Process of crystallization

Crystallization is an example of a separation process in which mass is transferred from a liquid solution, whose composition is generally mixed, to a pure solid crystal. Butter, margarine, ice cream, sugar, and chocolate all contain different types of crystals, although they all contain fat crystals. Ice cream has fat crystals, ice crystals, and sometimes lactose crystals. Key elements in the candy making process are in sugar's physical properties. Specifically, its solubility with its effect on the water's boiling point.

Crystallization occurs in two major steps.
*Nucleation: The appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The solute molecules or atoms dispersed in the solvent start to gather into clusters.
*Crystal growth: The increase in the size of particles and leads to a crystal state.

Nucleation involves formation of a crystalline state from the supersaturated liquid state. Once nuclei form, they grow into product-sized crystals through incorporation of additional molecules into the crystal lattice. This is called spontaneous nucleation.

Seed crystals are small crystals, generally of the solute, which then grow by deposition on them of further solute from the solution. This growth continues until the solution concentration falls to the saturation line. Below the saturation curve there is no crystal growth, crystals instead dissolve.

Controlling crystallization to obtain the desired crystal content, size distribution, shape, and polymorph is key to manufacturing products with desired functionality and shelf life. The crystalline phase plays such a large role in appearance, texture, spreadability, and flavor release in many food products including chocolate, margarine, butter, and shortening..
Process of crystallization