Macération carbonique is a vinification technique in which red grapes are macerated in an anaerobic environment. Entire bunches are placed in a sealed tank. The grapes at the bottom of the tank burst under the pressure of the mass of grapes and will start fermenting. The CO2 that is produced due to the fermentation drives the oxygen from the tank, creating an anaerobic environment. Because the first grapes (at the bottom of the tank) already ferment before the anaerobic environment is in place, this is also called Macération semi-carbonique. Therefore, strictly speaking, Macération carbonique should be done in small volumes so that the grapes are not crushed. CO2 gas is then added to these intact grapes in the tank to immediately create an anaerobic environment. Under these anaerobic conditions, a degradation process (autolysis) will take place in the intact grapes. The carbon dioxide permeates the grape skins and stimulates this process. The grapes are slowly broken down by the grape’s own enzymes and alcohol is produced in small quantities as a by-product. After this the grapes are pressed and the (aerobic) alcoholic fermentation takes place. The resulting wine contains many primary aromas and colorants that have been released by the autolysis, but is low on tannins. The macération carbonique method is used in particular in the Beaujolais for making the Beaujolais nouveau wines.