Drying cacao, and what goes wrong

Wet beans coming out of a fermentation carry far too much water to store or ship. They have to come down to a level at which mould and other spoilage organisms cannot grow — which for most agricultural commodities is expressed as water activity rather than as a simple percentage, because it is availability of water rather than quantity that organisms respond to.

Too wet and mould grows, in the sack or the container, sometimes after the beans have left the farm. Too dry and beans become brittle, break in handling, and lose weight the farmer is paid for.

The catalogue does not print a target figure, because published targets vary between standards, contracts and regions and a single number quoted without its source would be treated as universal. What is not in dispute is that the acceptable band is narrow and that both edges have real costs.

Drying is not a separate stage that begins when fermentation ends. Chemical changes started in the ferment continue as moisture falls, and volatile acids — principally acetic — leave the bean during this period.

Drying too fast defeats that. The outside of the bean dries and hardens while the inside is still wet, which is called case hardening: the moisture and the acid inside are sealed in. The bean tests dry on the surface, may pass a superficial check, and produces sour, harsh chocolate months later. It can also rewet from the inside during storage as moisture equilibrates outward again.

This is why sun drying on raised beds, where beans are turned and can be covered, is generally preferred to any method that applies heat quickly, and why mechanical drying has to be run gently to work at all.

SMOKE TAINT is the most avoidable and least recoverable. Where beans are dried over a fire, or in an artificial dryer whose combustion gases contact them rather than being kept separate, phenolic smoke compounds are absorbed and stay. Nothing downstream removes them.

MOULD follows insufficient or interrupted drying — rain on an uncovered patio, beans heaped too deep, or drying stopped early. Beyond flavour, mould raises food-safety questions that are handled at the standards level.

CASE HARDENING, described above, is the quiet one. Unlike the other two it leaves no visible or aromatic signature at origin, and it is discovered as excessive acidity in a finished bar by somebody several countries away.

Most cacao is dried in the open, in the tropics, frequently in regions where the harvest overlaps with a wet season. That makes the weather during a specific fortnight a determinant of a lot's quality, and it is the clearest example of why post-harvest infrastructure is an economic question rather than only a technical one.

Raised beds, covered drying areas, movable roofs and adequate space all reduce weather exposure, and all require capital. A farm without them is not making a worse decision than a farm with them; it is drying in the rain because there is nowhere else to put the beans.