Veraison passed from about a month: The harvest will begin soon !
It's time to control precisely ripeness to estimate precisely the date of harvest and eventually forecast any additional operations to be carried out during the vinification.
To do this we conduct sampling of berries on every parcels in order to have a "snapshot" of the vineyard. Of course, this sampling must be rigorous and regular to be representative.
The first part of the berries (on the picture, you see each sample in plastic bag) is analyzed in the laboratory.
Three main parameters are measured, and more than the results, their evolution until harvest must be considered :
First is the alcoholic level which correspond to the measure of sugar in the grapes (yeasts convert about 17 grams of sugar per liter of grape juice to get 1 %vol of alcohol). The sugar concentration increased regularly until stabilizing at maturity and to assert AOC Cahors, 11.5 %vol of alcohol at least are required in the wine.
Second is total acidity which is the sum of the acids in grape berries that you find later in wine. It decreases until maturity before stabilization.
Finally the pH, which measures the strength of acids and is essential for aging of wine.
We complete these analysis by tasting berries, which is essential for estimating the aromatic potential and cellular decomposition of the skin and the astringency of the tannins of the pips which when ripe, have a characteristic "nutty" aroma or even "roasted".
So the date of the harvest will be determined taking into account in addition to the present and future health of the vine, particularly considering weather forecast conditions.