Why Is Milk Homogenized?
Milk is homogenized to keep the milk fat evenly distributed throughout the milk, rather than rising to form a top layer of cream. This is how milk is homogenized: at the dairy plant, the milk is put into a tank called a homogenizer.
In the homogenizer the milk is forced under high pressure through many tiny holes. This simple process breaks up the milk fat into very small particles and distributes the fat equally throughout the milk. It makes the cream stay mixed with the rest of the milk. Most of the milk sold in the United States today is homogenized.
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 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.
Another application of homogenization is in soft drinks like cola products. The reactant mixture is rendered to intense homogenization, to as much as 35,000 psi, so that various constituents do not separate out during storage or distribution.