Oenological influences on the D/H ratios of wine ethanol

Within the European Union the determination of chaptalization of wine invol ves the comparison of the D/H ratios of ethanol with the ratios of authenti c wine samples that are similar to the suspect wine in terms of geographica l origin, grape variety, and vintage. In the frame of a databank project co mparison, wines are produced under official control on a small scale. To cl arify the influence of the different production conditions between commerci al wines and these databank wines, wines that were produced under varying c onditions were investigated by the H-2 NMR method. None of the parameters u nder investigation, such as yeast strain, fermentation temperature, or wine fining, showed a significant influence on the (D/H)(I) ratio of wine ethan ol, which is the most indicative parameter for the determination of the add ition of extraneous sugar to wine. For the (D/H)(II) ratio, different value s were found for different yeast strains used for fermentation and a slight decrease was observed with increasing fermentation temperature. At increas ing points of fermentation yield an increase of the D/H ratios was found in the present alcohol. The total increase of the (D/H)(I) ratio throughout t he fermentation was approximately 1 ppm, so that with a fermentation yield of more than 50% no statistical difference could be observed.