Study of the Interactions between High Molecular Weight Salivary Proteins and Red Wine Flavanols.

Current climate change is increasing inter- and intra-annual variability in atmospheric conditions leading to grapevine phenological shifts as well altered grape ripening and composition at ripeness. This study aims to (i) detect weather anomalies within a long-term time series, (ii) model grape ripening revealing altered traits in time to target specific ripeness thresholds for four Vitis vinifera cultivars, and (iii) establish empirical relationships between ripening and weather anomalies with forecasting purposes. The Day of the Year (DOY) to reach specific grape ripeness targets was determined from time series of sugar concentrations, total acidity and pH collected from a private company in the period 2009-2021 in North-Eastern Italy. Non-linear models for the DOY to reach the specified ripeness thresholds were assessed for model efficiency (EF) and error of prediction (RMSE) in four grapevine cultivars (Merlot, Cabernet Sauvignon, Glera and Garganega). For each vintage and cultivar, advances or delays in DOY to target specified ripeness thresholds were assessed with respect to the average ripening dynamics. Long-term meteorological series monitored at ground weather station by means of hourly air temperature and rainfall data were analyzed. Climate statistics were obtained and for each time period (month, bimester, quarter and year) weather anomalies were identified. A linear regression analysis was performed to assess a possible correlation that may exist between ripening and weather anomalies. For each cultivar, ripeness advances or delays expressed in number of days to target the specific ripening threshold were assessed in relation to registered weather anomalies and the specific reference time period in the vintage. Precipitation of the warmest month and spring quarter are key to understanding the effect of climate change on sugar ripeness. Minimum temperatures of May-June bimester and maximum temperatures of spring quarter best correlate with altered total acidity evolution and pH increment during the ripening process, respectively.

Proteins constitute one of the three main components of grape juice and white wine, phenolic compounds and polysaccharides being the others. A specific group of the total grape-derived proteins resists degradation or adsorption during the winemaking process and remains in finished wine if not removed by the commonplace commercial practice of bentonite fining. While bentonite is effective in removing the problematic proteins, it is claimed to adversely affect the quality of the treated wine under certain conditions, through the removal of colour, flavor and texture compounds. A number of studies have indicated that different protein fractions require distinct bentonite concentrations for protein removal and consequent heat stabilization.

La maîtrise de la typicité du vin s’élabore au niveau local ou communal d’une exploitation viticole et/ou d’une cave, unité de vinification. La cave coopérative de Saint-Hilaire­-d’Ozilhan (AOC Côtes-du-Rhône), dont le territoire communal s’étend sur une superficie de 1 670 ha, couvre près de 310 ha cultivés en vigne. Elle réalise des vinifications «au terroir», en utilisant des regroupements d’unités de sol en 9 unités de terroir potentiellement viticoles, définies en s’appuyant sur la parenté des substrats. Diverses sélections d’une même unité peuvent aboutir aussi à des vins différents, ce qui suggère une hétérogénéité spatiale de certaines unités définies.

Due to climate change, the occurrence of heatwaves and drought events is increasing, with significant impact on viticulture. Common ways to adapt viticulture to a changing climate include site selection, genotype selection, irrigation management and canopy management. The latter mentioned being for instance source-sink manipulations, such as leaf removal, with the aim to delay ripening.

The chemical composition of grape berries at harvest is one of the most important factors that should be considered to produce high quality wines. Among the different chemical classes which characterize the grape juice, the polyphenolic compound, such as flavonoids, contribute to the final taste and color of wines. Recently, an innovative non-destructive method, based on chlorophyll fluorescence, was developed to estimate the phenolic maturity of red grape varieties through the evaluation of anthocyanins accumulated in the berry skin. To date, only few data are available about the application of this method on white grape varieties.