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Changes occurring in milk during pasteurisation

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.


AS FARMI Piimatööstus, Linda 15, 41536 Jõhvi, Tel. +372 332 1404 piim@farmi.ee