CFPS Beer Faults and Off-Flavors 2

Question 1

What causes 'astringency' — a harsh, drying, puckering sensation — in finished beer?

Accepted Answer

Excessive polyphenol/tannin extraction from over-sparging or grain husks at high sparge temperatures

Answer

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.

Question 2

Which bacteria species is responsible for producing acetic acid (vinegar) in contaminated beer, especially when oxygen is present?

Accepted Answer

Acetobacter aceti

Answer

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.

Question 3

What causes the 'Band-Aid,' 'medicinal,' or 'antiseptic' off-flavor occasionally found in beer?

Accepted Answer

Chlorophenols formed when chlorine (from water or sanitizer) reacts with natural phenolic compounds

Answer

Chlorophenols form when residual chlorine in water or sanitizers reacts with phenolic compounds from malt/yeast, creating potent medicinal aromas at very low concentrations.

Question 4

What is the primary source of metallic off-flavors in beer, often described as blood, coins, or pennies?

Accepted Answer

Iron, copper, or aluminum contamination from corroded or reactive brewing equipment

Answer

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.

Question 5

What is the primary cause of 'gushing' — excessive foaming when a bottle or can is opened?

Accepted Answer

Residual fermentable sugars or microbial infection causing continued carbonation beyond intended levels

Answer

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).

CFPS - Certified Cicerone Practice Test

CFPS - Certified Cicerone Practice Test

CFPS Beer Faults and Off-Flavors 2