Determination of Lightstruck Character in Beer by Gas Chromatography-Mass Spectroscopy

Abstract

“Lightstruck character” is an unpleasant, foul, “skunky” smell that is formed when beer is exposed to light in the range of 350–500 nm. The principal compound responsible for this smell, 3-methyl-2-butene-1-thiol (MBT), has a reported sensory threshold of 4.4–35 ng/L in beer, which is an extremely low value compared to most volatile substances in beer. A method has been developed for the determination of MBT concentrations in beer below the current sensory threshold level of MBT using a purge and trap method and mass spectrometric detector-gas chromatography. This method was applied to the examination of the formation of MBT in bottled beer placed in plastic crates.