Mass-spectrometric study on13C/12C carbon and18O/16O oxygenstable isotopes distributions in grapes and wines from the BlackSea regions

The present study continues the 2015–2016 research project on biological characteristics of stableisotopes fractionation in grapes taking into account the agro-climatic growth conditions of this representativeof the C3-pathway of photosynthesis group of plants in different geographical Black Sea regions. The firstparts of the project were presented at the 39th and 40th Congresses of OIV in Bento Gonc ̧alves (Brazil) andSofia (Bulgaria). The scientific data on compositions of13C/12C carbon and18O/16O oxygen stable isotopes incarbohydrates, organic acids, and intracellular water were obtained for grapes of 2015–2016 growing seasonsin the four areas of the Crimean peninsula as well as in several areas of the Don Basin and the Western Caspianregion. This report presents the results of the 2017 season study of13C/12C carbon and18O/16O oxygen stableisotopes in carbohydrates and intracellular water of 12 red and white grape varieties (Aligote, Rkatsiteli,Sauvignon Zeleny, Chardonnay, Cabernet Sauvignon, Sauvignon Blanc, Merlot, Risling, Pinot Noir, CabernetFranc, Sira, Krasnostop) as well as in ethanol of wines made from corresponding grapes from the CrimeanPeninsula and South-West Coast of the Greater Caucasus. To measure the ratio of carbon isotopes13C/12Cin grape (must) carbohydrates and wine ethanol the Flash-Combustion technique (FC-IRMS/SIRA) has beenused, while the method of isotopic equilibration (EQ-IRMS/SIRA) has been used for the measurement of18O/16O oxygen isotopes ratio in the intracellular water of grapes (must) and in the water fraction of wine. TheGC-Combustion technique (GC-IRMS/SIRA) has been used for the first time to measure the carbon isotopes13C/12C distribution in ethanol of studied wines. It has been found that theδ13CVPDBvalues for carbohydratesof red and white grape varieties as a result of biological fractionation of carbon isotopes in the agro-climaticconditions of plant growth (2017 season) for the studied geographical areas formed the following quantitativeranges: from−26.72 to−23.35‰ (the Crimean Peninsula) and from−25.92 to−23.87‰ (South-West Coastof the Greater Caucasus). Theδ13CVPDBvalues for wine ethanol are in the following ranges: from−28.15to−24.47‰ (the Crimean Peninsula) and from−27.29 to−25.78‰ (South-West Coast of the GreaterCaucasus). Theδ18OVSMOWvalues in intracellular water of grapes of the 2017 season range from−1.24to 2.17‰ (the Crimean Peninsula) and from 1.08 to 4.09‰ (South-West Coast of the Greater Caucasus). Theresults of this study show, in comparison with the results of studies of the 2015 and 2016 seasons, a decreasein theδ13CVPDBvalues for carbohydrates of grapes and ethanol of wine, which is explained by the changedclimatic conditions of grapes growing in the vegetation period of 2017