الفهرس 
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Abstract
A total of 300 samples of frozen whole Tilapia nilotica (75), frozen whole Saurus (75), frozen Tilapia nilotica fillets (75) and frozen Saurus fillets (75) were collected from kalyobia fish markets under complete aseptic condition and Transported to laboratory with a minimum of delay. In the laboratory,each group (75) was examined bacteriologically and chemically, after thawing at room temperature (25 samples), under tap water (25 samples) and at refrigeration temperature (25 samples). 1- The log mean values of the Total Colony count, Total
Psychrotrophic count,Total Enterobacteriaceae count, Total Coliform count, Total Staphylococcus aureus 2- The results of chemical examination included the PH value, Total Volatile Nitrogen (TVN mg/100 gm), 3- The results obtained revealed that in case of samples thawed at room temperature, all bacterial counts were higher than those thawed under tap water and at refrigerator temperature. Also, bacterial counts in case of samples thawed under tap water were higher than those thawed at refrigeration temperature. This means that the best method for thawing frozen fish is the refrigeration temperature. Moreover, there was significant differences in all bacterial countSand chemical values between the frozen whole fish sample and the frozen fish fillet samples. This could be attributed to the effect of handling and processing which may add large number and new types of microorganisms. Moreover, the nature of the muscle tissue after filleting aidsthe microorganisms to grow and multiply than the whole closed fish. The differences in bacterial count and chemical values between type of fish appeared significant differenceses in some cases, and non significant differencesin others
4- Bacteria belonging to the following genera could be isolated
from each type of fish and each form at the different thawing temperatures, with different percentage of distribution according to the number of isolates as follows Escherichia coli, klebsiella pneumonae, Enterobacter aerogenes, Citrobacter diversus, Proteus vulgaris, Proteus morganii, Shigella flexneri, Serratia marscense, Pseudomonas, Flavobacterium, Alkaligens, Chromobacterium,Acinetobacter and Aeromonas A total number of (78) identical fish samples of fresh Tilapia nilotica and Saurus were collected from original sources of catching
under complete aseptic condition. Then/at the laboratory the samples were frozen and stored at -18°C and examined bacteriologically for
Total Colony count at 37°C for 24 hour and Total Psychrotrophic count at 7°C for 10 days/ and chemically for PH value, Total Volatile Ritrogen, Trimethylamine and Thiobarbituric aid value at different intervals/zero time, one week, two week, 3 week, one
month, then monthly till the 9th month of storage. The obtained results revealed that the Total colony count decreasedwith the prolonged storage, while Total Psyhrotrophic increased with the prolonged storage. The PH values decreased gradually with prolonged storage,
Total Volatile Nitrogen increased gradually then decreased with the prolonged storage, Trimethylamine increased with The storage and Thiobarbituric acid value also increased. The values at the 9th month of storage lowered in samples thawed at refrigeration temperature than that thawed at room temperature and under tap water.