Investigation of hop and beer bitter acids by coupling of high-performanceliquid chromatography to nuclear magnetic resonance spectroscopy

HPLC-NMR coupling is becoming used for various applications, including the analysis of natural products. Its great potential is demonstrated by the an alysis of hop bitter acids, such as humulones, isohumulones, dihydroisohumu lones and tetrahydroisohumulones, using on-line and stopped-flow technique s. H-1-NMR and two-dimensional NMR spectra recorded for all hop bitter acid s allowed unambiguous identification. It is shown, that hyphenation of HPLC and NMR spectroscopy offers unique opportunities for analysis and quality control of hops and beer. (C) 1999 Elsevier Science B.V. All rights reserve d.