Beer Flavor and Evaluation
The sensory toolkit
Flavor is a composite. Orthonasal aroma arrives before tasting; retronasal aroma travels up the back of the throat and supplies most of what people call "flavor." The tongue detects sweet, salty, sour, bitter, and umami, while the trigeminal nerve registers carbonation, alcohol warmth, astringency, and cooling. Evaluation order: appearance (color, clarity, head retention), aroma (swirl, short sniffs, avoid sniffing for more than a few seconds), flavor (sip, hold, note attack-midpalate-finish), mouthfeel (body, carbonation, warmth, astringency), and overall impression.
Off-flavor vocabulary
The exam expects you to name the compound, its descriptor, and its usual cause.
- Diacetyl - buttered popcorn, butterscotch; from incomplete fermentation or bacterial contamination.
- Acetaldehyde - green apple, raw pumpkin; young beer or oxidation of ethanol.
- DMS - cooked sweet corn; insufficient boil or covered kettle, worse in pale lagers.
- Lightstruck - skunky; UV exposure.
- Trans-2-nonenal - papery, cardboard; oxidation.
- Esters - fruity, banana (isoamyl acetate), pear, apple; yeast-driven.
- Phenols - clove, pepper, band-aid, medicinal; from yeast or wild contamination.
- Fusel alcohols - solvent, hot; warm fermentation.
Trap: questions deliberately mix esters and phenols. Fruity and banana are esters; clove and smoke are phenols. Likewise, "bitter" is not "astringent" - astringency is a drying, tannic mouthfeel.
Worked example: A lager tastes of buttered popcorn with a slick mouthfeel. The likely culprit is incomplete diacetyl rest or a Pediococcus infection; the fix is a warmer rest at the end of primary or rigorous sanitation. Extending lagering can reduce diacetyl because yeast reabsorbs it.