What does the presence of diacetyl indicate in beer?

The presence of diacetyl in beer is characterized by a buttery aroma and flavor. Diacetyl, a compound produced during fermentation, particularly by yeast, is known for imparting a distinctive buttery quality, reminiscent of buttered popcorn or butterscotch. While some levels of diacetyl can be acceptable in certain beer styles, especially if they are balanced and masked by other flavors, excessive diacetyl is often considered a flaw in beer production.

Understanding diacetyl’s role is important for brewers and evaluators because it can indicate fermentation issues, such as insufficient yeast maturation or incomplete fermentation. Recognizing and managing diacetyl levels is crucial for producing high-quality beer. Other options do not accurately describe the sensory profile associated with diacetyl, emphasizing why the buttery characteristic is the defining feature of this compound.