Grapes should be harvested at their optimal physiological maturity. In red varieties this means when the tannins.
At this point we initiate the maturation phase usually in oak barrels or in oak tanks and.
The winemaker, adds nutrients for the yeast and estimates the time the juice will be in maceration with.
White grapes instead are not fermented with the skins, but rather just the juice (therefore they are.
The enologist is trained to evaluate the quality by the taste the grapes in the vineyards as well.