Fermentation is a process commonly found in wines, beer, champagne, cacao, yoghurt and even bread making. In traditional coffee farming, all coffee undergoes some degree of fermentation – washed coffees pass through the pulping, washing, channel grading and final drying phase, while naturals are changing flavors and ‘developing’ as the fruit / mucilage dries around the seed.
As indigenous microbes and yeasts interact with the sugars of the coffee cherry, this chemical reaction releases enzymes and completely changes the composition and flavors found in the coffee. Anaerobic fermentation is a term used to describe fermentation without oxygen, usually in a sealed environment (to be correct, all fermentation actually happens in the absence of oxygen).
Fermentation requires accurate management of key variables such as: water quality, temperature, sugars, pH, and time. (Sasa Sestic was the first competitor in the World Barista championships, describing his winning coffee and performance as carbonic maceration).
Many farmers we are working with will sort out ultra-premium lots of cherry, (both pulped or whole cherries) and use large round plastic bins, larger tanks, or even grain-pro plastic bags - like fermentation tanks. As the microorganisms begin to break down the glucose molecules, a chemical reaction generates C02 and heat.
This process deepens and enhances the potential flavors of the coffee and allows incredible control over the fermentation process. Producers are able to measure the pH, brix (sugar content) and temperature, with coffee fermented for 2 days for example, tasting completely different to the same coffee left to ferment for 5 days. Cherry left for too long fermenting will develop negative winey unbalanced and extreme flavors and aromas and is to be avoided at all costs.
Carbonic maceration is a term taken from the wine industry and used to describe “whole cherries” which are anaerobically fermented.
Here is how our Cultured Colombian Risarlada scoring a whopping 91.5 has been processed. We have the raw material in one hand (pulped coffee), the starter culture (lactobacillus) in another and finally the fresh fruits which are coconut and pineapple.
All this is doing its own fermentation process simultaneously but separately, then when we have the right conditions (brix and temperature) to mix the three of them together. First the fermented fruit and coffee is put together in tanks and finally the starter culture is added, the tanks are closed, and we start a common fermentation process (anaerobic), temperature and oxygen is regulated depending on the fruits fermentation level and the tanks are opened regularly. After 3-5 days this fermentation is completed, and the coffee is then hulled and taken to the drying beds. Clear distinguishable flavor notes of Pineapple, coconut, vanilla, passionfruit, caramel.
These experimental fermentation and processing methods require additional labor, energy, resources, and time, and increases potential risk to the farmer so is always priced at a premium, taking these factors into account. Enjoy.