After the first 48 hours: temperature, oxygen and transformation
In the first part of this series, we followed cacao from the freshly harvested pod through the first 48 hours of fermentation.
We saw how the activity of yeasts and bacteria begins to transform the pulp surrounding the seeds, how ethanol is produced, how the mucilage progressively loses its structure, and how the entry of oxygen begins to change the fermentation ecosystem.
At around 48 hours, we enter a different stage of the process.
The temperature rises. Aeration becomes increasingly important. The activity of acetic acid bacteria intensifies, and the acids and heat produced around the seeds begin to trigger profound transformations within them.
But before we continue, there is something fundamental to understand: talking about day two, day three or day five helps us understand fermentation, but cacao does not follow a clock.
Fermentation may last three, four, five, six or even seven days. How it develops depends on genetics, fruit ripeness, pulp composition, climate, ambient temperature, the volume of the fermenting mass, the system used and the way it is managed.
During our work at origin, Marcelo — a farmer with a deep knowledge of cacao — repeatedly emphasised this idea: we cannot expect every cacao to respond in the same way simply because we apply the same number of hours and the same movements.
Protocols, measurements and control parameters exist. What does not exist is a universal recipe capable of ignoring the cacao in front of us.
After 48 hours: oxygen changes the process
At this point, the mass no longer behaves as it did at the beginning.
The progressive breakdown and drainage of the pulp allow more air to enter. This is combined with the aeration produced when the mass is moved or turned.
The increase in oxygen particularly favours the activity of acetic acid bacteria.
These bacteria use the ethanol produced earlier and oxidise it mainly into acetic acid. This is an exothermic reaction: it produces heat.
From this point onwards, following the evolution of temperature allows us to indirectly observe part of what is happening inside the fermentation.
The mass can reach approximately 45–50°C.
This does not mean that reaching a particular temperature guarantees good fermentation. What matters is observing how the mass reached that temperature, how long it remains at elevated temperatures and what happens afterwards.
The curve matters more than an isolated number.
The centre of the fermentation box does not ferment in the same way as the edges
A fermenting mass of cacao is not completely homogeneous.
Cacao in the centre may be at a different temperature from cacao close to the walls, in the corners or at the bottom of the box.
This was something Marcelo particularly encouraged us to observe during our work in Ecuador.
In places where nights are cold, the difference can become even more noticeable. A large mass retains heat differently from a small one; a thick wooden box may provide better insulation than another system; and the outer areas are more exposed to ambient temperature.
This is why the volume of cacao is also part of the fermentation process.
It is not enough to say that a cacao spent five days in a box.
We need to know what happened inside that box.
Turning does not simply mean mixing
Here we come to one of the producer’s most important interventions: turning the cacao.
Moving the cacao redistributes the seeds within the mass. Seeds that were in cooler areas may move towards the interior, while those that were in the centre may move towards the outer areas.
But something even more important happens: oxygen enters the mass.
This aeration favours oxidative reactions and the activity of acetic acid bacteria. As a result, a significant increase in temperature may occur after turning.
Turning, therefore, is not simply a mechanical operation to “mix the cacao well”.
It changes the microbiological and thermal conditions of the fermentation.
Nor does this mean that the more frequently cacao is turned, the better.
The timing and frequency should respond to the behaviour of the mass, its volume, the climate, the fermentation system and the cacao itself.
In some places, producers work with one or several scheduled turns. In others, the producer’s experience and the evolution of the mass determine when to intervene.
What matters is understanding what we are causing each time we open and move that mass.
Days 3–5: what happens outside begins to profoundly transform what is inside
By this stage, fermentation can no longer be understood simply by looking at the outside of the seed.
Acetic acid and other metabolites produced within the mass penetrate the seed tissues. At the same time, elevated temperatures and acidification alter the internal conditions of the bean.
The embryo loses its ability to germinate and the cell membranes begin to lose their integrity.
And this is decisive.
Inside a living seed, many compounds remain physically separated from one another. When this cellular structure is altered, enzymes and substrates that were previously compartmentalised can come into contact.
Numerous biochemical reactions then begin:
- Proteins change.
- Peptides and amino acids are formed.
- Sugars change.
- Polyphenols and pigments undergo transformations and oxidation.
- Astringency and bitterness may change.
And many of the precursors that will later be fundamental to cacao aroma begin to develop.
This is one of the reasons why fermentation is so decisive.
We are not simply removing the pulp that surrounded a seed.
We are transforming its interior.
The chocolate aroma is not yet fully formed
There is something particularly interesting here.
The aroma and flavour that we later identify as chocolate are not fully formed inside the fermentation box.
Fermentation prepares the ground.
The amino acids, peptides, reducing sugars and other compounds generated or transformed during this stage will later participate in new reactions during drying and, above all, during roasting.
This is why fermentation, drying and roasting should not be understood as completely independent processes.
What we do — or fail to do — at one stage affects what can happen at the next.
An extraordinary genetic variety contains enormous aromatic potential.
But that potential can also be lost through poor post-harvest handling.
Opening a seed can also help us read the fermentation
The producer does not need to observe only the outside of the fermenting mass.
