___ is responsible for buttery off-flavors in beer.

___ is responsible for buttery off-flavors in beer.

• A. gypsum
• B. hydrogen sulfide
• C. diacetyl
• D. acetaldehyde

Answer: (C)

Butteriness in beer comes from diacetyl, a flavor-active compound produced by yeast during fermentation. Diacetyl forms from yeast metabolism of amino acids and precursors like alpha-acetolactate, and it impart a creamy, buttery, or butterscotch note even at low levels. Brewers commonly use a diacetyl rest—raising the temperature late in fermentation—to encourage yeast to reabsorb diacetyl and reduce it to acetoin and 2,3-butanediol, which have little to no buttery character. Gypsum is a mineral used to adjust water chemistry, not a flavor culprit. Hydrogen sulfide carries a rotten-egg smell, and acetaldehyde gives a green-apple character. These do not create the buttery note. So diacetyl is the cause of buttery off-flavors.

Butteriness in beer comes from diacetyl, a flavor-active compound produced by yeast during fermentation. Diacetyl forms from yeast metabolism of amino acids and precursors like alpha-acetolactate, and it impart a creamy, buttery, or butterscotch note even at low levels. Brewers commonly use a diacetyl rest—raising the temperature late in fermentation—to encourage yeast to reabsorb diacetyl and reduce it to acetoin and 2,3-butanediol, which have little to no buttery character. Gypsum is a mineral used to adjust water chemistry, not a flavor culprit. Hydrogen sulfide carries a rotten-egg smell, and acetaldehyde gives a green-apple character. These do not create the buttery note. So diacetyl is the cause of buttery off-flavors.