الفهرس 
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Abstract
The influence of heat treatments at 70-90°C instantly on nitrogen distribution of cow’s and buffalo’s skim milk and contrary on whey protein denaturation were studied. While the second part, studied the influence of heat treatments and pH values on rheological properties of clotted cow’s and buffalo’s skim milk. Moreover, the third part studied the chemical composition and sensory evaluation of cheese made from whole milk (cow and buffalo) with the best of heat treatment and pH value.
The obtained results can be summarized as follow:
1. : The influence of heat treatments on nitrogen distribution in cow’s and buffalo’s skim milk:
• There were decreases and increases in cow’s milk of (TN, CN, NPN & C No.) and (WN, WPN, WN/TN & WPN/TN) in raw milk than that of heat treated milk, respectively.
• There were decreases and increases in cow’s milk of (WN, WPN, WN/TN & WPN/TN) and (TN, CN, NPN, C No. & WPD) with increasing heat treated milk in all treatments, respectively.
• There were decreases and increases in buffalo’s milk of (TN, CN, NPN, C No. & NPN/TN) and (WN, WPN, WN/TN & WPN/TN) in raw milk than that of heat treated milk, respectively.
• There were decreases and increases in buffalo’s milk of (WN, WPN, WN/TN & WPN/TN) and (TN, CN, NPN, C No., NPN/TN & WPD) with increasing heat treated milk in all treatments, respectively.
• Cow’s skim milk behaves the same trend of buffalo’s skim milk on nitrogen distribution and WPD in all treatments, while cow’s skim milk had higher values of (WPN, WN/TN & WPN/TN) and lower values of (TN, CN, NPN, C No., NPN/TN & WPD) than that of buffalo’s skim milk in all treatments, respectively.
• The raw skim milk had higher values of (WN, WPN, WN/TN & WPN/TN) and lower values of (TN, CN, NPN & C No.) than that of heat treated skim milk in all treatments, respectively owing to the denaturation effect of heat treatments.
• The (TN, CN, NPN, C No., NPN/TN and WPD) were increased with the raising of heat treatment, while the (WN, WPN, WN/TN & WPN/TN) were reduced in the same treatments, respectively.
• There were differences insignificantly of (TN, NPN & NPN/TN) in cow’s skim milk and of (NPN & NPN/TN) in buffalo’s skim milk. While, there were differences significantly of (WN, CN, WPN, C No., WN/TN & WPD) in cow’s skim milk and of (TN, WN, CN, WPN, C No., WN/TN & WPD) in buffalo’s skim milk.
2. The influence of heat treatments and pH values on some rheological properties of clotted cow’s and buffalo’s skim milk:
A. Cow’s milk:
• There were decreases and increases of (rennet clotting time) and (curd firmness & syneresis) in control samples than that of heat treated milk samples, respectively.
• There were increases and decreases of (rennet clotting time) and (curd firmness & syneresis) with increases of heat treatment in all samples, respectively.
• There were increases of curd firmness and syneresis in control samples than that of heat treated milk samples at studied pH values in all treatments.
• The control samples had higher rennet clotting time in most samples, especially at lower pH (6 and 5.6).
• There were increases of rennet clotting time and SY with increasing of pH values in all treatments.
• There were increases of curd firmness from pH 6.4 up to 6 and then decreases at 5.6.
• Our results points to select pH 6 of clotted cow’s skim milk, because it gives cured firmness nearest to control samples.
B. Buffalo’s milk:
• There were decreases and increases of RCT and CF & SY in control samples than that of heat treated milk samples, respectively.
• There were increases and decreases of RCT and CF & SY with