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Dernière mise à jour : Mai 2018

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PhD Elissa Abi-Habib

Impact of the variability of grape on the quality of red wines
Elissa

The polyphenols of grape berries (flavonoids: tannins and anthocyanins) play a key role in the development of the taste (astringency, bitterness) and the color of red wines. These compounds are mainly located in the solid parts of the grape (skin, seeds). Their extraction is modulated by their solubility in the must, which evolves during fermentation due to the increase of ethanol content. The insoluble components of the berries, including those of the pulp cells, also modulate the extraction through physico-chemical interactions with tannins. The final composition of red wine will then depend on the composition of the berries, but also on the wine-making practices and on their "extractability”. In addition, due to the high reactivity of polyphenols (nucleophilicity, oxidizability), their initial diversity increases during wine-making: once extracted, tannins and anthocyanins react chemically to form so called derived tannins and pigments. These changes have a significant impact on the quality of the wines (stabilization of the color, modulation of taste), because these new compounds have structures and properties that differ from those of their precursors. The relationships between the structural characteristics of the berries, their initial composition in polyphenols  and the composition of the wines are  still poorly understood. Furthermore, climate changes, as well as the development of new varieties and new vineyard management practices induce a variability in the raw material that has an impact on the qualitative characteristics of the wines.

The objectives of this thesis are to identify the relationships between the structural changes of polyphenols and of their organoleptic properties (color/astringency) from the berries until the end of the alcoholic fermentation. We wish: (i) to develop new approaches/tools to characterize the variability of the raw material and link these characteristics to those related to polyphenols in wines; (ii) to identify the respective impact of the diffusion of polyphenols from the skin to the must, their interactions and their chemical reactions on the composition of the wines for a given raw material.

  • Period : 01/10/2017 - 30/09/2020
  • Supervisor : Céline Poncet-Legrand (INRA Montpellier, UMR SPO)
  • Co-supervisor : Aude Vernhet (Montpellier SupAgro)
  • Contact : elissa.abi-habib-at-supagro.fr