Homogenization or homogenisation is any of several processes used to make a mixture of two mutually non-soluble liquids the same throughout. This is achieved by turning one of the liquids into a state consisting of extremely small particles distributed uniformly throughout the other liquid. A typical example is the homogenization of milk, where the milk fat globules are reduced in size and dispersed uniformly through the rest of the milk.
Homogenization (from "homogeneous;" Greek, homogenes: homos, same + genos, kind) is the process of converting two immiscible liquids (i.e. liquids that are not soluble, in all proportions, one in another) into an emulsion (an emulsion is a type of colloid, which is a substance microscopically dispersed throughout another substance; when both the dispersed and the continuous substances are liquids, the colloid is called an emulsion). Sometimes two types of homogenization are distinguished: primary homogenization, when the emulsion is created directly from separate liquids; and secondary homogenization, when the emulsion is created by the reduction in size of droplets in an existing emulsion. Homogenization is achieved by a mechanical device called a homogenizer.
One of the oldest applications of homogenization is in milk processing. It is normally preceded by "standardization" (the mixing of several different milking herds and/or dairies to produce a more consistent raw milk prior to processing and to prevent, reduce and delay natural separation of cream from the rest of the emulsion). The fat in milk normally separates from the water and collects at the top. Homogenization breaks the fat into smaller sizes so it no longer separates, allowing the sale of non-separating milk at any fat specification.
Milk homogenization is accomplished by mixing massive amounts of harvested milk to create a constant, then forcing the milk at high pressure through small holes. Yet another method of homogenization uses extruders, hammermills, or colloid mills to mill (grind) solids. Milk homogenization is an essential tool of the milk food industry to prevent creating various levels of flavor and fat concentration.
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