Carbonic maceration

The carbonic maceration (in French: carbonic maceration ) is an oenological process for red wine extraction . In Beaujolais , this method is mostly used to produce Beaujolais Primeur.

Technology and metabolism

With carbonic acid maceration, the grapes that are as intact as possible - no destemping , no crushing - are stored as a whole grape in the fermentation container. This requires manual picking and careful transport, as well as careful relocation. The container is under CO ₂ - inert gas provided to protect the product against oxidation. The enzymes in the berries make up about 1.5% ethanol , glycerin and succinic acid ; Malic acid is broken down. These solvents in turn extract the color from the berry skin and polyphenols from the seeds. The extracted berries appear milky white and burst under the pressure of the resulting CO ₂ formation. The process was already described by Louis Pasteur as intracellular fermentation .

Instead of an artificial protective gas atmosphere, a mixed form of the technologies can also be used. For this purpose, part of the grapes is then conventionally destemmed, mashed and fermented. The resulting fermentation carbonic acid then displaces the oxygen upwards. This proportion can be up to 50%. Such a mixed form is called macération semi-carbonique .

Grapes used for carbonic maceration should have a soft berry skin that supports this technology. This also has an influence on the later type of wine.

The further winemaking proceeds according to conventional cellar technology.

Wine type

The resulting wine type is rather fruity and light and not as heavily tannic as the other types of wine that are otherwise widespread in France. This has the advantage that it can be consumed very quickly. A long ripening time to incorporate the tannins is not required. The product is already drinkable and bottled six weeks after the harvest. The wines thrive on their freshness and should therefore be drunk quickly.

The wines produced by means of carbonic acid maceration have typical aroma components that come from ingredients such as acetaldehyde , certain amino acids , ethyl acetate , glycerine and methanol , which are produced in larger quantities than usual. Glycerine e.g. B. can be present in a concentration that is up to ten times higher.

Problems with the vinification

First of all, the grapes must be stored very carefully without damaging the grape skin. The spontaneous fermentation can bring unwanted microorganisms advantages that make the later wine for off-flavors. By-products of the described metabolism are volatile phenolic compounds, which smell strongly of bananas and tropical fruits, one also speaks of "candy clay".

history

The macération semi-carbonique has probably always been part of the oenological process, since the processing of grapes was a bottleneck for some winemakers or was not handled consistently. In its pure form it was discovered by chance in France in 1934 when scientists were investigating how long or over what period of time table grapes can be kept fresh. The grapes were kept under the carbon dioxide protective gas envelope mentioned above at temperatures around 0 ° C. After two months, the grapes started to ferment anyway. The wine produced from it was lighter, fruity and less tannic than with conventional mash fermentation.