title: Analysis of the components of hard resin in hops (Humulus lupulus L.) and structural elucidation of their transformation products formed during the brewing process.
abstract: The resins from hops (Humulus lupulus L.), which add the bitter taste to beer, are classified into two main sub-fractions, namely, soft and hard resins. α- and β-Acids in soft resin and their transformation during the wort boiling process are well-studied; however, other constituents in resins, especially hard resin, have been unidentified. In this study, we identified humulinones and hulupones as soft-resin components, in addition to 4'-hydroxyallohumulinones and tricyclooxyisohumulones A and B as hard-resin components. These compounds are all oxidation products derived from α- or β-acids. We also investigated compositional changes in the hard resin during the wort boiling process, which has a significant effect on the taste of the beer, by using model boiling experiments. The major changes were identified to be isomerization of 4'-hydroxyallohumulinones into 4'-hydroxyallo-cis-humulinones, followed by decomposition into cis-oxyhumulinic acids. These findings will be helpful in systematically evaluating and optimizing the effect of the hard resin on beer quality.
authors.affiliation: Central Laboratories for Key Technologies, Research and Development Division, KIRIN Company, Limited , 1-13-5, Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan.
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: Harumi
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Makiko
authors.initials: M
authors.lastname: Yamada
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Matsukura
authors.forename: Hideki
authors.initials: H
authors.lastname: Koizumi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Furihata
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Shindo
mesh_terms: D001515:Beer / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003517:Cyclopentanes / Q000737:chemistry; D005511:Food Handling / Q000379:methods*; D027582:Humulus / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D012116:Resins, Plant / Q000737:chemistry*; D013649:Taste
chemical_list: D003517:Cyclopentanes; D012116:Resins, Plant
keywords: 4′-hydroxyallo-cis-humulinone; 4′-hydroxyallohumulinone; Humulus lupulus L.; beer; cis-oxyhumulinic acid; hard resin; hop; hulupone; humulinone; soft resin; wort boiling