Effects of Drying Methods on Terpene Content in Hops and Beer

Dried hops are used in beer production for imparting bitterness and characteristic aroma. Herein, Cascade hop cones are dried using the following two methods: conventional hot-air drying at 52 °C and innovative low-temperature drying at 30 °C via heat-pump technology. The dried hops are used either as whole cones or processed into pellets for brewing. The terpenoid composition of fresh hops, dried cones, pellets and the resulting beers is analysed using headspace solid-phase microextraction coupled with gas chromatography–quadrupole mass spectrometry. Twenty-three mono- and sesqui-terpenes are identified in fresh hops, while 23–26 compounds are detected in dried hops and their corresponding beers, depending on the drying method. Beers brewed with cold-dried cones exhibit a higher concentration of terpenes, especially oxygenated terpenoids and sesqui-terpenes. By contrast, hot-dried pellets exhibit major proportion of monoterpenes and fewer sesquiterpenes. However, cold-dried pellets result in higher levels of oxygenated sesquiterpenes in the final product. These results suggest that hop-drying temperature and physical form markedly affect the aromatic profile of beer. Furthermore, variations in hop terpenoids can influence aroma development through yeast biotransformation during fermentation.