title: "Untypical aging off-flavor" in wine: synthesis of potential degradation compounds of indole-3-acetic acid and kynurenine and their evaluation as precursors of 2-aminoacetophenone.
abstract: Kynurenine (1) and indole-3-acetic acid (2) are considered as potential precursors of 2-aminoacetophenone (3), which is regarded to be the aroma impact compound causing an "untypical aging off-flavor" (UTA) in Vitis vinifera wines. The mechanism of the formation of 3 was studied using model fermentation and model sulfuration media spiked with 1 or 2 as potential precursors. Possible degradation products such as kynurenamine (4) and kynurenic acid (5), or skatole (6), 2-oxoskatole (7), 2-formamidoacetophenone (8), 2-oxindole-3-acetic acid (9), and 3-(2-formylaminophenyl)-3-oxopropionic acid (10) were evaluated by HPLC-UV of the fermentation and sulfuration media and comparison with synthesized 7, 8, 9, and 10. The synthesis of the possible precursor 4-(2-aminophenyl)-2,4-dioxobutanoic acid (11), a proposed metabolite of 1 failed because a spontaneous cyclization yields 5 and N-oxo-kynurenic acid (12), but not 11. It could be shown that the formation of 3 is triggered by an oxidative degradation of 2 after sulfuration with potassium bisulfite via the intermediates 10 and 8. However, no formation of 3 occurred during sulfuration of a model wine spiked with 1 or during fermentation of a model must spiked with 1 or 2.
authors.affiliation: Institute of Biochemistry and Food Chemistry, University of Hamburg, Grindelallee 117, D 20146 Hamburg, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Hoenicke
authors.forename: Ole
authors.initials: O
authors.lastname: Borchert
authors.forename: Kai
authors.initials: K
authors.lastname: Grüning
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Simat
mesh_terms: D000098:Acetophenones / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D005524:Food Technology; D007210:Indoleacetic Acids / Q000138:chemical synthesis* / Q000378:metabolism; D007737:Kynurenine / Q000138:chemical synthesis* / Q000378:metabolism; D009812:Odorants; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry; D013649:Taste; D013997:Time Factors; D014920:Wine / Q000032:analysis*
chemical_list: D000098:Acetophenones; D007210:Indoleacetic Acids; D007737:Kynurenine; C055495:2-aminoacetophenone; C030737:indoleacetic acid; D013455:Sulfur