Carbonic maceration

Carbonic maceration begins with whole, uncrushed grape clusters placed in a sealed vessel, which is then flushed with carbon dioxide to displace oxygen. The grapes at the bottom are crushed by the weight of the fruit above, releasing juice that undergoes conventional yeast fermentation, while the intact berries above ferment internally via anaerobic metabolism. Inside the berries, enzymes convert malic acid to ethanol and other compounds, producing distinctive aromas of banana, bubblegum, and kirsch. The process typically lasts 5–10 days, after which the grapes are pressed and the juice is finished with a standard fermentation. The technique is distinct from semi-carbonic maceration, where the CO₂ is generated by the fermentation itself rather than added externally.

The technique has been used in the Beaujolais region for centuries, but it gained international fame with the introduction of Beaujolais nouveau in the mid-20th century. The wine, released on the third Thursday of November, is made exclusively from Gamay grapes using carbonic maceration, resulting in a fresh, fruity wine meant for immediate consumption. The method is also employed in other French regions like the Loire Valley and in countries such as Spain, Italy, and the United States, often for producing easy-drinking reds from varieties like Grenache and Syrah. In some cases, winemakers use a partial carbonic maceration to add complexity to wines that also undergo traditional fermentation.

Wines produced by carbonic maceration are characterized by low tannins, low acidity, and bright, fruity flavors, often with notes of red berries, banana, and a distinctive 'fruity' ester profile. The technique reduces the extraction of phenolic compounds, leading to a lighter color and softer mouthfeel compared to conventional red wines. The presence of volatile compounds like ethyl cinnamate and isoamyl acetate contributes to the characteristic aromas. These wines are typically best consumed young, as they do not develop complex tertiary flavors with aging. The method also affects the concentration of anthocyanins, resulting in a more vivid but less stable color.

Beyond its use in red wines, carbonic maceration has been experimentally applied to white grapes, producing unusual, low-alcohol wines with tropical fruit notes. The technique is also used in the production of some rosé wines, where it imparts a distinctive fruitiness. In the Jura region of France, a variation called 'macération carbonique' is used for the rare 'vin jaune' style, though it is not the primary method. Some winemakers use carbonic maceration to soften wines from high-tannin varieties like Tannat, making them more approachable. The process also has a historical connection to the 'whole-berry fermentation' used in ancient winemaking, though the deliberate use of CO₂ is a modern innovation. Additionally, carbonic maceration has been studied for its potential to reduce the need for sulfur dioxide, as the anaerobic environment inhibits spoilage organisms.

Gamay

A red grape variety most associated with Beaujolais, known for producing light, fruity wines.

Malic acid

An organic acid found in grapes that is converted to ethanol during carbonic maceration.

Semi-carbonic maceration

A variation where CO₂ is produced by the fermentation of crushed grapes rather than added externally.