Characterization of the odor-active constituents in fresh and processed hops (variety Spalter Select)

By application of dilution to odor threshold techniques, trans 4,5-epoxy-(E)-2-decenal (metallic), linalool (flowery) and myrcene (geranium-like) were characterized as important odorants in hops. Among the 18 aroma-active compounds showing Flavor Dilution factors higher than 16, in particular, 4,5-epoxy-(E)-2-decenal, 1,(Z)5-octadien-3-one, 1,(E)3,(Z)5-undecatriene and 1,(E)3, (Z)5,9-undecatetraene were newly identified in the hop essential oil. Quantitative measurements performed by stable isotope dilution assays on nine odorants having FD-factors higher than 128 confirmed their flavor contribution, because they much exceeded their odor threshold. Hop drying led, in particular, to a degradation of (Z)-3-hexenal, identified as the most important odorant in fresh hop cones, and also the undecaenes.