title: Formation of pigment precursor (+)-1''-methylene-6''-hydroxy-2H-furan-5''-one-catechin isomers from (+)-catechin and a degradation product of ascorbic acid in a model wine system.
abstract: The present study investigates the contribution of ascorbic acid to the formation of pigment precursors in model white wine systems containing (+)-catechin as the oxidizable phenolic substrate. The two main colorless products in these systems were structurally characterized as isomers of (+)-catechin substituted at either C6 or C8 on the A ring with a furan-type unit, namely, (+)-1''-methylene-6''-hydroxy-2H-furan-5''-one-6-catechin and (+)-1''-methylene-6''-hydroxy-2H-furan-5''-one-8-catechin. A known degradation product of ascorbic acid, L-xylosone, was separately prepared and, when reacted with (+)-catechin, generated the same (+)-furanone-catechin isomers as in model white wine systems. Incubation of these isomers in wine-like conditions yielded yellow xanthylium cation pigments. This study has shown that undesirable spoilage reactions (yellow coloration) can occur from a breakdown product of ascorbic acid-L-xylosone.
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.
authors.forename: Célia
authors.initials: C
authors.lastname: Barril
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Clark
authors.forename: Paul D
authors.initials: PD
authors.lastname: Prenzler
authors.forename: Peter
authors.initials: P
authors.lastname: Karuso
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Scollary
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry*; D007536:Isomerism; D008954:Models, Biological; D010084:Oxidation-Reduction; D010860:Pigments, Biological / Q000737:chemistry*; D014920:Wine / Q000032:analysis*
chemical_list: D010860:Pigments, Biological; D002392:Catechin; D001205:Ascorbic Acid