Inside the Fermentation Box: How Kampura Prepares Raw Cacao for Craft Chocolate

Cacao fermentation is the post-harvest process in which freshly harvested cacao beans are placed in heaps (often within wooden boxes), usually covered with banana leaves, and left to ferment for several days. Natural yeasts and bacteria break down the sugary pulp surrounding the beans, generating heat and acid that kill the seed embryo and trigger the chemical changes that create chocolate's flavor precursors.

Without fermentation, cacao beans cannot develop the chocolate flavor that customers know, regardless of how they are roasted.

Why fermentation is key

Crack open a ripe cacao pod and the first thing you notice is the smell. The beans are wrapped in a white, slippery pulp that smells like tropical fruit, somewhere between lychee and passionfruit. Scoop the beans out, bite into one, and you get a mouthful of sour, tannic bitterness. There is no trace of chocolate.

That bitterness is not a defect. It is what a living cacao seed tastes like. The bean at this stage is a viable embryo with its own plan: germinate, push a root into the soil, grow a tree. Left alone, it will try to do exactly that, consuming the sugars and storage proteins inside the seed to fuel its growth. Those same sugars and proteins are the raw material that fermentation converts into chocolate flavor. If the bean is not killed during fermentation, it spends those resources on sprouting instead, and there is nothing left for the Maillard reaction to work with during roasting.

USDA researcher Dr. Lyndel Meinhardt has estimated that roughly one quarter of chocolate's final flavor comes from genetics, one quarter from the growing environment, one quarter from fermentation, and one quarter from roasting (from Raising the Bar: The Future of Fine Chocolate, Pam Williams & Jim Eber, 2012).

Fermentation is one of these four pillars, but it's the one that most people outside the industry know the least about.

Kampura ferments the cacao for all its products on-site, which is not always the case. Most ceremonial cacao brands have no direct control over this step.

The entrance to Kampura's organic cacao fermentation center in Caqui Creek, Guatemala.

A note on cacao lavado (washed cacao)

Not all cacao is fermented. In Guatemala, southern Mexico, and parts of Central America, the traditional method is cacao lavado: beans are washed free of their pulp and dried under the sun without a full fermentation. The practice likely predates fermentation itself. The earliest Spanish accounts of cacao post-harvest processing describe beans extracted from pods and cured in the sun, with no mention of fermentation. That said, the first peoples of Mesoamerica certainly fermented corn to later imbibe. The science is still out.

What's certain is that cacao lavado (washed) tastes different. Without fermentation to develop new flavor compounds, more of the bean's raw genetic character comes through: sharper bitterness, higher polyphenol content, a flavor profile shaped almost entirely by variety and growing conditions. This is not a defect. It is the flavor that millions of people in Mesoamerica prefer, and it is the base of traditional drinks like pozol, champurrado, and other regional drinking chocolates.

But fermentation develops the flavor compounds that most chocolate consumers outside these traditions have come to expect. This article focuses on fermented cacao because that is what Kampura produces for the specialty and craft chocolate market. Fermentation is one processing approach among others, not the only legitimate one.

What happens inside the fermentation box

Within hours of harvest, the beans and their surrounding pulp are loaded into wooden fermentation boxes, typically about 1.2 meters on each side. The pulp is acidic, rich in sugars, and hospitable to yeasts. What follows is a three-phase microbial succession that unfolds over roughly five to seven days, depending on the cacao variety.

In the first phase, yeasts dominate. The mass is dense and airless. Yeasts, including Saccharomyces cerevisiae (the same species that ferments beer and bread), consume the pulp sugars and produce ethanol, carbon dioxide, and heat. Temperatures climb from ambient, around 25–27°C (77–81°F), up to 35–40°C (95–104°F) over the first two days. The ethanol produced during this phase is not wasted. It becomes the fuel for Phase 3.

Overlapping with the yeast activity, lactic acid bacteria establish themselves during days one through three. They convert sugars and some ethanol byproducts into lactic acid. This matters for the finished product: the ratio of lactic acid to acetic acid in the fermented bean affects how acidity reads in the final chocolate. Lactic acid produces a smoother, rounder acidity. Acetic acid is sharper.

The third phase is where the outcome is decided. When the beans are turned, oxygen enters the mass. Acetic acid bacteria take over, oxidizing the ethanol into acetic acid. This reaction generates intense heat. Temperatures peak at 45–52°C (113–126°F). The combination of that heat and the acetic acid penetrating the bean is what kills the embryo. Fermenters call this "bean death," and it is the subject of the next section.

Turning is typically done every 24 to 48 hours, but the schedule is a guideline.

"Bean death" and why it matters

When heat and acetic acid penetrate the cotyledon cells, the embryo dies. Cell membranes rupture, and compounds that were kept in separate compartments inside the living bean mix for the first time. Two things happen at once.

Proteases cleave the bean's storage proteins into free amino acids. These are the inputs that roasting will later convert into chocolate flavor through the Maillard reaction. Without bean death, these amino acids stay locked inside intact proteins, and roasting has nothing to work with.

At the same time, polyphenol oxidase encounters the tannins that make raw cacao so bitter and astringent. It breaks them down. This is visible: the cross-section of a well-fermented bean turns from purple to brown. The cut test, slicing beans in half to check that color, is how fermentation quality is assessed at origin. At least 75% brown means adequate fermentation. Purple or slate means under-fermented. Black with a foul smell means it went too far.

Cacao bean cut test results. Sobre fermentado means "over-fermented" in English.

The art side of smell, timing, and judgement

A thermometer tells you the temperature of the mass. Your nose tells you what is actually happening inside it.

