Harvest is the highest time of the year for any wine maker. During harvest, the grapes are cut from the vines and brought to the winery, where they are treated and transformed into wine.
MATURITY OF THE GRAPES AND HARVEST
Deciding when to start harvesting the grapes is always very challenging. The ideal is to collect grapes when they have reached their optimal maturity. The optimal maturity of the grapes depends greatly of the type and the style of wine one makes, but the way maturity is measured is constant. It depends on 3 factors: Sugar concentration, Acidity in the grapes, and Color for the red grapes.
Measuring the richness in sugar with a refractometer
Sugar
Thanks to photosynthesis, the quantity of sugar keeps growing in the berries. The richer in sugar the grapes are, the more mature they are, and the higher the level of alcohol in the wine will be. When the grapes are ripe, the vine stops synthesizing sugar. The concentration of sugar in the berries increases by dehydration.
Acidity
As the concentration of sugar increases, the total quantity of acidity begins to drop. Of the 2 main acids in the grape (tartaric acid and malic acid) malic acid is the one that drops the fastest. The decrease of the amount of malic acid in the berries is a sign of maturity.
Tannins
With red varietals, the quantity of extractable tannins is also a precious indicator of the maturity of the grapes.
The optimal maturity of the grapes is when the sugar level, the acidity and the tannins are at the desired level for the wine. As it shows on the curves, the evolution of the sugar, the acidity and the tannins in the grapes follow different paths, so the decision to harvest the grapes needs to find a compromise between these 3 factors.
GRAPE HARVESTING : HAND OR MACHINE?
Grapes were traditionally harvested by hand. It is still the case in many vineyards in France. it is even mandatory to do so in some appellations, such as Champagne or Beaujolais villages.
Since the 70's, vines can also be harvested by machine. With a machine, the machine shakes the berries from the stalks. They are collected by conveyor belt.
