DEBITTERING OF TRYPTIC DIGESTS FROM β-CASEIN AND ENZYME MODIFIED CHEESE BY X-PROLYL DIPEPTIDYLPEPTIDASE FROM LACTOBACILLUS CASEI SSP. CASEI. LLG

Document Type: Regular Paper

Authors

1 Department of Food Science and Technology, Faculty of Agriculture, Ferdowsi University of Mashhad, 91775-1163, Mashhad, I. R. of Iran

2 Department of Food Science & Agricultural Chemistry, Faculty of Agriculture & Environmental Sciences, Macdonald Campus of McGill University, Montreal, Canada H9X3V9

Abstract

The proline-rich β-casein was digested in vitro with trypsin, and the oligopeptides produced
were then isolated by RP-HPLC and subsequently identified by amino acid analysis and ion mass
spectrometry. The peptide fractions from the complete digestion were then treated with purified x-prolyl
dipeptidyl peptidase (X-PDP) extracted from Lactobacillus casei ssp. casei LLG. Two bitter peptides (f53-97
and f203-209) containing X-Pro-Y-Pro in their amino acid residues were completely hydrolyzed by X-PDP,
while several peptides with a high degree of hydrophobicity were also decreased in a peak area. The
debittering effect of X-PDP from Lactobacillus casei ssp. casei LLG on enzyme modified cheese (EMC) was
also investigated by both subjective and objective methods. The bitterness of cheddar cheese slurries
supplemented with Neutrase® 0.5 L was completely eliminated after treatment with crude enzyme extract
from Lactobacillus casei ssp. casei LLG. Two hydrophobic peptides in EMC with Ala-Pro-Phe-Pro-Glu-Val
and Phe-Leu-Leu residues were hydrolyzed by crude enzyme extract. The RP-HPLC, and subsequently, ion
mass spectrometry analysis have shown that the debittering effect on EMC was due partially to the presence
of X-PDP.

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