Effects of mesoclimate on the yield, quality and phenolic maturity of Grenache

Wine production is a complex biochemical process that involves a heterogeneous microbiota consisting of different microorganisms such as yeasts, bacteria, and filamentous fungi. Among these microorganisms, yeasts play a predominant role in the chemistry of wine, as they actively participate in alcoholic fermentation, a biochemical process that transforms the sugars in grapes into ethanol and carbon dioxide while producing additional by-products. The quality of the final product is greatly influenced by the microbiota present in the grape berry, and the demand for indigenous yeast starters adapted to specific grape must and reflecting the biodiversity of a particular region is increasing. This supports the concept that indigenous yeast strains can be associated with a “terroir”.

The synthetic herbicide glyphosate has been used extensively in viticulture over many decades to combat weeds. Despite this, the possible influence of residual glyphosate on both the alcoholic fermentation of grape juice and the subsequent metabolite profile of wines has not been investigated. In this study, Pinot noir juice supplemented with different concentrations of glyphosate (0 µg L-1, 10 µg L-1 and 1000 µg L-1) was fermented with commercial Saccharomyces cerevisiae yeast strains. Using a combination of analytical methods, 80 metabolites were quantified in the resulting wines.

L’observation est effectuée entre 1996 et 1998. L’expérience a commencé avec des clones numérotés: 75, 95, 96 et 227 de la variété Chardonnay. Le porte greffe est le Kober 5 BB. La forme de conduite est le cordon. La taille est longue. La densité de plantation est 3,5 x 1 mètre (2857 ceps par 1/ha).

Winegrowing is still characterized by the extensive use of chemical fertilizers and plant protection products, despite strong recommendations to limit these practices. A part of these xenobiotics and metals are then found in grape juice and wine, causing a major health concern, as well as negatively affecting the fermentation process. In recent years, there has been renewed interest in non-Saccharomyces yeasts. These species have a wide phenotypic diversity, which would be exploited to broaden the aromatic palette of wines.

Climate change is having an unprecedented impact on the wine industry, which is one of the major agricultural sectors around the world. Global warming, combined with the variation in rainfall patterns and the increase in frequency of extreme weather events, is significantly influencing vine physiology and exposing, more frequently, plants to severe biotic and abiotic stresses. This represents a challenge for viticulturists who need to take complex decisions to adjust vineyard management and achieve oenological goals.