Isomeric influence on the oxidative coloration of phenolic compounds in a model white wine: comparison of (+)-catechin and (-)-epicatechin.
The reactions of (+)-catechin and (-)-epicatechin with glyoxylic acid were studied in a model white wine solution. When the reactions were performed in darkness at 45 degrees C, the (-)-epicatechin concentration decreased more rapidly than that of (+)-catechin, and the (-)-epicatechin sample had twice the 440 nm absorbance of the (+)-catechin sample after the 14 day incubation period. The main pigments generated were identified as xanthylium cation pigments regardless of the isomeric character of the phenolic compound. Using a combination of absorbance and ion current data, the xanthylium cation pigments generated from (-)-epicatechin were found to have combined molar absorptivity coefficients 1.8 times that of the xanthylium cation pigments generated from (+)-catechin. The implication of these results on the development of an index of white wine oxidation susceptibility is discussed.
Labrouche
Florian
F
National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga 2678, Australia.
Clark
Andrew C
AC
Prenzler
Paul D
PD
Scollary
Geoffrey R
GR
D000465:Algorithms; D002392:Catechin / Q000032:analysis*; D002853:Chromatography, Liquid; D003116:Color; D006038:Glyoxylates / Q000032:analysis; D007536:Isomerism; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D014920:Wine / Q000032:analysis*
D006038:Glyoxylates; D010636:Phenols; D002392:Catechin; C031150:glyoxylic acid