title: Identification of the odour-active cyclic diketone cis-2,6-dimethyl-1,4-cyclohexanedione in roasted Arabica coffee brew.
abstract: We investigated odour-active trace compounds in roasted Brazilian Arabica coffee. Aroma dilution extract analysis (AEDA) applied to the volatile oil extracted from roasted coffee brew revealed 34 odour-active compounds. Among these, a pungent-smelling unknown odour-active compound was determined. The volatile oil was fractioned by silica gel column chromatography. Gas chromatography-olfactometry (GC-O) and multidimensional gas chromatography-mass spectrometry (MDGC-MS) of the fraction which contained a significant amount of the target unknown compound revealed the cyclic 1,4-diketone, cis-2,6-dimethyl-1,4-cyclohexanedione, which had a pungent odour, and was thus first identified in roasted coffee. Model experiments revealed that cis-2,6-dimethyl-1,4-cyclohexanedione was formed via thermal degradation of sugars, especially monosaccharides, under alkaline conditions. Further, we demonstrated that 2-hydroxy-3-pentanone and 1-hydroxy-2-propanone, thermal degradation products of monosaccharides, were closely related to the formation of cis-2,6-dimethyl-1,4-cyclohexanedione.
authors.affiliation: Research and Development Center, Nagaoka Perfumery Co., Ltd., 1-3-30 Itsukaichi, Ibaraki, Osaka 567-0005, Japan. hironari-miyazato@npc-nagaoka.co.jp
authors.forename: Hironari
authors.initials: H
authors.lastname: Miyazato
authors.forename: Michiaki
authors.initials: M
authors.lastname: Nakamura
authors.forename: Seiji
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Shuichi
authors.initials: S
authors.lastname: Hayashi
mesh_terms: D001938:Brazil; D040503:Coffea / Q000737:chemistry*; D003069:Coffee / Q000737:chemistry*; D003512:Cyclohexanones / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D006801:Humans; D009812:Odorants / Q000032:analysis*; D009822:Oils, Volatile / Q000737:chemistry*; D013649:Taste
chemical_list: D003069:Coffee; D003512:Cyclohexanones; D009822:Oils, Volatile; C583213:cis-2,6-dimethyl-1,4-cyclohexanedione