ACE-inhibitory activities of peptide fractions (<3 kDa) and identification of peptide sequence by MALDI-ToF-MS in model cheeses incorporating different Lactobacillus species

In this study, the effects of five adjunct lactobacilli on the formation of angiotensin-converting enzyme inhibitory (ACE-i) peptides in model cheeses were investigated. A total of seven peptide fractions (less than 3 kDa) were obtained by means of a fraction collector coupled with a HPLC system. ACE-i activity and peptide sequence analysis of the seven fractions were determined by RP-HPLC and then MALDI-ToF-MS techniques, respectively. Peptides produced from αs1- and κ-caseins had higher amounts compared to those produced by other caseins. There were considerable differences between the fractions in terms of peptide sequences and ACE-i activities. In general, the peptide fraction containing Lactobacillus delbrueckii ssp. bulgaricus exhibited a higher level of ACE-i activity (79.56%) than the other samples. The next highest ACE-i activity was determined in the cheese containing L. plantarum and significant differences were observed between the ACE-i activities of the fractions. The highest ACE-i activity was identified in fractions including f1 (51.39%) for L. casei, f6 (33.49%) for L. helveticus, f4 (46.62%) for L. helveticus DPC4571 and f1 (47.96%) for cheese containing non-adjunct culture. In conclusion, use of lactobacilli as an adjunct in model cheese increased the peptide types and amounts and also ACE-i activity.