Long before the taste of chocolate
When we think about the flavour of cacao, we tend to look at origin, variety or roasting. Yet between the freshly harvested pod and the cacao we eventually come to know lies a decisive and largely invisible process: cacao fermentation.
It is not simply a period of rest. Nor is it a recipe that can be repeated identically anywhere in the world.
Cacao fermentation is a complex microbiological and biochemical process involving the pulp surrounding the seeds, microorganisms present in the environment, temperature, oxygen, time, the volume of cacao, climate, fruit ripeness and the genetic material itself.
And it begins even earlier than we often imagine.
It all begins inside the pod
When a ripe cacao pod is opened, we find the seeds surrounded by a white, moist and viscous pulp: the mucilage.
This pulp contains water, sugars — mainly glucose, fructose and sucrose — organic acids, pectins and other compounds. It is precisely this nutrient-rich medium that will later allow the development of the microbial communities responsible for fermentation.
But some producers do not open the pods immediately after harvesting them.
During our fieldwork in Ecuador, we encountered a particularly interesting practice: leaving harvested pods unopened for several days before extracting the seeds.
One of the producers we worked with calls this “el aguante” — allowing the pods to rest before opening.
His explanation comes from years of observation: by allowing the pod to rest, he notices changes in the amount and concentration of mucilage and considers that this period subsequently alters how the cacao behaves during fermentation.
The practice also exists beyond this particular farm and has a name in scientific literature: pod storage, or pod-opening delay.
And this is where knowledge from the field and scientific research begin to meet.
What happens while the pod remains closed?
It is tempting to think that during these days the cacao is already fermenting inside the pod. Some producers even describe prolonged resting periods as a form of “natural fermentation”.
Scientifically, however, we need to be more precise.
While the pod remains intact, physiological and biochemical transformations take place, but we should not automatically equate them with the microbial fermentation that subsequently occurs when the seeds and their pulp are extracted and gathered together.
Research has observed weight loss in the pod during storage, a reduction in the amount of pulp and changes in various components of the fruit.
A study published in 2024 is particularly interesting for us because it was conducted in Ecuador with Nacional cacao. The researchers compared pods opened immediately with pods stored for three and five days before opening.
The stored pods lost weight and showed a tendency to contain less pulp. In addition, cacao from these pods subsequently began fermentation somewhat more rapidly and reached higher maximum temperatures during the first 24–42 hours.
In other words: what happens before opening the pod can influence what happens afterwards.
Another study, conducted with Forastero cacao from Ghana, compared 0, 3 and 7 days of pod storage. It found changes in reducing sugars and free amino acids, as well as subsequent differences in certain volatile compounds related to aroma development. The authors point to processes such as respiration, moisture reduction and cellular degradation during this period.
This does not mean that there is a magic number of days that applies to all cacao.
Quite the opposite: variety, ripeness, climate, storage conditions and the desired sensory outcome all matter.
Opening the pod changes the whole environment
When the pod is finally opened and the mucilage-covered seeds are extracted, the system changes radically.
The seeds are gathered into a moist mass rich in sugars. They may be placed in wooden boxes, gathered into heaps, put into sacks or managed using other traditional systems depending on the region.
From that moment onwards, an extraordinarily dynamic succession of microorganisms begins.
We do not necessarily need to add them.
They are present on the fruit, the tools, the containers and in the processing environment.
Different species appear, grow, transform their surroundings and create conditions that favour or hinder the activity of those that follow.
This is why it is more accurate to speak of a microbial succession than to imagine three completely separate processes.
In simplified terms, the three major groups found during traditional cacao fermentation are yeasts, lactic acid bacteria and acetic acid bacteria. Microbiological research confirms their recurring presence, although their populations, species, proportions and behaviour can vary enormously between fermentations.
And the first protagonists are usually the yeasts.
The first hours: an environment rich in sugar and low in oxygen
At the beginning, the cacao mass is compact.
The mucilage fills the spaces between the seeds and limits oxygen penetration into the interior. At the same time, it contains the sugars that yeasts can metabolise.
In our field recordings, the producer described the first 48 hours in a remarkably graphic way:
“It only smells of alcohol.”
What he is perceiving has a microbiological explanation.
During the early stages, different yeasts use the sugars in the pulp and produce ethanol, among other metabolites. At the same time, the degradation of pectins contributes to the pulp gradually losing its viscous structure, allowing it to drain.
But the idea of a perfectly isolated “alcoholic” phase lasting exactly 48 hours would be too simplistic.
Microbial populations overlap. Lactic acid bacteria may be present from the early stages, and conditions are continuously changing within the same fermenting mass.
This is why the timings described by a producer are extraordinarily valuable for understanding their fermentation, on their farm and under their particular conditions, but they should not automatically become a universal rule.
As the pulp disappears, oxygen enters
As the pulp transforms and drains, spaces begin to appear between the seeds.
Air can penetrate more easily.
Turning the cacao mass further increases this entry of oxygen.
