The purpose of pasteurisation is to destroy infectious microbes and ensure the safety and quality of milk.
Pasteurisation is the heating of milk at 100 ºC. As a result of pasteurisation the milk's shelf life is prolonged. Dairy products are made of pasteurised milk, wherein the pasteurisation time and temperature may vary.
Changes occurring in milk during pasteurisation:
1) milk density, viscosity and gas content are reduced;
2) whey proteins denature partially (10-20%); due to the light-reflecting properties of the denatured whey proteins, the milk becomes whiter;
3) the chemical content of milk fat is not affected but the surfacing capability of the fat particles is reduced, because the merging ability of the fat particles is also reduced; the amount of poly-unsaturated and essential fatty acids remains the same;
4) the chemical content of lactose is not affected;
5) the amount of vitamins A, D and E is not affected significantly, but the vitamin C content may decrease by 5-20%; B12 by 1-10%; B9 by 3-5%; B6 by 1-5%; and B1 by 10%;
6) the enzymes found in raw milk are inactivated; and
7) the nutritional value of milk proteins remains the same.