Which of the following is most important to eliminate in order to prevent beer skunking?

To prevent beer skunking, the most important factor to eliminate is exposure to sunlight and fluorescent light. When beer is exposed to ultraviolet (UV) light, particularly from sunlight and certain types of artificial lighting like fluorescent bulbs, a chemical reaction occurs that can lead to the formation of off-flavors, often described as "skunky." This reaction predominantly affects beers packaged in clear and green bottles, as these materials provide little protection from UV light.

Preventing this exposure is critical for preserving the beer’s intended flavors and aromas, ensuring that the consumer experiences the product as the brewer intended. This is why many breweries opt for darker bottles or cans which effectively block out light and help to safeguard the beer's quality.

Other aspects, such as excessive oxygen or high fermentation temperatures, can negatively impact beer quality in different ways, but they do not lead to the specific issue of skunking in the same fashion that light exposure does. High fermentation temperatures can lead to off-flavors from yeast stress, while improper serving temperatures may affect the taste profile but do not inherently cause staling or skunking. Thus, avoiding light exposure is the most effective strategy to maintain the beer’s flavor integrity and prevent the undesirable taste associated with skunked beer.