Cow and buffalo's skim milk were heated at 70-90°C instantly in order to study its effect on nitrogen distribution and contrary on whey protein denaturation. The obtained results showed that the cow skim milk had higher values of WPN, WN/TN & WPN/TN and lower values of TN, CN, NPN, C No., NPN/TN & WP denaturation 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 heated skim milk in all treatments, respectively. In addition, the clotted cow milk had higher values of RCT and SY and lower value of CF than that of clotted buffalo's skim milk in all treatments. The increase of heat treatment of milk cause an increase of RCT and decrease of CF and SY in all treatments. Moreover, the control samples had higher and lower values of RCT and higher CF and SY than that of heated milk in all treatments. The decreases of pH values from 6.4 to 6.0 cause an increase of CF and then decrease with decreasing the pH up to 5.6 in clotted cow skim milk, while there were decreases of CF in clotted buffalo's skim milk up to pH 5.6 in all treatments.