CM Natural

The term 'CM Natural' describes a sophisticated hybrid processing technique that merges the foundational principles of natural processing with the controlled, anaerobic environment of carbonic maceration. In a standard natural process, whole coffee cherries are dried in the sun until the fruit dehydrates around the seed. A CM Natural, however, introduces a critical intermediate step: before drying, the whole cherries are placed in sealed, airtight stainless steel tanks that are flushed with carbon dioxide to displace oxygen.

This process is rooted in winemaking, specifically the production of Beaujolais Nouveau. By creating a carbon dioxide-rich, anaerobic environment, the coffee cherries are forced to undergo intracellular fermentation. Unlike traditional fermentation, which relies on external microbes acting on the surface of the fruit, carbonic maceration allows the enzymes inside the individual cherry cells to break down sugars and acids while the fruit is still intact. This internal metabolic shift is what distinguishes the method from standard anaerobic processing.

Once the desired level of intracellular fermentation is achieved, the cherries are removed from the tanks and typically moved to drying beds to complete the natural process. Because the fruit remains on the seed throughout both the fermentation and the drying phases, the resulting cup retains the heavy body and sweetness characteristic of natural coffees, but with significantly altered volatile compounds. This often manifests as intense, fruit-forward acidity and a smooth, wine-like complexity that is difficult to replicate through conventional methods.

Carbonic maceration was introduced to the specialty coffee industry by champion barista Saša Šestić, who utilized a CM Natural coffee to win the 2015 World Barista Championship. His success demonstrated that by manipulating the environment in which the cherry ferments, producers could exert greater control over the final sensory profile of the coffee, effectively 'designing' flavors that highlight specific fruity or floral characteristics.

For the farmer, this method requires significant investment in infrastructure, including airtight tanks, CO2 supply, and precise monitoring equipment to manage temperature and pH levels. It is a high-risk, high-reward endeavor; because the process is so sensitive to time and temperature, even minor deviations can lead to undesirable off-flavors. However, for roasters and consumers, these coffees offer a unique, experimental experience that pushes the boundaries of traditional terroir-driven profiles.

Today, the use of CM Natural processing is expanding beyond its initial niche, with producers in regions like Ethiopia, Nicaragua, and Indonesia experimenting with varying fermentation times and pressures. While some critics argue that such intensive processing can mask the inherent qualities of the coffee's origin, proponents view it as a vital tool for innovation. As research into the biochemistry of coffee fermentation continues, CM Natural stands as a primary example of how modern science is being applied to age-old agricultural practices to redefine the limits of coffee flavor.