Comparison of Procedures for Resveratrol Analysis in Beer: Assessment of Stilbenoids Stability through Wort Fermentation and Beer Aging

Three resveratrol extraction procedures were compared in beer. Two-step pre-cleaning with toluene and cyclohexane allows 76% trans-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 trans-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, trans-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.