Better knowledge of flavanoids in fresh lager beers: comparison of extraction methods as regards low-and higher-molecular-weight flavanoid recovery, use of thiolysis hyphenated to RP-HPLC-ESI(-)-MS/MS to determine flavanoid subunits

摘要

Elucidation of polyphenols involved in beer organoleptic properties is of prime importance for brewers. Unfortunately, the assays used to quantify them are too often general ones. This approach fails to take into account that each molecule can impart different properties to beer. To investigate beer flavanoids, five extraction methods were tested. As compared to acetone/water (70/30, v/v) elution of an LH-20 resin, small oligomers (P1, P2, and P3) were poorly recovered by liquid-liquid extraction with ethyl acetate or butan-2-one or by dimethylformamide elution of a polyamide cartridge. Higher oligomers were extracted by polyamide SPE or dialysis. To obtain a more detailed composition of higher oligomers, the dialysate was thiolyzed. Results were compared to previous data obtained on the LH-20 extract. It was concluded that "natural" beer oligomers exhibit a relatively low degree of polymerization whilst "chemically" synthesized oligomers most probably account for most of the "heavy" flavanoid content.