preservation of the nabulsi cheese

The traditional method used for preservation of Nabulsi cheese is to boil the salted cheese in brine of 18-20%, then the cheese is stored in cans of varying sizes without refrigeration with its boiling brine. Boiling of the Nabulsi cheese was found to be similar to milk pasteurization regarding its effect on microbial flora of the milk (Yamani et al., 1987).

In addition to the effect of boiling, there are two additional factors that contribute to preservation of Nabulsi cheese:

1-High salt concentration: salt concentration is 6.5-13.6% and 12.2-26% in Nabulsi cheese and brine respectively (Tukan and Humeid, 1991). This high salt concentration can inhibit the growth of most microorganisms that can cause spoilage to foods.

2-Tight closing of the cans: tight closing of the cans used in Nabulsi cheese storage can prevent contamination of the Nabulsi cheese and the escape of air which can support the growth of microorganisms that tolerate salt.

Abu-Ghoush (1992) investigated the possibility of improving the quality and safety of local Nabulsi cheese through utilization of the yogurt whey as a source of lactic acid and calcium in milk acidification and by using curd pasteurization as alternative to milk pasteurization or cheese boiling. It was found that acidification to pH values of 6.40, 6.20 and 6.0 decreased the curd cutting time by about 58%, 66%, and 69%, respectively and gave good curd strength. The selected heat treatments of the curd (65 ?C/ 15 min., 70 ?C/ 10 min. and 75 ?C/2 min.) were found to have an efficient pasteurization. The new method was also superior to the other methods with respect to the actual cheese yield, the same author also found that the cheese produced by the new method was more preferred to the boiled cheese in all quality parameters.

Herzallah (1994) studied the effect of different combinations of pH and salt concentrations of the brine on the storage ability and sensory quality of Nabulsi cheese. He found that the best pH/salt combination recommended for storage of this product was 10% salt, and pH 4.0. This combination resulted in a cheese with reduced numbers of total viable microorganisms, extended shelf life, improved texture, and combined with a moderate moisture content.

Yamani et al. (1987) studied the keeping ability of white brined cheese packed in plastic pouches, and compared cold (20 ?C) and hot (85 ?C±2 ?C) methods of brine filling. It was concluded that all the cold filled cheese samples remained organoleptically acceptable after one-year storage, while some of the hot filled samples showed softening and disintegration after 10 months of storage.

Humeid et al. (1990) investigated the feasibility of in-bag steaming of white brined cheese as a method of cheese preservation. The results of the study showed the technical feasibility of in-bag steaming of Nabulsi cheese as an alternative for boiling in brine. Pretests were done to compare in-bag steaming with in-brine boiling indicated the superiority of steaming, the advantages were less deformation and more uniformity of the heat treatment, which are related to the uniform arrangement of the product in the retort. From the hygienic point of view, the most important advantage of in-bag treatment is that there is no handling of the cheese after heat treatment. The cheese produced is organoleptically acceptable in all treatments for at least 9 months.

Yamani et al. (1998) studied the use of salt-tolerant lactic acid bacteria isolated from ovine and bovine milks for use in the production of Nabulsi cheese. It was found that the use of cultures derived from lactic acid bacteria from milks to increase the acidity of the cheese gave rise to cheeses that were as acceptable as the traditional products. In addition, the pH values of the cheese brines were in the range associated with stability during storage (pH 5.1 0- 5.3), and hence it is suggested that these locally derived cultures could be employed by the industry to manufacture a Nabulsi cheese from pasteurized milk that should: (a) be free from pathogens; (b) not deteriorate in-store at ambient temperature; and (c) have a flavor profile similar to the traditional Nabulsi cheese.

References

- Abu-Goush, M. 1992. Effect of the Addition of Yoghurt Whey to Cow's milk on Curd Formation and the Effect of Direct Pasteurization on Quality and Safety of White Brined Cheese. Master Thesis, University of Jordan, Amman, Jordan

- Herzallah, S. M. A Study of the Effect of Different Combinations of The Brine on the Storage Ability and Sensory Quality of Boiled White Cheese (Nabulsi). Master Thesis, University of Jordan, Amman, Jordan

- Yamani, M. I., Al-Nabulsi, A. A., Haddadin, M. S. and Robinson, R. K. 1998. The Isolation of Salt Tolerant Bacteria from Ovine and Bovine Milks for Use in the Production of Nabulsi Cheese. International Journal of Dairy Technology. pp: 86-89.

- Yamani, M. I., Humeid, M. A. and Tukan, S. 1987. Comparison of Keeping Ability of Nabulsi Boiled White Cheese Filled in Plastic Pouches Using Cold and Hot Brine. Dirasat. 14: 179-186.