Proteolytic activity of starter bacteria on buffalo casein peptides produced by coagulants of different origins

In the present study, the cell wall extracts of Lactococcus lactis ssp. lac tis (Lc. lactis), Lactococcus lactis ssp. cremoris HP (Lc. cremoris HP) and Lactobacillus casei ssp. casei(Lb. casei) were used to reveal their proteo lytic activities towards buffalo casein peptides obtained with chymosin, po rcine pepsin, Rennilase and Suparen. The proteolytic activity of the strain s on casein peptides at pH 5.4 and 15 degrees C for up to 10 days was monit ored by RP-HPLC, SDS-PAGE, as well as Cd-ninhydrin method. The results indi cate that the activity of proteases and peptidases of the strains tested de pends on the identity of casein fragment determined by the coagulant used. The enzymes of Lc. lactis and Lc. cremoris HP acted primarily on casein pep tides of MW > 19 kDa. The enzymes of Lb. casei showed higher proteolytic ac tivity and broader specificity towards a wide range of casein peptides. The enzymes of Lb. casei were the most proteolytic and of Lc cremoris HP the l east when determining the liberation of free amino acids from casein peptid es. The formation and elimination of the bitter peptides depend on the choi ce of coagulant as well as the starter strain. The bitterness in Suparen- a nd Rennilase-peptides could be reduced by the enzymes of all 3 strains test ed.