Scientific study of ¹³C/¹²C carbon and ¹⁸O/¹⁶O oxygen stable isotopes biological fractionation in grapes in the Black Sea, Don Basin and the Western Caspian regions

¹ Research Laboratory of Food Quality & Technology (PNIL), Peoples' Friendship University of Russia (RUDN), 117198 Moscow, ul. Mikluho-Maklaya, 8/2, Russian Federation
² Laboratory of Quality of the JSC Azbuka Vkusa, 127322 Moscow, ul. Milashenkova 4, Russian Federation
³ National Research Institute of Viticulture and Winemarking «Magarach», 298600 Yalta, ul. Kirova, 31, Crimea Republic
⁴ North Caucasian Regional Research Institute of Horti- and Viticulture, 350901 Krasnodar Region, Krasnodar, ul. 40-letya Pobedy, 39, Russian Federation

Abstract

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, South-west 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 δ¹³C_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 δ¹³C_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 δ¹⁸O_VSMOW− 13.90 to − 6.38‰) and with precipitation (averages from δ¹⁸O_VSMOW − 10.30 to − 9.04‰) the δ¹⁸O_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” ¹³C carbon isotope due to changes in isotopic exchange with the environment through a partial reduction in the intensity of transpiration and photosynthesis.