What does the term "skunky" refer to in the context of brewing?

The term "skunky" specifically refers to the off-flavors that arise from a photochemical breakdown of isomerized hop compounds, which is most often caused by exposure to light. This occurs when light interacts with a certain type of hop compound, particularly isohumulone, leading to the formation of compounds that are similar in aroma to that of skunk spray.

This phenomenon is especially prominent in beers packaged in clear or green bottles, which offer less protection against light compared to brown bottles. The skunky aroma can quickly become prevalent in such beers if they are exposed to light for an extended period. By understanding this, brewers can adjust their packaging choices and educate consumers on the importance of storing beer in a dark place to avoid this undesirable flavor.

Other options do not accurately describe the skunky characteristic. For instance, off-flavors created by yeast contamination pertain to various fermentation issues, while excessive use of hops can lead to bitterness rather than a skunky flavor, and improper fermentation temperatures can result in esters or phenols, which are distinct from the skunky flavor profile. Thus, the correct answer effectively explains the unique chemical reaction leading to skunkiness in beer.