Sometimes you just want basic information. No fluff, no confusion, nothing too technical. If you are a new brewer, new to the Beer Judge Certification Program, or are one of the many beer lovers who has begun paying attention to the ‘flavors’ in beer, you do not want the chemist’s version. You hear the words, though, and at some point, you will want to know what they mean. Use this as a Help Menu.

4-vinyl guaiacol – most often described as clove

This chemical is typically formed during fermentation of yeast strains used in crafting Bavarian wheat beer. It can also form with some wild yeast strains. You will notice the aromas of clove, although some describe it as a medicinal smell. On the palate, you may notice clove and a pungent hit of spice.

Trans-2-nonenal – most often described as wet cardboard

When beer has become “stale” or exposed to oxygen, it takes on the smell and taste often described as paper or wet cardboard. If you are not used to eating wet cardboard (most of us are not), you may perceive the flavors as candle-like, fatty, or similar to those fruity, waxy, melon-flavored lipsticks you tried as a pre-teen. It may also be described as sherry-like. Teo Musso, Master Brewer/Owner of Birrificcio Baladin, has experimented extensively with the infusion of pure oxygen into beer, with very positive results. This is under ‘controlled’ conditions, however, and is not the same as most beer that becomes old or oxidized. It is recommended that you protect beer from oxygen. Storing beer at temperatures that are too warm results in higher concentrations of Trans-2-nonenal.

Diacetyl – most often described as popcorn butter

If you typically consume high levels of butter in your diet, your sensitivity to this flavor – most often described as butterscotch, butter, or oily slickness on the roof of the mouth – may be diminished. You may be able to detect it if you close your mouth after swallowing and exhale out of your nose. For some people, this is perceived as a very unpleasant flavor. It is a desirable characteristic found in English Ales, and is often associated with Ringwood yeast. During fermentation, yeast excretes a chemical into the wort, and that chemical is converted into diacetyl. By using healthy yeast at lower fermentation temperatures, and by proper aeration, you can control diacetyl production in beer. You can also decrease diacetyl levels with a Diacetyl Rest during decoction.

Dimethyl Sulfide (DMS) – most often described as cooked corn

Although the presence of DMS may be described with similar parallels to cooked or creamed corn, the perception of tomato juice or oysters is detected by some palates when describing the same compound. Without a vigorous boil for 1-1/2 hours, followed by a fast cooling process, DMS cannot be converted and remains in beer. It can also be caused by improper sanitization practices or by wild yeast strains. If your carbon dioxide is tainted, these flavors will emerge as well. This is the easiest to check - bubble the gas through water and smell or taste it.

Isovaleric Acid – most often described as sweaty cheese

Hops need to be fresh and most brewers use properly processed hop pellets to ensure freshness. Certain Belgian-style beers do require the use of aged hops for preservative features and as a gentle bittering product. The use of old cheesy hops will impart the odor of sweaty socks, stale cheese, or rancid, fecal organics.

Acetaldehyde – most often described as green apples

During the conversion of sugars to alcohol, yeast converts the sugars to acetaldehyde before it is converted into ethanol. Watch that you allow enough time for the yeast to ferment the sugars in the wort. Without ample maturation, the beer appears “young”, and could be described as having a grassy aroma, or flavors of avocado, green or bruised apples, pumpkin, squash, or overripe melon. Watch for strong yeast strains, fermentation temperatures that are too high, or fermentations that are not long enough.

Alcohol – most often described as a warming sensation in the throat

By controlling the original gravity of the wort and ending fermentation at the right point, you can control the levels of alcohol. Note: This is not a flavor, but a sensation of warmth or heat in the throat. When combined with esters, it becomes fusel alcohol. This takes it one step further and adds a vinous spiciness. With higher fermentation temperatures, you will increase the possibility of higher fusel alcohols.

Esters – most often described as fruit

Fruitiness in beer (that is not caused by the addition of fruit), may form as the result of the yeast strain chosen, high fermentation temperatures, not enough aeration of wort, or pitching too much yeast into the wort. Descriptions vary: fruit, pears, bananas, ripe apples, anise, or nail polish remover.

Cheers!