Sipping on Science with Coffee Fermentation

Smooth, fruity, rich, bitter, buttery, and spicy—every sip of coffee speaks a different taste story. Recently, fermented coffee has been gaining popularity, and a lot of producers are trying different fermentation methods to unveil exotic flavors and distinctive notes in their coffee.

So what exactly is fermented coffee? To put it simply, it’s coffee that has undergone a planned and controlled fermentation. This can be a little confusing because every coffee bean goes through some sort of fermentation during the processing stages, right? Then how is this different?  In fermented coffees, the fermentation is an additional step that is done during processing.

Coffee producers follow different processes to separate the beans from the fruity layers of the cherry surrounding them. Normally, fermentation is an important but behind-the-scenes player in the process. When it comes to fermented coffee, things change. The fermentation is meticulously planned, becoming the star of the show and creating alluring new flavors of coffee.

Here are a few fermentation methods that are trending globally:

Anaerobic fermentation: 

Anaerobic fermentation is a unique method of fermentation that takes place in a limited oxygen environment. In this process, coffee cherries are carefully selected, cleaned, and sorted before being transported to the anaerobic processing station. The coffee cherries are usually sealed airtight in plastic bags or placed in special metal tanks designed to release gases and prevent pressure from building up. The cherries are fermented for a period of 12 to 100 hours, depending on the producer's experience and confidence with their coffee. Unlike other methods, no gases are pumped into the bag or container, and it is left alone to ferment in an environment with limited oxygen. This process produces a bright, crisp, and clean coffee with more traditional flavour notes.

Carbonic Maceration

With a long-established history in the wine industry, carbonic maceration has gained widespread recognition for its use in harvesting and processing wine grapes. It involves fermenting coffee in an environment rich in carbon dioxide. Coffee cherries are first harvested and then placed into barrels, typically constructed from airtight stainless steel. These coffee cherries are then put in barrels, where carbon dioxide is injected, facilitating the breakdown of varying amounts of pectin within the cherries. This method is remotely similar to the anaerobic fermentation method, the only difference being that in carbonic maceration, the coffee beans are not pulped before being sealed into the tanks or barrels for the fermentation process. Coffeeza’s Salawara Single-Estate coffee follows this process. The result is a bright, winey coffee with strong red fruit notes. While still regarded as an experimental approach, this method presents numerous opportunities to push boundaries and unlock greater flavour potential for coffee fermentation.

Fruit fermentation:  

Another latest advancement in coffee processing within the coffee industry is the practice of fermenting coffee with some fruit. In this process, first the wet-processed or semi-washed beans are perfectly pulped. Then slices of or mashed fruit are added along with the coffee beans, and they are set for fermentation. After this, the seeds are dried and packed to be sent to the roastery. Coffeeza’s Baarbara Single-Estate coffee is produced by a pineapple fermentation process wherein coffee beans ferment with pineapple slices. This innovative method enhances the coffee's inherent sweetness and body while also infusing a delicious fruity essence into each cup. Coffee producers have progressed from mere experimentation to achieving consistent success through various methods of coffee fruit fermentation. A few plantations do fermentation with grapes, oranges, wine yeast, passionfruit, and more, which has opened up a myriad of possibilities within the realm of specialty coffee.

Koji fermentation

Rooted in ancient Japanese technique, which is traditionally associated with the production of soy sauce, miso, and sake. It has now found its way into the realm of coffee. The Koji fermentation method uses the spores of a filamentous fungus to produce excellent fermentation, enhancing the complexity and body of the coffee. In this procedure, the coffee cherries are given a 3-day initial stage of fermentation before being treated with the fungus spores and allowed to continue fermenting for an additional 60 hours. Following this, the drying process is completed to reach the desired final moisture level, after which the grain is hulled before being packaged and transported to the roasters. One amazing feature of koji is that it can grow on any starch, including the skin, mucilage, and pulp of coffee beans, which is a great advantage for coffee farmers who choose this technique. The final coffee flavor varies greatly depending on the degree of roasting, but you will notice notes ranging from chocolate and gingerbread to tropical fruits like pineapple and mango. The mouthfeel has a long-lasting, rounded, and full-bodied texture that is buttery and smooth.

Double fermentation:

The process of repeated fermentation, commonly referred to as double washing, is widespread in East Africa. This procedure involves washing and fermenting coffee twice. Coffee beans are collected and sorted, then placed in water-filled canals or tubs for a length of time to allow fermentation. At times, it is left open for dry fermentation. The following step involves cleaning and canal washing for the coffees. After repeating the previous round of fermentation and washing, the second round moves on to the drying phase. According to coffee tasters, it makes a cup of coffee that is incredibly clear and has flavours of bright, crisp fruit.

Barrel Aged Coffee

There is one more fermented coffee innovation with a boozy twist called barrel-aged coffee. In this process, unroasted green coffee is carefully placed inside barrels that have previously housed whiskey, gin, rum, wine, and an array of other alcoholic beverages. The beans absorb subtle notes and nuances from the prior processing, adopting uniquely fantastic new flavors. This method is gaining so much popularity that coffee producers and roasters are now forming strategic partnerships with distilleries to make this unique brew. 

Besides these six methods, there is yeast fermentation, which uses wine yeast and is similar to the koji fermentation process, and nitro fermentation, which uses nitrogen instead of carbon and is similar to the carbonic maceration process.

Countless other fermentation procedures are being created and experimented with every day, pushing the boundaries and creating new experiences for coffee producers and enthusiasts. As we continue to explore these fermentation methods and bring them to you, we invite you to try the Coffeeza Salawara and Baarbara Single Estate coffee capsule blends. If you like them, do let us know what you would like us to try next to excite your coffee palate.