Performance of alternative drying techniques on hop (Humulus lupulus L.) aroma quality: An HS-SPME-GC-MS-O and...

Economically feasible and effective hop drying strategies are urgently needed to respond to the increasing number of microbrewers in US. In this study, hops were dried by dehydrator-drying (52 °C), oven-drying (52 °C) and freeze-drying (25 °C) until the final moisture content reached 8-10%. Headspace solid-phase microextraction-gas chromatography-mass spectrometry-olfactometry (HS-SPME-GC-MS-O) was employed to analyze the aroma profiles in all dried hops. Methyl octanoate, β-myrcene, trans-α-bergamotene, linalool and geraniol were perceived as high-intensity aromas in all samples. Generally, dehydrator-dried hops contained the highest contents of aroma compounds among all groups, showing an increase of 5-23% and 6-37% when compared to freeze- and oven-dried hops, respectively. Principal component and hierarchical cluster analyses also revealed aroma content differences from three drying methods. Dehydrator drying at 52 °C was therefore considered as an alternative and promising drying approach for smaller-scale hop processing, which can largely benefit regional producers and local craft breweries.