Carbonic Maceration

Carbonic Maceration is a red wine-making process in which a small amount of sugar is transformed into ethanol through the ‘self-destruction’ of whole grapevine berries without the intervention of yeasts. It is used typically to produce light-bodied, brightly coloured, fruity red wines for early consumption, most famously in the Beaujolais region of France.

Whole bunches of grapes are carefully placed into a tank in an anaerobic (oxygen-free) atmosphere, using carbon dioxide from gas bottles or from fermenting must. An intracellular fermentation takes place within the intact berry and a small amount of ethanol (around 2%) is formed, along with traces of many aromatic compounds, such as glycerol. There is also a decrease in malic acid levels and an increase in pH. The maceration period is usually between 1 – 3 weeks. After a while, the weight of the upper grapes splits the berries in the lower layer which begin to ferment in the normal way. The wines produced tend to have a very particular aroma reminiscent of bananas, kirsch, cherry and plum.

The technique is ideal for making early drinking ‘primeur’ wines and for adding complexity to wines fermented in the traditional fashion. Many winemakers keep a proportion of their vintage whole in order to encourage some carbonic maceration flavours.