title: Method for the simultaneous assay of diacetyl and acetoin in the presence of alpha-acetolactate: application in determining the kinetic parameters for the decomposition of alpha-acetolactate.
abstract: A simultaneous assay method for diacetyl and acetoin was developed to investigate the formation of diacetyl during the brewing of alcoholic beverages. A GC-MS analysis after the extraction from neutralized sample by ethyl acetate gave accurate assay results. The detection limit was below 0.1 mg/l and the assay was quantitative from 0.1 to 100 mg/l for both compounds. Unlike other methods, the assay results were unaffected by the presence of alpha-acetolactate (up to 26 mg/l), which easily decomposes to diacetyl or acetoin, because the extraction condition prevents the decomposition and extraction of this acidic compound. Since our assay is compatible with samples that contain alpha-acetolactate, the kinetic parameters for decomposition of alpha-acetolactate to diacetyl and acetoin were determined. The decomposition rate constants were affected by the ethanol concentration. Overall kinetics for the decomposition of alpha-acetolactate was formulated as a function of ethanol concentration, pH and temperature. The kinetics can be applied to alcoholic beverages such as sake.
authors.affiliation: National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan. kobayasi_k@nrib.go.jp
authors.forename: Ken
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kusaka
authors.forename: Tosirou
authors.initials: T
authors.lastname: Takahashi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sato
mesh_terms: D000093:Acetoin / Q000032:analysis* / Q000737:chemistry; D000465:Algorithms; D003198:Computer Simulation; D003931:Diacetyl / Q000032:analysis* / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D005504:Food Analysis / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007700:Kinetics; D007773:Lactates / Q000032:analysis* / Q000737:chemistry; D008832:Microchemistry / Q000379:methods*; D008956:Models, Chemical; D014920:Wine / Q000032:analysis*
chemical_list: D007773:Lactates; D000431:Ethanol; C006359:alpha-acetolactate; D000093:Acetoin; D003931:Diacetyl