Which process step caused this flavour

Every entry below names what you perceived, the stages that can produce it, and — the part that matters — a discriminating observation that separates them. A single tasting note rarely identifies one cause, and pretending otherwise is how confident wrong explanations get repeated.

Two cautions before the list. Genetics and origin set the range of what is possible before any processing happens, so a bean that was never going to be fruity will not become fruity through good fermentation. And recipe sits on top of everything: sugar, milk solids and total cocoa percentage change perceived acidity, bitterness and texture regardless of how the beans were handled.

SOURCES: fermentation, drying, conching.

Volatile acidity — the sharp, vinegary kind — is acetic acid produced in fermentation that was not driven off afterwards. Fast drying traps it, because a bean whose surface dries hard retains acid inside. A short or cool conche leaves it in the finished chocolate, because driving off volatiles is one of the things conching does.

DISCRIMINATING OBSERVATION: acetic sharpness is smelled as much as tasted and dissipates as the chocolate warms in the mouth. Fruit-derived acidity — citric, malic, tartaric — reads as brightness attached to a fruit character and stays present through the finish. If the sharpness has no fruit attached to it, suspect the ferment-and-dry combination rather than the origin.

SOURCES: under-fermentation, dark roasting, high cocoa percentage, poor-quality shell removal.

These two get conflated constantly and are different sensations. Bitterness is a taste. Astringency is a tactile drying and puckering, from polyphenols binding salivary proteins.

Under-fermented beans retain more polyphenols, so they are astringent AND bitter together, usually with a flat, raw character. A dark roast produces bitterness without much astringency, alongside toasted, coffee-like notes. High cocoa percentage simply means more cocoa solids and less sugar, so both rise together with no accompanying fault. Shell fragments left after poor winnowing add a dry, dusty astringency.

DISCRIMINATING OBSERVATION: astringency without roast character points backwards to fermentation. Bitterness with roast character points at the roaster. Both rising smoothly as you move up a maker's percentage range is recipe, not fault.

SOURCES: drying, over-fermentation, storage.

Smoke taint comes from drying beans over or near a fire, or in a badly designed artificial dryer where combustion gases contact the beans. It is a drying fault and it is not removable.

Ham-like and putrid notes indicate over-fermentation, where organisms beyond the useful succession have taken hold. Mould and musty character can come from insufficient drying, from rewetting during drying, or from storage and transport in humid conditions.

DISCRIMINATING OBSERVATION: smoke is aromatic and phenolic and reads as a bonfire or a smoked food. Mould reads as damp and earthy. Neither is a roast character, and a maker who describes either as 'smoky notes from the origin' is describing a defect.

SOURCES: refining, conching.

Grittiness is particle size. Refining reduces solid particles below the threshold at which the tongue detects them individually, and a bar that feels sandy or gritty has not been refined far enough — or has been refined unevenly, leaving a tail of larger particles.

A related but distinct sensation is a thick, claggy, slow-melting body, which is more often a fat and flow problem than a particle one.

DISCRIMINATING OBSERVATION: rub a small piece between finger and thumb, or press it against the roof of the mouth. Discrete detectable particles are refining. A smooth but heavy, coating texture is fat content and flow behaviour.

SOURCES: tempering, cooling, storage.

These three travel together because they share a cause. Cocoa butter can crystallise in several different forms, only one of which gives the hard, glossy, cleanly snapping, well-contracting result. Tempering is the process of ensuring that form dominates.

Badly tempered chocolate is dull rather than glossy, breaks softly or bends, releases poorly from a mould, melts too readily on the fingers, and develops fat bloom quickly. Cooling too fast or too slowly after moulding produces similar outcomes even from correctly tempered chocolate.

DISCRIMINATING OBSERVATION: dull plus soft plus poor release, all at once and from the moment it set, is a temper problem. A bar that was glossy and has since gone pale and streaky in storage is bloom, which is a different event happening later.

SOURCES: storage temperature fluctuation, moisture, and — for one variety of it — the original temper.

Fat bloom is cocoa butter migrating to the surface and recrystallising, usually driven by temperature swings, and it leaves a pale, sometimes streaky or marbled film. Sugar bloom is sugar dissolving in surface moisture and recrystallising as it evaporates, leaving a grittier, more crystalline deposit.

DISCRIMINATING OBSERVATION: touch it, then taste it. Fat bloom feels slightly greasy and melts away against a warm finger; sugar bloom feels dry and gritty and does not melt. Neither is mould and neither is a safety problem — both are cosmetic and a change in texture rather than a spoilage.

SOURCES: storage, packaging, time, and recipe.

Cocoa butter oxidises slowly and picks up odours readily, so chocolate stored near anything aromatic acquires it. Milk chocolate and white chocolate stale faster than dark, because milk fat oxidises more readily and there are fewer cocoa solids and polyphenols present.

DISCRIMINATING OBSERVATION: a bar that tastes of what it was stored next to is odour transfer, and a bar that tastes of nothing in particular with a faint cardboard edge is oxidation. Neither is recoverable, and both are arguments for cool, dry, sealed and odour-free storage rather than for a refrigerator.