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How-To Guide

Moisture in Cacao — What It Does to Your Roast

Why the beans stall

Put a probe in a cacao roast and you see something that surprises people the first time: the bean temperature climbs, then flattens out for a while near the boiling point of water, then starts climbing again.

Nothing is broken. That plateau is the moisture leaving. While there is free water in the bean, the energy you apply goes into evaporating it rather than raising its temperature — so you can turn the heat up and watch the number refuse to move. It is the same reason a pan of boiling water stays at boiling however high the flame.

Understanding that plateau is most of what you need to know about moisture, because the moment it breaks is the one landmark cacao actually gives you. Coffee gets first crack. Cacao gets this — but only if you can see the bean temperature.

How much water is in there

Cacao arrives fermented and sun-dried, and the trade generally specifies moisture capped around 7–8%. Below roughly that, the beans store safely; above it, mould risk rises sharply in shipping and storage, which is why the specification exists at all.

What matters for roasting is that the specification is a ceiling, not a target. Two sacks that both comply can sit at meaningfully different moisture levels, and they will not roast the same. Nor will the same sack in January and in July if it has been sitting in a humid space — dried cacao will take moisture back on from the air.

This is a large part of why a time-and-temperature recipe that worked last month can miss this month on the same equipment. Nothing changed except the water.

Reading the drying phase

Three things are worth watching.

How long the plateau lasts. Longer means wetter. If it runs noticeably longer than your usual, you are working with a damper batch and everything downstream shifts.

How hard you pushed to get through it. The temptation is to crank the heat and blast through the stall. Resist it. The outside of the bean is not protected by the moisture in the same way the inside is, so aggressive heat during drying scorches the surface of a bean that is still wet in the middle — the classic under-developed-but-burnt result.

How cleanly it breaks. A sharp transition into the climb generally means an evenly dried, well-sorted batch. A vague, gradual one often means mixed bean sizes or uneven drying, in which case some beans have finished drying while others have not, and the roast will be uneven no matter what you do afterwards.

What you cannot do about it

You cannot correct high moisture with a hotter roast. Heat does not make water leave faster in any useful way — it just damages the exterior while it waits. What you can do is give the drying phase the time it needs and stop treating total roast time as fixed. A wetter batch takes longer. That is not a failure, it is the batch.

Storage is the other lever, and it is the easy one. Keep beans sealed and somewhere stable rather than in a humid workshop, and you remove a variable you would otherwise be chasing.

Why this is invisible without a probe

Everything on this page is a bean-temperature observation. In an oven, or in any roaster that only reports air temperature, the entire drying phase is happening where you cannot see it — and because moisture varies batch to batch, it is the phase most likely to make two "identical" roasts come out different.

The RoastPilot controller reads bean temperature off a thermocouple in the rotisserie handle and graphs it live, so the plateau, its length and the moment it breaks are all just there on screen. Then it saves the curve, so next time you can see immediately whether this batch is behaving like the last.

Related: why bean temperature is everything · how long to roast cacao beans

Common questions

What moisture content should cacao beans have?

The trade generally specifies moisture capped around 7–8%, because above that mould risk rises sharply in shipping and storage. Treat it as a ceiling rather than a target — two compliant sacks can sit at noticeably different moisture levels and will not roast identically.

Why does the bean temperature stall during a cacao roast?

Because the energy is going into evaporating water rather than raising temperature. While free moisture remains, the beans hold near the boiling point of water however much heat you apply — the same reason boiling water stays at boiling. The moment that plateau breaks is the one reliable landmark cacao gives you.

Can I roast wetter cacao hotter to speed it up?

No. Extra heat does not remove water meaningfully faster, it just damages the outside of the bean while the inside is still wet — producing cacao that is scorched on the surface and under-developed inside. A wetter batch simply needs a longer drying phase.

Does cacao pick up moisture in storage?

Yes. Dried cacao will reabsorb moisture from humid air, which is a common reason a roast that worked last month misses this month on the same equipment with the same settings. Keeping beans sealed and somewhere stable removes a variable you would otherwise spend time chasing.

Keep reading

Where the roast ends and chocolate begins

Everything above is roasting — heat, time, temperature, moisture, how a bean behaves in a turning drum. That is our trade, and we will talk about it all day.

What happens after the roast is a different craft, and not ours. For fermentation, origin selection, winnowing technique, refining, conching, tempering and recipes, go to Chocolate Alchemy — John Nanci has been the reference on craft chocolate since 2004. Their complete bean-to-bar guide, the Ask the Alchemist archive and the forum will take you further than we could, and they run an all-day drum roasting seminar worth the trip.

Get the roast right with us. Get the chocolate right with them.

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