الفهرس 
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Abstract
Fish is an important food source for humans because it contains many essential nutrients such as easily digestible proteins by more than 18.5%, and contains all the essential amino acids necessary for human body. Fish is not only a source of animal protein, but also a source of essential unsaturated fats, vitamins and minerals. Fish is rich in calcium, iron and iodine. It is scientifically known that an individual’s iodine needs can be covered by eating only one kilo of fish.
A total of 120 random fish samples represented by Tilapia nilotica, Mugil cephalus, Carp and Sardine (30 of each) were subjected to bacteriological examination for aerobic plate count, psychrophilic bacterial count, Enterobacteriaceae count, coliforms count to evaluate their quality.
The mean values of aerobic plate count / g of Tilapia nilotica, Mugil cephalus, Carp and Sardine were 5.7×105, 2.6×105, 4.9×105 and 5.4×105 cfu/g, respectively.
The mean values of psychrophilic bacterial count / g of Tilapia nilotica, Mugil cephalus, Carp and Sardine were 4.3×105, 3.6×105, 6.4×105 and 1.2×106 cfu/g, respectively.
The mean values of Enterobacteriaceae count / g of Tilapia nilotica, Mugil cephalus, Carp and Sardine were 6.6×103, 1.6×104, 3.4×104 and 1.1×104 cfu/g, respectively.
The mean values of coliforms count / g of Tilapia nilotica, Mugil cephalus, Carp and Sardine were 6.2×103, 9.9×103, 1.1×104 and 9.5×103 cfu/g, respectively.
In order to improve the quality of fresh Tilapia fillets, six different treatment methods were used, including lactic acid, nisin in different concentrations by dipping. Then, all groups were chilled and stored in a refrigerator at 4±1oC, and they were examined on a regular basis. The recommended treatment methods for extending the shelf life of chilled fish fillets were mentioned. 0.8% nisin was the least effective treatment on bacteriological status of fish and extend shelf life of fish fillets for only 6 days, while 3% lactic acid was the most effective treatment used and extend shelf life of fish fillets for about 15 days.
The various sources of microbial contamination of fish, such as pollution of sea and rivers with sewage water, lethal waste, and waste from ships that are thrown into the sea to reach the gut of fish. As well as the pollution of Nile from factories that dump their chemical and organic waste into the river, as well as agricultural drainage water with the pesticides it carries, or may be from the air and insects in the fish market as well as suggested sanitary procedures to enhance fish quality, were discussed such as trying to use some preservatives, which reduces the microbial load on fish, such as using lactic acid in concentrations of 2-3% for 5 minutes., and control measures were adopted to limit contamination from the time of fish capture until consumption such as such as preventing and criminalizing the discharge of polluted water into sea and river, and trying to prevent sale of fish in traditional shops, but rather it is sold in licensed places with a health certificate.