As an expert sommelier and brewer, I can tell you that there is a particular compound in hops, called isohumulone, that can react with light and riboflavin to create a chemical compound that is very similar to the aroma of a skunk. This reaction occurs quite rapidly, often within a matter of minutes, and is commonly referred to as being “lightstruck” or “skunked.”
When it comes to beer, this lightstruck aroma is generally considered undesirable and can greatly affect the overall taste and enjoyment of the beverage. Brewers take great care to ensure that their beer is protected from light, as exposure to UV rays can trigger this chemical reaction. This is why beer is typically packaged in dark brown or green bottles, or even in cans, which offer better protection against light.
The reason why this reaction occurs is due to the presence of riboflavin, also known as vitamin B2, which is naturally found in hops. When riboflavin absorbs light, it enters an excited state and can react with isohumulone to produce the skunk-like aroma compound. This is similar to how sunlight can cause fading or discoloration in other substances, such as fabrics or paints.
It's worth noting that not all beers are susceptible to becoming lightstruck. For example, beers that are heavily hopped or have a higher alcohol content tend to be more resistant to this reaction. Additionally, beers that are packaged in cans, which offer complete protection from light, are less likely to become skunked.
Personal experiences have taught me the importance of storing beer properly to avoid lightstruck flavors. I recall a time when I accidentally left a six-pack of beer on the windowsill for a few hours on a sunny day. When I finally opened one of the bottles, I was met with a distinctive skunky aroma that completely overpowered any other flavors. It was a disappointing experience, as I had been looking forward to enjoying that particular beer.
To summarize, the compound responsible for the skunk-like aroma in beer is formed when isohumulone reacts with light and riboflavin. This reaction occurs quickly and can negatively impact the taste and enjoyment of the beer. Brewers take precautions to protect their beer from light exposure, such as using dark bottles or cans. It's essential for beer lovers to store their beer properly to prevent it from becoming lightstruck and developing that unwelcome skunky flavor.