Carbonic maceration is an alternative winemaking technique that relies on enzymatic fermentation, with sugars converted to alcohol inside the grapes. The resulting wines are typically medium-bodied, offering a fun and fruit-packed expression of liquid joy, often with tropical notes and soft tannins.
Carbonic maceration, sometimes called whole-berry fermentation, is an alternative to the standard red wine production method, in which grapes are pressed and yeasts start fermentation in an aerobic (meaning oxygen rich) environment. For carbonic maceration, whole clusters of grapes are placed in a fermentation tank, which is then sealed. Grapes at the bottom of the vessel burst open due to the weight of the clusters above, and the wild yeasts present on the skins cause fermentation to begin. Before long carbon dioxide, a byproduct of fermentation, fills the top of the tank. As this occurs, enzymes within the rest of the grapes will do the job typically left to yeast. They will break down sugar and create alcohol – inside the berries themselves! When carbonic maceration is complete, the grape clusters are pressed and the juice allowed to rest in tank. Oak barrels may or may not be used during aging.
Wines made this way are distinctive, to be sure. Since a significant portion of fermentation occurs inside the grapes, the resulting wine exhibits exuberant fruitiness, like tropical punch with a kick! In addition, the much lower degree of skin contact means fewer and softer tannins. While theoretically carbonic maceration could be applied to any grape, it works best with naturally fruit-forward varietals like Gamay, the red grape of Beaujolais. In fact, all Beaujolais Nouveau is made via carbonic maceration.
Of course, there are times when a winemaker will choose to utilize partial carbonic maceration. He or she can stop the carbonic process while there is still residual sugar in the must. Then the juice can be fermented via the usual, aerobic process until it reaches the desired level of dryness. This approach results in a wine that offers that signature juicy fruit, but with additional structure and depth. Wines from the Beaujolais Crus—ten villages that produce the finest examples from the region—typically use this approach. A great many Cotes-du-Rhone reds do as well, and there are other examples from around the world.
Carbonic maceration may not be the most common fermentation method, but wines made this way are definitely worth checking out.