Sensomics Analysis of Key Bitter Compounds in the Hard Resin of Hops (Humulus lupulus L.) and Their Contribution to the Bitter Profile of Pilsner-Type Beer

Abstract

Recent brewing trials indicated the occurrence of valuable bitter compounds in the hard resin fraction of hop. Aiming at the discovery of these compounds, hop's ε-resin was separated by means of a sensory guided fractionation approach and the key taste molecules were identified by means of UV/vis, LC-TOF-MS, and 1D/2D-NMR studies as well as synthetic experiments. Besides a series of literature known xanthohumol derivatives, multifidol glucosides, flavon-3-on glycosides, and p-coumaric acid esters, a total of 11 bitter tastants are reported for the first time, namely, 1",2"-dihydroxanthohumol F, 4'-hydroxytunicatachalcone, isoxantholupon, 1-methoxy-4-prenylphloroglucinol, dihydrocyclohumulohydrochinone, xanthohumols M, N, and P, and isoxanthohumols M, N, and P, respectively. Human sensory analysis revealed low bitter recognition threshold concentrations ranging from 5 (co-multifidol glucopyranoside) to 198 μmol/L (trans-p-coumaric acid ethyl ester) depending on their chemical structure. For the first time, LC-MS/MS quantitation of these taste compounds in Pilsner-type beer, followed by taste re-engineering experiments, revealed the additive contribution of iso-α-acids and the identified hard resin components to be truly necessary and sufficient for constructing the authentic bitter percept of beer. Finally, brewing trails using the ε-resin as the only hop source impressively demonstrated the possibility to produce beverages strongly enriched with prenylated hop flavonoids.

Nuclear Magnetic Resonance (NMR) Spectroscopy in Food Science: A Comprehensive Review

“…However, it is plausible for NMR vendors to incorporate these experiments in their instrumentations and pulse sequence libraries, and thus create a more user friendly environment for these applications. Another important point related to compositional analysis is that because there is no perfect analytical technique, the combination of NMR with other methods is strongly encouraged (Avonto, Rua, Lasonkar, Chittiboyina, & Khan, ; Biais et al., ; Cotte et al., ; Di Anibal, Callao, & Ruisánchez, ; Dresel, Dunkel, & Hofmann, ; Spiteri et al., ; Valdes, Beltran, Mellinas, Jimenez, & Garrigos, ).…”

Phenolic Substances in Beer: Structural Diversity, Reactive Potential and Relevance for Brewing Process and Beer Quality

“…The part that is insoluble in n ‐hexane is termed hard resin. (Almaguer et al., ) Hard resin phenolics comprise prenylflavonoids (total prenyflavonoids in commercial hop cultivars: 0.1 to 0.59 g/100 g hop cones (Prencipe et al., )) and multifidol glucosides (total concentration of co‐, n‐, ad‐multifidol glucopyranosides in hop pellets type 90 (Herkules): 2.4 g/100 g (Dresel, Dunkel, & Hofmann, )). In hop hard resin, xanthohumol is accompanied by 13 other prenylated chalcone compounds, all of which are present at 10‐ to 100‐fold lower concentrations than xanthohumol (Stevens & Page, ), and by a chalcone bearing a geranyl moiety (Stevens, Ivancic, Hsu, & Deinzer, ).…”

“…Prenylchalcones or prenylflavonoids are only found in a limited number of plant families, whereas xanthohumol is solely found in hops (Stevens & Page, ; Venturelli et al., ). The other phenolic compounds, which are part of the hard resin, co‐, n‐, and ad‐multifidol glucopyranosides, are implicated in the bitter taste of hop hard resins (Dresel et al., ). These compounds are (acyl‐) phloroglucinol derivatives, just like hop α‐ and β‐acids (Biendl, ; Bohr, Gerhäuser, Knauft, Zapp, & Becker, ).…”

Química Do Lúpulo

“…1 Em um outro estudo, a resina-ε foi investigada por análise sensorial, UV-vis, CLAE-EM e RMN 1D/2D. 61 Foram encontrados na resina-ε resíduos de polifenóis e um total de 11 compostos de gosto amargo inéditos que foram relatados pela primeira vez na literatura: 1",2"-dihidroxanthohumol-F, 4'-hidroxitunicatachalcona, isoxantholupona, 1-metoxi-4-prenilfloroglucinol, dihidrociclohumulonahidroquinona, xanthohumol-M, xanthohumol-N e xanthohumol-P. 61 Neste mesmo trabalho, os autores também quantificaram estes compostos em cervejas tipo pilsen revelando a contribuição ativa dos compostos da resina-ε para o amargor da cerveja. De modo que, segundo os autores do trabalho, seria possível fabricar cervejas enriquecidas com flavonoides prenilados pela adição de resina-ε.…”

“…De modo que, segundo os autores do trabalho, seria possível fabricar cervejas enriquecidas com flavonoides prenilados pela adição de resina-ε. 61…”