Bifidobacterial growth-promoting effect of yak milk -casein hydrolysates produced with different proteases

The growth-promoting effects of kappa-casein hydrolysates produced by four different proteases (trypsin, alcalase, papain and chymosin) on bifidobacteria (Bb12 and BBMN68) viability were evaluated. Results showed that the obtained kappa-casein hydrolysates possessed better property for improving the viability of Bb12 and BBMN68 than native kappa-casein. The bifidobacterium viability and pH drop were dependent on the added hydrolysates. The addition of kappa-casein hydrolysates improved the viability of Bb12 and BBMN68 to a variable extent. The kappa-casein hydrolysate produced with papain (KCHP) is the best for Bb12 and kappa-casein hydrolysate produced with trypsin (KCHT) is the best for BBMN68. Proper amino acid profiles improved the viability of Bb12 and BBMN68. The bifidobacterial growth-promoting capacity of kappa-casein hydrolysate may be due to its high content of Ala, Met, Tyr, Phe and Arg residues, especially Tyr which is richer in para-kappa-casein than in casein glycomacropeptide (GMP). In addition, the sialic acid content of kappa-casein hydrolysate produced with the tested proteases did not show a direct relationship with its bifidobacterial growth-promoting effect. The obtained peptides possessed growth-promoting activity for Bb12 and BBMN68 existed in para-kappa-casein.