Carbonic maceration

Carbonic maceration means fermenting whole coffee cherries — skin, fruit and seed intact — inside a sealed tank filled with carbon dioxide, so the fruit ferments from the inside out before anything is crushed or pulped. It is lifted, name and all, from winemaking.¹²

Royal Coffee’s technical guide gives the wine lineage in one line: carbonic maceration is “a term lifted from the wine industry, where whole grapes are fermented without pressing the juice”.¹ The same idea, applied to coffee: instead of squeezing the fruit off first, you leave the cherry whole and let the fermentation happen inside it.

This makes carbonic maceration the strictest, most specific member of the anaerobic family — it is one particular way of running a sealed, oxygen-starved ferment, defined by keeping the cherry intact and flooding the tank with CO₂.³

What actually happens in the tank

Royal Coffee describes a workflow that looks a lot like any sealed ferment, with one decisive difference at the front:¹

1. Sort by floating. The cherries are “siphoned to remove low-density ‘floaters’” — the underripe, hollow or insect-damaged fruit that bobs to the top of water.
2. Seal, whole. The remaining cherries “added to an airtight tank with a one-way valve” — the same one-way fitting every sealed ferment needs so carbon-dioxide pressure can escape but no air gets back in.
3. Flush with CO₂. Carbon dioxide is pushed into the tank to drive the oxygen out from the start, rather than waiting for the microbes to breathe it up.
4. Ferment slowly, inside the skin. “Because the skins of the cherries are left in tact, fermentation may take days or weeks” — far longer than a conventional open-tank ferment measured in hours.

Royal Coffee adds a detail the shorter guides skip: pressure in a full tank is not even. “Varying levels of pressure in the tank create different available sugars and pectins for the microbes to macerate” — cherries at the bottom are pressed by the weight above them, while those at the top ferment “slowly and almost entirely inside the skin of the fruit”.¹ So a single tank runs two ferments at once.

The one thing that separates it from “anaerobic”

The dividing line is what goes into the tank, not how much oxygen is in it. Royal Coffee states it plainly: “The main thing that differentiates anaerobic coffee fermentation from carbonic maceration of coffee is that in carbonic maceration the cherry is left in tact, and not pulped prior to entering a sealed tank.”¹

	Goes into the sealed tank	Fermentation site
Carbonic maceration	Whole cherries, skin on	Inside each intact fruit
Anaerobic fermentation (typical)	Depulped seed + mucilage	On the seed, in the shared liquid

You will also see semi-carbonic maceration — a looser version where the tank starts with some air still in it rather than a pure CO₂ flush, before the microbes finish stripping the oxygen themselves.

To verify

In practice the two words blur, and no standards body defines either. The clean whole-cherry-vs-depulped split above is Royal Coffee’s; other sources put whole cherries under the anaerobic umbrella too (see Anaerobic fermentation, which keeps that broader usage). Because no trade body or standards organisation publishes a definition of “carbonic maceration” or “anaerobic” for coffee, a bag labelled one may describe the same tank as a bag labelled the other. Read the producer’s own protocol where one exists rather than trusting the word on the label.

Where it came from

Carbonic maceration is a Beaujolais technique — the method behind that region’s light, fruity red wines, where whole grapes ferment intracellularly in a CO₂-rich vat before pressing. Adapting it to whole coffee cherries is the direct ancestor of the sealed-tank experimentation that reshaped specialty coffee in the 2010s.¹²

Who first carried it into coffee is disputed, and this wiki does not settle it.

To verify

The Sasa Sestic / 2015 story is uncorroborated here. Sasa Sestic is widely credited with porting carbonic maceration from wine to coffee and using a carbonic-macerated Colombian lot to win the 2015 World Barista Championship. This wiki has been unable to confirm that account against a primary source — see the fuller discussion and the competing Daterra/Beaujolais origin story on Anaerobic fermentation. Treat any first-date or inventor claim as unverified.

What it tastes like, and why

The reported cup is the same loud, fruit-forward, wine-like profile as anaerobic lots generally — “intense, candy-like fruit notes,” smooth body, and vinous or spirit-like character — because the underlying chemistry (a long, oxygen-starved, lactic-leaning ferment) is the same.⁴³ Some roasters also describe fruit-forward, earthy notes and a buttery sweetness in carbonic lots specifically.³

These are tasters’ descriptions, not measurements. The reason carbonic maceration can push flavour this far is time: keeping the skin on lets the ferment run for days or weeks without the spoilage that would wreck an open tank, and that long, slow maceration is where the intensity comes from.

Why it matters

Carbonic maceration is the purest expression of the argument running through all of experimental coffee processing: is the flavour coming from the farm or from the fermentation? By leaving the cherry whole and driving the ferment with CO₂ and time, the producer takes maximum control of the cup after the picking is done — which is exactly why the intense, showy results delight some buyers and worry others who ask whether the coffee’s origin is being revealed or buried. That debate is covered in full on Anaerobic fermentation and Coffee fermentation.

For a reader, the shortcut: “carbonic maceration” on a bag promises the same wine-like intensity as “anaerobic,” with the extra signal that the cherries went into the tank whole — but the terms overlap so much that the promise, not the precise method, is the reliable part.

Related

• Anaerobic fermentation · Coffee fermentation — its parent family and the umbrella science
• Washed process · Natural process · Honey process · Pulped natural — the drying methods a carbonic lot still has to finish as
• Coffee cherry — the whole intact fruit the method depends on
• Cupping · Coffee scoring · Q Grader — how the resulting cup gets judged
• Project Origin — the green coffee buyer that sells a carbonic-maceration range, CM Selections, as a catalogue line
• Daterra · Sasa Sestic · World Barista Championship · Geisha · Best of Panama · Cup of Excellence

Official links

• Official site — Specialty Coffee Association (coffee standards and green-coffee research)

Footnotes

1. Royal Coffee — A Guide To Carbonic Maceration And Anaerobic Fermentation In Coffee — green-coffee importer’s technical guide; the whole-cherry/depulped distinction, the siphoning-and-valve workflow, the “days or weeks” duration, the wine-industry lineage and the uneven-pressure detail all confirmed via WebFetch ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

2. Daily Coffee News (Roast Magazine) — A Guide to Carbonic Maceration and Anaerobic Fermentation in Coffee (3 June 2019) — cited in the research report as calling these “emergent processes gaining rapid popularity”; WebFetch returned HTTP 403, not independently confirmed ↩ ↩²

3. Trinidad Coffee — What Is Anaerobic Coffee? — cited in the research report for the fruit-forward, earthy, buttery sensory notes; not independently fetched ↩ ↩² ↩³

4. Coffeester — Anaerobic Fermentation in Coffee — cited in the research report for the candy-like fruit and vinous/spirit-like sensory language; not independently fetched ↩