Melaku, Mekonnen (2007) Effect of Low Temperature Preservation on the Physicochemical and Microbiological Qualitieis of Selected Fish Species of Lake Ziway. Masters thesis, Addis Ababa University.
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Abstract
With the purpose of determining the effect of frozen storage on quality of fish fillet and evaluating the existing low temperature preservation technique in the case of Fish Production and Marketing Enterprise, samples from the same lot of commercially harvested and processed tilapia fish (Oreochromis niloticus) fillets were frozen at -18 ± 2oc. The physicochemical and microbiological analyses were carried out at regular 15 days interval on tilapia fish fillets stored for up to 90 days. The fresh fish fillets were found to contain 18.52±0.08% protein, 0.37 ± 0.01% fat, 79.87 ± 0.01% moisture and 0.98 ± 0.01% ash contents. During the entire period of storage, the protein, moisture and ash contents were significantly (p < 0.05) decreased to 17.25 ± 0.088%, 78.50 ± 0.71%, and 0.88 ± 0.02% respectively. However, the fat content of the fish fillets increased significantly (p < 0.05) to 0.56 ± 0.01 after 90 days of frozen storage. The TVB-N and pH values were also increased significantly (p < 0.05) from 12.04 ± 0.48 mg N/100g and 6.43 ± 0.01 to 21.75 ± 0.35 mg N/100g and 6.61 ± 0.01 respectively. The total bacterial load in fresh fish fillets was reduced from 2.57x106 to 8.2x105 CFU/g after 90 days of frozen storage. The total coliforms and faecal coliforms were also decreased from 460 MPN/g and 23 MPN/g to 23 MPN/g and undetectable level, respectively. From these results it was concluded that freezing, if not properly used, has a negative effect on reduction of nutritional value of fish products. The storage of tilapia fish fillets under frozen condition showed a significantly (p < 0.05) higher deterioration of product quality. The nutritional quality, as estimated by the proximate composition analysis, underwent a gradual loss of nutrients until day 90, in agreement with loss of freshness of the fish fillets observed for the TVB-N. Furthermore, the results revealed that gradual biochemical changes reduce the quality of frozen fish fillets as the duration of storage increases. Under frozen condition, the overall nutritional quality of tilapia fish fillets was found to depend on duration of frozen storage.
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | Q Science > Q Science (General) |
| Divisions: | Africana |
| Depositing User: | Vincent Mpoza |
| Date Deposited: | 21 Jun 2018 13:44 |
| Last Modified: | 21 Jun 2018 13:44 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/5492 |
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