Seeds can be taken, cut open and examined to see what is happening in the cotyledons.
Colour, structure, texture and degree of transformation all provide information.
During our work in Ecuador, Marcelo took a seed from the centre of the mass, opened it and pressed it. A small reddish drop appeared, which he associated with the progression of acetic acid inside the bean.
This is a very interesting example of where we need to distinguish observation from interpretation.
We know scientifically that the acids produced during fermentation penetrate the seed and that the combination of acidification and temperature triggers important internal transformations.
But we cannot state, based solely on visual observation, that a particular droplet emerging from a seed is acetic acid.
This does not diminish the value of the observation.
Quite the opposite.
It allows us to formulate questions and understand the signals used by someone who has worked with cacao for years. Science can then help us determine the mechanisms behind those signals.
What happens after the fifth day?
Not all cacao will have completed fermentation by the fourth or fifth day.
Some fermentations may continue for six or seven days.
By this stage, the mass is very different from the one initially placed in the box.
Much of the mucilage has disappeared. The aromas have changed. The temperature has passed through different phases. The inside of the seeds has been transformed, and the availability of the initial substrates used by microorganisms has decreased considerably.
Microbial populations do not remain constant either.
As available sugars decrease and temperatures remain high, many populations of yeasts and lactic acid bacteria decline. In experimentally studied fermentations, temperatures may remain around 45–50°C during a later phase before the process gradually loses intensity.
But reaching the seventh day is not the objective.
If a cacao requires seven days under certain conditions, it may need to remain there for that long.
Another cacao may be ready sooner.
Duration is not, in itself, a measure of quality.
Fermenting for longer does not mean fermenting better.
What if we leave the cacao fermenting for too long?
Insufficient fermentation can prevent the internal transformations necessary to build a good aromatic profile from developing properly.
But excessive fermentation is not desirable either.
Extending the process beyond what is necessary can favour unwanted sensory changes and increase the risk of defects.
This brings us to one of the most delicate aspects of post-harvest work: knowing when to stop.
And that decision should not depend exclusively on the calendar.
So how does the producer know when fermentation is coming to an end?
There is no single signal that can provide the answer on its own.
- Follow the evolution of temperature.
- Observe how the mass responds after turning.
- Smell it.
- Check how much mucilage remains.
- Examine the external appearance of the seeds.
- Open them and observe the cotyledons.
- Monitor parameters such as temperature and pH when the appropriate instruments are available.
- And subsequently carry out physical tests, cut tests and sensory evaluation.
The evolution of temperature is particularly interesting.
During periods of intense microbial and oxidative activity, the mass generates heat. When this activity begins to decrease, its thermal evolution also changes.
But again, an isolated temperature should not become a recipe.
We need to read the whole picture.
Five days in Palanda are not necessarily five days in Esmeraldas
This was perhaps one of the most interesting ideas to emerge from our conversations at origin.
Place matters.
Marcelo spoke to us about Palanda, where nights can be considerably cold and retaining the heat of the fermenting mass becomes particularly important.
In a much warmer and more stable environment, its behaviour may be different.
The cacao itself also changes.
A variety with particular pulp and sugar characteristics will not necessarily behave in the same way as another. Nor does a pod harvested at its optimal stage of ripeness begin under the same conditions as an unripe or excessively ripe fruit.
- Rainfall changes.
- The harvest changes.
- Batch size changes.
- The container changes.
- The microorganisms present in the environment change.
This is why the statement we repeatedly heard in the field — “there is no fermentation protocol” — needs to be understood correctly.
It does not mean working without control.
It does not mean that protocols do not exist.
It means that the protocol must serve the cacao, rather than forcing the cacao to serve the protocol.
To ferment is to observe
Today we can measure temperature, pH, acidity, moisture, microbial populations and numerous chemical parameters.
All of this is enormously valuable.
But on cacao farms there is also knowledge built over years of harvests: touching the mass, recognising a change in aroma, observing how much mucilage remains, opening a seed, comparing the centre of the box with its edges, and recognising how a particular cacao responds when the climate changes.
We do not need to choose between these two forms of knowledge.
Scientific research allows us to understand mechanisms that we cannot see.
The experience of those who work with cacao every day allows them to interpret a real fermentation while it is happening.
When the two come together, we understand the process better.
And perhaps one of the greatest lessons of fermentation is precisely this:
Good fermentation is not about completing seven days. It is about understanding what is happening during those seven days.
At Sumay, we look for cacao in which origin, genetics, biodiversity and post-harvest work are all part of the same idea of quality. Conscious Cacao, our Nacional cacao from Ecuador, comes from the Andean Chocó and is processed in micro-lots, through agriculture connected to highly biodiverse ecosystems and careful processing designed to respect the cacao’s own character.
In the next part
So far, we have followed fermentation through time.
But another fundamental question remains:
Does it matter where we ferment cacao?
Wooden boxes, sacks and heaps or piles affect variables such as heat retention, drainage, aeration, the size of the fermenting mass and the possibilities for turning.
In Part III, we will look at how these systems work, why they are used and what we really know about their influence on the final result.
