Efeito do polimorfismo do gene da beta- caseína na qualidade do leite da raça Sindi.

Abstract

Zebu breeds are among the most adapted to the hot and dry climate, among them the Sindhi breed stands out for having dual aptitude (meat and milk), high feed efficiency and milk with a high content of total solids, mainly fat and protein. About 80% of the total milk proteins are made up of caseins, which in turn are divided into alpha-casein S1 and S2, beta-casein and kappa-casein. There are 13 variations of the beta-casein alleles: A1, A2, A3, A4, B, C, D, E, F, H1, H2, I, G, however, A1 and A2 are the most frequent. The consumption of A1 milk is associated with an increased frequency of diseases and there is evidence that the A2 variant is not so harmful to human health. There is evidence that the Sindhi breed has a high frequency of the A2 allele of beta-casein and that it has a positive effect on the characteristics of milk. Therefore, the aim of this work was to evaluate the effect of the genetic polymorphism of beta-casein on the physical-chemical composition, sensory analysis and profile of milk fatty acids of the A1A2 and A2A2 genotypes of beta-casein, in Sindi cows. Twelve Sindi cows subdivided into two groups with distinct genotypes of beta-casein (A1A2 and A2A2) were used for milk production. In the physical-chemical composition of milk, the content of protein, fat, SNG, titratable acidity and relative density at 15 ° C were evaluated. Sensory analysis was also performed and the fatty acid profile of milk of both genotypes was determined. The data of the physical-chemical analysis and fatty acid profile were submitted to the Tukey test, at 5% significance level (P <0.05), and the data referring to the sensory analysis were analyzed according to the Chi-square test a 5% (P <0.05). There were no differences between groups in terms of fatty acid profile and sensory analysis (P> 0.05). Protein content (3.30 and 3.18%), SNG (9.49 and 9.15%) and density (1.031 and 1.030) were different between genotypes A1A2 and A2A2, respectively (P <0.05). It is concluded that the recessive and dominant genes for beta-casein exert little effect on the physicochemical characteristics, and no effect on the fatty acid profile and sensory analysis of milk.