Radicaloid-type oxidative decomposition of beer bittering agents revealed.
trans-Isohumulones, dihydroisohumulones, tetrahydroisohumulones, and humulinones, which are important hop-derived flavor components of beer, were found, by using electrolysis of organic solutions, to be stable against oxidation, like weak acids; however, they are readily oxidized in their anionic forms as present in beer. Oxygen- and carbon-centered radicals were formed by oxidation and identified by using spin trapping under aerobic and anaerobic conditions, followed by EPR (electron paramagnetic resonance) spectroscopy. Generated radicals were reactive, most likely degrading into products lacking the tricarbonyl chromophore; this is typical of five-membered-ring hop derivatives. Thus, flavor-active beer constituents may degrade oxidatively in the absence of oxygen, thereby leading to reaction products that escape UV detection.
Huvaere
Kevin
K
Faculty of Pharmaceutical Sciences, Laboratory of Pharmacognosy and Phytochemistry, Harelbekestraat 72, Ghent University, 9000 Ghent, Belgium.
Andersen
Mogens L
ML
Olsen
Karsten
K
Skibsted
Leif H
LH
Heyerick
Arne
A
De Keukeleire
Denis
D
D001515:Beer; D003517:Cyclopentanes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005421:Flavoring Agents / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D027582:Humulus / Q000737:chemistry; D010084:Oxidation-Reduction; D013649:Taste
D003517:Cyclopentanes; D005421:Flavoring Agents; D005609:Free Radicals; C081209:isohumulone