Behaviour of Antioxidants Derived from Hops During Wort Boiling

The oxidative stability of wort at different stages during wort production and the radical scavenging characteristics of α-, β-, iso-α-acids and a hop polyphenol extract were evaluated using ESR spectroscopy and DPPH• radical quenching measurements. Radical generation in unhopped wort was significantly, positively correlated with heating rate prior to boiling but not with dissolved oxygen content. Hop α- and β-acids showed similarly significant radical quenching abilities, while iso-α-acids and a hop polyphenol extract displayed a negligible effect. Isomerization of α-acids to iso-α-acids reduced wort's antioxidative capacity. Commercially available hop products with varying polyphenol content showed similar radical inhibiting properties, which were a function of hop acid content. Relative to an unhopped treatment, hop additions to wort resulted in significantly lower amounts of Strecker aldehydes in stored beer.