What is carbonic maceration in coffee?

Carbonic maceration is a form of anaerobic fermentation borrowed directly from Beaujolais winemaking: whole coffee cherries are placed in a tank saturated with CO2, which triggers intracellular fermentation inside each berry before any external enzymatic activity kicks in. The cup signature: high-impact fruit, luminous red-fruit notes and a finish often compared to light red wine.

The technique was brought into specialty coffee by Australian-Serbian producer Sasa Sestic, who won the 2015 World Barista Championship with a carbonic-maceration coffee. It is a direct transposition of the method used for primeur wines in and around Lyon since the 1930s. In oenology, whole grape clusters are placed in a CO2-saturated vat: fermentation begins inside each berry, whose enzymes convert sugars into ethanol and signature aromas (banana, kirsch, sour candy). Applied to coffee, the principle is identical: whole cherries enter a sealed tank, and oxygen is flushed out by CO2 injection until saturation.

Over 48 to 120 hours, at 15-22 °C, two metabolic streams run in parallel: intracellular fermentation inside the cherries under CO2, and extracellular microbial fermentation in the juice pooling at the bottom. Lack of oxygen shuts down Acetobacter, narrows the yeast community to tolerant strains, and pushes the product toward fruity esters and lactic acids. After maceration, cherries can be depulped and then dried (carbonic washed variant), dried whole (carbonic natural variant), or treated with a thermal shock (brief hot-water bath) to stabilise the profile. Producers monitor Brix and pH on exit to standardise their lots.

In the cup, carbonic maceration delivers some of the most immediately recognisable profiles of modern specialty coffee: high-impact ripe red fruit, red-wine notes, griotte cherry, grenadine, sometimes fruit brandy. The body is syrupy, acidity soft and lactic, the finish long. Critics argue the method erases terroir — a carbonic Colombian and a carbonic Ethiopian can be hard to tell apart blind. Supporters, including much of Europe's barista scene in London, Copenhagen, Brussels and Ghent, see that as the point: process becomes a full ingredient alongside variety and altitude. In Brussels, Ghent and Antwerp, specialty cafés often list a carbonic lot on slow-brew as a signature discovery pour.

Carbonic maceration vs other fermentations