Beer Bottle - Lightstruck Beer

Lightstruck Beer

Lightstruck, or "skunked" or "skunky", beer has been exposed to ultraviolet and visible light. The light causes riboflavin to react with and break down isohumulones, a molecule that contributes to the bitterness of the beer and is derived from the hops. The resulting molecule, 3-methylbut-2-ene-1-thiol, is very similar chemically and in odour to the musk-borne mercaptans that are a skunk's natural defences.

In some cases, such as Miller High Life, a hop extract that does not have isohumulones is used to bitter the beer so it cannot be "lightstruck". A dark brown glass bottle gives some protection to the beer, but green and clear glass bottles offer virtually no protection at all.

There are also other solutions available to improve beer bottled in clear and green glass from becoming skunked or light-struck. There are specialty coatings that can be baked into the glass and offer additional protection from UV light.