The influence of k-casein genotype on the coagulation properties of milk collected from the local Latvian cow breeds

S. Petrovska¹,*, D. Jonkus¹, J. Zagorska² and I. Ciprovica²

¹ Latvia University of Agriculture, Faculty of Agriculture, Institute of Agrobiotechnology, Street Liela 2, LV-3001 Jelgava, Latvia
² Latvia University of Agriculture, Faculty of Food Technology, Department of Food Technology, Street Rigas 22, LV-3004 Jelgava, Latvia
*Correspondence: solvitapetrovska@gmail.com

Abstract:

Cheese production is becoming increasingly more diversified all over the world. The information on milk coagulation properties among Latvian dairy cow breeds and its suitability for cheese production still remains unclear. At the same time, milk with good renneting properties collected from the native Latvian cows can be used for the production of Protected Denomination of Origin (PDO) cheeses. The purpose of this research was to analyse the influence of the milk protein genotypes present in Latvian native cattle breeds on the milk coagulation properties. The data was collected in 2016 from 56 Latvian brown, 26 Latvian blue and 13 Holstein black and white cows i. Highest frequency of AA κ-casein genotype was found in Latvian brown breed (0.593), while AB genotype was more often present in the Latvian blue breed (0.636). It has been found that the presence of κ-casein genotype resulted in no significant difference in milk composition and milk coagulation properties among studied cattle breeds. We have observed a tendency that the most desirable milk coagulation properties were present in BB genotype. A significant effect of breed on milk composition has been found (p < 0.05). Milk yield of Holstein Black and White was 32.0 ± 2.99 kg, while in Latvian blue it was only 17.6 ± 1.32 kg. Higher milk yield was obtained in Latvian blue breed in comparison to that of the brown breed – 19.10 ± 0.76 kg. Better milk coagulation properties were observed in Latvian brown breed – shorter milk renneting time (16.86 ± 1.15 min), highest curd yield (24.0 ± 0.79%) and curd firmness (3.21 ± 0.17 N).

Key words:

Effect of k-casein and ß-lactoglobulin genotypes on the milk rennet coagulation properties

I. Kübarsepp, M. Henno, H. Viinalass and D. Sabre

Institute of Veterinary Medicine and Animal Science, Estonian Agricultural University, Kreutzwaldi 1, 51014 Tartu, Estonia; e-mail: ivik@eau.ee

Abstract:

Purpose of this study was to find connections between milk renneting properties of dairy breeds in Estonia and the genetic variants of k-casein and ß-lactoglobulin. Milk (n = 2161) and blood (n = 87) samples were taken from Põlula Research Farm where all dairy cattle breeds are represented: Estonian Holstein (EHF) – 45 cows, Red-and-White Holstein (RHF) – 12 cows, Estonian Red (EPK) – 26 cows and Estonian Native (EN) – 4 cows) raised in Estonia. Milk samples were analysed for fat, protein, calcium, and phosphorus contents, somatic cell count, and rennet coagulation parameters. Rennet coagulation properties of milk from cows of four experimental groups were higher in EK group. No noncoagulated milk samples were observed in this group. Estonian Red breed has the second-best rennet coagulation properties of milk. Percentage of noncoagulated milk samples in the group of EPK (3.6%) was lower than in the groups of EHF and RHF (percentage of noncoagulated milk samples 5.0% and 7.7%, respectively). All measured rennet coagulation parameters were significantly better for the k-casein BB and worse for the k-casein AA genotype. k-Cn BB exhibited also the lowest percentage of noncoagulated milk samples and samples that did not reach K₂₀ 30 min after enzyme addition. ß-Lg genotypes had no significant effect on milk rennet coagulation parameters, but it was possible to observe tendencies that milk rennet coagulation time was the shortest and the percentages of noncoagulated milk samples and samples with poor coagulation properties (NK₂₀) were lower for the ß-Lg AA genotype. Better milk rennet coagulation properties among native breeds are explicable with a higher frequency of k-Cn B allele. The frequency of k-Cn B allele has been decreased among Estonian Holstein cows.

Key words:

genetic variants, k-casein, milk coagulation properties, milk proteins, ß-lactoglobulin