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Fields of Expertise: Phenolic compounds: structure, analysis, reactions, and organoleptic properties, grape and wine polyphenols

Author details: Véronique Cheynier is Director of Research at INRAE. She has been working at UMR Sciences Pour l’Oenologie (Joint Research Unit Sciences for Enology, formerly Vine Produce Institute), in Montpellier, France since her appointment as a junior scientist at INRA in 1983, until retiring in 2023. She was trained as « ingénieur agronome » at Institut National Agronomique Paris-Grignon and graduated with a doctorate in analytical chemistry from the same Institute in 1983. In 1984-1985, she spent a year at the University of California, Davis, as postdoctoral researcher working on wine polyphenols under the guidance of Pr. Vernon L. Singleton. Since then, her research has been devoted to the structure of phenolic compounds, their analysis, their biosynthesis in plants, their reactions in plant transformation products and their influence on the quality of foods and beverages, especially colour and astringency. She is the author of over 250 scientific papers and book chapters.  She received the scientific prize of Groupe Polyphenols (GP) in 2000 and has been GP President from 2012 to 2016.

Abstract: One of the pioneers in polyphenol chemistry, Edwin Haslam, started his testimony paper, published in 2007, with the following sentence: « Progress in scientific research hinges on the continual discovery of new methods and techniques ». This will be illustrated in the present review, using grape and wine phenolics as case study. Indeed, phenolic compounds are essential for wine quality, responsible for the colour of red and rosé wines but also for browning of white wines and contributing to taste and mouthfeel properties, Although major grape phenolic compounds, i.e. anthocyanins, hydroxycinnamoyltartrates and proanthocyanidins, have been described over 50 years ago, new developments in analytical chemistry have enabled much progress in the characterization of their structures and reactions during wine-making and of structure-property relationships. Owing to the developement of HPLC coupled with diode array detection and mass spectrometry (HPLC-DAD-MS), numerous reactions products have been detected in wines or model solutions and their formation process and properties have been established. However, these products represent only the emerged part of the wine « polyphenol iceberg ». More recently, metabolomics strategies inspired from petrolomics have demonstrated that the complex phenolic composition of red wines results from random cascade reactions involving grape phenolics but also other wine constituents such as yeast metabolites. Information on the composition of these complex mixtures can be obtained using a combination of methods, including UV-visible spectrophotometry, size exclusion chromatography, HPLC-DAD-MS analysis before and after depolymerisation, and NMR but their characterization is still an analytical challenge. Untargeted metabolomics using high resolution mass spectrometry and/or NMR associated with chemometrics should help unravel links between phenolic profiles, processes and quality traits if applied to large enough and well characterized sample sets. However, new strategies are needed for data analysis and in particular annotation of HRMS signals, because of the large number of isomers potentially showing different properties. Finally, new paradigms considering groups of compounds sharing specific reactivities and properties and competing reaction pathways governed by matrix composition and process conditions for prediction of wine composition and organleptic properties need to be developed.