Effect of processing and storage of brined white (Nabulsi) cheese on fat and cholesterol oxidation

Brined white (Nabulsi) cheese was studied for cholesterol oxidation and for oxidative and hydrolytic rancidities during cheese processing, during storage in closed transparent and light-protected glass jars at room temperature for 3, 6 and 9 months and during storage on an open tray exposed to atmospheric air and light for 1, 2 and 3 weeks. The peroxide value (PV), free fatty acid (FFA) content and 7-ketocholesterol level were determined. The cheese processing steps (curd formation, salting and boiling in brine) had no significant effect on PV, FFAs and 7-ketocholesterol. However, the storage conditions had a significant effect (p less than or equal to 0.5) on these parameters. Peroxides were not detected or were very low in the freshly boiled cheese, while the FFA content was 2.9 g kg(-1). The PV and FFA content increased to approximately 5 meqkg(-1) and 11 g kg(-1) respectively after 9 months of storage in transparent or light-protected jars. The 7-ketocholesterol level was 1.2 mug g(-1) in the freshly boiled cheese and reached maximum values of 2.3 and 5.2 mug g(-1) after 9 months of storage in light-protected and transparent jars respectively. Cheese samples displayed on an open tray showed a higher increase in PV, FFAs and 7-ketocholesterol than samples stored in closed jars, reaching values of 6.1 meqkg-1, 6.8 g kg (-1) and 8.8 mug g(-1) respectively after 3 weeks of storage. (C) 2002 Society of Chemical Industry.