Methylene blue reduction test is done for estimating -

<p> Methylene blue reduction test:- Indirect method of detecting microorganisms in milk. The test is carried out on the milk accepted for pasteurization. It is based on the observation that bacteria growing in milk bring about a decrease in colour impaed to the milk. In conducting the tests definite quantities of methylene blue are added to 10 ml of milk and the sample is held at a uniform temperature of 37 deg C until the blue colour has disappeared. The milk which remains blue the longest is considered to be the best quality milk. The test thus serves as s confirmation of heavy contamination and compared with direct counts of bacteria, it saves time and money. {Reference: Park&;s textbook of community medicine 23 rd edition. Pg no. 655}