My college RA imparted many words of wisdom, but none were heeded so vigorously as the proscription against letting cold beer get warm. This, he confidently stated, caused beer to “skunk.” These words hit home for our entire floor and we carefully planned our purchases of warm or cold beer accordingly. But no matter how careful we were, it seemed that we still had our fair share of skunked beer. There are two reasons for this: (1) light, perhaps even more than temperature, creates those “off” flavors; and (2) we were buying Busch Light, where skunkiness is a feature rather than a bug.
Beer is not unique in its sensitivity to light. Wine can also “skunk,” but, oenophiles, being a bit persnickity about terminology, prefer to call this phenomenon “light-struck.” Whatever the name, the process and result is the same. When light, particularly UV, hits wine, it excites riboflavin (a.k.a. vitamin B2) that is naturally present. The riboflavin needs to get rid of this energy, but the wine bottle, being a closed system, can only interact with compounds already in the bottle. One group of compounds, also naturally in wine, that reacts with riboflavin consists of sulphur-containing amino acids. The riboflavin uses the light’s energy to oxidize these amino acids, resulting in byproduct of hydrogen sulphides and other unpleasant smelling sulphurous compounds called mercaptans. Hydrogen sulphide smells like rotten eggs, while mercaptans -- chemically similar to a skunk’s spray -- cause a skunky aroma.
And these reactions happens quickly. The wine industry has spent a significant amount of time and money studying this problem and found that white wine, in a clear bottle, can be adversely affected by only a few hours of direct exposure to fluorescent lighting. Green glass offers more protection, while amber glass affords the most. Similarly, the tannins and pigments in rosé and red wines slow down the chemical reaction, increasing the exposure time needed to damage the wine. But, consider how premium red wines are often showcased:on a shelf to themselves with bright lights to attract the eye. This is a case where the reality of sales technique overrules the best practices of wine storage.
Wine drinks best when it is laid down on its side in a dark, cool place. In stores, most wine is shown with one “display” bottle and the inventory that is either below or behind it, lying on its side and hopefully shielded from light. Always grab a bottle from the inventory area and, as strange as it might sound, look for the dusty one. This means that the wine has been sitting there, undisturbed, in ideal storage conditions, for a while, and is thus less likely to be skunked...er, um, light-struck.
As a final note for the beer-lovers, there is a super simple way to avoid skunked beer. Buy cans! More and more good brewers are switching to cans, and there is a huge variety of premium beers now available that way. Many of my favorite breweries, including Ballast Point, Sixpoint, and Golden Road, all sell their beers in stores this way. Just do yourself a favor and be sure to steer clear of the Busch Light.