Beer aficionados know that a good pint can start with the scent of malt and hops but, if nursed for too long, can end up stinking. Now, chemists know exactly how beer forms the compound responsible, a sulfur-containing molecule akin to the one in skunk glands.
As far back as 1875, researchers reported that light can initiate the skunky-beer smell and taste. But it wasn't until recently that chemists Malcolm D.E. Forbes of the University of North Carolina in Chapel Hill and Denis De Keukeleire of Ghent University in Belgium decided, over a few beers, to figure out precisely how.