Heat treatment of milk

Sirovo mlijeko nakon mužnje sadrži veći ili manji broj mikroorganizama. Međutim, ako tijekom ili nakon mužnje u mlijeko dospiju mikroorganizmi iz neposredne okoline, njihov broj u sirovom mlijeku može narasti do nekoliko stotina tisuća/mL. Prema Pravilniku o kakvoći svježeg sirovog mlijeka (2000), mlijeko mora sadržavati manje od 100.000 mikroorganizama/mL. Mlijeko i mliječni proizvodi nezamjenjiva su komponenta u proizvodnom lancu hrane. Potrošači mlijeko i mliječne proizvode konzumiraju kao gotove proizvode ili ih koriste za pripremu različitih vrsta jela. Zbog sigurnosti potrošača obavezna je toplinska obrada mlijeka kada se ono prerađuje iz otkupa, jer sirovo mlijeko može sadržavati patogene mikroorganizme, koji su veoma opasni za ljudsko zdravlje. Stoga se u pogonu svake mljekare, koja otkupljuje mlijeko, provodi obavezna toplinska obrada sirovog mlijeka u svrhu uništenja patogenih i što većeg broja ostalih vegetativnih mikroorganizama ili prisutnih spora te radi inaktivacije enzima. Cilj toplinske obrade je produljenje trajnosti mlijeka te dobivanje zdravstveno sigurnih proizvoda, a da se pritom očuva njegova hranjiva vrijednost. Sterilizacija mlijeka se provodi za inaktivaciju spora i pri tome se primjenjuju temperature više od 100ºC. Cilj rada je opisati vrste toplinske obrade mlijeka i uvjete pod kojima se ona provodi. U radu su prikazane faze kroz koje prolazi mlijeko u mljekari, od hlađenja pa sve do završne toplinske obrade. Detaljno su opisane pasterizacija i sterilizacija. Navedeni su utjecaji toplinske obrade na promjene kemijskog sastava i svojstva mlijeka, enzimatsku aktivnost te na količinu i kvalitetu proizvedenog sira. Također je opisan rad izmjenjivača topline, kao i postupak pranja i dezinfekcije linije za pasterizaciju.After milking raw milk contains microorganisms. During the milking or in the period after milking microorganisms could reach milk and their number in raw milk can raise to sevral hundred thousand/mL. According to the Regulations on quality of the fresh raw milk (2000), the milk must contain up to 100 000 microorganisms/mL. Milk and dairy products are indispensable componentin the food chain. Consumers consume milk and dairy products as final products or use them for the preparation of various food. For the safety of the consumers, heat treatment of milk is required when milk is collected from the far, since raw milk can contain pathogenic microorganisms, which are harmfull for human health. Therefore, the operations of each dairy implement require heat treatment of raw milk to destroy the pathogens and of a large number of the other microorganisms or the present dispute and to inactivate the enzyme. The aim of heat treatment is to prolong shelf life of milk to obtain a safe product, and that it preserves nutritional value. Sterilization of milk is conducted to inactivation of the dispute and thereby the applied temperature of more than 100˚C. Aim of this thesis is to described the type of heat treatment of milk and the conditions under which it is conducted as well as to show the technological steps, from cooling to the final heat treatment. Pasteurization and sterilization are described in detail. Treatment influences on chemical composition and other properties of milk, enzymatic activity and the quantity and quality of the produced cheese, that were described to. Also the work of heat exchangers, as well as the washing and disinfection lines for pasteurization of milk were described