Protein composition affects variation in coagulation properties of buffalo milk

The aim of this study was to investigate the effects exerted by the content of casein and whey protein fractions on variation of pH, rennet-coagulation time (RCT), curd-firming time (K-20), and curd firmness of Mediterranean buffalo individual milk. Measures of milk protein composition and assessment of genotypes at CSN1S1 and CSN3 were obtained by reversed-phase HPLC analysis of 621 individual milk samples. Increased content of alpha(S1)-casein (CN) was associated with delayed coagulation onset and increased K-20, whereas average pH, RCT, and K-20 decreased when beta-CN content increased. Milk with low kappa-CN content exhibited low pH and RCT relative to milk with high content of kappa-CN. Increased content of glycosylated kappa-CN was associated with unfavorable effects on RCT. Effects of milk protein composition on curd firmness were less important than those on pH, RCT, and K-20. Likely, this occurred as a consequence of the very short RCT of buffalo milk, which guaranteed a complete strengthening of the curd even in the restricted 31 mm time of analysis of coagulation properties and for samples initially showing soft curds. Effects of CSN1S1-CSN3 genotypes on coagulation properties were not to be entirely ascribed to existing variation in milk protein composition associated with polymorphisms at CSN1S1 and CSN3 genes. Although the role of detailed milk protein composition in variation of cheese yield needs to be further investigated, findings of this study suggest that modification of the relative content of specific CN fractions can relevantly influence the behavior of buffalo milk during processing.