After the harvest, the white berries are squeezed in a mill. The result is the so-called mash. For white wine production, the mash is squeezed either directly or after a short life. The resulting juice, the "must" is stored in tanks and begins to ferment there. Fermentation is initiated by yeasts, which are a natural part of grapes and juice, or are added as pure cultures. It is formed from the fructose of the grapes alcohol and carbon dioxide. Any non-fermented fruit sugar remains in the wine and is called residual sugar.
In the case of red wines, the red grapes are usually destemmed directly after harvesting. By this measure, an undesirably high tannin content is avoided. In contrast to the white wines, the red wines are fermented for at least 10 to 12 days under careful supervision on the mash. The resulting alcohol or heating dissolve the color pigments and other important ingredients from the berry skins.
By storing in large oak barrels, the full-bodied red wines are harmonious, velvety and round.
Common to both is that they are made from red wine grapes but processed like white wine grapes. Some red wine grape varieties have white fruit juice, the dyes are usually located only in the berry skins. Some of the color pigments from the berry skin go into the juice when pressed.