Effects of the mashing process on polyphenols and antiradical activity of beer

Mashing is one of the key steps in beer brewing which influences the sensory quality of beer. Polyphenols can affect the quality and stability of beer. In pilot brewing experiments (200 l) of pale lager, the influence of the mashing on the content of polyphenols in beer was investigated for four variants, listed from the least to the most intensive: infusion (INF), single decoction (1DM), double decoction (2DM), and triple decoction (3DM). The profiles of proanthocyanidins, flavonoids, and prenylflavonoids were determined by UHPLC‒MS/MS. Antioxidant activity was measured using two methods, ARA-DPPH (1,1-dipyridyl-2-picryl hydrazyl) and RC-DCPI (2,6-dichlorophenol indophenol). The results showed a significant effect of decoction mashing on polyphenols in beer. The values of total polyphenols, reducing capacity RC-DCPI, and antiradical activity ARA-DPPH were higher for the decoction than for the infusion by 22%, 38%, and 26%, respectively. Flavanols and proanthocyanidins increased from INF to 3DM (by 16% and 38%, respectively). Even the hop-derived flavonols and prenylflavonoids increased from INF to 3DM by 10% and 37%, respectively. These results suggest that decoction mashing, especially the more intensive variants, results in a significant increase in all flavonoids in beer, with a possible benefit for the sensory stability of beer and/or the health of beer consumers.