Milk and dried milk, buttermilk and buttermilk powder, whey and whey powder — Determination of phosphatase activity (Reference method)

Can be applied for the control of proper pasteurization of the products specified in the title of this standard. Uses a principle of determination based on the dilution of the liquid product or the reconstituted liquid product with a buffer at pH 10.6 containing disodium phenylphosphate and incubation at 37 degrees centigrade for 1 h. By reaction with the alkaline phosphatase present in the product phenol is liberated which reacts with dibromopquinonechloroimide. Then the colour formed is measured photometrically.