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What causes skunking in beer?

  1. Exposure to moisture

  2. Presence of oxidizing agents

  3. Sunlight and fluorescent light

  4. Use of plastic containers

The correct answer is: Sunlight and fluorescent light

Skunking in beer primarily occurs due to exposure to sunlight and fluorescent light. This phenomenon is mainly attributed to the interaction between light and certain compounds in the beer, particularly iso-alpha acids, which are derived from hops. When these compounds are exposed to light, they can break down into 3-methyl-2-butene-1-thiol (MBT), a compound that has a very strong, unpleasant odor reminiscent of skunk spray. This reaction is especially prominent in beers packaged in clear or green bottles, which provide little protection from ultraviolet (UV) light. Brown bottles offer more protection against light penetration, thus reducing the likelihood of skunking. Therefore, understanding the importance of light exposure on beer quality is crucial for anyone involved in beer service or storage.