Beer Faults and Off-Flavors 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 Beer Faults and Off-Flavors flashcards as text
What causes 'astringency' — a harsh, drying, puckering sensation — in finished beer?
Answer: Excessive polyphenol/tannin extraction from over-sparging or grain husks at high sparge temperatures
Polyphenols/tannins leach from grain husks when sparge water is too hot (above 170°F) or wort drops too low in gravity, binding to salivary proteins and causing astringency.
Which bacteria species is responsible for producing acetic acid (vinegar) in contaminated beer, especially when oxygen is present?
Answer: Acetobacter aceti
Acetobacter oxidizes ethanol to acetic acid in the presence of oxygen, producing a sharp vinegar off-flavor that is a serious contamination fault in most beer styles.
What causes the 'Band-Aid,' 'medicinal,' or 'antiseptic' off-flavor occasionally found in beer?
Answer: Chlorophenols formed when chlorine (from water or sanitizer) reacts with natural phenolic compounds
Chlorophenols form when residual chlorine in water or sanitizers reacts with phenolic compounds from malt/yeast, creating potent medicinal aromas at very low concentrations.
What is the primary source of metallic off-flavors in beer, often described as blood, coins, or pennies?
Answer: Iron, copper, or aluminum contamination from corroded or reactive brewing equipment
Iron and copper ions from reactive metals (old equipment, corroded fittings) dissolve into beer, catalyzing oxidation and contributing distinct metallic flavors even at very low concentrations.
What is the primary cause of 'gushing' — excessive foaming when a bottle or can is opened?
Answer: Residual fermentable sugars or microbial infection causing continued carbonation beyond intended levels
Gushing occurs when refermentation continues in the package due to residual sugar/yeast or microbial contamination, or from nucleation sites caused by hop compounds (primary gushing).
Which compound is responsible for the 'rotten egg' or 'sulfury' aroma sometimes present in lager yeast fermentations?
Answer: Hydrogen sulfide (H2S) produced by stressed or nutrient-deficient yeast
Hydrogen sulfide is produced by yeast under stress from nutrient deficiency, high fermentation pressure, or certain lager yeast strains; it normally dissipates with CO2 during active fermentation.