Direct detection of beer photodegradation in commercial bottles and introduction of a new Light-Struck Flavour Susceptibility Index

Exposure of beer to light results in the formation of undesirable flavours or complete spoilage. Photo-damaged beerhas a specific, so-called skunky or light-struck flavour (LSF). The compound responsible for LSF is 3-methylbut-2-ene-1-thiol (MBT). Riboflavin (RF) plays a key role in the formation of MBT. It absorbs light in the blue part of thespectrum and transfers excitation energy to isohumulones. This process is accompanied by the decomposition of RF,which causes a decrease in the absorbance of the sample at 450 nm. The decomposition is directly related to theformation of LSF. In this study, the decrease in absorbance associated with the defined illumination of model and realbeer directly in commercial bottles was measured. The decrease in absorbance correlated with the decrease in RFconcentration and the formation of LSF detected by the sensory panel. The Light-Struck Flavour Susceptibility Indexwas introduced as a rate of the beer susceptibility to light degradation and the formation of LSF.