A small wetting quantity of a nitro-phenylphosphate indicator substance is applied to the dairy product which is then heated to within the temperature range 36 - 37 degrees C and incubated at this level for a predetermined period. The sample develops a color which indicates the degree of previous heat treatment on a known scale. The process rapidly determines whether a sample of milk or other dairy product has been subjected to adequate heat treatment. A small wetting quantity of a nitro-phenylphosphate indicator substance is applied to the dairy product which is then heated to within the temperature range 36 - 37 degrees C and incubated at this level for a predetermined period. The sample develops a color which indicates the degree of previous heat treatment on a known scale. The color difference also indicates the absence of alkaline phosphatase. The indicator substance is provided as a substrate buffer solution is mixed in with or applied to the sample dairy product. Alternatively, the dairy product is applied to an indicator paper which has been wetted with the indicator buffer solution.
