Below is the January article. Hopefully I can get this working how I want it and this will become that submission.
Many of the wines produced in the Beaujolais region of France use a particular type of maceration that intends to help preserve the aromas and flavors expressed in the fruit. It is called semi-carbonic maceration. Although this process is used for Beaujolais Nouveau, it is also frequently used for many other of its more traditional and “serious” Beaujolais wines. This particular type of maceration is also widespread around the world, where consumers have responded to the quality of wines produced with this method.
The first thing coming to mind is the peculiarity of the term: why carbonic?, and even more interesting, why is it semi-carbonic? Let’s see what it really entails.
Semi-Carbonic Maceration: First Alcoholic-Fermentation Stage
Before picking the grapes, the winemaker must plan carefully how she is going to conduct the process and all its steps, as an error can have undesirable consequences. Since it involves CO2, a gas that displaces air and the oxygen it contains, workers must be careful.
The grapes in Beaujolais are usually hand-picked and put in tanks without discarding the bunches’ stems. These grapes go into tanks but they are neither pressed nor crushed. As more grapes accumulate in the tank, the sheer weight over the bottom grapes will make them burst or open. Juice from these grapes will start accumulating at the bottom of the tank.
Natural yeasts on the grape skins will immediately start a normal fermentation process on the juice. Since this is the well-known and usual fermentation process, CO2 will be produced. Since the density of CO2 is higher than that of regular air, it accumulates in the tank’s bottom and drives away the normal air in the tank. This creates an anaerobic environment for the middle and lower parts of the tank. Yeasts carrying out the alcoholic fermentation at the bottom of the tank need oxygen to perform their work. As oxygen disappears, they die off and the alcoholic fermentation ceases.
It is worth noting that some winemakers attempt to have a better control of the process by adding CO2 directly into the tanks when they consider the alcoholic fermentation has reached the stage they desire.
Now, the free-run juice at the bottom of the tank, the one that has undergone a traditional alcoholic fermentation through yeasts is racked off and collected.
Semi-Carbonic Maceration: Enzymatic Fermentation Stage
The anaerobic environment then starts an enzymatic and biochemical fermentation process inside the grapes that are intact. This enzymatic fermentation creates a small amount of alcohol but through a completely different set of chemical reactions: some 2% of the malic acid in the grapes is converted to ethanol. This gives the juice a smoother taste, as the malic acid tends to give it a rough, strong feeling in the palate. Additional compounds are also created that give the wine an aroma and taste of candy, raspberry, cranberry, bananas and pears.
Semi-Carbonic Maceration Method: Second Alcoholic Fermentation Stage
The grapes that have undergone the intra-berry enzymatic fermentation are then collected and pressed. This creates a second volume of juice, but this one is different since it contains less malic acid—remember it was converted to alcohol—and a substantial amount of sugars.
The free-run juice that underwent the first alcoholic fermentation is now blended with the newly-pressed juice and they undergo a traditional alcoholic fermentation. This new fermentation will be done by yeasts and will have no contact with the grape skins. This process creates a light wine with powerful aroma and flavors of fruits and flowers. It will be characterized by lighter tannin content.
Semi-Carbonic Maceration Method: Final Stages
At this point, what happens to this wine depends on the desire of the winemaker. Usually the wine goes through malolactic fermentation, where more of the malic acid in the wine is converted into lactic acid. This softens the wine more. However, malolactic fermentation is different since it is a process driven by bacteria and not by yeasts. The wine may then be set to age either in oak casks or, more frequently in Beaujolais, in concrete or stainless-steel tanks. Aging may be carried out on its lees, if the winemaker wants to add that flavor to the finished product.
Semi Carbonic Maceration: Now You Know
We hope that by now you know: it is carbonic because carbon dioxide (CO2) plays an important role in causing one of the fermentations (the enzymatic fermentation) and stopping another (the first alcoholic fermentation). It is semi-carbonic because only one of the two-fermentations is caused by the CO2. And it is a maceration process because most of it happens when the skins and the juice are in contact.