Tempering

Article index

		Objective
		Field of application
		Description of techniques, methods and equipment
		a) Single stream tempering
		b) Twin stream tempering
		c) Multi-stage tempering

Objective

Tempering serves three purposes:

to ensure product quality and appearance
to enable handling of liquid chocolate for various applications, e.g. demoulding
to ensure viscosity control and enable net weight requirements to be met.

Tempering is also the controlled thawing of meats.

Field of application

Tempering is applied in the manufacture of chocolate and chocolate containing products. Chocolate formulations containing cocoa butter, or cocoa butter equivalents, need to be tempered before use. This is because cocoa butter can exist in various crystalline forms, which if left untempered transform into unstable forms that impact severely on production capability and product quality. The tempering process ensures that the crystallisation of the fat occurs into stable forms which then enables products to be manufactured with good gloss, hardness or snap and delays the formation of grey white spots on the surface known as fat bloom. Poorly tempered chocolate results in the formation of the unstable crystalline forms, which subsequently give rise to poor appearance and texture. Chocolate may be under-tempered, well-tempered or over-tempered depending on the particular application.

Description of techniques, methods and equipment

The tempering process involves the melting of all the fat crystals present by heating to at least 40°C or above, then cooling the mass to typically below 30°C (known as the seeding temperature). This allows formation of stable crystalline forms, which, on holding, enables a further desirable transformation to occur. Finally the mass is warmed slightly to melt out any remaining unstable crystalline forms and to establish further crystallisation of the stable forms. Depending on the particular recipe or formulation, temperatures and holding times will vary accordingly to ensure the optimum product quality.

a) Single stream tempering

Uses the standard technique of inducing crystallisation of the stable forms from liquid followed by changes in temperature. The product is carried by a conveyor screw feed into a tempering tube where it is tempered in three stages.

b) Twin stream tempering

This requires an already seeded stream to be introduced into a molten untempered chocolate stream.

c) Multi-stage tempering

This is based on gentle cooling to produce seed crystals, followed by gentle reheating to allow the formation of stable crystalline forms. The cooling and reheating zones are made up of multistages maintained at the required temperature ranges via a jacketed recirculating water system. Various tempering machines are available based on this principle and are widely used in industry for a wide range of applications.

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