碩士 / 大葉大學 / 生物產業科技學系 / 99 / Live tilapia (Orechromis niloticus) immediately sacrificed by hitting were used as raw materials in this study. Three types of samples including roundfish, three pieces fillet, and crushed meat were prepared. They were stored in a refitted refrigerator with 100, 300, and 500 kV/m strength of high-voltage electrostatic field (HVEF). Changes in appearance, freshness, color, quality, and meat properties were investigated during storage period. The rate of freezing and defrosting were also determined. Results were obtained as follows:
1. The time needed for freezing and defrosting the round fishes were 0.74 and 0.51, respectively, using HVEF at 500 kV/m. This indicated that HVEF treatment could accelerate the transition time to pass through the zone of maximum ice crystal formation while freezing or defrosting. Injury prevention in texture of fish muscle could also be inferred.
2. Color of the round tilapia stored in a common refrigerator gradually faded from grey-black to brown in color, followed by the development of ammonia odor and the turbidity of eyes. All the extrinsic deteriorations could be decreased by the HVEF above 300 kV/m.
3. Early on storage, pH of tilapia meat decreased due to glycolsis, but subsequently increased by growth of microorganisms. However, this tendency was slow down when the HVEF strength was 500 kV/m.
4. No matter with or without the HVEF treatment, no obvious changes in “Hunter L” but decreased in “Hunter a” and increased in “Hunter b” were observed. The variations of whiteness and chroma were similar to the tendency of “Hunter a” and “Hunter b”, respectively.
5. Both VBN and K values of tilapia meat increased with increasing storage period, they exceeded the hygienic standard at 6th day, 60% and 25 mg/ 100 g, respectively. But for the HVEF treatment by 500 kV/m, K value approached 60% until 8th day, while VBN only was only 20.47 mg/100 g by 300 kV/m. The efficiency of HVEF on retardation of freshness was shown.
6. Total plate counts (TPC) reached 6.91 x 106 CFU/g meat at the 8th day, while still didn’t exceed the sanitary standard (3.45x 105 CFU/g meat) was observed for that of HVEF with 500 kV/m at the same time. HVEF showing inhibition effect on microorganisms was confirmed.
7. Solubility of water-soluble and salt-soluble proteins of the tilapia meat decreased to the minimum values at the 8th day. No matter whether HVEF treatment or not, no significant difference was found.
8. As an indicator of lipid oxidation, TBA value reached 0.127 during refrigeration at 4℃ at 8th day. As long as HVEF treatment, rancidity inhibition effect (85% in TBA to contrast) was shown.
9. In summary, HVEF was a practicable device for tilapia preservation based on the positive evaluation of freezing and defrosting rates, biochemical indices, microorganism inhibition and appearance. We expect the HVEF can be widely used for replacing the uses of preservatives in keeping the freshness of fish product.
Key Words : high-voltage electrostatic field, tilapia, freshness and quality
| Identifer | oai:union.ndltd.org:TW/099DYU00111053 |
| Date | January 2011 |
| Creators | Yang, Shang-Yen, 楊尚晏 |
| Contributors | Ko, Wen-Ching, Hsieh, Chang-Wei, 柯文慶, 謝昌衛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 97 |
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