N. RETTBERG (1), S. Thoerner (1), L. A. Garbe (2); (1) VLB Berlin, Berlin, Germany; (2) VLB Berlin/TU Berlin, Berlin, Germany

Poster

Hop essential oil is a mixture of several hundred odorants, in which mono- and sesquiterpenes, as well as oxygenated mono- and sesquiterpenes (terpenoids), play a central role. Some compounds (e.g., monoterpene alcohols) occur in a multitude of isomeric structures, whereas differences in the stereochemistry go along with remarkable changes in flavor. Sesquiterpenes occur in several hundred skeletal types, and the introduction of functional groups (e.g., by oxidation) leads to a barely manageable number of structures. Even though their impact on hop aroma is comparatively low, they are bioactive and distinguished by their antifungal properties. In the current study a LIPODEX E (octakis-(2,6-di-O-pentyl-3-O-butyryl)-gamma-cyclodextrin) phase was applied to analyze the hop essential oil of five U.S. hop cultivars by gas chromatography-mass spectrometry. LIPODEX E consists of eight (gamma-cyclodextrin) glucose units bonded through alpha-1,4-linkages; regioselective alkylation of the hydroxyl groups leads to lipophilic phases well suited for GC enantiomer analyses. The results of enantioselective GC-MS were compared with those of straight phase (DB-5MS) separation: standard targets such as myrcene, caryophyllene, humulene, linalool, and geraniol could be easily separated on both columns. The results of quantification using stable isotope-labeled standards matched within deviations of <10%, whereas a tendency toward slightly lower terpene concentrations was found using the LIPODEX E column. In the chromatograms obtained from LIPODEX E (25 m) separation >180 single peaks were detected; straight-phase (30 m) separation yielded approx. 150 under matching temperature and flow conditions. Application of the LIPODEX E phase showed superior separation performance for flavor and bioactive (oxygenated) sesquiterpenes such as humulene/caryophyllene epoxides, alpha-limonene diepoxide, alpha- and beta-eudesmol, viridiflorol, cubenol, tao-cadinol, alpha-bisabolol and alpha-bisabolene epoxide, or farnesol.

Nils Rettberg (born in 1983) is a trained brewer and maltster, holding a diploma in biotechnology/brewing science from the Berlin Institute of Technology (TUB). Since 2011 Nils is a Ph.D. student at the TUB Chair of Bioanalytics, coincidently he is employed in the VLB Department for Special Analyses. At TUB his work includes courses for students of biotechnology and brewing science, ranging from the basics of chemical-technical analysis to the application of sophisticated modern analytical techniques. At VLB Nils is involved in several research projects dealing with the analysis of raw materials, beer, food, and associated biotechnological products. Nils’ scientific focus is on beer and beverage analysis using mass spectrometry in combination with a stable isotope dilution technique. Initiated by his diploma thesis on “Flavour Active Epoxydecenals from Lipid Oxidation” he developed a deep interest in hop aroma, (oxygenated) lipids, and carbonyls—in short, those molecules that make beer either terribly good or horribly stale.