Photodegradation of Beer and Formation of Lightstruck Flavor

Beer as well as all other non-distilled fermented beverages suffers from light induced chemical changes which result in flavor degradation. As a consequence, specific off-flavor called lightstruck (skunky) is developed in beer exposed to light. The compound responsible for skunky flavor is 3-methylbut-2-en-1-thiol. The present review summarizes the knowledge about light induced beer aging. It focuses on the chemical composition of substances affecting the degradation processes in beer, mechanisms of lightstruck flavor formation, history of the study of these processes and finally the possibilities of controlling and reducing the lightstruck flavor formation.