Determination of changes in potential of hydrogen ( pH),total volatile nitrogen (TVN) and trimethylamine (TMA) in three types of fish (Oreochromis niloticus ,Clarias lazera and Mormyrus niloticus ) 30 of each collected from markets of El Qualiobeya governorate,Egypt. The results revealed that The mean value of pH in examined samples were 6.36 ± 0.05 ; 6.19 ± 0.03 and 6.07 ± 0.02 for Oreochromis niloticus ,Clarias Lazera and Mormyrus niloticus respectively.
The mean value of Total Volatile Nitrogen (TVN) were 21.58 ± 0.49 mg% ; 16.73 ± 0.41 mg % and 14.15 ± 0.28 mg% for Oreochromis niloticus , Clarias Lazera and Mormyrus niloticus respectively.
The un accepted samples were 16.67%, 6.67% and 3.33% in Oreochromis niloticus,Clarias lazera and Mormyrus niloticus respectively. Trimethyl Amine(TMA) values were 8.85 ± 0.22 mg% for Oreochromis niloticus; 6.61 ± 0.15 mg% for Clarias lazera and 5.97 ± 0.13 mg% for Mormyrus niloticus .
The un accepted samples were 20% ,13.33% and 3.33% in Oreochromis niloticus, Clarias lazera and Mormyrus niloticus respectively.