INFLUENCE OF GENETIC-POLYMORPHISM OF CAPRINE ALPHA(S1)-CASEIN ON PHYSICOCHEMICAL AND TECHNOLOGICAL PROPERTIES OF GOATS MILK

The present work aimed to study the effet of alpha(s1)-casein genetic variants on physico-chemical characteristics, cheese-making properties, and heat stability of goat's milk. The study was based on an analysis of 153 individual milk samples which were obtained from 3 types of goats homozygous at the alpha(s1)-Cn locus: AA, EE and FF (51 samples of each type). Results showed that genotype had a very significant effect (AA > EE > FF) on fat, total nitrogen, protein and casein content, and on casein number (casein N/total N). Whereas alpha(s1)-casein type had a limited effect on mineral and salt equilibria, it had a marked influence on micellar size (AA < EE and FF) and to a lesser extent on micellar mineralization. As far as technological properties were concerned, the most important differences were observed with rennet gel strength (AA > EE > FF) and gel strengthening rate (AA > EE and FF). Micro-scale cheese-making carried out on 23 small bulk milks showed that dry matter and nitrogen recovery coefficients were 4 to 5% lower in FF than in AA milks. On the other hand, no difference was found in heat stability between the 3 types of milk.