Chocolate defects and where they come from

Under-fermentation gives astringency, sourness and a flat green or raw-bean character, with beans that stay purple inside. Over-fermentation gives ammoniacal, hammy or putrid notes.

Neither is recoverable. Roasting can mask under-fermentation slightly by adding cocoa depth over the top; nothing removes the astringency, because the polyphenols were never broken down.

Smoke taint — ham, campfire, bacon — comes from wood-fired dryers venting through the beans. Mould and musty notes come from interrupted drying, case hardening or damp storage.

Both are irreversible and both are common. Musty notes in particular are frequently misattributed to the roast when the beans arrived that way.

Under-roasting leaves green, raw notes and unconverted precursors. Over-roasting gives ashy, carbonised bitterness that flattens everything else.

These are the maker's defects rather than the farmer's, and unlike the earlier ones they are avoidable with attention rather than with equipment.

Grittiness means under-refining. A waxy or greasy mouthfeel suggests a fat that is not cocoa butter, or too much of it. Dull, soft, streaky chocolate that will not snap is a tempering failure.

Fat bloom — grey film — is unstable crystals converting. Sugar bloom — a rough gritty surface — is condensation dissolving surface sugar. Both are storage or tempering failures, both are visually alarming, and neither makes the chocolate unsafe.

Several pairs get confused. Bitterness is a taste and normal at high percentage; astringency is a dry rough sensation and usually means under-fermentation. Acidity is bright and integrated; sourness is sharp and separate and usually means acetic acid that never left. Smoke is hammy and comes from drying; burnt is ashy and comes from roasting.

Getting these pairs right is what turns a complaint into a diagnosis.