Peptides modulate Cu(II) reactivity toward hop-derived polyfunctional thiols in beer

Polyfunctional thiols are beneficial contributors to beer aroma yet are labile to oxidation reactions and thus difficult to maintain throughout the brewing process and in finished beer. Recent studies in our lab and elsewhere have demonstrated that relatively low concentrations of copper in wort and beer can adversely affect the stability of hop-derived polyfunctional thiols; however, in this present study, we show how a barley-derived dipeptide can modulate polyfunctional thiol stability using glycyl histidine (Gly-His) as a model dipeptide. We demonstrate that Gly-His, which was previously shown to interact strongly with Cu(II) in sweet wort, binds to Cu(II) to form stable complexes in beer. This binding could potentially delay the loss of the several hop-derived polyfunctional thiols that are beneficial and critical to the aroma quality of hop-forward beers.