Thursday, October 27, 2011

Crystallization in food processing

The process of forming crystals from solution is known as crystallization. It is a physical method of separation to obtain the solid in a pure form.

Crystallization is a term that describes several different phenomenon related to the formation of a crystalline lattice structure.

In food industry crystallization process is used for two specific purposes. Firstly, it is used to separate out a solid phase of different composition from liquid phase and one or both the fractions may be valuable.

Alternatively, crystallization is used without effecting separation of fractions in order to control or bring about desirable changes to the texture of the solid product.

Crystallization is often a four step process that includes:
*Generation of a supersaturated state
*Nucleation – formation of nuclei
*Propagation – crystal growth
*Maturation – crystal perfection or continued growth

Controlling crystallization in food processing requires control of the relative rates of nucleation and growth. To make the appropriate number and size of ice cream requires that the proper conditions are met during ice cream manufacture.

To make smooth texture of ice cream, many small crystals must be formed during processing.

Crystallization may serve for the recovery of crystalline products – (sugar, glucose, lactose, citric acid, salt), for the removal of certain undesirable components or for modification of certain food products in order to obtain a desirable structure.

In the process of crystallization of triglycerides, it is a complex phenomenon characterized by fairly slow growth rates and polymorphic transitions of their crystallized phases.

In crystallization of sucrose, it is the final step in the recovery of sugar from sugar cane or sugar beet. Also called ‘sugar boiling’, sugar crystallization of sugar is a complex process requiring precise control, skill and experience.

In principle, crystals are always pure. Impurities, which are sometimes found can be removed by washing.

In fondant processing, the temperature at which the syrup is nucleated is a critical parameter.

If nucleation is induced at temperature other than the optimal temperature, fewer crystals will be form than the maximum number, and the texture of the fondant will be unsatisfactory.
Crystallization in food processing
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