The phenomenon of beer turning skunky after exposure to light has been reported in the literature for more than 100 years, Forbes notes, but only now have scientists pinpointed the underlying mechanism. Using a type of spectroscopy that exploits electron spin, the researchers compiled a computer simulation of the reaction by which light-sensitive molecules in hops degrade into unpleasant-smelling products.
Via techdirt, [1] Chemists Determine Cause of ‘Skunky’ Beer [2]
I don't drink beer (I don't really care for the taste, stinky or not) but a few friends of mine do drink it, so I'm passing it along.