TECHNOLOGICAL PROPERTIES OF MILK OF UKRAINIAN COWS BLACK-AND-WHITE DAIRY BREED WITH DIFFERENT GENOTYPES OF KAPPA-CASEIN FOR MANUFACTURE OF FERMENTED MILK CHEESE

Abstract

The article presented experimental material on the study of cheese suitability of milk from cows of the Ukrainian Black-and-White dairy breed with different genotypes of kappa-casein. Isolation of genomic DNA from individual samples of biological material taken from experimental cows was carried out using a commercial kit of reagents "DNA sorb B" manufactured by AmpliSens. Biolog-ical raw materials were samples of hair bulbs. Polymorphism of marker genes was determined by PCR-RFLP. Evaluation of the cheese suitability of milk by rennet, fermentation and rennet-fermentation samples was carried out in accordance with the require-ments of DSTU 7357: 2013 DSTU 7357: 2013, the active acidity of milk during the souring process was taken into account with a portable measuring instrument testo 206-pH1 pH meter. According to the results of previous studies, it was found that the active in the direction of growth the yield of fermented milk cheese, especially with an increased content of somatic cells in milk and a reduce in the duration of the formation of milk clots, appeared the rennet of animal origin of domestic production "Calf abomasum". In gen-eral, milk of all groups turned out to be suitable for making cottage cheese, since the time spent on coagulation of proteins under the influence of the experimental rennet did not exceed the current requirements of the regulatory documentation (40 min). Under these conditions, a probable acceleration of the formation of casein clots in the product samples of cows with the BB genotype by 1.6 min or 10.7% relative to animals with the AA genotype was observed and a decrease in the duration of its clotting time - by 1.2 min or 8.2%, in contrast from individuals with the AB genotype. As part of the visual determination of the state of milk of cows of all groups according to the quality classes of the obtained protein clots, it was noted that, according to the results of the rennet test, they are characterized by a dense structure, ease in the release of whey and the absence of visible voids. According to fermentation and rennet-fermentation tests, the milk of cows with the AA genotype corresponded to the II cheese suitability class according to a satis-factory quality assessment, while the milk of cows with the AB and BB genotypes belonged to the I cheese suitability class with an assessment “good”. The concentration of free hydrogen ions in milk during the day after milking did not significantly affect the ability of protein clots to coagulate. With an increase in the souring time at room temperature, the milk slightly lost its original properties. So, milk from cows with different genotypes at the kappa-casein locus was suitable for the manufacture of various types of dairy prod-ucts, including cottage cheese. At the same time, the best technological properties are inherent in the milk of cows with genotypes AB and BB.