Influence of milk heat treatment on the proteolytic changes during cheese ripening

Abstract

The main objective of this research was to investigate the influence of milk heat treatment on the profile of proteolytic changes during cheese ripening. The cheeses were manufactured with different milk heat treatments -65°C/20 min. (cheese A) and 95°C/5 min. (cheese B). The effect of milk heat treatment on the proteolytic changes was observed through dynamics of water soluble nitrogen (WSN) and soluble nitrogen in 5%PTA (SN in 5%PTA). The cheeses based or milk protein coaggregates showed different dynamic of proteolytic changes than cheeses made from milk heat treated by standard pasteurization. The content of WSN showed typical increase with intensive progress during first days of ripening and slowly retard in later phases of cheese ripening. The dynamic of WSN of cheese B differs with atypical figures (uniform increase of WSN during cheese ripening). The content of WSN of cheese B was higher (669.85 mg%) than content of WSN of cheese A at the end of cheese ripening. The cheese A differs with intensive increasing of SN in 5% PTA. The content of SN in 5% PTA of cheese A was higher (1.53 times) than same of cheeses made of milk in which coaggregates were formed.

U radu je ispitivan uticaj termičkog tretmana mleka na profil proteolitičkih pramena tokom zrenja sireva. Sirevi su izrađivani od mleka termički tretiranog na temperaturama: 65°C/20 min (sir A) i 95°C/5 min (sir B). Efekat termičkog tretmana mleka na tok proteolitičkih pramena posmatran je kroz dinamiku azotnih materija rastvorljivih u vodi (RN) i u 5% fosfovolframskoj kiselini (PTA). Sirevi izrađeni na bazi koagregata proteina mleka pokazuju izmenjen tok biohemijskih pramena u odnosu na sireve izrađene od mleka podvrgnutog standardnom režimu termičke obrade. Sadržaj rastvorljivog azota sira A pokazuje tipičan tok sa intenzivnijim porastom u početnoj fazi i blagim usporavanjem u kasnijoj fazi zrenja. Dinamika rastvorljivog azota sira B odlikuje se atipičnim tokom (ujednačeni porast tokom celokupnog zrenja) i dostiže veću vrednost (669,85 mg%) u odnosu na sir A (484,73 mg%). Sir A odlikuje se intenzivnijim porastom azotnih materija rastvorljivih u 5% PTA koje na kraju zrenja dostižu za 1.13 puta veću vrednost u odnosu na sir B.