REMOVAL OF BITTERNESS FROM THE BITTER PEPTIDES EXTRACTED FROM CHEDDARCHEESE WITH PEPTIDASES FROM LACTOCOCCUS-LACTIS SSP CREMORIS SK11

Intracellular peptidases were extracted from the cell lysate of Lactoc occus lactis ssp, cremoris SK11 that had been grown in milk. Peptidase activities were determined using 12 synthetic derivatives of p-nitroa nilide. The X-prolyl-dipeptidyl amino peptidase exhibited the highest activity. Activities of aminopeptidase A and Pro iminopeptidase were l ow, and the activity of pyrrolidone carboxylyl peptidase was minimal u nder the conditions of the assay. The optimal pH and temperature for o verall enzyme activity were 7.5 and 30 degrees C, respectively. Incuba tion of the enzyme extract with peptide fractions from Cheddar cheese resulted in the degradation of some peptides, as observed by HPLC anal ysis. In a 4-h hydrolysis at pH 7.0 and 35 degrees C, sensory bitterne ss intensity of the bitter peptide fractions was significantly decreas ed. Five peptides that were responsible for bitterness in Cheddar chee se were isolated. Their origins were identified as alpha(s1)-CN(f1-7), (f1-13), (f11-14), alpha(s2)-CN(f191-197), and beta-CN(f8-16). These bitter peptides were rich in Pro, and Pro commonly occurred in the pen ultimate position. The calculated hydrophobicities suggested that the isolated bitter peptides were both hydrophobic and hydrophilic.