The Methods of the Makers: Carbonic Maceration

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Studying Viticulture and Oenology at Stellenbosch University in South Africa, furthered my fascination in the wide variety of wine making techniques and the wine styles that they produced. I am particularly interested in the revival and repurposing of traditional and even ancient methods, to craft the fashion of today. Join me as I explore and explain the tricks of the trade in my new blog series - 'The Methods of the Makers'

First up - Carbonic Maceration. There has been quite the buzz surrounding carbonic maceration, with the winemaking style firmly in fashion,  more and more producers out of Beaujolais are making use of the technique.

From Vine to Wine

To understand carbonic maceration, we must first quickly look at how traditional alcoholic fermentation takes place. To simplify everything, let us address this technique in the context of red wine fermentation only.

When grapes are harvested, they are received in the cellar and processed. Traditionally this is done by undergoing the following steps.

Destemming and sorting from aboveAfter destemming the grapes are inspected using the sorting line, funnelling individual grape berries into the crush

Destemming releases the grape berries from the stem. Destemming is a crucial step when working with a cultivar such as Cabernet Sauvignon, as the stem often hasn’t ripened by the time of harvest. If unripe stems remain with the bunches during fermentation, they impart aggressive bitter tannic compounds in the wine. 

white grape crushingGrapes going through the crusher, done in the exact same way regardless of grape colour 

From here the all-important sorting takes place, getting the chance to pick out less-than-optimal fruit, berries that haven’t ripened or are mouldy, removing leaves and any other unwanted debris. The big difference between a good wine and great wine starts with rigorous sorting. The sorted berries are sent to the crusher which, releases the juice from within the grape.

Red wine fermentation occurs on the skins of the grape. In the skin we find the building blocks of what gives red wine its colour, anthocyanins are able to bind with many other components found within the grape juice and fermentation must. The combinations of which are responsible for the depth of colour in a red wine. The majority of grape tannins are also found in the skin, giving the grippy mouthfeel you commonly associate with red wine, further contributing to the colour stability of the wine, and the flavour profile.

From the crush everything is pumped into a stainless-steel tank, often winemakers will leave the grape juice and skins to “cold soak”. Wherein the tanks temperature is set very low to delay the fermentation process. Allowing time for the better extraction of colour and primary aromatic compounds, prior to fermentation.

Alcoholic fermentation is the chemical reaction that takes place, converting the sugars in the grape juice into alcohol by yeast. Fermentation can occur naturally by allowing the natural ambient yeast found on the berries skins to get to work. Alternatively, a yeast addition can be made, winemakers carefully consider which yeast will best enhance the specific grape characteristics in the wine.

Grape skins after fermentationGrape skins after fermentation are hand loaded into the press

So, what is carbonic maceration?

Carbonic maceration occurs when whole bunches of grapes, uncrushed and unbroken, are placed in a carbon dioxide rich tank. The lack of oxygen causes the grape berries to undergo intracellular fermentation. For this reason, it is easier to understand that the grape clusters have to be hand harvested, as an altercation to the berries or becoming loose from the rachis, reduces the amount of carbonic maceration that is able to take place.

Hand harvested grapes

Small amounts of ethanol are produced from the intracellular fermentation, around 1.5-2%. This phenomenon produces beneficial by-products that enhance the phenolic composition of the berries and change the mouthfeel of the end wine. Once intracellular fermentation reaches 1.5-2% the berries naturally burst, releasing the juice into the tank. The winemaker will send the grapes to the press or manually breakdown the grapes and alcoholic fermentation will continue as normal.

In theory all the whole bunches in the carbon dioxide rich tank undergo carbonic maceration, however the reality is rather different. The bunches at the bottom of the tank get crushed under the weight from above, beginning normal alcoholic fermentation. It is only the top bunches that ever truly undergo pure intracellular fermentation. Never the less a distinct and recognizable flavour profile still prevails.

The Flavour Profile

Due to the unique reactions that occur within the grape during carbonic maceration, as you can imagine there is a unique and specific tasting profile to match. Larger aromatic compounds are broken down and reform to create the main aroma compounds associated with wines having undergone carbonic maceration. The first is known as benzaldehyde and gives the wine notes of almond, cherry and kirsch. Kirsch is the overwhelming descriptor used when describing a carbonic wine. From here the names are a little easier and make more sense; vinylbenzene as the name suggests has a plastic scent and ethyl cinnamate has a cinnamon aroma.

Why Do It?

Carbonic maceration produces wine that are fruit forward, lighter in style, bright red in colour, low acid, low tannin wines that are intended to drink young. Usually, a technique associated with the Gamay grape in the Beaujolais region, and is becoming ever more popular with winemakers around the world.

Next time we will have a look at the Beaujolais region, having a look at where it all started and giving some examples of Roberson Wines you can try.

Can't wait? Try....

Domiane Dupeuble has been making wines from Gamay since 1512. Vines are tended on granite soils without the use of chemicals or additives. The wines are of incredible value, and stand up to Pinot Noir from Burgundy. 

The wine is bright red in colour, capturing you from the minute it enters your glass. Fruit forward raspberry, blackberry and blueberry give the wine an intensely concentrated body. Once the fruit notes wash away you are left with a gorgeous lingering cinnamon spice. A young and lively wine that is the perfect example of a Beaujolais wine. 

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