(CNN) Have you ever opened a bottle of
beer, poured it into a clear glass and left it outside sitting in the sun?
Maybe you've come back to it after a while to take a sip -- and something isn't
quite right.
If you've
experienced this funky taste, it's from a chemical compound similar to the
stinky smell skunks produce. That's why the beer brewing community has dubbed
this process "skunking."
Chuck
Skypeck, the technical brewing projects director at the Brewers Association said
the cause of skunking wasn't really understood until around the 1960s.
When beer is
exposed to strong light, a photooxidation reaction takes place, creating the
compound 3-methyl-2-butene-1-thiol. To prevent the process of skunking from
occurring and preserve the beer flavor, brewers opt for darkly tinted glass.
The popular
choice among brewers is brown. But that's not the only color seen in beer
bottles; some come in green glass, too. What's behind that choice? Given that
green is not as protective from light, the reason for its use is mainly
marketing, according to Skypeck.
"Most
European brewers use green glass. Their green bottles are their image. And again,
we're talking decades ago, there was a certain association of quality and
uniqueness with green glass," Skypeck said.
When it
comes to choosing glass as the packaging material over plastic, Skypeck said glass
perceived as more environmentally friendly and looks higher quality to
consumers.
Cans are
also a popular choice for packaging and don't let in light, but skunking is
still possible due to a process known as thermal aging. More studies are needed
in this area, according to Skypeck, to determine which packaging is optimal to
prevent skunking.
As for any
other guidance on storing beer to prevent changes to the taste, Skypeck has a
simple rule: cold and dark.
"Beer is basically water, barley, sometimes wheat, and yeast - it's a food product. And just like any other food product, it's subject to losing its freshness," he said. "What really causes any food product to lose its freshness - besides this photochemical reaction we talked about -- is exposure to oxygen and exposure to warmer temperature."
From CNN (adapted)
