Off-Flavors and Quality Control Flashcards
6 cards from real CFPS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Off-Flavors and Quality Control flashcards as text
What aroma is associated with acetaldehyde in beer, and what causes it?
Answer: Green apple or fresh-cut grass, caused by incomplete fermentation when yeast haven't fully reduced it to ethanol
Acetaldehyde is an intermediate in yeast fermentation; its green apple character indicates fermentation was cut short or yeast were stressed before completing the reduction to ethanol.
The compound responsible for a 'skunky' or 'lightstruck' aroma in beer is:
Answer: 3-methylbut-2-ene-1-thiol (MBT)
MBT is produced when UV or blue-spectrum visible light breaks down iso-alpha acids from hops, generating a potent thiol compound detectable at concentrations as low as 4 parts per trillion.
What off-flavor is described as 'cooked vegetables, creamed corn, or cabbage' and is caused by dimethyl sulfide (DMS)?
Answer: A cooked or vegetal character from DMS, which forms from S-methylmethionine (SMM) during wort production
DMS originates from SMM, a precursor present in pale malts that converts to DMS during wort boiling; a vigorous, uncovered boil drives off DMS, while poor boil vigor or slow chilling allows it to accumulate.
Acetic acid off-flavor in beer smells and tastes like:
Answer: Vinegar or nail polish remover
Acetic acid (vinegar) is produced by Acetobacter bacteria converting ethanol to acetate in the presence of oxygen, and is a common spoilage defect in inadequately protected beers.
What is the cause of a 'Band-Aid' or 'medicinal' off-flavor in beer?
Answer: Chlorophenols formed by wild yeast (especially Brettanomyces) or the reaction of chlorine sanitizers with phenolic compounds
4-chlorophenol and related compounds form when chlorine-based sanitizers react with phenolic precursors in wort/beer, or when Brettanomyces produces vinyl phenol compounds with a medicinal, Band-Aid character.
Which sensory threshold concept explains why a trained taster can detect an off-flavor that most drinkers miss?
Answer: Flavor threshold — trained tasters develop lower detection thresholds and can identify off-flavors at sub-threshold levels for average consumers
Regular sensory training lowers a taster's detection threshold for specific compounds through neural sensitization — trained Cicerones can identify off-flavors at concentrations undetectable to untrained palates.