Fermentation starts within the grape itself for wines made using the carbonic maceration wine making method.
The bunches of grapes are placed whole in the vat. The lack of oxygen in the grapes causes the yeast to feed on the sugar. This way the enzymatic fermentation begins inside the grape itself and the bunches do not get in to contact with the grape juice.
By putting the grapes into the vat the grapes are crushed by their own weight and the first grape juice is extracted. The sugar in the grape juice is then mixed with yeast and the alcoholic fermentation begins. When the alcoholic fermentation is finished the grapes are pressed.
The carbonic maceration method is traditional in Beaujolais and Rioja Alavesa.
This special method is gradually gaining popularity in other regions.