Milk pasteurization can be tested by -

<p> Pasteurization of milk:- Heating of milk to such temperatures and for such periods of time as are required to destroy any pathogens that may be present while causing minimal changes in the composition, flavour and nutritive value. Methods of pasteurisation:- 1. Holder method- milk is kept at 63-66 deg C for at least 30 minutes and then quickly cooled to 5 deg C. 2. HTST method- high temperature and sho time method. Very large quantities of milk can be pasteurized by this method. 3. UHT method- ultra high temperature method. Pasteurization kills 90% of bacteria in milk including the more heat resistant tubercle bacillus and Q fever organism. But it will not kill thermoduric bacteria or bacterial spores. Despite pasteurization, bacteria are bound to multiply. In order to check the growth of microorganisms, pasteurized milk is rapidly cooled to 4 deg C. Hygienically produced pasteurized milk has a keeping quality of not more than 8-12 hours at 18 deg C. Tests of pasteurized milk:- 1. Phosphatase test 2. Standard plate count 3. Coliform count. {Reference: Park&;s textbook of community medicine 23 rd edition, pg no. 655}