EFFECTS OF CRUDE ENZYME OF LACTOBACILLUS-CASEI LLG ON WATER-SOLUBLE PEPTIDES OF ENZYME-MODIFIED CHEESE

The effects of crude enzyme extract of Lactobacillus casei ssp. casei LLG on the water-soluble peptides of enzyme-modified cheese (EMC) were studied by reverse phase HPLC and amino acid analysis. A wide range o f peptidolytic activities (aminopeptidase 1615.44 unit/ml; x-prolyldip eptidyl peptidase 66.73 unit/ml; proline-iminopeptidase 38.63 unit/ml) were detected in the crude enzyme extract. Bitter enzyme-modified che ese (EMC N24) was prepared with Neutrase(R) 0.5L for 24 h at 45 degree s C and treated with (EMC NL72) and without (EMC N96) the crude enzyme for 72 h at 35 degrees C. The percent peak areas of two hydrophobic p eptides (peak I and peak II) in EMC N24 were increased from 1.63% to 3 .65% and from 0.88% to 3.23% in EMC N96, respectively, but decreased t o below the detectable range in EMC NL72. The bitterness of EMC N96 ma y have been related to the increase in areas of these two peaks. Based on the amino acid compositions, peak I was identified as the alpha(sl )-casein fraction 26-31 (Ala-Pro-Phe-Pro-Glu-Val), and peak II as the beta-casein fraction 190-192 (Phe-Leu-Leu), respectively. The results suggest that both aminopeptidase and proline-specific peptidases prese nt in the crude extracts are responsible for degrading the hydrophobic peptides in bitter EMC.