Red wine astringency: evolution of tribological parameters during different harvest dates

Among the items preserved in gene banks, the old standard and autochthonous varieties represent an increasing value, since these varieties may have properties to make their cultivation more effective under changing climatic conditions. The increasingly extreme weather is a huge challenge for the viticulture. Collectional varieties can also play important role in protection against pests and pathogens. A genebank ensures not only the preservation of rare varieties, but also gives the opportunity for more knowledge and research of these varieties.

Cognac vineyard is mainly dedicated to brandy production. Within the vineyard restructuring context, one part is turned over wine varieties for wine production (about 1,500 ha planted from 1999 to 2005). Today, the new wine producers need technical references about qualitative potential of the « Charentes Terroir », varieties and adapted vineyard management.
In order to answer to this professional request, an observatory of 18 plots of Merlot and 12 plots of Sauvignon have been laid out since 2003 and 2004 on various kinds of pedoclimate.

The objective of this study is to review the scientific evidences and to advance into the knowledge of the molecular mechanisms of astringency. Astringency has been described as the drying, roughing and puckering sensation perceived when some food and beverages are tasted (1). The main, but possibly not the only, mechanism for the astringency is the precipitation of salivary proteins (2,3). Between phenolic compounds found in red wines, flavan-3-ols are the group usually related to the development of this sensation. Other compounds, phenolic or not, like anthocyanins, polysaccharides and mannoproteins could act modifying or modulating astringency perception by hindering the interaction between flavanols and salivary proteins either because of their interaction with the flavanols or because of their interaction with the salivary proteins.

The terroir offers great variability in the typicity of the wines produced. Following tastings integrating several vintages, the multiple factor analysis of the sensory data revealed a group of taste criteria contributing to the notion of “Power”, referenced “Power and Harmony”, which makes it possible to differentiate wines from various terroirs of the Middle Loire Valley (Pages et al ., 1987).

Considérant d’une part la judicieuse mise au point d’un label de qualité contrôlée des miels suisses (STÖCKLI et al. 1997), considérant d’autre part l’élaboration d’une carte des paysages végétaux (HEGG et al. 1993),