When we think of coffee, we often picture green mountains, hands picking ripe red cherries, and the comforting aroma filling the air as we brew a cup. But before that magical moment, an invisible world comes to life inside every bean.
During fermentation, millions of microorganisms—yeasts, bacteria, and natural fungi—work silently, transforming the chemistry of coffee and creating the aromas and flavors we love.
Yeasts: These transform the sugars in the mucilage into alcohol and carbon dioxide, releasing aromatic esters that give fruity, floral, and sweet notes, such as honey or wine.
It all begins once the coffee cherries are harvested and the beans are still covered by a sticky layer called mucilage, rich in sugars and nutrients, which is the perfect feast for microbes. Yeasts are the first to act: they consume the sugars and convert them into alcohol and carbon dioxide, releasing aromatic compounds called esters, responsible for the fruity and floral notes that may remind us of honey, wine, or tropical fruits. Next, lactic acid bacteria, the same type found in yogurt or kefir, spring into action, transforming the remaining sugars and alcohol into lactic acid, adding smoothness and a pleasant, rounded acidity. Finally, acetic bacteria complete the symphony by converting some of the alcohol into acetic acid, which, when balanced, gives the coffee a bright and sparkling sensation.
If fermentation gets out of control, it can produce unpleasant flavors, but when managed carefully, it results in a cup full of complexity and life.
Acetic bacteria: These transform part of the alcohol into acetic acid, creating a lively, sparkling acidity that balances the flavors of the coffee.
At El Mejor Aroma Antioqueño, we consider fermentation to be an art guided by nature. Each farm, each altitude, and each microclimate has its own microbiome, a unique community of microorganisms that acts as a fingerprint of the land. No two fermentations are alike: temperature, humidity, water quality, and resting time can completely transform the flavor. That's why we observe as much as we measure, trusting the rhythm of our mountains and the purity of our water to guide the process. During fermentation, these tiny organisms not only create aromas, but also form chemical precursors that, once the beans are roasted, will turn into notes of caramel, nuts, or chocolate. In other words, fermentation sets the stage for roasting to reveal the full expression of the coffee. That's why a we observe as much as we measure, trusting the rhythm of our mountains and the purity of our water to guide the process.
There are many styles of fermentation: the traditional method in open tanks, which produces clean and balanced profiles; anaerobic fermentation, in which oxygen is limited to develop exotic and fruity notes; or natural processes, in which whole cherries ferment slowly while drying, intensifying sweetness and aroma. Some producers use selected yeasts to control the result, while others rely on the wild microflora of their region, opting for authenticity over predictability.
The fascinating truth is that this microbial life defines the identity of coffee. The same variety can have a floral flavor in one distant place
Lactic bacteria: Convert the remaining sugars and alcohol into lactic acid, contributing smoothness, natural sweetness, and around, pleasant acidity.
