sum of the parts.
Green apple or rotting apple: Similar to diacetyl, acetaldehyde is a byproduct of primary fermentation and gets cleaned up as long as the yeast is given enough time. Can I interest you in a nice, dry cider instead?
Vegetal, cooked cabbage or cooked corn: Dimethyl sulfide (or DMS, because that is way easier to say) is as gross as the descriptors sound. Not that cabbage or corn is disgusting—but would you drink juice made from them? This can have a number of causes, but I find it most often in hoppy beers. It makes the beer an instant drain-pour for me.
Paint thinner or nail-polish remover: Oh, yes. Over-stressed yeast (usually at higher-than-normal fermentation temperatures combined with oxidation) can cause a beer to become solvent-like. There’s no getting around it, either; you can’t cover this one up. It just sits there like an 800-pound gorilla and dares you to drink more. Be wary of the gorilla, folks.
Skunk: The first sip of beer I can remember was of my Canadian dad’s Moosehead Lager. I remember it pretty clearly—because it tasted like fizzy skunk spray. For good reason, too; the compound causing that flavor is called mercaptan and is the chemical in skunk spray. Light is beer’s enemy; UV light rays react with compounds in the hops and create that distinctive off-flavor. If a beer is sitting on a shelf in clear, green or blue bottles … keep walking. Even with brown bottles, after a while, that beer is destined to become light-struck. This is one reason why the market is being flooded with canned craft beers, and I don’t see that trend slowing at all. At one point, international beer brands like the aforementioned Moosehead, Heineken and Amstel were bottling their beers in green bottles to the point where people thought mercaptan was just an acceptable beer flavor. It is not, and I implore you to discourage this by not buying any beer in a clear, blue or green bottle.
Oxidation: I use the term instead of the descriptor, because this one has a lot of range. Mostly, an oxidized beer will give off flavors and aromas of paper or wet cardboard—associated with stale beer. It can even resemble decaying vegetables. A well-aged beer, however, can have very pleasant oxidized notes of honey or sherry. Brewers go to great lengths to package their beer with as little free oxygen inside as possible, but it’s always there, and you run the risk of it overtaking your bottled or canned beer the longer you take to enjoy it. Lower temperatures and darkness slow this process down, so age your beer accordingly.
Medicinal, smoky or plastic: Yeast is such an interesting life form. It’s ubiquitous in our environment and is highly survivable and adaptable. Brewing yeast strains are no different. Whole dissertations have been written on fermentation. Some of the more enjoyable compounds that emerge in varying degrees from fermentation are esters and phenols. If you’ve had Belgian ales or perhaps a German hefeweizen, you are already familiar with them. Esters can produce a wide range of fruity flavors such as banana, bubblegum, citrus or pomegranate. Phenols have their own range that includes clove and white pepper—but this is the light side of phenols. The dark side can come out when the yeast is in a more-stressful environment and throws out highly medicinal (think “bandage”), smoky or plasticky aromas and flavors. They are definitely unpleasant.
Astringency: This is a sensation more than a flavor, but it’s often indicative of a flawed process. Overly steeped or milled grains are a common culprit, as is over-hopping. If you’ve ever had a red wine or tea that was steeped too long, and it seemed to suck all the moisture out of your tongue as it passed over, you’ve experienced astringency. Tannins (usually from the husks of grain) and polyphenols (usually from hops) should be mitigated as much as possible so that your beer is refreshing and doesn’t require you to alternate sips of water to compensate.
There are more off-flavors (grassy, yeasty and sulfuric being among them), but you can search for yourself and dive deep.
Lest you think these don’t show up very often, I’ve experienced each one of these at least once in the past three months. Here’s a tip for tasting that can help you discern subtle flavors in anything: After you swallow the beer, exhale through your nose with your mouth closed. You have a separate olfactory sense called the retronasal system, and it can pick up things your orthonasal system (your nostrils and mouth) might have missed.
Yeah, you’re right, I just got dry and pedantic. How to fix that?
WHO WANTS TO SHOTGUN A BEER?!
Brett Newton is a certified cicerone (like a sommelier for beer) and homebrewer who has mostly lived in the Coachella Valley since 1988. He currently works at the Coachella Valley Brewing Co. taproom in Thousand Palms. He can be reached at firstname.lastname@example.org.