And then the ecosystem changes again.
Lactic acid bacteria participate in the metabolism of sugars and acids present in the pulp. At the same time, as oxygen availability increases, acetic acid bacteria encounter the conditions they need to oxidise the ethanol previously produced by the yeasts, converting it mainly into acetic acid.
This reaction releases heat.
The temperature of the mass begins to rise and can reach approximately 45–50°C in well-developed fermentations, although the exact temperature curve depends on numerous factors.
And something fundamental happens here.
Until now, we have mainly been talking about what happens around the seed.
From this point onwards, decisive transformations begin to occur inside it.
External fermentation triggers an internal transformation
Acetic acid and other metabolites penetrate the seed tissues as the temperature rises.
The combination of heat, acidification and other changes causes the embryo to die and progressively disrupts cellular organisation.
This allows enzymes and compounds that were previously separated to come into contact.
Profound transformations of proteins, sugars, polyphenols and pigments then begin.
Amino acids, peptides and reducing sugars are formed, which will later be essential as aroma precursors. Changes also occur in polyphenols, associated with reduced astringency and bitterness and with changes in the colour of the cotyledons.
This brings us to one of the most important ideas for understanding cacao:
Fermentation does not, by itself, create all the aroma we recognise as chocolate. It prepares the seed so that those aromas can develop later.
Many of the precursors formed during fermentation will subsequently participate in reactions during drying and, especially, roasting.
This is why a cacao can possess extraordinary genetics and still lose much of its potential if post-harvest handling is poor.
So, is there a perfect cacao fermentation protocol?
During our conversations in Ecuador, one provocative statement came up repeatedly:
“There is no fermentation protocol.”
Taken literally, that would not be correct.
Protocols do exist, as do control parameters, temperature and pH measurements, fermentation times, turning criteria and numerous scientific studies dedicated precisely to controlling and reproducing the process.
But behind that statement was a much more interesting observation:
There is no universal protocol capable of ignoring the cacao and the place.
The producer spoke to us about wetter and drier years; cold nights; different varieties; white and purple seeds; pods at different stages of ripeness; small and large quantities of cacao.
Science also finds enormous variability.
In Ecuador, significant differences have been documented between fermentations carried out in different locations and using different systems, as well as effects associated with the fermentation device, turning, time, drying and other post-harvest practices.
Even volume matters.
A small mass loses heat more easily than a large one. A thick wooden box can help retain temperature in a region with cold nights. Turning redistributes seeds located in warmer and cooler areas and, in addition, introduces oxygen.
Fermenting cacao means, to a large extent, learning to read a living material that is constantly changing.
And that helps explain why two producers can begin with excellent fruit and obtain completely different results.
We have only just begun
After the first 48 hours, the transformation accelerates.
Temperature rises. Oxygen availability changes. Microbial populations shift. Acids penetrate the seed. The cotyledons change in colour and structure.
The producer observes the temperature, touches the mass, smells it, turns it and decides when to intervene.
And every decision leaves its mark.
In the second part of this series on cacao fermentation, we follow the process day by day, from those first hours dominated by yeasts to the point when the temperature begins to fall and the producer has to make one of the most delicate decisions in the entire process: when to remove the cacao from fermentation.
About this series
This Sumay Library series was born from Sumay Cacao's fieldwork in Ecuador in 2026, from conversations and recordings with producers and specialists, and from comparing those observations with scientific literature.
Our purpose is to approach cacao through different forms of knowledge: listening to those who work with it every day, observing processes at origin and comparing those experiences with the available research.
Series · Cacao Fermentation
Part I — Long before the taste of chocolate
Sources and references
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Hinneh, M., Semanhyia, E., Van de Walle, D., et al. (2018). Assessing the influence of pod storage on sugar and free amino acid profiles and the implications on some Maillard reaction related flavor volatiles in Forastero cocoa beans. Food Research International, 111, 607–620. DOI: 10.1016/j.foodres.2018.05.064.
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Streule, S., Freimüller Leischtfeld, S., Chatelain, K. & Miescher Schwenninger, S. (2024). Effect of Pod Storage and Drying Temperature on Fermentation Dynamics and Final Bean Quality of Cacao Nacional in Ecuador. Foods, 13(10), 1536. DOI: 10.3390/foods13101536.
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Streule, S., Freimüller Leischtfeld, S., Galler, M. & Miescher Schwenninger, S. (2022). Monitoring of cocoa post-harvest process practices on a small-farm level at five locations in Ecuador. Heliyon, 8(6), e09628. DOI: 10.1016/j.heliyon.2022.e09628.
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Hamdouche, Y., Meile, J.-C., Lebrun, M., Guehi, T. S., Boulanger, R., Teyssier, C. & Montet, D. (2019). Impact of turning, pod storage and fermentation time on microbial ecology and volatile composition of cocoa beans. Food Research International, 119, 477–491. DOI: 10.1016/j.foodres.2019.01.001. Sumay Cacao
