Yield is a roasting problem wearing a winnowing costume
People troubleshoot poor winnowing at the winnower — adjusting airflow, re-running the fraction, buying a better machine. Sometimes that is right. Often the batch was decided several steps earlier, in the drum.
One of the roast's four jobs is to dry and embrittle the husk so it separates cleanly from the nib. Get that right and cracking and winnowing are straightforward. Get it wrong and no amount of fan adjustment fully recovers it.
We build roasters, not winnowers — Chocolate Alchemy sells those and will tell you far more about winnowing technique than we can. What we can tell you is what the roast does to the husk before it ever reaches the machine.
How husk release actually works
Inside a fermented, dried bean the shell sits against the nib with some moisture between and within them. Roasting drives that moisture out. As the shell dries it shrinks, becomes brittle, and loses its grip on the nib — so cracking shatters it into pieces that are light relative to the nib and can be separated by air.
Two properties matter, and they pull in opposite directions:
- How well the shell has released — more roast, better release.
- How the shell fragments — more roast, smaller fragments.
That tension is why yield has a sweet spot rather than simply improving with more heat.
Under-roasted: the shell clings
Not dried enough, the shell stays leathery rather than brittle. Cracking tears it instead of shattering it, and pieces stay attached to nib.
You then get to choose which loss you prefer. Winnow aggressively enough to remove the clinging husk and you blow good nib out with it. Winnow gently to protect the nib and you carry husk through into the melanger — where it becomes grit in the finished bar, and no downstream step removes it.
Symptoms: visible shell still attached after cracking; unusually heavy husk fraction; grit in the finished chocolate.