Georgia Lytra, Celine Franc, Margaux Cameleyre, Jean Christophe Barbe
Unité de recherche Œnologie, EA 4577, USC 1366 INRA, ISVV, Université de Bordeaux, F33882 Villenave d’Ornon France
Email contact: georgia.lytra[@]agro-bordeaux.fr
AIM: Levels of esters derived from substituted acids increase during the first years of aging (1, 2) and some of them are strongly involved in red wine fruity aromatic expression (3). Considering such a role, the analysis of their precursors remains indispensable (4). The goal of this research was to develop a method to level substituted acids, including their enantiomeric forms.
METHODS: Substituted esters and acids were analyzed by GC-MS. The development and optimization of hydroxycarboxylic acid quantitation and enantiomeric separation method consisted of: ester elimination of wine sample, acid extraction, derivatization, extraction and analysis of derivative methyl esters by GC-MS, using a Chiraldex G-TA column. The quantitation and enantiomeric distribution of substituted esters and acids were established in 31 commercial Bordeaux red wines.
RESULTS: Quantitation and enantiomeric distribution of esters and acids showed a strong positive correlation between the age of wine and levels of substituted esters and only a few correlations between acid enantiomers concentrations and age: e.g the decrease in (2R)-2-hydroxy-4-methylpentanoic acid concentration over time, for at least 20 years, may be due to esterification, leading to the increase of the corresponding ester. Variations in the ratio of substituted ethyl esters to their corresponding acids over time detected thanks to these analytical advances suggested that, in general, acids were continuously esterified during aging.
CONCLUSIONS: An assessment of the overall “aromatic potential” of these esters involved in red wine fruity aroma enhancement may be predicted, thanks to the development of the quantitation method of the corresponding acids.