Innovations in Post-Harvest Coffee Processing: Carbonic Maceration

Several attempts are being made in the coffee sector to discover new and exotic flavors. An emerging process that is gaining rapid popularity is carbonic maceration due to the incredible and unique flavors it offers. Carbonic maceration involves anaerobic fermentation of coffee and finds its origin in the wine industry where whole grapes are fermented instead of being crushed.

The same principle is applied for coffee where instead of being de-pulped, the coffee cherry is added to the fermentation tank (made of metal or plastic) and sealed. The coffee is allowed to ferment for as long as three months.

As the coffee ferments the sugars, the sugars are broken down by microbes into carbon dioxide and alcohol. As the amount of carbon dioxide rises pressure within the system rises proportionately, and a valve is installed to release excess pressure, without adding oxygen into the chamber.


The valve at the simplest is a hose submerged in a bottle of water that releases carbon dioxide to bubble out, while fresh air cannot pass through. More sophisticated processors may use a regulator to hold pressure at a consistent level before letting the gas escape. As the fermentation advances, the drum becomes more and more carbon-rich with less oxygen which substantially alters the end flavor profile.



The rate of fermentation is largely influenced by temperature. The tanks are best kept in a cool area because the heat generated from the breakdown of mucilage would accelerate the fermentation is a positive feedback loop. Such a hypoxic environment supports several communities of microorganisms like lactic-acid bacteria as opposed to conventional open-air fermentation which favors yeast. These microorganisms will generate various aromatic compounds while breaking down the mucilage or cherry and those compounds are chiefly responsible for the final flavor. The rise in pressure will also help in seeping in the compounds into the seed, producing a more intense flavor profile.


Closing Note

Carbonic maceration for coffee processing is the latest of innovations occurring in pioneering coffee farms such as Ethiopia’s Kerchanshe Trading PLC. The advantage of adopting such experimental practices is that it can encourage creativity in an industry largely dependent on tradition, and open newer markets for produces seeking relief from C-market price fluctuations.