Development of a semi-controlled setup for manipulating drought and heat stress in open field trials

The traditional methods of grape extraction of enochemical compounds use very often mechanical energy by pistons such as the pigeage or mechanical energy produced by must (delestage, pumping over). Recent trend by winemaker is trying to introduce in the fermentation tank, whole berry grape to avoid even minimal oxidation. Unfortunately, the use of the traditional mechanical techniques aforementioned, very often do not guarantee the optimal extraction with residual sugars in the marc. Use of resonance waves (airmixingtm) and a slight overpressure by CO2 (adcftm) permit to work on whole berry guaranteeing the perfect extraction.

Oenococcus oeni is an essential microorganism in winemaking due to its role in malolactic fermentation (MLF).

Among the many compounds in wine, condensed tannins play an important role in the organoleptic properties of the products; they are partly responsible for astringency, bitterness and also contribute to the color. This research work aims to study the oxidation state of these bio-heteropolymers which is an important lock in the analysis of processed products in order to better control their quality. Indeed, their identification remains at present a challenge because of the large heterogeneity of their degrees of polymerization (DP) based on 4 monomers (epicatechin, catechin, epigallocatechin, epicatechin-3-O-gallate) thus multiplying the number of oxidation products.

La mise en valeur d’un terroir au travers du vin signifie dans un premier temps le respect du cahier des charges de l’A.O.C correspondante. Dans un second temps, elle sous-entend d’être à l’écoute des évolutions scientifiques, techniques et sociétales afin de satisfaire une production plus respectueuse de l’environnement et de la santé des hommes. Les recherches effectuées par l’Unité Vigne et Vin du centre INRA d’Angers ont débouché sur le concept d’UTB, Unité Terroir de Base (R.Morlat). UTB définit une aire de terrain ou le fonctionnement de la vigne est homogène en tous points.

A consequence of climate change is the modification of grape harvest quality and physico-chemical parameters of the obtained wine: increase in alcoholic degree, decrease in pH, and modification of the extractability of macromolecules, which leads to problems of microbiological, tartaric, colour and colloidal stability. In order to respond to these problems, the winemaking processes must be anticipated and adapted with a better knowledge of macromolecule extractability in grapes and their evolution, according to the grape variety, vintage and winemaking process. The purpose of this study was to understand 1) how the harvest date can influence the extractability of macromolecules, polysaccharides and phenolic compounds, which are responsible for wine stability 2) how to adapt the winemaking process to the harvest date in order to optimise wine quality.