Adulteration of ewe and goat cheeses on the market of Republic of Croatia

Sirevi od kozjeg/ovčjeg mlijeka smatraju se patvorenim ukoliko se dokaže prisutnost od minimalno 1% udjela kravljeg mlijeka. Stoga je cilj ovog rada utvrditi pojavnost patvorenja ovčjih i kozjih sireva na tržištu Republike Hrvatske. Metoda dokazivanja patvorenja obuhvaćala je izolaciju kazeina iz sira (n=25), izoelektrično fokusiranje γ2 i γ3-kazeina dobivenih hidrolizom β-kazeina djelovanjem plazmina kao referentnu metodu, te detekciju i kvantitativno određivanje γ-kazeina kravljeg, kozjeg i ovčjeg mlijeka metodom dezintometrije. Rezultati za svaki pojedini uzorak sira uspoređeni su s deklaracijom i unešeni u tablicu kako bi se dokazala eventualna prisutnost patvorenih ovčjih i kozjih sireva na tržištu Republike Hrvatske. Metoda izoelektričnog fokusiranja, koja se primjenjuje kao referentna za ovakve vrste analiza, pokazala se prikladnom za detekciju kravljeg mlijeka u ovčjim i kozjim sirevima. Rezultati ovog rada utvrdili su patvorenje kod 24% uzoraka sira sa tržišta Republike Hrvatske, odnosno udio kravljeg mlijeka u patvorenim sirevima bio je u rasponu 2% do 18%.Cheeses made from goat/ewe's milk are considered to be adulterated if more than 1% of cow's milk is added. Therefore, the aim of this thesis was to determine the possible adulteration of goat and ewe's cheeses with cow's milk on the market of the Republic of Croatia. The sampling method involved isolation of casein from cheese (n=25), using the reference method of isoelectric focusing of γ2 and γ3-casein obtained from β-casein which is hydrolysed by plasmin, and detection and quantification of γ-casein from cow's milk by the method of densitometry. The obtianded results for each sample of cheese were compared with the product declaration in order to prove the possible presence of adulterated goat and ewe's cheese with cow's milk on the market of the Republic of Croatia. The isoelectric focusing method, which is used as a reference method for this type of analysis was suitable for detection of cow's milk in cheeses produced from goat's or ewe's milk. The results of this thesis showed that 24% of cheese samples from the market of Republic of Croatia were adulterated, with addition of cow's milk in range from 2% to 18%