The Role of Flavanoid Polyphenols in Beer Stability

Abstract

Treatment of different beers with polyvinylpolypyrollidone (PVPP) at 100 g/hl was shown to remove polyphenols and simultaneously to diminish the endogenous reducing capacities by 9-38%. Polyphenols contributed up to 60% of the endogenous reducing capacities of the untreated beers. Additions (100–200 mg/L) of various simple flavanols to PVPP-treated beer were shown to restore reducing capacity, but simple flavanols accounted for only about 25% of the reducing capacity of untreated beer. Experiments were conducted to determine whether the colloidal stabilization of lager beers by treatment with PVPP also affected flavor stability. When lager beer was treated on a pilot scale with varying dosages of PVPP, the resulting improvements in colloidal stability were not accompanied by obvious changes in flavor stability during forced aging. Different amounts of prodelphinidin B3, procyanidin B3, and (+)-catechin were added to samples of a PVPP-stabilized lager beer that were then force-aged. The simple flavanols were rapidly oxidized during aging and became potent initiators of chill haze but accounted for only about 20% of the haze formed in unstabilized beer. No significant effects, either of PVPP treatment or of flavanol additions on the development of staling indicators were detected.