In beer terminology, what does the term "skunky" refer to?

The term "skunky" in beer terminology specifically refers to a light-struck flavor that develops when beer is exposed to light, particularly ultraviolet light. This phenomenon occurs mainly in beer packaged in clear or green bottles, as these types of bottles do not adequately protect the beer from light exposure.

When light interacts with certain compounds in the hops, particularly the iso-alpha acids, it causes a chemical reaction that produces a compound called 3-MBA (3-methylbutanal), which is responsible for the undesirable skunky aroma and flavor. This off-flavor can significantly detract from the overall enjoyment of the beer, leading to a perception of it being spoiled or faulty.

Understanding this concept helps beer enthusiasts appreciate the importance of proper packaging and storage conditions, as well as the reasons why many breweries opt for brown bottles which provide better protection from light.