Grade A designates quality fluid milk and is the grade purchased in retail stores and delivered to consumers. Milk used for manufacturing milk products butter, cheese, and ice cream is designated by the term Manufacturing Grade.

These grades are based on the conditions under which the milk is produced and handled, and on the bacterial count of the final product. The grades and their meanings vary only slightly, according to local regulations. Where the U .S. Public Health Service Grade A Pasteurized Milk Ordinance has been adopted, uniform standards are prescribed.

This food is among the most perishable of all foods. Milk, as it comes from the cow, provides an excellent medium for bacterial growth and is subject to many possible flavor changes unless it is protected constantly from contamination each step of the way from the cow to the consumer.