Determination Of Phosphatase Activity In Butter Milk, Whey, Milk Powder

The enzyme phosphatase is also found in milk products. There is differences between the procedure for measuring the phosphatase activity of milk and milk products. It can also be measured as below:


  • Whatman filter paper No. 2
  • Samples of milk products
  • Water bath
  • Comparater
  • Test tubes
  • Pipette
  • Zinc sulphate (30%)
  • Potassium ferrocyanide (15%)


  1. Prepare liquid suspension of milk product and take 2 ml of liquid product to be tested in a clean and dry test tube.
  2. Transfer 15 ml of buffer substrate into it, and place onto a water bath.
  3. At the same time, take 15 ml of buffer substrate and 2 ml of boiled liquid product and place in water bath.
  4. After 2 hours remove both the tubes.
  5. Add 0.5 ml of zinc sulphate (30%), replace the stopper and shake vigorously and allow to stand for 3 minutes.
  6. Add 0.5 ml of potassium ferrocyanide (15%), mix thoroughly and filter through Whatman filter paper No. 2.
  7. Collect the clean filtrate in a test tube and compare the filtrate of the boiled sample in the comparater using the special disc.
  8. All the samples giving reading in excess of 10 mg of p-nitrophenol shall be recorded unsatisfactory.


Dr. R. C. Dubey – Practical Microbiology

Gaurav Singh

Editor in Chief Medical Microbiology & RDT Labs - RDT Labs Magazine | BSc Medical Microbiology | MSc Microbiology

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