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| Author(s): |
Alessandra Aparecida Zilio Cozzo de Siqueira
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2001-12-13 |
| Examining board members: |
Marilia Oetterer;
Marta Helena Fillet Spoto;
Julio Marcos Melges Walder
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| Advisor: | Marilia Oetterer |
| Abstract | |
The objective of this study is to enhance the shelf-life of processed fish, combining ionizing radiation and refrigeration with minimal processing. The physical, chemical, nutritional and microbiological characteristics of the specie Tilapia nilotica (Oreochromis niloticus) were studied in eviscerated samples and in commercial cuts. The fish were separated into samples irradiated with 1.0, 2.2 and 5 kGy and non-irradiated samples. They were stored at temperatures ranging from 0.5C to -2C for 20 and 30 days. During storage, the level of moisture in the non-irradiated samples decreased and the levels of protein and lipid increased while the irradiated samples remained stable. The levels of pH, TVB-N and NPN increased in the non-irradiated samples but tended to remain stable in the irradiated fish samples. During storage, microbiological analyses for the presence of coliforms proved the efficiency of the irradiation process. The irradiated samples had a microbiological content below the levels established by the Brazilian seafood legislation, whereas the non-irradiated samples had a higher microbiological content and were not in conformity with the officially permitted levels. Salmonella spp. and Staphylococcus aureus were not detected. The levels of amino acids in muscles and fatty acids in oil remained stable in the irradiated fish stored samples but decreased in the non-irradiated ones. Lipid-oxidation, measured by the TBARS test, showed a tendency to increase when the dose of irradiation increased. The storage products after 30 days showed good acceptability for sensorial parameters, aparance, odour, color and texture, so it is possible to increase the shelf life of a minimally processed tilapia using combined irradiation and refrigeration. (AU) | |