New approach for wine authenticity screening by a cumulative ¹H and ²H qNMR

¹ Peoples' Friendship University of Russia (RUDN), 117198 Moscow, ul. Mikluho-Maklaya, 8/2, Russian Federation
² National Research Institute of Viticulture and Winemarking «Magarach», 298600 Yalta, ul. Kirova, 31, Crimea Republic
³ North Caucasian Federal Scientific Center of Horti, Viti- and Viniculture, 350901 Krasnodar Region, Krasnodar, ul. 40-letya Pobedy, 39, Russian Federation

Abstract

New methodological approach for rapid control of wine authenticity without sample preparation, based on the quantitative NMR spectroscopy (qNMR) of the protium ¹H and deuterium ²H nucleus is suggested. The content of dominant (e.g. water, ethanol) and some minor (e.g. glycerol, organic acids) components of wine are determined from qNMR ¹H spectra for authentication of molecular composition. The sum of all exchanging hydrogen atoms of wine's components provide the ¹H signal with a chemical shift of 4.8 ppm. Accounting for their content from ¹H spectrum allows us calculate the ²H isotopic content in wine water from integral intensity of corresponding signal in the ²H qNMR spectrum using an internal or external standard with a known content of the ²H isotope. The possible addition of water can be found from comparison of this value with values of surface and/or ground waters from corresponding viticulture areas. This approach was used for white and red wines from the Black Sea region (Krasnodar area & Crimea peninsula). The ²H contents in investigated wines range from 157 to 165 ppm. The maximum ²H isotope content in surface waters does not exceed 148 ppm. A qNMR measurement of wine according to the proposed approach takes some minutes, that significantly exceeds the laboriousness of methods based on IRMS/SIRA (e.g. δ¹³C, δ¹⁸O). The error of qNMR measurements is less than 2.0%. The qNMR screening of deuterium (²H) in ethanol can be used for detection of possible wine chaptalization. This approach is similar to the known SNIF-NMR method. The positive difference with this method is the use of minimal quantity of enriched ²H standard and measurement of integral intensities of all signals instead of heights. It allows to reduce measurements' time as well as to measure the ²H content of all fragments of ethanol molecules – CH₃⁻, CH_2⁻, OH-groups. The publication has been prepared with the support of the “RUDN University Program 5–100”.