Tempering

Controlling which crystal form the cocoa butter sets in. The reason chocolate snaps, shines, and releases from a mould.

Step 37 of 43Both at the factory and in a kitchen

Cocoa butter is polymorphic: it can crystallise in six different forms, and only one of them — conventionally numbered form V — has the properties chocolate needs. Form V melts just below body temperature, which is why chocolate melts in the mouth; it contracts on setting, which is why a moulded bar releases; and it produces a hard snap and a glossy surface.

Tempering is the process of ensuring that form V, and only form V, seeds the set. The chocolate is melted fully to erase all existing crystals, cooled to a temperature at which several forms including V will nucleate, then warmed slightly to melt the unstable ones off, leaving form V seeds to propagate through the mass.

Untempered chocolate sets in unstable forms which convert over days into the stable form VI, migrating fat to the surface as it goes. That is bloom: the pale grey streaking on old chocolate. It is a crystal problem, not mould and not a hygiene failure.

What it does

Seeds the cocoa butter with form V crystals so the chocolate sets in the single stable polymorph that gives snap, gloss, contraction and a melt just below body temperature.

Why it matters

It is the difference between a bar that snaps and shines and one that is soft, dull, fingerprint-marked and prone to bloom. It has no effect on flavour and total effect on everything else.

Typical temperature: 27–32°C
Why the range is wide: Dark, milk and white chocolate each have their own working temperatures, and milk and white run a degree or two cooler than dark because milk fat interferes with crystallisation. Any single temperature quoted without saying which type it applies to is wrong for two of the three.

Variants

Tabling. Pouring two thirds of the melted chocolate onto a cool marble slab and working it until it thickens, then returning it to the warm remainder. The traditional method and the most controllable by eye.
Seeding. Adding finely chopped already-tempered chocolate to melted chocolate as a source of form V crystals. The most practical domestic method.
Machine tempering. A continuous tempering machine holds the curve automatically. Standard at any production scale.

When it goes wrong

Streaky, dull, soft chocolate that will not release from the mould and blooms within days — all of which are the same fault, an incorrect crystal form, presenting differently.

Commonly misunderstood

That bloom means the chocolate has gone off or grown mould. Fat bloom is cocoa butter that has migrated to the surface as unstable crystals converted to stable ones. It is harmless and the chocolate is edible; it is a texture and appearance problem. Sugar bloom, a separate phenomenon caused by moisture, looks similar and is also harmless.

Defines

CouvertureCouverture is formulated for the tempering step — the extra cocoa butter that defines the grade is what gives tempering something to work with.

Flavour developed here

WaxyThis stage is where the note is created, amplified or destroyed. A coating that does not clear from the palate. Almost always compound coating rather than chocolate.

Techniques that depend on this

Tempering chocolateThe physics is identical to the factory step — cocoa butter polymorphism — and it is modelled once rather than duplicated on both sides of the factory door.
Melting chocolateMelting destroys the crystal structure tempering created, which is why anything melted must be re-tempered before it will set properly.

Required by

BonbonA bonbon that will not release from its mould is reporting a tempering failure. The gloss on a modern bonbon exists partly to display that it was right.

Covered in

How to taste chocolateWhat the look-and-snap step is diagnosing.
Why chocolate meltsHow the right crystal form is achieved and why it matters.
How to temper chocolateThe crystal science the method is controlling.
Why temper chocolateThe full account of the crystal forms and the tempering curve.
Cocoa butter crystal formsThe procedure that manages the polymorphism.
Tempering without a thermometerThe crystallography the technique is managing.
Fat bloom vs sugar bloomThe crystallography that determines whether a bar blooms.
Why chocolate will not releaseThe crystallography that produces contraction.

Compared in

Hand tempering vs machine temperingSet against Machine tempering, with the practical consequence of each difference.

History and culture

Easter chocolateThe process without which a hollow moulded shell will not release from the mould at all.

Sources

ChocolateHQ editorial synthesis — ChocolateHQ(citation identity confirmed; passage not re-read)
The Science of Chocolate — Royal Society of Chemistry(citation identity confirmed; passage not re-read)