Carbonic maceration is a winemaking technique, often associated with the French wine region of Beaujolais, in which whole grapes are fermented in a carbon dioxide rich environment before crushing. Conventional alcoholic fermentation involves crushing the grapes to free the juice and pulp from the skin with yeast serving to convert sugar into ethanol. Carbonic maceration ferments most of the juice while it is still inside the grape, although grapes at the bottom of the vessel are crushed by gravity and undergo conventional fermentation. The resulting wine is fruity with very low tannins. It is ready to drink quickly but lacks the structure for long-term aging. In extreme cases such as Beaujolais nouveau, the period between picking and bottling can be less than six weeks. During carbonic maceration, an anaerobic environment is created by pumping carbon dioxide into a sealed container filled with whole grape clusters. The carbon dioxide gas permeates through the grape skins and begins to stimulate fermentation at an intracellular level. The entire process takes place inside each intact berry. Ethanol is produced as a by-product of this process but studies have shown that other unique chemical reactions take place that have a distinctive effect on the wine. History The process of carbonic maceration occurs naturally in a partial state without deliberate intervention and has occurred in some form throughout history. If grapes are stored in a closed container, the force of gravity will crush those at the bottom, releasing grape juice. Ambient yeasts present on the grape skins will interact with the sugars in the grape juice to start conventional ethanol fermentation. Carbon dioxide is released as a by-product and, being denser than oxygen, will push out the oxygen through any permeable surface (such as slight gaps between wood planks), creating a mostly anaerobic environment for the uncrushed grape clusters to go through carbonic maceration. Some of the earliest documented studies of the process were conducted by the French scientist Louis Pasteur, who noted in 1872 that grapes contained in an oxygen-rich environment before crushing and fermentation produced wines of different flavors than grapes produced in a carbon dioxide-rich environment. This was because the fermentation process had already started within the individual grape clusters before yeasts were introduced during conventional fermentation. Wine production The use of carbonic maceration is closely associated with the production of Beaujolais nouveau wine from the Gamay grape in the Beaujolais region and