Within the pasteurization process, milk goes through a fat removal process, resulting in skim milk. This on-line process continues with homogenization, a simple mechanical process which reduces the size of milk fat globules to minute particles allowing for a consistent suspension and preventing separation. The hot milk is then quickly cooled to 1 to 4 degrees Celsius and packaged in sterile containers. A best before date is stamped on the package prior to shipment in refrigerated trucks to grocery stores. Pasteurization is a heat process which destroys harmful bacteria, thus eliminating the risk of developing such potentially serious infectious diseases as salmonellosis, tuberculosis, brucellosis, listeriosis, and campylobacteriosis.
Pasteurization has no significant effect on milk's nutritional value.
Despite a minimal reduction of such vitamins as thiamin, vitamins B12 and C during pasteurization, pasteurized milk still remains an excellent source of calcium, phosphorus, protein, riboflavin, and vitamins A and D, and a good source of thiamin and vitamin B12. The loss of vitamin C is not nutritionally significant because milk is not an important source of vitamin C in the diets of humans. The Federal Government, in recognizing the importance of pasteurization of milk, passed a law in 1991 which allows only pasteurized milk to be sold in Canada. Injections of rBST generally increase milk production of dairy cows by 10 to 15 percent, but increases of up to 40 percent have been recorded. BST is present naturally in trace amounts in all milk, and milk from rBST treated cows contains similar trace amounts.