Fermentation defects
The four ways a fermentation goes wrong, what each tastes like, and why under-fermentation is by far the most common.
Fermentation faults account for more disappointing chocolate than any other single cause, and they come in a small number of recognisable kinds.
Under-fermentation leaves the bean purple inside, with polyphenols unreduced — the result is bitter, sharply astringent and flat, with a raw quality no roast removes. It is the most common fault because fermenting properly costs days of labour that a farmer paid by weight may not be rewarded for.
Over-fermentation pushes past the useful range into winey, then ammoniacal, then putrid. Under-acidification, from insufficient turning, leaves the bean incompletely killed. And contamination — from dirty boxes or previous batches — introduces off flavours that are essentially random.
What it does
Nothing — this record describes failure modes rather than a technique, and exists because the faults are diagnosable from the finished bar.
Why it matters
Under-fermentation is the single most common quality fault in chocolate, and it is reliably identifiable by astringency in the finished bar.
What it does to the flavour
Under-fermentation gives bitterness with pronounced astringency; over-fermentation gives winey then hammy notes; contamination gives unpredictable off flavours.
When it goes wrong
Under-fermentation, and it is an economic outcome rather than a technical one — the incentive to ferment properly depends on whether grading rewards it.
Commonly misunderstood
That a harsh, drying bar is simply a high percentage. Astringency indicates unreduced polyphenols, which means fermentation rather than cacao content.
Related
Flavour developed here
Covered in
- Fermentation explainedWhat each specific failure mode does to the finished bar.
- Chocolate defects and their causesThe fermentation failures in detail.
- The microbiology of cacao fermentationWhat the failures look like and how they are identified.
Sources
- ChocolateHQ editorial synthesis — ChocolateHQ(citation identity confirmed; passage not re-read)
- Chocolate Science and Technology — Wiley-Blackwell(citation identity confirmed; passage not re-read)