EFFECT OF THE 3 MOST FREQUENT CASEIN HAPL OTYPES OCCURRING IN THE NORMAN BREED USED FOR CHEESE-MAKING

In the Norman cow breed, the influence of three casein haplotypes alph a(s1)-Cn B, beta-Cn B et kappa-Cn B (BBB), alpha(s1)-Cn B, beta-Cn A(2 ) et kappa-Cn A (BA(2)A) and alpha(s1)-Cn C, beta-Cn A(2) et kappa-Cn B (CA(2)B), was compared on the composition of milk and its aptitude f or cheese production. The physicochemical composition of 89 samples (4 0 BBB, 30 BA(2)A et 19 CA(2)B) selected on the basis of genotype, fili ation and lactation stage, as well as their behaviour during coagulati on with rennet were determined. The same samples were used to make Sai nt-Paulin type cheese from 6 kg of milk (one milking). The kappa-casei n proportion was greater in BBB and CA(2)B milks than in BA(2)A milk. The micelle size varied conversely with the proportion of kappa-casein in total casein and was much greater for milk BA(2)A (15% more as com pared to CA(2)B milk) than for milk BBB and CA(2)B. The coagulation ab ility was higher for milk CA(2)B than for milk BA(2)A. The homozygote variant B of kappa-casein had a higher coagulation ability than varian t A. In manufacture of micro-cheeses with individual milk of same comp osition, the association kappa-Cn B and beta-cn B variants led to an i ncrease in the cheese yield mainly due to a better retention of the am ount of fat in the curd of cheese BBB. The microstructure of BBB curd was closer than these of curd BA(2)A. At the end of the ripening perio d (45 days), BBB cheeses were firmer, less elastic and more breakable than the other two haplotypes. Neither the cheese composition, nor the degree of proteolysis, nor the pH of the ripened cheeses appeared to be responsible for these texture differences which existed since the c oagulation stage.