Carbonic maceration is a unique method of fermenting grapes into wine. While it doesn’t completely ferment all of the sugar into alcohol, it does impart a unique character on the wine.
What makes this method of fermentation so different is that you begin with whole, unbroken grape clusters still on the stems. The grapes are then placed in a sealed fermentation container filled with carbon dioxide.
The carbon dioxide discourages yeast fermentation and encourages enzymes naturally present in the grape to be released. Once released the enzymes break down the sugars into alcohol. Thus the sugars are fermented without the help of any micro-organisms.
The most notable wine produced using this method is Beaujolais Nouveau which is made from Gamay grapes. Characterized by its fruity flavors and lack of tannins, this red wine is meant to be consumed the same year the grapes are harvested. The entire process from harvest to bottling takes between six and eight weeks.
Traditionally Beaujolais Nouveau is available by the end of November in America. It has become somewhat of a tradition among winos to drink Beaujolais Nouveau at Thanksgiving.
Many believe that the quality of this wine in a given year is an early indicator of the quality of the entire vintage. Other wine makers and tasters alike believe this to be a bit of a stretch. Admittedly it is hard to imagine drawing any conclusions about an entire vintage based on a single style of wine that was cranked out in a matter of weeks.
To pull this off successfully you’re going to need to be very careful while handling your grapes to ensure that no grapes are broken open, this is critical. Take the unbroken fruit and place it in a seal-able fermentation container filled with carbon dioxide. This is done to prevent oxidation and to inhibit spoilage micro-organisms from taking hold.
With the grape clusters placed gently in the carbon dioxide flushed container seal the lid, place your airlock, and start monitoring the temperature. It takes approximately five to fifteen days for carbonic maceration to complete. During this time only about 3% alcohol by volume is produced. Thus you’ll need to follow this fermentation a yeast fermentation.
A lot of heat is generated during carbonic maceration. Make sure that the grapes don’t get too warm otherwise it may take on cooked flavors. Generally speaking keeping your temperature below 90° F / 32° C will prevent this.
After carbonic maceration has finished open the fermentation vessel and then crush and press your grapes to release the remaining sugars and the alcohol produced thus far. Once extracted the remaining juice should be stabilized and inoculated with your yeast of choice.
Traditionally a wine made this way would not spend any more time on the skins. Sufficient color, flavor, and aroma extraction is achieved during carbonic maceration thus an extended maceration is not needed. It is also important to limit tannin extraction so that the wine may be consumed sooner. More tannic wines need more aging to become palatable.
Amateur wine makers could use a plastic fermentation bucket with a sealing lid and airlock to perform carbonic maceration. Filling the container with carbon dioxide could be done one of a couple different ways. One option would be to purchase carbon dioxide tanks and simply purge the container. This requires you to have the proper hoses and regulators to work with the gas.
A second option would be to place food grade dry ice in your fermenter with the lid and airlock in place. As the dry ice sublimates carbon dioxide gas is released filling the container. It might be a good idea to have an extra piece of dry ice to put above the grapes after they’ve been added to be sure that as much oxygen as possible is displaced.
Not all dry ice is food grade however, so research this carefully. Even dry ice meant for cooling food may not be clean enough to actually mix with your wine. What you want is a dry ice meant to be used to make mixed drinks or in other modernist cooking methods.
Please be careful when working with both carbon dioxide and dry ice. Carbon dioxide is odorless, invisible, and heavy so it will pool up on the floor of an enclosed room. This is important to remember if you have pets or little ones who are much shorter than you are.
After carbonic maceration as well as crushing, and pressing your grapes be sure to allow the juice time to cool down to a reasonable temperature before you inoculate your yeast. A good temperature to shoot for is 80° F / 27° C or so.
Once your yeast of choice has started fermenting the remaining sugar you can complete the wine making process as you would for any other wine. Keep in mind that even if you used carbonic maceration of a red wine grape it won’t need to be aged all that long unless you extracted a lot of tannins.
Photograph by: Colby Otero