Everyone knows how much skunked beer sucks. The good people at The American Chemical Society have released a video that uncovers the molecular chemistry behind the ickiness, and teaches you how to avoid losing precious brews to skunking.

Hops are one of the ingredients that give beer the bitter taste we know and love, but they’re also one of the culprits of beer skunking. During the brewing process, hops are boiled down to release flavor compounds called isohumulone. These iso-alpha acids break down when they hit sunlight, mixing with your brew’s sulfur-containing proteins. The result: 3-methyl-2-butene-1-thiol. This compound is nearly identical to skunk spray, and detectable at a rate as low as 1 part per billion.


For that reason, skunked beer is also known as “light-struck beer.” Aluminum cans and brown bottles tend to be the norm in craft beer packaging because they do the best job at keeping light out of the picture, which prevents skunking.

What’s the essential takeaway? Light + hops = skunked grossness. Skunked beer is not a result of heat and temperature change. That said, heat does increase the rate of oxidation, which can lead to a stale beer taste.

Luckily, making sure your beer doesn’t skunk is as easy as keeping it in the shade. Thanks, science!

[via The American Chemical Society/Reactions]