Zh. DIMITROV and I. GOTOVA
LB-Bulgaricum PL C. R&D Center, BG – 1000 Sofia, Bulgaria
DIMITROV, Zh. and I. GOTOVA, 2014. Assay of the peptide matter of cheese during ripening by fast sizeexclusion HPLC method. Bulg. J. Agric. Sci., 20: 813-817
The release of peptides from milk proteins is one of main processes during the ripening of cheese. The quality of the cheese is related to both the content of peptide matter and the distribution of molecular weight of peptides. Several bioactive functions are attributed to certain low molecular weight peptides. The aim of the present work is the development of fast method for evaluation of peptide matter of cheese together with assay of the distribution of molecular weight of the peptides. For this purpose a size-exclusion HPLC separation of peptide matter was used and fluorescence detection after post-column derivatization of peptides. The method was applied to a newly developed starter for Bulgarian white brined cheese with increased ability in production of bioactive peptides. The inhibition of Angiotensin-converting enzyme (AC E, 22.214.171.124) was the main beneficial effect of the bioactive peptides released during the cheese ripening. Using the developed method a comparison of the peptide matters was performed between cheese produced with starter with increased AC E inhibitory activity and a control cheese produced with long time used commercial starter. The difference between the contents of low-molecular weight peptides was more then twice. By help of this method it was possible not only to evaluate quantitatively the total peptide matter in the cheeses, but to distinguish between high-, middle-, and low- molecular weight peptides only within one hour. The ratio between the peptides with different molecular weight is important for the quality of the cheeses.