CHEESE-MAKING PROPERTIES OF RAW AND PASTE URIZED MILK WITH RESPECT TOMILK PROTEIN POLYMORPHISM

It is evident that B variant of kappa-casein (kappa-Cn) system has fav ourable effects on cheesemaking properties of milk. But some researche rs believe that this effect is true of raw milk only, not of pasteuriz ed milk. In traditional cheesemaking countries, milk not treated therm ally is used for cheese production. There is not such a tradition in t his country, total cheese production uses pasteurized milk. Hence the objective of this paper was to evaluate what the actual effect of milk pasteurization is like. Milk coming from 48 cows was investigated in total, and the phenotype of milk proteins was determined after electro phoresis on starch gel with urea and mercaptoethanol. A diluted microb ial rennet Fromase (1 : 50 000) was used for these research purposes. Coagulation time was evaluated at a temperature of 32 degrees C (CK in s) and the following characteristics were evaluated after incubation of renneted milk for I hour at this temperature according to the rate of penetration of a freely falling body (under constant conditions): c urd firmness (PS in mm), curd quality (KS - class 1 = good to class 3 = bad quality) and the volume of released whey (OS in mi) in raw and p asteurized milks. Pasteurization temperature was 63-65 degrees C and i t took 30 minutes. The results were evaluated in beta-lactoglobulin (b eta-Lg) and kappa-casein (kappa-Cn) systems. Long-time pasteurization worsened all the investigated cheesemaking properties of milk in gener al (Tab. I, Fig. 1). If the milks were classified according to the bet a-Lg system, all the investigated values became worse in the order BE < AA < AB, both of raw and pasteurized milk (Tab. II, Pig. 2). In the kappa-Cn system the precedence of kappa-Cn B was maintained also in pa steurized milk, while the order from the worse to the best quality AA < AB < BE was identical for all the investigated cheesemaking properti es (Tab. III, Pig. 3). Hence the advantage of better cheesemaking prop erties in milks with kappa-Cn B can also be applied to the production of cheese from thermally treated milk.