What happens during the fermentation of cocoa?

Sourdough and kombucha have celebrated a comeback in the home office period. And some even dared to try (water) kefir, yoghurt or miso. However, very few people know that one of our favorite sweets – namely chocolate – is fermented. Fermentation is of crucial importance in the manufacturing process from cocoa to chocolate. Why is this and what happens during the fermentation process? Find out here!

The fermentation makes the difference

Fermentation is essential to the flavor profile and acidity of cocoa beans. Unfermented cocoa, on the other hand, is considered completely inedible. By the way, for the pea or, in our case, bean counters among us: to be precise, it is not the cocoa beans that actually ferment, but the yeast, bacteria and enzymes that ferment the white pulp that surrounds the cocoa beans. Thus, the cocoa beans get the full pounding of the acid, heat and enzyme effects, causing them to change internally and externally - through the fermentation of the pulp.

Fresh cocoa beans before fermentation ©Lydgate Farms

Why does the pulp ferment?

As long as the pulp is inside the cocoa pod, it is sterile. However, once the cocoa beans and juicy pulp have been removed from the pod, naturally occurring yeast and bacteria quickly find their way into the sweet pulp. These microbial "vaccines" come from your immediate environment. As with other ferments, the bacteria can come from things like the hands of workers, the outside of the pod, flying insects, or just the air. In the case of a "planned" fermentation, which aims for certain fermentation effects, a specially tailored microbial "cocktail" with selected contents can also be added.

fresh, cut cocoa beans ©Lydgate Farms

The fermentation process

Fermentation methods vary depending on regional preferences and available resources. Individual cocoa farmers and cocoa cooperatives make different decisions regarding their equipment. There are differences in the choice of fermentation crates, the duration and number of days they ferment their cocoa, and the frequency with which they turn the cocoa in the crates.
However, there are processes and procedures that are similar in all fermentation methods. These include, for example, the anaerobic and aerobic phase. These are each influenced by a wide variety of factors, such as the degree of ripeness of the beans, the climatic conditions, the quality of the cocoa beans and the batch size.

The anaerobic phase

When there is a lack of oxygen in an environment, it is called anaerobic conditions. Because the pulp encloses the cocoa beans tightly, they form a kind of barrier that prevents air from penetrating the beans. The juicy pulp consists mainly of water, as well as a high sugar content and various acids. The combination of acid and sugar creates the perfect conditions for the microorganisms to work. Yeasts, lactic acid bacteria and fruit pulp enzymes in particular play an important role here. Through anaerobic respiration - caused by the absence of oxygen - the yeasts use up the simple sugars and produce carbon dioxide, ethanol and small amounts of energy. The lactic acid bacteria, in turn, convert acid and glucose (and other carbohydrates in the pulp) into lactic acid. If you open the fermentation box in this phase, you can observe this "work" directly on the surface. Small bubbles of carbon dioxide are bubbling and wafting on the cocoa-pulp mixture.
The enzymes present also help to break down the pulp and convert it into liquid. Incidentally, the so-called “sweat water” sounds more disgusting than it is and is now being converted into delicious juices by startups such as KOA . Once the cellulose - i.e. the pulp - has broken down, more air can flow into the process. At the same time, the citric acid is broken down, which also runs off with the sweat water, increasing the overall pH of the fermentation process. The increased air supply and the rising pH finally ring in the aerobic phase.

A typical fermentation box with a banana leaf covering the cocoa ©Lydgate Farms

The hot (aerobic) phase

In contrast to the anaerobic phase, the aerobic phase is characterized by the fact that the environment contains oxygen. This environment is created by regularly “turning” the cocoa in the fermentation boxes during cocoa processing. By "turning" oxygen gets to the cocoa beans. Depending on the fermentation profile, fermentation box, insulation and amount of beans to be fermented, the influence of oxygen varies. At the same time, regularly turning the cocoa beans means that the fermentation process is more even throughout the batch.
It gets very hot during the aerobic phase! By the way, you can find out here why we find the concept of raw cocoa somewhat questionable. But back to the aerobic phase: this step is dominated by the acetic acid bacteria, which oxidize ethanol and acids to produce acetic acid. This acetic acid, in turn, is further broken down into carbon dioxide and water by the extra oxygen.
The decomposition process of the ethanol releases heat, which significantly increases the overall temperature of the cocoa. Depending on the fermentation profile, the cocoa beans are turned over with varying frequency, heat escapes, the temperature drops but at the same time quickly builds up again due to the oxygen supply. The aim of this process is to break down cell walls through the combination of heat and diffusion of acid and ethanol. The cocoa beans can no longer germinate and the "chemically" altered structure within the beans has - depending on the fermentation style - developed the first aromas.

Cocoa beans during fermentation ©Lydgate Farms

No fermentation, no chocolate

Unfermented, raw cocoa beans have a very bitter taste. While the sweet pulp tempts animals to eat, the bitter kernels (cocoa beans) are spit out and thus spread. The astringent taste and the reddish color of the fresh cocoa beans come from the anthocyanins (polyphenols) they contain. The polyphenol content decreases as a result of the fermentation – and later, above all, as a result of the roasting of the cocoa beans, which promotes the development of the taste.
A few manufacturers have made it their goal to work with unroasted cocoa beans. Unfortunately, many don't do it so well. A great example of unroasted bean chocolate with a great fermentation profile is New York's Raaka. Like no other manufacturer, the Raaka team manages to process the original taste of the fermented cocoa beans into really good and fair chocolate. Would you also like to try such a chocolate? With a bit of luck, you can try one of the rare Raaka chocolates at our Theyo tastings as a team event . An exciting pleasure trip that is guaranteed to taste good for everyone!
You want to know what happens before fermentation during the cocoa harvest? Here you can learn more about cocoa cultivation and harvest ...