There are two methods of pasteurization in use today; batch and continuous flow. The batch pasteurization process starts with a large quantity of milk that is held in a heated vat at 149°F/65°C for thirty minutes. The pasteurization process finishes with quick cooling to about 39°F/4°C. The pressurized milk is held at 161°F/72°C, for a minimum of 16 seconds. It is then chilled back to 39°F/4°C or cooler, through a heat exchanger to pre-warm cold milk just entering the system. The goal in heat treating milk is to ensure the destruction of all disease-causing microbes. This ensures the quality, safety, and a longer shelf life of the milk for the end consumer.
The dairy industry works with the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) to ensure the safety and quality of dairy products. The FDA works closely with the state government to ensure the Grade A Pasteurized Milk Ordinance (PMO) is followed. Created by the U.S. Public Health Service, the PMO sets the standards for milk production, milk transport vessels, pasteurization, product safety, equipment sanitation and labeling. Processing plants also have routine inspections to ensure quality and safety.