Bioactive peptides in long-time ripened open texture semi-hard cheese
Bovine milk is an excellent source of bioactive peptides. The bioactive peptides are in an inactive state in the protein and are released during enzymatic activity, e.g. during cheese ripening. Specific properties of bioactive peptides from ripened cheese has been reported, e.g. antihypertensive, antioxidative, antimicrobial, immunomodulatory and mineral binding. This work was made to screen for bioactive peptides in the Swedish long time ripened open-texture cheese, Präst cheese from Skånemejerier. Cheeses with three different ripening times available at the market were investigated; Prästost (ripened for 8 months), Allerum (1 year) and XO (2 years). A solution of the pH 4.6-soluble N-compounds was made using a citrate dispersion of the cheese and then lower the pH to below 4.6. Separation of the peptides in the pH 4.6 soluble fractions was conducted by reverse phase high performance liquid chromatography (RP-HPLC). For identification of the peptides, on-line electrospray ionisation mass spectrometry (ESI-MS) was monitored. Suggested identities of the peptides were given by using MS/MS analysis of the most intense ions in the mass spectra. All three kind of cheese contained similar profiles of bioactive peptides. Peptides from the N-terminal part of ?S1-casein were a group of bioactive peptides (ACE-inhibitory and antioxidative) accounting for a high presence in Präst cheese. Caseinphosphopeptides (CPPs) were another group of bioactive peptides found in Präst cheese, e.g. ?-casein f(8-28), f(29-93)A1 and f(29-93)A2. The most dominating peaks in the medium ripened Präst cheese and Allerum (long ripened) were identified as ?S1-casein f(1-6), f(1-7), f(1-9), f(1-13) and f(1-14) as well as ?-casein f(8-28),(29-93)A1 and f(29-93)A2. In XO (extra-long ripened) the most dominating peaks were identified as ?S1-casein f(1-6), f(1-7), f(1-9) as well as ?-casein f(29-93)A1 and f(29-93)A2.