title: Flavin-induced photodecomposition of sulfur-containing amino acids is decisive in the formation of beer lightstruck flavor.
abstract: Photooxidation of sulfur-containing amino acids and derivatives readily occurs upon visible-light irradiation in the presence of flavins. The sulfur moiety seems pivotal for interaction, as was determined from kinetic analyses using laser flash photolysis spectroscopy. After photooxidation, the resulting radical intermediates were characterized by addition to a spin trap, followed by electron paramagnetic resonance spectroscopy and evaluation of the coupling constants. The presence of the proposed radical intermediates was strongly supported by the identification of the reaction products using mass spectrometry. Accordingly, feasible degradation pathways for various sulfur-containing amino acids and derivatives were proposed. It was finally proven that flavin-induced photoproduction of sulfhydryl radicals and recombination with a 3-methylbut-2-enyl radical, derived from the photodegradation of hop-derived isohumulones, are decisive in the formation of beer lightstruck flavor.
authors.affiliation: Ghent University, Faculty of Pharmaceutical Sciences, Laboratory of Pharmacognosy and Phytochemistry, Harelbekestraat 72, B-9000, Ghent, Belgium.
authors.forename: Kevin
authors.initials: K
authors.lastname: Huvaere
authors.forename: Mogens L
authors.initials: ML
authors.lastname: Andersen
authors.forename: Michael
authors.initials: M
authors.lastname: Storme
authors.forename: Jan
authors.initials: J
authors.lastname: Van Bocxlaer
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
authors.forename: Denis
authors.initials: D
authors.lastname: De Keukeleire
mesh_terms: D000603:Amino Acids, Sulfur / Q000737:chemistry*; D001515:Beer; D004578:Electron Spin Resonance Spectroscopy; D005415:Flavins / Q000737:chemistry*; D005421:Flavoring Agents; D008401:Gas Chromatography-Mass Spectrometry; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013113:Spin Labels
chemical_list: D000603:Amino Acids, Sulfur; D005415:Flavins; D005421:Flavoring Agents; D013113:Spin Labels