Contribution of viticultural and oenological factors to the aromatic potential of white Colombard wines from the south west of France Gascony vineyard

The aim of this work is to determine the influence of viticultural and oenological factors to the aromatic potential of white wines from Colombard variety in the south west of France Gascony vineyard. The main aromatic sensing of Colombard wine comes from two varietal thiols: 3-MercaptoHexan-1-ol (3MH) and its acetate (Ac3MH). These compounds are released by enzymatic activities from yeasts during alcoholic fermentation.
The protocol consists to uptake 65 samples of grapes at their arrival in the wineries during harvest. With them, we have constructed a data base including agronomical-viticultural factors and chemical analysis on grape and must. Further, the grapes have been processed into white wines in our experimental winery at a pilot scale of 25 liters in standardized conditions. Some oenological variables as fermentation rate or turbidity have been associated to the base.
These data have been explored in the order to predict the concentrations in varietal thiols in wines and also in relation with sensory perception by expert winemakers.
First results show that, for the vintage 2006, training system factors do not mainly contribute to the aromatic potential of the wine. Nitrogen concentration of the must, inducing high fermentation rate appears to be more reliable with varietal thiols concentration in wine. Also, samples harvested in the later period show a higher aromatic level in both 3MH and Ac3MH.