Study on the effect of malt and decoction mashing on polyphenols and antiradical power of wort

Abstract

Mashing is one of the key operations in beer brewing. Together with polyphenolic compounds it can affect the quality and stability of beer. In our pilot brewing trials of pale lager (200 L), malts of three barley varieties were compared using either infusion or double decoction mashing. Total polyphenols, anthocyanogens and flavanoids were determined in sweet and hopped wort. Free phenolics were measured by HPLC coupled with coulometric detection. Antiradical power was determined by RC-DCPI, ARA-DPPH and ESR-T150 methods. In this way the influence of mashing method and barley variety on polyphenols and antiradical activity of sweet wort was demonstrated showing that the effect of mashing was stronger (ANOVA). The results showed significantly higher, i.e. by tens of per cent, levels of all polyphenols studied in both the decoction sweet wort and hopped wort. The decoction process resulted in higher levels of the antiradical power, ARA-DPPH (37–47%) and RC-DCPI (25–60%). A cluster analysis partitioned 28 free phenolic compounds in sweet wort primarily by variety and secondarily by mashing. The Malz malt showed a greater increase in polyphenols, free phenolic compounds and antiradical power in the decoction process compared to the Bojos and Sebastian malts. Decoction mashing introduces higher levels of phenolic antioxidants into the beer with the potential to improve the sensory stability of the beer and provide health benefits to the consumer. The different behaviour of malts and barley varieties needs to be better elucidated in further research.