Learn how to ferment cacao beans at home, fresh from the pod. In this tutorial, chocolatier Simon Knott explains how to ferment cocoa step-by-step and the science of cocoa fermentation.
As an aspiring bean-to-bar chocolate maker, learning to ferment cacao beans is a valuable skill to have. While not an essential skill, especially if you are purchasing your cocoa beans already dried, knowing how cocoa fermentation works will give you a more complete understanding of bean-to-bar chocolate-making in general and the important role that fermentation plays in chocolate flavour development.
And, if you are lucky enough to have access to fresh cocoa pods, then this article serve as a comprehensive guide for you to start fermenting cacao at home, including specifics such as temperature and humidity control.
Now, over to chocolatier Simon Knott to explain how to ferment cacao beans at home.
Photo credit: Photos throughout this article are original, taken at the Australian Chocolate Farm in October 2023. Thank you to the Australian Chocolate Farm for kindly showing us their cocoa farm and allowing us to photograph on their premises, and to the lovely owners for answering our one-million questions about their bean-to-bar chocolate-making process.
How to Ferment Cacao Beans at Home
By Simon Knott, Professional Chocolatier
The cocoa flavour we all know and love is created directly from the fermentation of cacao beans sourced from cacao pods.
In their raw state, cacao beans have a very bitter taste and a slimy texture from the surrounding white membrane or mucilage. The mucilage is a glutinous polysaccharide, which retains moisture and food to keep the beans fresh and, in the wild, aids seed germination.
In the fermentation of cacao beans, the mucilage is a very important part of the fermentation and flavour development process. There are several methods of fermentation:
Basic Fermentation
Some cocoa pod farmers use the most basic and cheapest method, where the beans and mucilage are removed from the pods and placed in heaps outdoors on banana leaves. The pile is then covered with extra banana leaves to protect it.
Basket Fermentation
In the second process, basket fermentation, a woven wicker basket is lined with banana leaves and filled with about 15 to 25 kg of beans and mucilage.
Box Fermentation
Lastly, the more industrial process of box fermentation involves different wooden boxes, which can be stacked. The volume of the boxes depends on the size of the enterprise and varies from small (50-100 Kg), medium (100-300 Kg) and large (500 Kg+).
The boxes are filled with beans and stacked to help fermentation by retaining heat and excluding oxygen. After a few days, the contents are rotated between the boxes to ensure even fermentation of the beans.
How to Ferment Cacao Beans at Home
Some cocoa farmers still use traditional methods to process their cocoa beans, which only require simple equipment and techniques. Living in tropical and subtropical climates, maintaining the required fermentation temperature is straightforward. For the home fermenter, maintaining the fermentation temperature can be more of a problem, although there are workarounds to achieve it.
Ingredients
Fresh cacao pods
Cacao pods usually contain about 60 beans, which equates to 120 g of finished chocolate.
Decide how much chocolate you want to make and choose pods which are of the same species, a similar size and a similar ripeness.
Equipment
- Wooden crate or plastic box, both with small holes in the bottom
- Large tray to stand your wooden crate or plastic box in
- Thermometer
- Large spoon to stir the beans
Method – How to Ferment Cocoa Beans
Step 1: Prepare the Cacao Beans
Cut open the ripe cacao pods (as shown) and transfer the beans and mucilage into the plastic box or crate.
Attach the crate lid or plastic top to limit the oxygen flow.
Place the crate or box in the tray to catch the run-off liquid.
Step 2: Find a Fermentation Location
Next, place the cocoa beans somewhere warm to ferment.
The fermentation process requires the beans to be kept at around 125° F (51° C).
For home processing, use a nearby radiator, a car heated by the sun, or a heated blanket.
With the latter, be very careful to ensure the run-off juice is kept well away from the blanket electrics. A heat mat designed for fermenting beer or raising seedlings is an excellent option.
Use a thermometer to monitor the temperature during fermentation. The beans will naturally generate their own heat, so change the box’s location to keep it around the advised temperature.
Step 3: Monitor the Fermentation
Keep checking the beans through the fermentation process, and after two days, remove the lid and regularly turn the beans in the box to expose them to more oxygen.
Occasionally, a bean might be attacked by microorganisms. This is usually evident from a colour change; the infected bean must be removed.
Ensure the beans are draining effectively into the tray underneath. They are likely to rot if they are left sitting in the run-off alcohol.
Step 4: Fermentation Finish
The whole fermentation process should take about six days.
Notice when the beans change to a mid-brown, which signifies the end of fermentation and most of the mucilage should have disappeared, as it was converted to alcohol.
Step 5: Drying
The beans are then ready for the next stage of drying. The beans are simply extracted from the boxes and laid out on mats in a thin layer to dry out.
Science of Cocoa Beans Fermentation
Cocoa Beans Fermentation Stages
Fermenting cacao beans involves complex biochemical processes that are entirely natural. Fermentation aims to create a cacao bean with the colour and flavour of the chocolate products we all love. There are several stages to the fermentation, each of which has a pivotal part in creating cacao beans that can be used for chocolate production:
Stage 1: Anaerobic Fermentation
Anaerobic = Without Air/Oxygen
The natural sugars present in the mucilage are a food source for the bacteria and yeasts, which settle from the air onto the cocoa beans.
The beans are tightly packed in the boxes, so there is little air available, which creates an anaerobic atmosphere, where the microorganisms produce carbon dioxide and ethanol or alcohol.
This anaerobic phase lasts for a couple of days and produces waste run-off liquid, which filters out of the base of the box.
Stage 2: Aerobic Fermentation
Aerobic = With Air/Oxygen
The next phase is aerobic fermentation, introducing oxygen to the cacao beans. This is achieved by spreading the tightly packed beans across several boxes and aerating them. Additionally, a turning process with paddles helps to ensure all the beans are exposed to oxygen.
Over the next couple of days, the aerobic fermentation phase produces acetic acid and ethanol and generates heat, often between 30-45° C. The acetic acid starts to act on the cell wall of each cacao bean, breaking it down.
At the same time, within the bean, complex enzyme reactions occur with the acetic acid, which starts the production of the traditional cocoa flavour and colour we know. So that at the end of the third day, the beans are chocolate brown, and most of the mucilage will have been converted to ethanol and run-off liquid.
Tips for How to Ferment Cacao Beans at Home
In both stages of fermentation, temperature and humidity must be controlled to regulate adverse effects.
Temperature
If the temperature varies too much on either side of the ideal 125° F (51° C) limit, then fermentation will either slow down too much or halt altogether.
Humidity
Similarly, if the humidity increases beyond 8%, mold growth is likely to damage the beans, or if humidity falls below 5%, then the bean quality becomes brittle.
Cacao Quality
In their processing, cocoa farmers have always learnt to ferment similar cacao pod species, sizes, and ripeness. Otherwise, smaller pods are unlikely to ferment properly, while larger pods will go beyond ideal fermentation.
Conclusion
We hope you’ve enjoyed this article from chocolatier Simon Knott on how to ferment cocoa beans at home. To learn the full bean-to-bar chocolate-making process, make sure to check out our guide one how to make chocolate from cocoa beans (bean to bar) where we lay out the whole process, or learn how to make your own cocoa powder with Chef Prish.
Happy chocolatiering!
