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This study aims to determine volatile compounds in red wines of Zweigelt and Rondo varieties using HS-SPME/GC-MS (headspace solid-phase microextraction gas chromatography - mass spectrometry), and to find a marker and/or a classification model for the assessment of varietal authenticity. Wines were produced from the two varieties, and 67 volatile compounds were tentatively identified in the test wines. The relative concentrations of volatiles were used as an input data set, divided into two subsets (training and testing), to the support vector machine (SVM) and k-nearest neighbor (kNN) algorithms. A subset of 6 volatiles was chosen for evaluation, and it was found that 2 of the volatiles in particular gave an accuracy of 100%. One of the chosen volatiles in Zweigelt wines was absent from the Rondo wines. Further chemometric analysis identified two further volatiles of importance for SVM . The classification model approach needs expanding for mixed varieties, and when the same varietal wines are produced in different geographical locations.

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The 87Sr/86Sr isotopic ratio is a well used marker for geographical origin reflecting the geology on which the crop or animal is raised. It has already been used as a provenance marker for evaluating of wine geographical origin from wine producing regions worldwide. This paper discusses the challenges on using strontium isotope signatures for wine authenticity and provenance. It recomends having a robust database of strontium isotopic values, as well as combining it with other discriminating parameters, namely trace elements for the identification of wine provenance. 

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Polyphenols are a diverse group of natural compounds contributing to the organoleptic properties of wine. Their distribution and content in wines is dependent on grape variety, where the grapes are grown, oenological practices, and storage conditions and time. Hence they are good markers for wine authenticity. This review examines the analytical methods to determine polyphenols especially the metabolomic studies using NMR (nuclear magnetic resonance) or MS (mass spectrometry) combined with chemometrics, and previous studies utilising polyphenols for wine authenticity.

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NMR has been used for the authenticity of wines for over 30 years, but has evolved significantly in the last two decades. It was developed as the official method for added water and sugar to wine, but its use in metabolomics gives a lot of information on grape varieties, cultivation techniques and vintage. NMR can also yield information on geographic origin.

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This article reports a recent webinar to discuss the role of NMR in the non-targeted authenticity analysis of wine, and in particular Spanish wine. The NMR analysis is able to identify and quantify several hundred compounds present in the wine. Reference databases have been built up of these compound profiles using authentic wine, and these are used on wine samples to verify whether they are authentic or not. The method has been adopted by the  Estación Enológica de Haro (EEH) part of the Institute of Vine and Wines Sciences in La Rioja, which serves the wine industry across Spain, and analyses 25,000 samples annually and conducts around 263,000 analyses every year from private clients.  

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This research is by the same French team, who reported using elemental strontium and strontium isotopes as markers for geographic origin and authenticity of Bordeaux wines, which was reported as a 27 April 2019 News item. In this research, lead (Pb) concentrations and Pb isotope ratios of 43 authentic Bordeaux wines from prestigious châteaux and 14 suspicious Bordeaux origin were determined to evaluate their potential as markers for authenticity and geographical origin. Total Pb concentrations in Bordeaux wines have drastically decreased over the past 50 years corresponding to changes in environmental lead concentrations with a clear shift of isotopic signatures towards geological values. The Pb isotopic ratios determined in both sets of samples clearly demonstrated that the suspicious Bordeaux wines displayed Pb isotopic signatures statistically distinctive from those obtained for authentic Bordeaux wines. Three isotopic ratio signatures using the geological and environmental Pb isotopes data that characterise European and Asian sources were used to give a non-ambiguous discrimination between authentic Pauillac AOC and the counterfeit wines.   

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Russian researchers have published a method based on sugar profiles to determine wine authenticity. The glucose-fructose Iindex (GFI) and disaccharide content can be used as marker for wine from different grape varieties. The method can detect when extra grape must has been added before fermentation, as well as wines from arrested fermentation. For sweet wines the glycerol content has to be measured as well. 

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