engleski

The application of the RP-HPLC method for determination of free amino acids in the ripening process of ewe cheese from the island Krk

Ewe cheese from the island Krk is highly nutritional and possesses a specific flavour and smell. It belongs to a group of semi-hard and full-fat cheeses and is produced on several family farms. In the process of cheese making the key phase is ripening which directly influences the quality of the final product. Ripening along with drying represent the chemical changes mostly catalysed by enzymes, amongst which proteolytic enzymes hold an important role. Proteolytic enzymes are degrading milk protein to the peptides of different length and amino acids, whose ratio significantly influences the texture and organoleptic characteristics of cheese. The aim of this study was to determine the amino acid content and their ratio in the ewe cheese during ripening process. This study was performed with the ewe cheese samples collected at the farms located on the island Krk, which are breeding Croatian autochthonous sheep. The cheese samples were taken on the 1st, 30th, 60th, 90th and 120th day of the ripening process. The content and ratio of free amino acids in the cheese samples was determined by reversed phase high performance liquid chromatography (RP-HPLC). The amino acids soluble in trichloroacetic acid were transformed into 6-aminoquinolyn-N-hydroxysuccinimidyl carbamates with Waters AccQ Tag package, separated on Waters AccQ Tag C18 column and detected at l 254 nm. The content and ratio of free amino acids increased during the cheese ripening process. Cheese produced in summer period contained higher content of free amino acids than cheese produced in spring. Mature cheese contained the highest concentration of Glutamic Acid, Leucin, Valine, Lysine, Phenylalanine, Proline and Isoleucine. The presence of these amino acids is characteristic for hard ewe cheeses and our study confirmed the same.

Cheese ripening process; free amino acids; RP-HPLC method

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