Genetic variants of milk proteins and their effects on the yieldand quality of cheese.

Abstract

Abstract Milk protein genes, which are inherited by simple Mendelian genetics, could be used as marker traits for production and milk compositional traits. Genetic variants of certain milk proteins have been shown to be associated with coagulating properties of milk, cheese yield and cheese composition. In most of the cases, the observed differences in cheesemaking properties between some genetic variants are the result of their associations with the levels of fat and casein in the milk, which significantly influence cheese yield and composition. However, in some instances, differences between genetic variants are the result of the direct effect as a result of substitution of amino acids along the polypeptide chain leading to a change in the conformation and hence altering the physiochemical properties of the protein. Differences in heat stability, protein/protein interactions, and rate of proteolysis of different genetic variants are some examples of the direct effects in some cheese varieties. In bovine species, most studies have demonstrated that the B variant of κ-casein and the B variant of β-lactoglobulin (which are associated with higher levels of fat and casein in the milk) give higher cheese yield and better cheese composition than the A variant of the two proteins. Most research on caprine milk has concentrated on the αas1-casein loci. Variant A, which is associated with higher levels of synthesis of αs1-casein and total casein, is more suitable for cheese production than either variant E or F. In the ovine species, it has been shown that variant D of αs1-casein is not favourable for cheesemaking, while β-lactoglobulin A milk is more suitable than β-lactoglobulin B for the making of cheese.