Fermentation produces a distinct aroma sequence. It starts fresh and fruity, shifts to a strong yeast smell, moves through wine and ethanol, and finishes with a sharp vinegar that gradually softens into something fruitier. An experienced fermenter reads these transitions to judge when to turn the box, when to leave it alone, and when to move the beans to drying.

Turning is typically done every 24 to 48 hours, but the schedule is a guideline. Turn too early and you cut the anaerobic phase short. Turn too late and you trap excess heat or acid. The person standing over the box makes the call based on what they smell, what the temperature reads, and what the mass looks and feels like. This is learned through seasons of repetition, not from a manual.

Fermenting mixed genetics is a challenge

Different cacao varieties ferment at different rates. Criollo-type beans may finish in two to four days. Forastero types need five to seven. When a farm grows multiple varieties, as Kampura does, every harvest puts genetically different beans into the same box.

There is no universal protocol for this. The fermenter compensates in real time, adjusting turn timing and reading the mass temperature and aroma as a combined signal from beans that are each responding at their own pace.

Our Kampura team did not arrive at its current protocol quickly. Early fermentation batches required outside consultation with specialists who had worked across multiple cacao origins and genetic profiles. From there, the protocol was refined over seasons of trial, sensory evaluation, and adjustment. Each harvest brought slightly different ratios of varieties into the box, and each one taught the team something about how to read the batch as a whole rather than defaulting to a fixed schedule. The process today reflects that accumulated experience, and it continues to evolve as the farm's trees mature and its genetic mix shifts over time.

A sampling of Kampura's cacao genetics can be seen in the range of colors among these freshly-collected pods.

How fermentation connects to drying

After fermentation, beans are spread to dry. The target is 6–8% moisture content. Below 5% and the bean becomes brittle and damaged. Above 8% and mold becomes a risk during storage and shipping.

Drying is not a neutral step. It helps develop flavor. Acids inside the bean continue to evolve as moisture leaves. Slow drying lets volatile acids evaporate, producing mellower flavor in the finished chocolate. Faster mechanical drying traps more acid, producing sharper, fruitier profiles. The drying rate is a final opportunity to shape the bean's chemistry before it reaches the roaster. We take that opportunity seriously.

At Kampura, beans are sun-dried in a covered high-tunnel structure on wire mesh beds. Each lot is recorded and tracked through the drying process, which means any finished product can be traced back to its specific fermentation/drying batch.

On-site fermentation and drying

Kampura is an organic cacao operation in Izabal, Guatemala that has regenerated former cattle pasture into a thriving agroforestry system. The land produces fine-flavor cacao that is fermented, lightly roasted, and stone-ground at origin into ceremonial cacao and other products.

We manage fermentation on the farm in wooden boxes. No intermediary handles the beans between harvest and finished product. Kampura grows many different cacao varieties in an agroforestry system, which means each fermentation batch includes beans of varying genetics. The protocol was developed with outside consultation from fermentation specialists and refined through seasons of hands-on trial, sensory evaluation, and adjustment.

All processing happens at origin in Guatemala. Beans are fermented, sun-dried in a covered high-tunnel on wire mesh beds, lightly roasted, and stone-ground into cacao paste that is sold as blocks and flakes for drinking, baking, chocolate making, and more.

Ceremonial cacao is a drink made from pure cacao paste that has been fermented, dried, lightly roasted, and stone-ground. Unlike cocoa powder, it contains the full natural cocoa butter of the bean and is typically melted into hot water or milk to create a rich cacao beverage.

FAQ

What does fermented cacao smell like?

The aroma changes through the process. It starts fresh and fruity, shifts to yeast, moves through wine and ethanol, and finishes with a vinegar smell that gradually softens. A well-fermented batch has a clean, fruity-acidic smell at the end. An ammonia or putrid smell indicates problems.

How can you tell if cacao is properly fermented?

The cut test. Slice beans in half lengthwise and look at the cross-section. Well-fermented beans are brown inside. Purple or slate-colored interiors mean under-fermentation. Black or foul-smelling interiors mean the fermentation went too far.

What is cacao lavado?

Cacao lavado (washed cacao) is the traditional processing method in Guatemala, Mexico, and parts of Central America. Beans are washed free of pulp and dried without fermenting. The result tastes different from fermented cacao: more of the raw genetic character comes through, with higher polyphenol content and sharper bitterness. It is the base of traditional drinks like pozol and tascalate, and the preferred form of cacao for millions of people in Mesoamerica. 

Does fermentation affect caffeine or theobromine?

Not significantly. Caffeine and theobromine levels are determined mostly by genetics. Fermentation changes flavor precursors, polyphenol structure, and acidity, not alkaloid content.

Why do different cacao varieties need different fermentation times?

Varieties differ in polyphenol content, pulp sugar levels, and bean size. Criollo types have lower polyphenol loads and thinner cotyledons, so they ferment faster (2–4 days). Forastero types are denser and more polyphenol-rich, requiring 5–7 days.

Learn more

Not All Cacao Should Be Fermented — The Chocolate Professor
The case for cacao lavado and why fermentation is not the only legitimate approach to post-harvest processing.

Cocoa bean fermentation — Wikipedia
Overview of fermentation methods, microbiology, and regional variation.

The Science of Cacao Fermentation — JayArr Chocolate
The three-phase microbial succession and its connection to Maillard chemistry during roasting.

Dynamics of cocoa fermentation and its effect on quality — Nature / Scientific Reports
Peer-reviewed research on how fermentation parameters affect final bean quality.

Cocoa bean turning as a method for redirecting the aroma compound profile — ScienceDirect
Research on how turn timing affects aroma profiles.

The Fermentation-Flavor Connection in Chocolate — The Fermentation Association / FCIA
Webinar on how fermentation quality determines chocolate flavor.

Cacao Services, Inc.
Agricultural and scientific consulting for cacao farms worldwide.