Chocolate and Cocoa Processing: Tempering, Moulding, Enrobing, Ganache
This domain tests cocoa butter crystallography and the process controls that depend on it, plus the practical handling of chocolate mass, cocoa powder and ganache fillings.
Core rules
- Cocoa butter crystallises in six polymorphs; form V (beta) is the desired stable form, melting near 32–34 °C. Form IV and VI produce dull surfaces, poor snap and bloom.
- Tempering: melt fully (dark ~45–50 °C, milk lower), cool to form crystals (~27–28 °C), then reheat to melt unstable forms and leave form V seeds - typically ~31–32 °C dark, ~29–30 °C milk. Verify with a temper meter (temper index/slope) or by a controlled snap-and-gloss check, never by temperature alone.
- Viscosity is described by plastic viscosity and yield value. Lecithin mainly lowers yield value and plastic viscosity; PGPR lowers yield value at low dose.
- Moulding: deposit at correct weight, vibrate to remove air, cool in a tunnel around 10–15 °C with a dew point below the product temperature, demould.
- Enrobing: curtain, blowing, vibration, then cooling; excess chocolate is returned and re-tempered.
- Ganache: an oil-in-water emulsion with a water activity typically below ~0.65 for ambient shelf life; sugar/glucose balance and correct emulsification prevent splitting.
- Seizing: a little water in melted chocolate makes sugar particles clump and turns the mass into a stiff paste. Keep water out or deliberately reformulate to a water-containing system.
Worked example
Moulded dark bars show grey streaks and poor snap after two weeks. A temper meter shows a flat slope, indicating under-tempering. Reasoning: without sufficient form V nuclei, the fat crystallises into unstable forms and later transforms, releasing heat and migrating fat to the surface as bloom. Correct by re-setting the tempering curve - melt, cool, reheat - verifying the temper index before the depositor, and confirm the cooling tunnel temperature and dew point.
Traps
- Confusing sugar bloom (dissolves on a wet finger) with fat bloom (does not).
- Adding chocolate to a bowl over steam and letting condensate drip in.
- Over-tempering, which raises viscosity and causes mould short-fills.
- Using a lauric cocoa butter substitute in a product that also contains cocoa butter.