Whole milk, once approved for use, is pumped into storage silos where it undergoes pasteurization, homogenization, separation and further processing.
Pasteurization:
Involves heating every particle of milk to a specific temperature for a specified period of time and cooling it again without allowing recontamination.
Homogenization:
Involves pushing the raw milk through an atomizer to form tiny particles so that the fat is dispersed evenly throughout the milk, stopping the fat from floating to the top of the container.
Separation:
Involves spinning milk through a centrifuge to separate the cream from the milk. After separation, the cream and remaining milk are remixed to provide the desired fat content for the different types of milk being produced.
For "whole milk," the cream is reintroduced until the fat content reaches 3.25%. For "low fat milk," the fat content is 1%. For "skim milk" (sometimes called nonfat milk) the fat content is .05%.