Évolutions qualitative et quantitative des flores microbiennes de moûts de pommes à cidre au cours de la fermentation: relations avec le terroir et la composition physico-chimique des fruits

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Winemaking generates significant amounts of by-products, such as grape pomace and wine lees, which are primarily used for distillation and composting.

Dans le cadre de recherches sur la mise en évidence et le déterminisme d’un «effet terroir »un réseau de parcelles du cépage Cabernet Franc greffé sur S04, a été suivi de 1979 à 1990 en Val de Loire (A.O.C. Saumur-Champigny, Chinon et Bourgueil). Des analyses chimiques (N,P, K, Ca, Mg, Fe, Mn, Zn) ont été réalisées sur le sol, les feuilles au stade véraison, les moûts en cours de maturation et à la vendange et enfin sur le vin, pour 18 sites (répartis dans 12unités terroirs de base) et 7 millésimes différents.

Grapevine physiology and production are challenged by forecasted increases in temperature and water deficits. Within this scenario, photoselective overhead shade films are promising tools in warm viticulture areas to overcome climate change related factors. The aim of this study was to evaluate the vulnerability of ‘Cabernet Sauvignon’ grape berry to solar radiation overexposure and optimize shade film use for berry integrity. A randomized complete block design field study was conducted across two years (2020-2021) in Oakville, Napa Valley, CA, with four shade films (D1, D3, D4, D5) differing in the percent of radiation spectra transmitted and compared to an uncovered control (C0). Integrals for gas exchange parameters and mid-day stem water potential were unaffected by the shade films in 2020 and 2021. By harvest, berries from uncovered and shaded vines did not differ in their size or primary metabolism in either year. Despite precipitation exclusion during the dormant season in the shaded treatments, yield did not differ between them and the control in either season. In 2020, total skin anthocyanins (mg/g fresh mass) in the shaded treatments was greater than C0 during berry ripening and at harvest. Conversely, flavonol concentrations in 2020 were reduced in shaded vines compared to C0. The 2020 growing season highlighted the impact of heat degradation on flavonoids. Flavonoid concentrations in 2021 increased until harvest while flavonoid degradation was apparent from veraison to harvest in 2020 across shaded and control vines. Wine analyses highlighted the importance of light spectra to modify wine composition. Wine color intensity, tonality and anthocyanin values were enhanced in D4 whereas antioxidant properties were enhanced in C0 and D5 wines. Altogether, our results highlighted the need of new approaches in warm viticulture areas given the impact that composition of light has on berry and wine quality.

Une étude préliminaire des situations météorologiques journalières a été réalisée pour l’Afrique du Sud et pour les mois de février (période de maturation des raisins dans la Province occidentale du Cap), à l’image de la classification synoptique réalisée aux latitudes tempérées en France (Jones & Davis, 2000), afin d’étudier les relations entre le climat et la viticulture à des latitudes plus basses.