How Does a Beer Get Skunky?

Published on Tuesday, May 15, 2007, by Nicole Solis / Edit Post

A skunked beer tastes like a skunk smells. It’s commonly thought that subjecting beer to variations in temperature will skunk it. However, skunkiness in beer is caused not by heat, but by light.

Isohumulones, the bitter compounds in hops used in beer, are very sensitive to natural light (artificial light affects them, too, but not nearly as fast). “If light reaches them, they break down very quickly and react with traces of sulfur compounds in the beer,” says Charles Bamforth, chair of the Food Science and Technology Department at the University of California–Davis and a top researcher in brewing science. This process produces MBT (3-methyl-2-butene-1-thiol), which not only smells like skunk, it’s also chemically very similar to the noxious compound in a skunk’s spray. And it’s potent. Some people can detect MBT at concentrations as low as one-billionth of a gram in a 12-ounce beer.

Cans offer the best protection against damaging light waves, and brown bottles rate a close second. “If you have really strong light for a very long time, then even in brown glass, the beer goes skunky,” says Bamforth. “But in a clear glass or a green glass, it’ll happen very, very quickly”—as in a matter of seconds, not hours. Pilsners, traditionally bottled in green glass, are very susceptible to skunking.

Allowing chilled beer to get warm and then trying to chill it again still isn’t a good idea. Heat speeds up oxidation, and the beer begins to taste like cardboard. To preserve the flavors in your beer, always store it in a cool, dark place, like, say, your refrigerator.

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  • seadragon: the problem is that UV light is NOT THE ONLY CULPRIT. near-UV wavelengths in the blue part of the spectrum are also offenders.

    http://media.libsyn.com/media/basicbrewing/bbrskunking.pdf

  • I found a company online with some new technology for clear and green glass bottled beer. They apply a permanent clear coating that blocks UV light to help prevent skunked beer. I bet this would help Corona, Dos Equis, Heinken and some of the other beers associated with being skunky. www.skspolytech.com

  • beer in colour less bottles that is left in the sun or exposed to flourescents goes skunky really fast. I know that from experience. direct sunlight is worse so don't let bottles sit in the back for too long before bringing them into storage and leave the lights where you have your beer.

    Heineken light goes skunky easily because it is half way there already. It is not the so called "European"...+READ

    beer in colour less bottles that is left in the sun or exposed to flourescents goes skunky really fast. I know that from experience. direct sunlight is worse so don't let bottles sit in the back for too long before bringing them into storage and leave the lights where you have your beer.

    Heineken light goes skunky easily because it is half way there already. It is not the so called "European" flavour Heineken light is slightly different than others and seems to be more susceptible. Some of the Canadian beers and light ale are also but storing in the dark prevents that.-COLLAPSE

  • Science to the rescue! PopSci.com reports that German scientists have discovered a process to extract riboflavin from beer to prevent it from skunking. The sponsor of the research? Green-bottle-loving Heineken.
    http://www.popsci.com/scitech/article/2009-08/news-flash-land-oktoberfest-longer-lasting-brews

  • Heineken is particularly suceptible to this flaw, in my experience. There are so many skunky Heinekens around that I've known people who believe it's part of the "european" flavor of the beer! Flourescent lights are worse than incandescent in inducing skunkiness because of the higher ratio of U/V, and I cringe every time I see those green bottles in the coolers being bombarded 24x7 by the light...+READ

    Heineken is particularly suceptible to this flaw, in my experience. There are so many skunky Heinekens around that I've known people who believe it's part of the "european" flavor of the beer! Flourescent lights are worse than incandescent in inducing skunkiness because of the higher ratio of U/V, and I cringe every time I see those green bottles in the coolers being bombarded 24x7 by the light tubes. *That's* why I pull the 6-pack from the back (if I must buy beer at a 7-11, etc.) It doesn't have to do with which is coldest (most beer I drink is overchilled for the style anyway).-COLLAPSE

  • Beer is not naturally skunky, ever. It's strictly a byproduct of being lightstruck.

  • man...that's bad news for yuengling drinkers (green bottles only)...but interesting...thanks for the trivia

  • Some beer is naturally "SKUNKY"