Flavour stability is a key factor in the beer production process. The stabilizing effect of six commercial phenolic-rich extracts was studied. The extracts were added to beer before bottling. Quality parameters (colour, turbidity, foam and dissolved oxygen content), antioxidant activity by 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), total polyphenols content, and sensorial analysis by a trained panel were performed over the course of storage. The beers were analyzed every 3 months for a total period of 6 months. Results indicated that all studied phenolic-rich extracts positively affected the beer flavour stability. In particular, the condensed tannins showed a significant protective effect. The condensed green tea tannins resulted as the most promising source of natural antioxidant able to prolong beer shelf-life and bring interesting organoleptic characteristics to beer. Also, grape seed tannins appeared suitable to boost flavour stability and improve organoleptic properties of beer.
Keywords: ABTS; DPPH; FRAP; antioxidant; beer flavour stability; beer quality; beer shelf life; condensed tannins; grape seed tannins; phenolic extract; tea tannins.