Vinification is the process of turning grapes into wine. It takes about 1.5 kg of grapes to make one litre of wine. The winemaking process involves several stages, including stemming, crushing, pressing, maceration, and finally, fermentation. The sequence of these steps differs according to the type of wine being made. Alcoholic fermentation is a major phase in the winemaking process: it is a natural phenomenon during which the sugars in the grapes are transformed into alcohol by the action of fermenting yeasts. This transformation is accompanied by the release of carbon dioxide.