Prolongation of the keeping quality of Mozzarella cheese by treatment with sorbate.

An attempt was carried out for prolongation of the shelf-life of Mozzarella cheese by incorporation of potassium sorbate into the cheese. Three manufacturing techniques were used: a) addition of potassium sorbate to kneading water (at level of 6%), b) addition during brine salting (at level of 0.5%) and c) dipping the cheese into potassium sorbate solution (6%) directly prior to packaging. Control cheese was made without potassium sorbate treatment. The resulting cheeses were divided into two portions, one of which was contaminated with Penicillium roqueforti and then packaged, while the second one was packaged without contamination. Both were stored at refrigerator (5 +/- 1 degree C) temperature and analysed periodically until spoilage. The results showed that treatment with potassium sorbate did not affect the organoleptic properties of the cheeses, except that a slight objectionable bitter flavour was observed in fresh cheeses treated with sorbate using the techniques of dipping or in brine salting then it was disappeared during storage. However, the overall acceptabilities of the sorbate-treated cheese were increased up to 10 weeks of storage compared with 4 weeks for untreated cheeses. Treatment with potassium sorbate in kneading water or brine appeared to be more effective than dipping. Addition of potassium sorbate inhibited microbial growth, especially that of moulds and yeasts. The sorbate-treated cheeses had higher moisture, pH values and lower acidity than the control. Fat, salt and total nitrogen were unaffected during storage. Levels of soluble N, non-protein N and total volatile fatty acids in sorbate-treated cheeses were slightly higher than in the control. Furthermore, addition of potassium sorbate increased the meltability and improved the fat leakage of Mozzarella cheese.