The newly extruded milk contains lysozyme and other antibacterial active ingredients. The lysozyme activity of a cup of raw milk was reduced by 50% when heated in the microwave oven to 50 degree. However, if raw milk is heated to 50 degree using a conventional heat source, the lysozyme activity in it is almost the same as before heating
It takes longer to heat liquid milk to 50 degree with a conventional heat source than it does with a microwave.
the enzyme is inactivated not by heating but by the microwave that generates heat.