Characterization of the vine varieties by isotopic analyses

Abstract

Several series of wines were prepared in standard conditions from well defined varieties (Cabernet-Sauvignon, Carignan, Chasselas, Chardonay, Grenache Noir, Riesling, Sauvignon, Syrah et Ugni Blanc) harvested in 1991 in three different regions of production in France (Alsace, Bordeaux and Languedoc). In order to study the influence of the year of production as well, the same varieties grown in Anjou were considered for three different periods of time : 1983, 1984 and 1988. The stable isotope composition of these wines was determined by 2H-NMR spectroscopy ((D/H)_I and (D/H)_II isotope ratios of ethanol) and by Mass Spectrometry for water (²H and ¹⁸O) and ethanol (¹³C). The variations observed for the wines of the different varieties are explained in terms of the climatic conditions (temperature, precipitation and insolation) which governed the regions of production during the vine vegetation cycles considered. It is shown that similar behaviour is observed for the ²H and ¹⁸O contents of the water of musts and wines but they differ from the Craig relationship existing in meteorological waters. The early vine varieties cultivated in the different regions considered give wines with a higher concentration in the heavy isotopes than the later varieties as far as the ethanol (D/H)_I parameter is concerned.