Fish is one of the most highly perishable food products. The aim of this study was to investigate microbiological and chemical changes of Nile tilapia fillet during ice storage. Nile tilapia samples were collected from Lake Zeway, Ethiopia. The fillet was stored at 0°C for 30 days on ice. Total plate count, total and fecal coliform, total volatile base nitrogen and pH was measured at the interval of four days. Regardless of age and sex, Total plate count varied between 4 to 11.74 log cfu/g. Total coliform counts fluctuated between <3 to >1100 MPN/g. However fecal coliform changed between 23 to <3 MPN/g. Total volatile base-Nitrogen has increased from 7.5 to 42.0 mg N/100 g. Similarly, pH has increased from 6.1 to 7.6 during the ice storage period. The eventual increase observed in mean total plate count could be due to multiplication of organisms favored at the storage condition. The increased total coliforms may be attributed to fillet quality and temperature fluctuations. The increment in TVB-N during ice storage is associated with activity of micro-organisms during later stages of deterioration. The increase in pH values is due to the formation of basic decomposition products. Finally, Post mortem change of Nile tilapia fillet was noticed and bacterial metabolites like Total volatile base-nitrogen, Total plate count and pH were invariably increased throughout the storage time indicating that they are good parameters to predict shelf life.

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This study was aimed to investigate the influence of age and sex on minerals content and fatty acids profile of Nile Tilapia (Oreochromis niloticus) fillet. Samples were cool transported from Lake Zeway to Food Science and Nutrition laboratory of Addis Ababa University. Minerals content were analyzed using Flame Atomic Absorption spectrophotometer and Fatty acid profile was determined using gas chromatography. Female fish contained significantly (p<0.05) higher calcium and phosphorus as compared to male. Calcium and zinc significantly (p<0.05) decreased as age of fish increased but phosphorus significantly (p<0.05) increased with increase in age of the fish. Sex had no significant effect (p>0.05) on Iron and Zinc content. Monounsaturated fatty acids constituted the largest proportion of total unsaturated fatty acids in both sexes. Oleic acid was relatively higher in female than male. Conversely, the polyunsaturated fatty acids were higher in male as compared to female.

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