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 15 and 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.
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.
