The effect of phenotypic combination of κ-CN, β-Lgand PRL genetic variants on cheesemaking properties of milk from cows of Ukrainian Black-and-White Dairy breed have been studied.

9 samples of milk were selected from individual cows with different complex genotypes κ-CN/β-Lg/PRL to provide for cheesemaking. 3000 ml of each sample were weighed for the making of laboratory-scale pickled cheese. Rennet coagulation time was determined in milk samples. Cheese and whey samples were analyzed for yield, fat and total protein.

Milk from cows of investigated herd has fair cheesemaking properties as its rennet coagulation time was not higher than 40 minutes. Formed under the influence of enzyme curds were largely homogeneous and dense and only occasionally broken. Whey was mostly transparent. The best indices of rennet coagulation time (26.1 min) were observed in milk from cows with complex genotype κ-CN AB / β-LG BB / PRL GG. The longest (32.2 min) rennet coagulation time was observed in milk from cows with genotype κ-CN AA/β-LG AA/PRL AG. For the duration of milk coagulation complex genotypes κ-CN/β-LG/PRL are ranked in the following order: АВ/ВВ/GG>AB/AB/GG>АВ/AA/GG> AA/AВ/GG>AA/AВ/АG>AA/AA/GG>AA/BB/GG>AA/AA/AA>AA/AA/AG. From the sequence of phenotypic combinations we can see that favorable for cheesemaking milk properties are determined by expression of alleles B on κ-CNandβ-LGgenes and also allele G on PRL gene.

Both components of milk coagulation – coagulation phase and curd firming phase – were the least in milk from cows with complex genotype κ-CN AB/β-LG BB/PRL GG. The longest duration of coagulation phase (27.0 min) was observed for genotype κ-CN AA/β-LG AA/PRL AG, the longest duration of curd firming phase (7.0 min) – for genotype κ-CN AA/β- LG AA/PRL AA. The differences between the lowest and highest values of duration of coagulation and curd firming stages were 5.5 (25.6 %) and 2.4 (52.2 %) min respectively. We can assume that forming of curd will be the main problem in the process of cheese making from milk of cows with complex genotype κ-CN AA/β-LG AA/PRL AA.

During the production of pickled cheese the largest volume of whey was separated from milk curds from cows with genotypes κ-CN AA/β-LG AA/PRL AA and AA κ-CN/β-LG AA/PRL AG – 2570 and 2.600 ml respectively.

Protein and fat content in these samples of whey were highest as well, i.e. higher proportion of nutrients passed in whey in comparison with other samples. Low water-retaining capacity of curds affected the output of finished products. The lowest yield of cheese (326 g) was obtained from milk of cows with genotype κ-CN AA/β-LG AA/PRL AG. Meanwhile, the highest cheese yield (463 g), thus lowest milk consumption per 1 kg of finished product (6.5 kg) was observed for milk from cows with genotype κ-CN AB/β-LG BB/PRL GG. The difference between the highest and lowest indices of milk consumption per 1 kg of cheese was significant – 2.7 kg.

The highest fat content (29.1 %) we observed in cheese from cows with genotype κ-CN AA/β-LG AB/PRL GG, while the lowest fat content (26.8 %) – in cheese from cows with genotype κ-CN AA/β-LG AA/PRL AG. In the last one we observed the lowest protein content (17.3 %) as well.

It was revealed that the best cheesemaking properties had milk from cows with complex genotype κ-CN АА/β-LG ВВ/PRLGG.This milk was characterized by the shortest rennet coagulation time, particularly coagulation and curd firming phases.

The lowest milk consumption per 1 kg of pickled cheese – 6.5 kg – was observed for cows with afore-mentioned genotype, which is on average 1.5 kg less than for animals with other genotypes. The yield of cheese from 3 liters of milk from cows with genotype κ-CN AB β-LG BB/PRL GG was 463 g. It has the highest protein content (20.2 %) and one of the highest fat content (28.2 %).

Key words: complex genotype, κ-CN, β-LG, PRL, milk production, rennet coagulation, cheesemaking properties, pickled cheese.