CHEESE MILK PASTEURISATION

Heating the milk for some time at temperature 63 to 95 ° C in order to destroy the viable microbial cells in it, it is called pasteurization.
In the dairy industry, pasteurization is considered to be effective, if heating continues:
by 63 °C 30 minutes,
by 75 do 80° C 1 do 2 minutes,
by 80 do 95°C moment,
it is worth mentioning, that with the use of modern tubular or plate apparatus, a satisfactory degree of pasteurization can be obtained, even by keeping the milk at temperature only for a dozen or so seconds 72 do 73°C.
Approx 99% viable bacteria, and their spores and some thermophilic bacteria are not lost.
You might believe, that pasteurization of milk will transform cheese making, first of all, it will free them from the nightmares of various cheese defects caused by harmful bacteria, like for example. coli-aerogenes. One could be deluded, that the course of the cheese maturation process will now be freely directed, when we removed it from the milk 99% bacteria, and in their place we have given pure cultures. It was to be expected, that since the use of pasteurization, certainty in the processing and uniform quality of various products will be achieved.
So far, all these hopes have only been fulfilled in a small part. For too many other kinds of obstacles are encountered, for which it is not yet known how to overcome them.
First of all, the maturation process of the cheeses is still little understood. This applies even to the most thoroughly researched cheeses, like Emmental. So not knowing all the intricate processes of maturation, universal cultures of bacteria cannot be used. It explains, why rennet cheeses, especially hard, made from pasteurized milk, using one-sided pure cultures do not have this full advantage, what are the characteristics of the same type of cheese made from raw milk.
Nevertheless, pasteurization of cheese milk is often used, which is even desirable, e.g. in the manufacture of non-fermented curd or rennet cheeses. The leaven made of the right lactic acid bacteria is then sufficient. When it comes to the pasteurization of milk intended for cheese with an intricate course of maturation, this case is more difficult.
The choice of temperature to be used in the pasteurization of the cheese milk varies. When kneading delicate cream cheeses, protective pasteurization at low temperature is applied, i.e.. at 63 ° C by 30 or just 20 minutes over high temperature pasteurization, i.e.. do 95°C. Most preferably and preferably pasteurization temperatures are used in the manufacture of cheddar and chester cheeses 72 do 74°C. Some cheesemakers heat the milk to even higher temperatures, e.g. do 95°C, arguing, that instantaneous heating to this temperature in many cases gives a more favorable result than heating, e.g., to 85 ° C for several minutes. However, protective pasteurization with 60 up to 63 ° C and it's only through 20 minutes has the most supporters in cheese making, especially in the manufacture of soft cheeses. Pay attention to this, that the changes taking place in pasteurized milk are all the greater, the higher the temperature and the longer it worked. It is also associated with the transfer of more or less albumin into the cheese. The yield of cheese from pasteurized milk may be several percent higher than from unpasteurized milk. In rennet cheese, this excess albumin is like a foreign body, which changes the course of puberty usually to a disadvantage. What is obtained then is something other than raw milk.
After all, pasteurization of cheese milk is beneficial, when it comes to remaking the uncertain, even somewhat defective, but still in its chemical composition little changed milk. The results are all the better, the more healthy raw milk was added to it, which has a positive effect on the fermentability of the mixture.
On some occasions I have benefited only from pasteurization of perishable milk to reduce the amount of bacteria, e.g. in summer time. Then I mixed them with the right amount of less contaminated milk, although also too infected with bacteria. In the assessment, I used a reduction test. Example: there is milk to be processed, which became discolored in 20 minutes, that is, it contains approx 200 millions of bacteria in 1 cm3. I have a mix of other fresh milk known from previous days, that it consistently withstands the reductase test to say the least 5,5 hours, that is, containing approx 200 000 bacteria in 1 cm3. Putting half pasteurized milk into the cauldron, which I am adopting now, that it does not contain any, or few bacteria and raw milk, I get a mixture containing: 100 000 bacteria in 1 cm³, probably useful, for it is taken from healthy milk. Such a mix
in terms of the number of bacteria it is classified as very good.
You can stop at this state of bacteria, you can also afford the addition of pure leaven culture. However, it must not be forgotten, that the pasteurization of the milk changed by bacteria does not restore the properties of the delicious milk, which it was before the infection.
We know, that the complex changes more or less as a result of pasteurization: protein + minerals. The effect of the rennet is weaker, the clot becomes more flaccid and less contractile than normal. The addition of calcium chloride in the amount 20 do 50 g na 100 1 admittedly, it strengthens clotting, however, it does not restore the normal contractility of the clot.