Green apple flavor in beer is likely caused by bacterial contamination.

Green apple flavor in beer is likely caused by bacterial contamination.

• A. True
• B. False
• C. Yeast
• D. Light exposure

Answer: (B)

Green apple notes in beer come from acetaldehyde, a compound produced by yeast during fermentation. When fermentation is incomplete or yeast is stressed—due to temperature, age, or other conditions—acetaldehyde isn’t fully reduced to ethanol and can remain in the beer. That leftover acetaldehyde has a recognizable green-apple aroma and flavor, which is a common flaw rather than a desirable trait. Bacterial contamination, on the other hand, tends to produce sour, funky, or off flavors like lactic sourness or buttery notes, rather than a crisp green apple character. Light exposure creates other off-flavors (often skunky or papery) but not the green apple note described here. So the statement isn’t correct because the green apple flavor is more closely tied to acetaldehyde from yeast, not to bacteria.

Green apple notes in beer come from acetaldehyde, a compound produced by yeast during fermentation. When fermentation is incomplete or yeast is stressed—due to temperature, age, or other conditions—acetaldehyde isn’t fully reduced to ethanol and can remain in the beer. That leftover acetaldehyde has a recognizable green-apple aroma and flavor, which is a common flaw rather than a desirable trait.

Bacterial contamination, on the other hand, tends to produce sour, funky, or off flavors like lactic sourness or buttery notes, rather than a crisp green apple character. Light exposure creates other off-flavors (often skunky or papery) but not the green apple note described here. So the statement isn’t correct because the green apple flavor is more closely tied to acetaldehyde from yeast, not to bacteria.