AUTOMATED REPORTING ON THE QUALITY OF HOPS AND HOP PRODUCTS

The quality of a hop variety or a hop product can readily be assessed by a fully automated sequence of selective extraction. fractionation a nd quantitative analysis. To illustrate the elegance of the method, ni ne hop varieties and three hop extracts were compared with respect to the content of important marker compounds in the hop oils and of the h op acids. Supercritical fluid extraction at different densities of car bon dioxide was applied to extract selectively. the hop oils and the h op acids, respectively. The hop oils were further fractionated into an apolar and a polar fraction by solid phase extraction and consecutive elution with n-hexane and ethyl acetate. Separation and identificatio n were achieved by capillary gas chromatography coupled to mass spectr ometry. Myrcene, beta-caryophyllene, alpha-humulene and beta-farnesene in the apolar fraction, linalool, undecan-2-one. tridecan-2-one and h umuladienone in the polar fraction were selected for quantitative eval uation of the respective hop oils. Sulphur-containing compounds were r evealed by capillary gas chromatography using sulphur-selective atomic emission detection. Complete separation and quantification of all hop alpha-acids and beta-acids was effected by microemulsion electrokinet ic chromatography coupled to diode array detection.