What is carbonic maceration?
You’ve probably seen the words ‘carbonic maceration’ before, perhaps on the label of a wine bottle, or in the description of a wine you’ve browsed online, but what is it? Carbonic maceration and semi-carbonic maceration are winemaking techniques aimed at creating a different style of wine.
Justo González Morilla | 14th August 2019
First, the science behind it
Let’s start with full carbonic maceration. First, whole bunches of grapes are carefully placed into a sealed stainless steel vat, filled with carbon dioxide. As there’s no oxygen a special fermentation reaction starts at the intracellular level, brought about by complex enzyme reactions. This reaction differs from that of yeasts or other microbial organisms. It produces alcohol and other compounds such as volatile esters (these are what give wines, certain aromas). The reaction also forces the grapes to split open and release their juice. When the alcohol level reaches around 2%, the enzymatic reaction naturally ceases.
Next, the winemaker presses the grapes, to extract the fermenting juice and transfers it to another container (usually another vat, or a barrel). Yeasts are then added, and contact with oxygen will finish the job of transforming all of the sugar into alcohol. Full carbonic maceration is actually quite a rare winemaking technique, but one famous example of where this is used popularly is in Beaujolais Nouveau.
Semi-carbonic maceration follows the same principle, but this time, the whole bunches of grapes are thrown into a container only partially filled with carbon dioxide (sometimes none). The grapes at the very bottom, are crushed from the pressure and weight from the pile of bunches on top. The juice from these crushed grapes in contact with the wild yeasts present on their skins start a normal fermentation process which releases further carbon dioxide. The gas, in turn, fills up the container creating an oxygen-free environment that favours intracellular fermentation that we mentioned earlier.
Semi-carbonic maceration creates wines with more colour and tannins than full carbonic maceration, but less noticeable aromas of confectionary. These wines can be sold as such or used in blends to increase the final wine’s fruitiness or enhance its complexity.
Next, let’s dive into the history
Carbonic and semi-carbonic maceration have one flagship wine and region, Beaujolais, France. If you’ve had a Beaujolais wine before (Beaujolais Nouveau, Beaujolais AOC, Beaujolais Villages) you can probably recognise its distinctive profile.
The father of the current modern technique of carbonic maceration is considered to be Jules Chauvet, a chemist, a Beaujolais winemaker and a pioneer of natural winemaking. The newer style of wine, Beaujolais Nouveau took hold in the region and unfortunately didn’t have an immediate positive impact on the image of Beaujolais wine.
It jumped on to the international stage, selling an image of cheap, fruity and unfussy wines. This affected the reputation of the 10 ‘cru’ appellations of the region (Moulin-a-Vent, Fleurie, Morgon, etc.) which almost vanished from people’s minds. This happened during the 1970s when Beaujolais or ‘Bojo’ day became a national event in France and attracting international attention. Beaujolais Nouveau officially goes on sale on the third Thursday of November, not long after its harvest.
Other regions that have been using semi-carbonic maceration to produce young, juicier and uncomplicated wines are Rioja, Spain (notably in Rioja Alavesa), the Loire valley’s production of some Cabernet Francs, and California with its production of some Zinfandels.
Profile of the wine
A winemaker might choose to apply carbonic maceration or semi-carbonic maceration for two main reasons. One is to lower the tannins of the resulting wine. For example in grape varieties well-known for producing very tannic wines such as Carignan, Cabernet Sauvignon or Mourvedre. This technique will produce a wine version of these grapes that is more approachable and easy-drinking and definitely meant to be drunk young.
The second reason is to intensify the fruity character of the wine. Apart from the intensity, it also adds distinctive aromas of confectionary, bubblegum, banana, Kirsh, cinnamon, and candy floss. How strong these aromas are, will depend on whether full or semi-carbonic maceration took place, and how much of the blend went through these processes.
The common telltale sign of carbonic or semi-carbonic maceration is the presence of bubblegum or candied fruit aromas, although it will not always be obvious and will depend on a few different factors, one of them being the grape variety used.
Besides the aromas, the amount of tannins is significantly lower and so is the acidity, although to a lesser extent, which means the wine is lighter in body. This style makes a perfect wine to be drunk by itself and should ideally be served slightly chilled. Those white wine drinkers looking to flirt with red wine should definitely try this style of wine first. In any case, wines made with these techniques, won’t benefit from bottle ageing and will likely develop unwanted or unattractive aromas as time goes by.
As the release date for Beaujolais Nouveau 2019 is soon approaching why not set a reminder in your calendar, then get your hands on a bottle or two and share with a few friends? If you haven’t tried Beaujolais before, I’m sure you’ll make it your next guilty pleasure.