الفهرس 
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Abstract
Objectively, the present study was aimed to experiment the combination between milk fat and NaCl substitution for reducing calories and sodium ion to find out to what extent they would maintain their physical properties and sensory acceptance of cast Feta cheese made using dried milk protein concentrated previously, indeed by the ultrafiltration technique.
Technically, to achieve this study, cast Feta cheese, i.e. it was filled in the liquid phase before coagulation without whey drainage, whereas skimmed milk powder was arithmetically mixed with dried milk protein concentrate and reconstituted with warm tap water at 45oC providing that the final formulation should be contained the total solids of 21% and12% protein. In the base of full cream Feta cheese, the fat content was adjusted to 16% using butter oil (the control). For other treatments, butter oil was replaced with maltodextrin at the level of nil, 25, 50, 75 or 100%. All formulas were heat treated at 72o C for 2 min., at which they were homogenized at 200 bar then cooled to the suitable renneting temperature (at 40o C). Potassium sorbate was added at the level of 0.015% and salted to 2.5% Toble salt (NaCl), whether alone or replaced with potassium chloride (KCl) at the level of nil, 25, 50 or 75%. Glucono delta lactone was added at the level of 2.5% then fresh daily rennet solution (4% microbial rennet powder) was added at the rate of 2 ml /10 Kg pre-cheese, which was packaged into plastic containers (100g) and incubated at the same temperature for the complete coagulation (within 30 min.). All cheese containers were cold stored at 5±1o C for 3 months.
The obtained results could be summarized as follow:
1. Compositionally, the proportional fat replacing with maltodextrin in fresh cast Feta cheese making led to gradual reduction in the dry matter (DM) content and increment in the ash content. Both of protein and lactose contents were in full cream cast Feta cheese (the control) lower than those of fat replaced cheeses. Although the DM content of cheese mostly reduced, both of the protein and lactose contents mostly increased, while the ash was not influenced by NaCl replacement with KCl.
2. Periodically, although all ripening indices did not exhibited any obviously significant trending either towards the fat or NaCl replacement, the water soluble nitrogen / total nitrogen (TN) and non-protein nitrogen / TN percentages proportionally increased about the value lowered as the cold storage period (CSP) prolonged.
3. Rheologically, both of cheese hardness, chewiness and gumminess value strengthened but springiness and cohesiveness weakened by fat replacing. While both of hardness and chewiness weakened but springiness strengthened as NaCl was replaced with KCl. While cohesiveness did not appear any clear trending toward NaCl substitution. Nevertheless, all parameters of texture profile declined as the CSP of cast Feta Cheese was prolonged.
4. Microbiologically, total bacterial count (TBC) increased while yeasts and molds (Y&M) of cheese lowered as the fat was replaced. Also, both TBC and Y&M lowered by NaCl replacement. Although TBC increased after the 1st week and then decreased, Y&M continued to gradual increase by CSP prolonging.
5. Organoleptically, all sensory attributes of Feta cheese gained gradual lower scores either when the fat and NaCl were replaced or CSP was prolonged but still keeping their acceptable panelist quality until the end of experimental period provided that the level of fat replacement does not exceed 75% and that the level of replacement of NaCl does not increase than 50%.
Finally, the foregoing results led satisfactory to conclude that Feta cheese could be successfully made with fewer calories and sodium content to meet the needs of some special health purposes while maintaining good chemical, rheological and microbiological properties, provided that the percentage of fat replacement does not exceed 75% and that the percentage of sodium chloride replacement does not exceed 50%.