Primarna proteoliza kozjeg bijelog sira u salamuri praćena SDS-PAGE sistemom visokog molariteta

The aim of this work was to investigate primary proteolysis of white brined goat cheese prepared from raw milk and to correlate with the results obtained with high-molarity Tris buffer electrophoretic system. Proteolytic changes of white brined cheese were monitored by three parameters, the total protein, the water soluble proteins and the degree of proteolysis, whereas the change of major casein fractions was followed by electrophoresis in reducing conditions. Ripening caused a decrease of the total protein content, whereas in the first forty days the water soluble protein and the degree of proteolysis increased. Both casein fractions (αs- and β-casein) of goat cheese were susceptible to primary proteolysis but to the different extent. αs1- casein disappeared during processing, whereas during 60-days of ripening the content of αs2 and β-casein was reduced by 38.90 %, and 30.72 %, respectively. Such trends of major casein fractions were strongly correlated with the degree of proteolysis and the moisture content, whereas no correlation was found between them and the water soluble protein content. The results of our investigation clearly suggested that SDS-PAGE method based on high-molarity Tris-buffer system could be a very useful for purposes of monitoring the white goat cheese proteolysis.Cilj ovog rada bio je ispitati proces primarne proteolize bijelog sira u salamuri pripremljenog od sirovog kozjeg mlijeka i staviti u korelaciju s rezultatima dobivenim SDS-elektroforetskom metodom koja se bazira na primjeni Tris pufernog sistema visokog molariteta. Proteolitičke promjene bijelog sira u salamuri praćene su pomoću tri parametra: ukupnih proteina, u vodi topljivih proteina i stupnja proteolize, dok je promjena glavnih kazeinskih frakcija praćena elektroforezom u reducirajućim uvjetima. Zrenje sira uzrokuje pad sadržaja ukupnih proteina, dok sadržaj u vodi topljivih proteina i stupanj proteolize raste tijekom 40 dana zrenja. Obje kazeinske frakcije (αs- i β-kazein) podliježu procesu proteolize, ali u različitom stupnju. αs1-kazein se razgrađuje tijekom pripreme sira, dok se tijekom zrenja sira sadržaji αs2- i β-kazeina reduciraju za 38.90 % i 30.72 %. Ovakva promjena glavnih kazeinskih frakcija u jakoj je korelaciji sa stupnjem proteolize, sadržajem ukupnih proteina i sadržajem vlage, dok nije uočena korelacija između ovih parametara i u vodi topljivih proteina. Rezultati naših istraživanja jasno pokazuju da SDSelektroforetski sistem zasnovan na visoko molarnim Tris- puferima može biti vrlo korisna metoda za praćenje proteolitičkih promjena tijekom zrenja kozjeg bijelog sira u salamuri