Pasteurization is a preventive measure of public health. The quality of post pasteurized milk is tested by:

Phosphatase test is based on the fact that raw milk contains an enzyme called phosphatase which is destroyed on heating at a temperature which corresponds closely with the standard time and temperature required for pasteurization. At 60 deg C for 30 minutes phosphatase is completely destroyed. Consequently, the test is used to detect inadequate pasteurization or the addition of raw milk. Other methods: Standard plate count and Coliform count. Ref: Park's Textbook of Preventive and Social medicine, 19th edition, Page 522.