Carbonic maceration in coffee: the process that is conquering the wine world
In specialty coffee, there are classic processes—washed, honey, natural—and experimental processes that are just beginning to redefine what coffee can taste like. Carbonic maceration is the most famous of these experimental techniques, and it is producing profiles that would have sounded impossible ten years ago.
Notes of red wine, fermented fruit, and sweet spices. Coffees that seem to be on the border between two worlds, but that still faithfully express their character as single-origin coffee. And, in a way, they are—because the technique literally comes from the world of wine.
The Origin: From Beaujolais to Antioquia
Carbonic maceration was invented in the 1930s in the French region of Beaujolais as a way to produce young, fruity wines without the astringency of traditional methods. The idea was to seal whole grapes—without crushing them—inside a tank flooded with carbon dioxide (CO₂) and let them ferment from the inside.
The result was wines with unique profiles: fruitier, smoother, with fewer tannins. The style defined the region.
In the world of coffee, the technique began to be explored around 2015–2016, first in Costa Rica and Colombia. The hypothesis was simple: if it works in wine, it could work in coffee, which after all is also a fruit. And it worked—producing profiles so distinct that in 2019, a Colombian coffee with carbonic maceration won the World Barista Championship.
What Exactly Happens Inside the Tank
Carbonic maceration in coffee works like this:
- Selected Whole Cherry — harvested coffee fruits (cherries) are placed whole inside an airtight tank, without pulping.
- CO₂ Injection — carbon dioxide is injected into the tank to displace all oxygen and create an anaerobic (oxygen-free) environment.
- Intracellular Fermentation — with no oxygen available, enzymes inside the cherry activate a distinct fermentation: alcoholic, slow, deep.
- Controlled Time — the process can last between 48 and 200+ hours, depending on the profile the producer wants to achieve.
- Pulping and Drying — at the end of maceration, the beans are pulped and dried, usually with additional techniques to preserve the generated compounds.
The difference with a standard natural fermentation is enormous: in a common fermentation, external microorganisms play a primary role, and the result heavily depends on environmental conditions. In carbonic maceration, the environment is sealed, controlled, and predictable.
Why This Radically Changes Coffee Flavor
During anaerobic fermentation, compounds are generated that simply do not appear in an oxygenated fermentation:
- Complex Fruity Esters — molecules responsible for aromas like banana, strawberry, fermented apple, young red wine.
- Specific Organic Acids — malic acid, lactic acid, and others that create wine- and yogurt-like profiles.
- Aromatic Aldehydes — compounds that contribute spicy, sweet, and floral notes.
- Reduced Astringency — bitter compounds typical of coffee are moderated.
The result is a coffee that retains its essence—it is still coffee—but with a new aromatic complexity reminiscent of wine and exotic fermented fruits.
Why It's So Hard to Do Well
Carbonic maceration is a high-risk, high-reward process. When done well, it produces extraordinary coffees. When done poorly, it produces coffees with incurable defects.
The technical challenges are several:
- Specialized Equipment — airtight tanks, CO₂ injection systems, temperature and pH sensors.
- Strict Temperature Control — anaerobic fermentation generates heat; it must be kept between 59 and 77 °F (15–25 °C), ideally lower.
- Perfect Cherry Selection — any defective fruit contaminates the entire tank.
- Exact Timing — a few hours less and flavors are missing; a few hours more and stale alcohol appears.
- Total Traceability — each batch is an experiment: documentation is what allows for replication of success.
Because of all this, carbonic maceration coffees are rare, expensive, and produced by only a small group of producers worldwide who have the necessary resources and experience.
Carbonic Maceration at Green Hills
Our Bronze Coffee is the result of applying controlled carbonic maceration to a selected batch from Hacienda Las Mercedes. We developed the process on the farm, with the equipment and documentation necessary to maintain the profile between harvests.
The cup profile is completely different from traditional processes: notes of fermented fruits, young red wine, sweet spices, with a dense body and a long, complex aftertaste.
It's a coffee to be enjoyed with attention. To train the palate. To understand how far a bean can go when a producer decides to go further.
Frequently asked questions
What is carbonic maceration in coffee?
Carbonic maceration is a processing technique borrowed from winemaking, in which whole coffee cherries are sealed in an oxygen-free tank filled with carbon dioxide. Without oxygen, fermentation happens largely inside the intact fruit rather than on its surface. The result is an aromatic profile that conventional processing does not produce.
Where does the technique come from?
It was developed in the wine industry, most famously in Beaujolais, France, as a way to make fruit-forward wines with soft tannins. Coffee producers later adapted the same principle of anaerobic, carbon dioxide-rich fermentation to coffee cherries.
How is it different from a conventional fermentation?
In conventional processing, fermentation happens with oxygen present and is driven mostly by microorganisms acting on the mucilage. Under carbon dioxide the oxygen-dependent microbes are suppressed and enzymatic activity inside the fruit takes over. Different pathways mean different aromatic compounds in the finished bean.
Why is carbonic maceration hard to do well?
It requires sealed tanks, a controlled carbon dioxide atmosphere and close monitoring of temperature, pH and time, because the window between a distinctive cup and a defective one is narrow. Small deviations can push a lot toward vinegar or solvent-like flavors. It also demands consistent documentation to repeat a profile from one harvest to the next.
What does a carbonic maceration coffee generally taste like?
Cups from this technique are usually described as intensely fruit-forward, with fermented fruit and wine-like character, a dense body and a long finish. The exact profile depends on the variety, the farm and how the fermentation was managed, so it varies a great deal from one lot to another.
How should I brew a carbonic maceration coffee?
Filter methods usually let these aromatics show most clearly, and a slightly coarser grind helps avoid over-extracting an already intense cup. Grind just before brewing and use water at about 198-205 °F (92-96 °C). Taste it black first, before deciding whether it needs anything else.
Experience in your cup what the wine world learned 90 years ago. Our Bronze Coffee is carbonic maceration from Hacienda Las Mercedes — limited production, unique profile.