No abstract

The present study continues the 2015–2016 research project on biological characteristics of stable isotopes fractionation in grapes taking into account the agro-climatic growth conditions of this representative of the C3-pathway of photosynthesis group of plants in different geographical Black Sea regions. The first parts of the project were presented at the 39th and 40th Congresses of OIV in Bento Gonçalves (Brazil) and Sofia (Bulgaria). The scientific data on compositions of 13C/12C carbon and 18O/16O oxygen stable isotopes in carbohydrates, organic acids, and intracellular water were obtained for grapes of 2015–2016 growing seasons in the four areas of the Crimean peninsula as well as in several areas of the Don Basin and the Western Caspian region. This report presents the results of the 2017 season study of 13C/12C carbon and 18O/16O oxygen stable isotopes 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, Cabernet Franc, Sira, Krasnostop) as well as in ethanol of wines made from corresponding grapes from the Crimean Peninsula and South-West Coast of the Greater Caucasus. To measure the ratio of carbon isotopes 13C/12C in grape (must) carbohydrates and wine ethanol the Flash-Combustion technique (FC-IRMS/SIRA) has been used, while the method of isotopic equilibration (EQ-IRMS/SIRA) has been used for the measurement of 18O/16O oxygen isotopes ratio in the intracellular water of grapes (must) and in the water fraction of wine. The GC-Combustion technique (GC-IRMS/SIRA) has been used for the first time to measure the carbon isotopes 13C/12C distribution in ethanol of studied wines. It has been found that the δ13CVPDB values for carbohydrates of red and white grape varieties as a result of biological fractionation of carbon isotopes in the agro-climatic conditions of plant growth (2017 season) for the studied geographical areas formed the following quantitative ranges: from − 26.72 to − 23.35‰ (the Crimean Peninsula) and from − 25.92 to − 23.87‰ (South-West Coast of the Greater Caucasus). The δ13CVPDB values for wine ethanol are in the following ranges: from − 28.15 to − 24.47‰ (the Crimean Peninsula) and from − 27.29 to − 25.78‰ (South-West Coast of the Greater Caucasus). The δ18OVSMOW values in intracellular water of grapes of the 2017 season range from − 1.24 to 2.17‰ (the Crimean Peninsula) and from 1.08 to 4.09‰ (South-West Coast of the Greater Caucasus). The results of this study show, in comparison with the results of studies of the 2015 and 2016 seasons, a decrease in the δ13CVPDB values for carbohydrates of grapes and ethanol of wine, which is explained by the changed climatic conditions of grapes growing in the vegetation period of 2017.

Abstract. The report considers the agroclimatic conditions in the Black Sea districts of cultivation and processing of grapes -the Black Sea Lowland, the Crimean Peninsula and the South-west coastal areas of the Greater Caucasus. The IRMS/SIRA techniques -Flash combustion (FC-IRMS/SIRA) & Isotopic equilibration (EQ-IRMS/SIRA) -were first applied for the evaluation of carbon and oxygen isotopes ratios in the components of grapes from the Crimean Peninsula.

The report presents the results of a study of carbon and oxygen stable isotopes in carbohydrates and intracellular water of red and white grapes of 2016 wine-growing season in the Crimean peninsula areas, Southwest coast of the Greater Caucasus, the Don basin and the Western Caspian region. The mass concentration of reducing sugars in the studied grape samples has been from 17.5 to 25.0 g/100 ml, titrated acids concentration (based on tartaric acid)-from 6.0 to 9.1 g/l, the buffer capacity 34.1-63.2 mg-Eq/l. Red and white wine made from respective grapes contained from 0.5 to 3.6 g/l of residual sugar; from 11.1 to 14.5% ethanol by volume; buffer capacity was 35.2-52.6 mg-Eq/l. It has been found that the δ 13 C VPDB values for carbohydrates of red and white grape varieties as a result of biological fractionation of carbon isotopes in the agro-climatic conditions of plant growth for the studied geographical areas are ranging from −26.74 to −20.74 (the Crimean peninsula); from −27.31 to −21.58 (South West Coast of the Greater Caucasus), from −27.33 to −24.73 (Don Basin) and from −26.64 to −23.17 (West Caspian). The δ 13 C VPDB values for ethanol of the red and white dry wines range from −28.52 to −24.26 (the Crimean peninsula); from −29.23 to −24.52 (South West Coast of the Greater Caucasus); from −28.97 to −26.22 (Don Basin); from −29.14 to −25.22 (Western Caspian). Compared with the surface water and groundwater (averages from δ 18 O VSMOW −13.90 to −6.38) and with precipitation (averages from δ 18 O VSMOW − 10.30 to −9.04) the δ 18 O VSMOW values in intracellular water of grapes are the following: for the Crimean peninsula grapes, from 0.40 to 4.97 ; the South West Coast of the Greater Caucasus, from-2.11 to 6.29 ; the Don Basin, from −2.21 to 6.26 ; the Western Caspian, from −0.24 to 1.44. It has been noted that in conditions of water shortage caused by low rainfall or lack of rainfall and irrigation, grapes are prone to the accumulation of "heavy" 13 C carbon isotope due to changes in isotopic exchange with the environment through a partial reduction in the intensity of transpiration and photosynthesis.