Previously, we compared strongly hopped and unhopped beers using gas chromatography-olfactometry (GC-O) and sensory evaluation, and identified around 30 hop-derived odorants contributing to the hop aroma in beer. In the present study, we examined changes in the concentrations of two of these components, terpenoids and esters, and investigated their origins, by comparing beers using aged hops and hops stored at 4 °C. The beers hopped with aged hops had a citrus/estery character, while that using normal cold-stored hops had green and hop pellet-like characteristics. New odorants synthesized during the hop-aging process were not detected in the odorants extracted by a solvent assisted flavor evaporation (SAFE) method. The beers using aged hops contained increased concentrations of 3-methyl-2-butene-1-thiol (MBT), beta-ionone, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl 4-methyl-pentanoate, 2-phenylethyl-3-methylbutanoate, and 4-(4-hydroxyphenyl)-2 -butanone. We predicted that the substrate short chain acids of these esters were partly generated in the degradations of humulone or luplone. By contrast, the concentrations of linalool, myrcene, and (Z)-3-hexen-l-ol were reduced in the beers hopped with aged hops. The enantiomeric excess of linalool persisted throughout the hop-aging process according to the results of a multidimensional GC/mass spectrometry analysis. We propose that the observed changes in the balances of these components are largely responsible for the distinctive characteristics of beers using aged hops.
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