“This beer tastes like movie theater popcorn,” is a phrase that could be good to hear, but only if someone were releasing On the Waterfront: An American Adjunct Lager Tribute to the Oscars™.
With the amount of experimental brews available, it may be difficult to know whether or not a particular flavor is desired by the brewer or is the result of a problem.
Brewing beer is chemistry, so knowing the technical reason for an off-flavor will go a long way in helping you determine if it’s simply a bad recipe or something else contributing to your dissatisfaction.
Recipe error, improper ingredient storage or handling, poor brewhouse practices, retailer stock rotation, packaging, or draft line cleaning can all negatively impact the flavor of beer.
As the number of breweries is increasing and pretty much anything you can think of is being turned into a recipe, it is becoming more important to know what is and isn’t supposed to be part of the flavor profile.
Inexperience in brewing and in brewery maintenance can lead to some pretty dramatic differences between different batches of the same beer.
Sometimes a pretty serious mistake can be hidden by an excessive hop addition or dumping fruit extracts into the fermenters. Respectable breweries will dump bad batches of beer instead of serving something under the guise of creativity or experimentation.
After familiarizing yourself with the following information, you’ll know if you really are supposed to taste the buttery mashed potatoes from Thanksgiving dinner in that Turkey & Raisins Brown Ale you’ve been nursing.
Off Flavors
Chemical: Diacetyl
Aroma/Flavor: Movie Theater Popcorn Butter
Expected Cause: Although diacetyl is made during the brewing process, the yeast generally reabsorbs it as it flocculates (settles) during fermentation. Faulty yeast, low fermentation temperatures, or shortened wort boils can contribute to elevated levels of diacetyl. However, dirty or infected draft lines are most likely the culprit when experiencing the flavor while drinking at a bar that doesn’t have an adequate maintenance plan in place.
Chemical: Acetaldehyde
Aroma/Flavor: Green Apples
Expected Cause: Immature Beer. This is something you do not want to drink on St. Patrick’s Day. “Green beer,” as many brewers call it, is beer that has not completed the fermentation process. It is either served too early, or has had the still-active yeast removed to clean up the presentation. Inversely, acetaldehyde can be produced as a by-product of oxidation, so it could also be due to a really old beer.
Chemical: Methyl Mercaptan
Aroma/Flavor: Skunk
Expected Cause: Lightstruck. This is an extreme problem if you are experiencing this from a draft line. The primary cause of skunky beer is exposure to light. UV rays and florescent lights both impact beer by breaking down the alpha acids from the hops, which in turn reacts with the hydrogen sulfide produced by the yeast. Clear and green glass bottles are bad for beer storage, while brown glass, cans and kegs provide the best protection.
Chemical: Dimethyl Sulphide / DMS
Aroma/Flavor: Sweet Corn, Cooked Cabbage
Expected Cause: Primarily formed when heating up lightly-kilned malt, it typically is cooked out during the boil. There will be a minor remnant in most beer styles, but it is most noticeable in pale ales or lagers. Desirable in a few styles (like lagers), potent or excessive amounts of this flavor are most likely do improper brewhouse practices or bacterial contamination.
Chemical: Hydrogen Sulfide
Aroma/Flavor: Rotten Eggs, Sulfur
Expected Cause: Brewing Beer. Hydrogen Sulfide is present in all beer, although the concentration can vary greatly depending on style and ingredients. Lager yeasts generally produce more sulfur aromas than ale yeasts. Carbon dioxide will counteract the sulfuric flavors and aromas during the conditioning or lagering phases before a beer is served or packaged.
Chemical: Isoamyl Acetate
Aroma/Flavor: Banana or Fruit Esters
Expected Cause: Brewing Beer. Isoamyl Acetate is common in all beer as a result of fermentation (yeast turning the sugars into alcohol). High fermentation temperatures, under-pitching yeast, and low oxygen levels can contribute to the estery flavor in a beer. Some brewers embrace the fruity or spicy flavor profiles and will use a yeast that enhances these characteristics in German hefeweisen and Belgian ales.
Chemical: Ferrous Sulfate
Aroma/Flavor: Metal
Expected Cause: Poor quality metal pipes in the brewery, packaging (bottle caps or cans), or improperly stored grains can lead to a metallic flavor and mouthfeel. If your beer tastes like blood, pennies, or ink it has most likely absorbed extra metal.
Chemical: Ethyl Acetate
Aroma/Flavor: Nail Polish
Expected Cause: Fermentation Issue. Overly high fermentation temperatures and stressed yeast will result in this undesired chemical byproduct. Ethyl Acetate is more often present when attempting to brew higher alcohol beers than a moderate ale or lager.
Chemical: 2,6-Dichlorophenol
Aroma/Flavor: Bandages, Astringent
Expected Cause: External contamination of beer or brewing with ingredients that have come into contact with chlorophenols, including incorrectly rinsed draft lines after cleaning.
Chemical: Trans-2-Nonenal
Aroma/Flavor: Paper, Wet Cardboard
Expected Cause: Oxidation. This is generally what people are referring to when talking about a beer that has gone stale. Oxygen exposure leads to this papery flavor. Poor capping/corking, using a picnic pump on a keg for an extended period of time, and simply aging a beer can result in oxidation. Certain beer styles (barleywines, old ales) are made with aging in mind, and the brewers will tailor their ingredients to capitalize on the toffee or wine-like characteristics that can develop with extended aging.
Bacteria: Lactobacillus/Pediococcus
Aroma/Flavor: Sour, Vinegar, Funky.
Expected Cause: Infection. With the rising popularity of the Sour, Lambic, and Berliner Weisse styles, it should not be too difficult to determine whether or not your mouth should be puckering when drinking a beer. These microbes produce diacetyl, capryllic acid, and lactic acid, which can give it a goaty, wet sock, or funky aroma and flavor. If any of these flavors occur in anything but one of the styles listed above, chances are that there is an infection due to poor keg cleaning or improper draft line maintenance.
Infected? What am I supposed to do?
Remain calm. This small list of potential problems is not as intimidating as it may seem.
For the most part, these off-flavors (or infections) will not harm you. At most, you’ll have an unpleasant taste in your mouth.
If you get something on draft that is not supposed to taste sour or buttery, you can send it back and switch to bottles, as it is probably a draft line cleanliness issue.
Inquire what the establishment’s line cleaning schedule is. If it is lax or non-existent, you may want to find a new place to do your drinking.
If all other possibilities have proved inconclusive, you should only contact a brewery with a clear and concise description of the flavor problem. Make sure to provide a breakdown of what you were drinking and what the flavor problem was.
Never report a problem for something you just don’t care for; only report something that could be a problem and should be corrected. Bad reviews can be added to apps like Untappd.
Of course, sometimes telling someone not to brew a Rum Barrel-aged Menthol Venison Chowder Porter can reap benefits, too.
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