Alkaline phosphatase in cow and non-cow milk and cheese – Determination of enzyme activity as an indicator for the completeness of the pasteurisation process
The pasteurisation process is the most important stage of dairy production. Indigenous enzymes are used to assess the completeness of the process. The determination of alkaline phosphatase (ALP) activity by the fluorimetric method is accepted as the reference method for the verification of pasteurisation. Legislation from the European Union accepts a level of 350 mU·L-1 of ALP activity as safe for consumption of cow milk. For non-cow milk and cheese this limit has not been established yet. There are differences in the ALP activity among various species of dairy cattle.
The quality of dairy products depends on the milk’s quality from which the products are made. Contamination or an addition of raw milk to pasteurised milk can cause the hazard of pathogen contamination of the product. Pasteurisation that is performed incorrectly can influence the final product by the denaturation of whey proteins, inactivation of enzymes, destruction of beneficial bacteria or chemical changes, which can have an effect on the increase or the decrease of substrate availability for bacteria and enzymes. Because of this the heat treatment of milk for consumption and production of the dairy products should be limited (1, 2).
PROCESS OF HEAT TREATMENT
The heat treatment is designed to eliminate potential pathogenic microorganisms from raw milk with minimal chemical, physical and organoleptic changes in the milk. There are many combinations of time-temperature practices applied to milk processing. The lowest temperature, 63-65°C for 30 min (LTLT pasteurisation – low temperature long time) is for the destruction of psychrotrophs; higher temperature, 72-85°C for 15-30 s called HTST pas ...