What does pasteurization consist of?
Pasteurization is a heat treatment designed to increase the storage time of some foods. By exploiting the bactericidal action of heat, it is able to deactivate enzymes and destroy most of the microorganisms present in the food, even if some forms still manage to survive.
The duration of the treatment varies in relation to the nature of the food and the degree of contamination. The higher the initial microbial load (called bioburden), the more drastic the pasteurization treatment must be.
As shown in the table, the higher the temperature reached, the shorter the time required for pasteurization. These two quantities are also conditioned by the type of plant; for example, rapid pasteurization or HTST uses thin layer systems that allow homogeneous heating and ensure rapid reaching of the thermal center.
Difference between pasteurization and sterilization
The pasteurization treatments all take place below 100 degrees (60-95 ° C); once this temperature is exceeded, we are talking about sterilization which, to be effective, should in any case take place at temperatures equal to or higher than 120 ° C.
Quite simply, with pasteurization it is possible to destroy almost all vegetative forms (disinfection), while sterilization eliminates even the most resistant ones, called spore-forming ones.
For this reason, fresh pasteurized milk has a shelf life of seven days, while UHT sterilized milk must be consumed within three months. For the same reason, pasteurized milk must always be stored at temperatures no higher than 4 ° C and, once opened, it can be kept in the refrigerator for no more than two or three days.
