Comparison of procedures for resveratrol analysis in beer: Assessment of stilbenoids stability through wort fermentation and beer aging

Abstract

Three resveratrol extraction procedures were compared in beer. Two-step pre-cleaning with toluene and cyclohexane allows 76% frani-resveratrol recovery by solid-phase extraction (SPE) before RP-HPLC-MS/MS analysis. This procedure proved much more efficient than liquid/liquid extraction, which requires solvents that are too hydrophobic for stilbenoids. SPME-GC-MS, where the main limiting factor is non-reproducibility from fibre to fibre, is an interesting alternative for resveratrol quantification in complex mixtures where pre-cleaning is too difficult. With the optimized SPE procedure, 5 μg.L -1 irans-resveratrol was detected in four commercial beers. However, concentrations of stilbenoids in beer should be higher taking into account the presence of cis-stilbenoids. During fermentation, frani-resveratrol was partially regenerated from its glucoside, more stable through beer aging. Adding a stilbenoids-enriched ethanolic hop extract after fermentation significantly increases the beer stilbenoids potential. © 2008 The Institute of Brewing & Distilling.