CASEIN DIVERSITY IN CAPRINE MILK AND ITS RELATION TO TECHNOLOGICAL PROPERTIES - HEAT-STABILITY

Caprine milk is characterized by a genetically linked diversity in cas ein content. Of particular importance is the genetic polymorphism of a lpha(s1)-casein, which is under the influence of seven known alleles c ontrolling the level of alpha(s1)-casein expression in milk. In this a rticle, the effect of alpha(s1)-casein genotype on milk composition an d heat stability is considered. Two different types of caprine milk we re used: milk high in alpha(s1)-casein from animals heterozygous AE or BE with respect to alpha(s1)-casein genotype and milk low in alpha(s1 )-casein from animals homozygous FF. Milk high in alpha(s1)-casein was less stable upon heating than milk low in alpha(s1)-casein. Unlike bo vine milk there was no recovery in heat stability at pH values greater than 7.0. These differences were associated with factors in the serum rather than the casein fraction and could not be explained by the var iation in the protein composition, beta-lactoglobulin to casein ratio or the small variation in Ca2+ and lactose levels between the two milk s. On the other hand, milk low in alpha(s1)-casein had a higher urea c ontent, which had a significant stabilizing effect.