What does it mean to pasteurize a food or drink?

Pasteurization is the thermal process that allows you to extend the storage time of liquid or semi-liquid foods: what you need to know.

Used in the food sector to ensure a longer conservation of food, pasteurization is a treatment that allows you to destroy those agents that would cause alteration in liquid or semi-liquid products , such as bacteria, fungi and yeasts. Without losing, if not in a small part, chemical, physical and organoleptic characteristics. This is the case of fruit juices, milk, but also eggs and beer.

The first pasteurization

The inventor of this procedure was the French chemist Louis Pasteur , who in 1860 discovered that the wine, heated to a temperature of about 55 ° C for a few minutes, in the absence of oxygen did not undergo acidification, and stopped fermenting. The discovery was the first step towards improving conservation techniques and Pasteur later applied the same process to vinegar and beer.

How pasteurization takes place

The heat treatment to which food is subjected by heat exerts a bactericidal action , which destroys pathogenic microorganisms without the products undergoing organoleptic alterations , as opposed to what happens with sterilization. Given, however, the low temperature at which it operates, pasteurization does not destroy spores and thermophilic microorganisms , that is, those that can tolerate temperatures of 60 ° C. Consequently, to ensure a good preservation of the food, it is necessary to intervene further with other chemical substances, thus refrigerating the food or storing it under vacuum .

Types of pasteurization

Depending on the food and the bacterial load present, a different pasteurization process is envisaged: high, low or rapid . We talk about the first in case of temperature between 75 and 85 degrees, for 2-3 minutes . The second in the case of temperatures ranging between 60 and 65 degrees, for an average duration of about half an hour . Rapid pasteurization – identified by the acronym HTST – High Temperature Short Time – when the temperature is high ( 75-85 degrees) for only 15-20 seconds : the liquid is passed between two heated metal plates, obtaining a rise in a very short time homogeneous temperature. A last type of procedure is the UHT,typical of preserved milk, in which the sterilization of the food is also obtained, since the temperature is even higher .

Pasteurized foods

Some pasteurized foods are those we usually buy: we have already mentioned, for example, milk, whether it is fresh or preserved. The legislation in force recognizes at least 5 types of pasteurized milk – high quality fresh pasteurized, fresh pasteurized, microfiltered pasteurized, pasteurized, high temperature pasteurized and ESL (extended shelf life) – with rules of very precise conservation . Even the beer undergoes this thermal treatment: occurs after packaging (in the case of drums using the plate pasteurizer) at a temperature of 60 ° C and for about 20 minutes, which allows to prolong the conservation.

Finally, even the eggs are pasteurized. Or rather, certainly the tetrapak egg whites in brick , first produced for the exclusive prerogative of pastry shops today very popular for the preparation of fit foods . And certainly also the eggs already shelled and packaged just for the preparation of desserts. The eggs we buy fresh, on the other hand, are not pasteurized , but it is possible to proceed with this technique even at home, especially when we need them to be eaten raw, such as in tiramisu or for mayonnaise. How you do it? We explained it to you here .

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