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

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−, CH2−, OH-groups. The publication has been prepared with the support of the “RUDN University Program 5–100”.

Methodological issues of grape and wine water evaluation by quantitative nuclear magnetic resonance deuterium spectroscopy (2H(D)-qNMR)

“…The experimental data obtained using the developed method correlate with the results of preliminary studies of the period 2015-2016 [11], according to which the isotope ratio of water in wines from the Crimea and Krasnodar region was from 157.0 to 166.0 ppm, and isotope ratio of surface and ground water in Krasnodar region did not exceed 148.0 ppm.…”

Determining sugar and molasses origin by non‐exchangeable hydrogen stable isotope of ethanol and carbon isotope ratio mass spectrometry

“…Thus, the sugar molecules cannot be analyzed by IRMS directly to obtain relevant information that reflects the original biochemical or environmental conditions of the samples (Zhang et al., 2002). Therefore, different methods, such as Site specific Natural Isotopic Fractionation by Nuclear Magnetic Resonance (SNIF‐NMR) and Cumulative Screening‐quantitative Nuclear Magnetic Resonance (CS‐qNMR), have been developed to isolate non‐exchangeable hydrogen to achieve a more accurate and precise determination of the isotopes in the sugar samples (Doner et al., 1987; Dunbar & Schmidt, 1984; Ivlev et al., 2019; Katerinopoulou et al., 2020; Lao et al., 2021; Mohammed et al., 2021; Schuler et al., 2022; Wassenaar et al., 2015).…”

“…Nuclear magnetic resonance (NMR)‐based methods to obtain non‐exchangeable hydrogen stable isotope information use different internal standards and require 19 F nucleus stabilization for the calculation of signal integration (Ivlev et al., 2019; Kalabin et al., 2018; Smajlović et al., 2023). Even though NMR‐based methods can be used to authenticate the botanical and geographical origin and detect adulterations in various products, they are quite expensive in terms of equipment acquisition, method application, and maintenance, consequently giving considerably high analysis costs per sample.…”

The intra-laboratory study of EIM-IRMS® (Ethanol Isotope Measurement–Isotope Ratio Mass Spectrometry) method performance with CS-qNMR (Cumulative Screening–quantitative NMR)

“…Because of all these reasons Russian scientists developed a new modified NMR method called Cumulative Screening-quantitative Nuclear Magnetic Resonance (CS-qNMR) method, so that they could get the same (D/H) I and (D/H) II values in wine ethanol in comparison to SNIF-NMR ® . As the principle of all NMR measurements is basically the same, CS-qNMR and SNIF-NMR ® methods are different only in choice of internal working standard, calculation over integral intensities of signals instead of calculation over signals heights and without the need for stabilization on 19 F nucleus (Kalabin et al, , 2018Ivlev et al, 2019).…”