| Sažetak | Paški sir jedan je od najpoznatijih hrvatskih tradicionalnih sireva, a proizvodi se od mlijeka autohtone Paške ovce na otoku Pagu. Specifična mediteranska klima, aromatični biljni pokrov i djelovanje bure daju mlijeku i siru jedinstven okus. Zrenje je ključna faza u proizvodnji Paškog sira, tijekom koje enzimi pokreću sintetske i kataboličke procese koji izravno utječu na kvalitetu sira. Tijekom zrenja sira, uslijed proteolitičkih procesa, dolazi do razgradnje proteina pri čemu nastaju slobodne aminokiseline koje utječu na formiranje specifičnog mirisa, okusa i arome Paškog sira. Sastav i udio ovih aminokiselina značajno utječu na teksturu i senzorska svojstva sira, uključujući njegovu završnu aromu, koja se mijenja ovisno o trajanju zrenja. Uzorci Paškog sira (n=15) različite zrelosti (0., 30., 60., 90., 120. dana) prikupljeni su u mini sirani u Kolanu. Sastav slobodnih aminokiselina u siru određen je vezanim sustavom tekućinske kromatografije visokog učinka - spektometrija masa (HPLC-MS/MS) bez kemijske modifikacije. Priprema uzoraka provedena je u Referentnom laboratoriju za mlijeko i mliječne proizvode Zavoda za mljekarstvo Agronomskog fakulteta Sveučilišta u Zagrebu, a HPLC-MS/MS analize provedene su u Laboratoriju za spektometriju masa i funkcionalnu proteomiku u Zavodu za fizičku kemiju, u Institutu Ruđer Bošković. Ukupna količina slobodnih aminokiselina povećavala se zrenjem. U Paškom siru utvrđeno je da su prevladavale glutaminska kiselina, valin, fenilalanin, leucin i lizin. 60. dana zrenja najviši udio utvrđen je za glutaminsku kiselinu (1319,05 ± 415,03 mg/100 g suhe tvari), valin (1635,15 ± 443,31 mg/100 g suhe tvari), fenilalanin (1661,14 ± 342,58 mg/100 g suhe tvari), leucin (2032,29 ± 541,02 mg/100 g suhe tvari) i lizin (891,88 ± 575,92 mg/100 g suhe tvari). Na temelju dobivenih rezultata, zrenje Paškog sira ne smije biti kraće od 60 dana jer nakon toga dolazi do daljnje razgradnje slobodnih aminokiselina koje značajno doprinose njegovom karakterističnom okusu. |
| Sažetak (engleski) | Cheese „Paški sir“ is one of the most famous traditional Croatian cheeses and is made from the milk of the indigenous Paška sheep on the island of Pag. The special Mediterranean climate, the aromatic vegetation and the effect of the bora give milk and cheese a unique flavour. Ripening is a key stage in the production of cheese „Paški sir“, during which enzymes trigger synthetic and catabolic processes that directly affect the quality of the cheese. During cheese ripening, proteolytic processes break down proteins, producing free amino acids that influence the formation of the specific odour, flavour and aroma of cheese „Paški sir“. The composition and proportion of these amino acids have a significant influence on the texture and sensory properties of the cheese, including its final flavour, which changes depending on the ripening period. Samples of cheese „Paški sir“ (n=15) with different ripening periods (0, 30, 60, 90, 120 days) were collected in a small cheese dairy in Kolan. The composition of free amino acids in the cheese was determined using a coupled system of high performance liquid chromatography - mass spectrometry (HPLC-MS/MS) without chemical modification. Sample preparation was performed in the Reference Laboratory for Milk and Dairy Products of the Department of Dairy Science, Faculty of Agriculture, University of Zagreb, and HPLC-MS/MS analyses were performed in the Laboratory of Mass Spectrometry and Functional Proteomics in the Department of Physical Chemistry, Ruđer Bošković Institute. The total amount of free amino acids increased as the cheese ripened. Glutamic acid, valine, phenylalanine, leucine and lysine were found to be the predominant amino acids in cheese „Paški sir“. On the 60th day of ripening, the highest concentrations were found for Glutamic acid (1319.05 ± 415.03 mg/100 g dry matter), Valine (1635.15 ± 443.31 mg/100 g dry matter), Phenylalanine (1661.14 ± 342.58 mg/100 g dry matter), Leucine (2032.29 ± 541.02 mg/100 g dry matter) and Lysine (891.88 ± 575.92 mg/100 g dry matter). Based on these results, it is recommended that the ripening period for Paški sir should not be less than 60 days, as the further degradation of free amino acids after this time significantly improves the distinctive flavour of the cheese. |
