碩士 / 國立臺灣海洋大學 / 食品科學系 / 101 / Rock porgy (Oplegnathus fasciatus) is an important newly cultured fish with high economic value. This study was to investigate the chemical compositions and flavor ingredients of rock porgy cultured with different levels of dietary protein and lipid. Comparison with wild fish was also conducted. In addition, changes in chemical compositions and freshness index of rock porgy during storage were studied to establish the shelf life.
Cultured rock porgy with increase of dietary protein (35%~55%) revealed that the muscle protein tended to increase and decreased afterward, and crude lipid and fatty acid decreased with increase of dietary protein. Moisture showed no difference in groups. Cultured rock porgy with increase of lipid (4%~16%) revealed that the muscle moisture increased and crude protein decreased with increasing dietary lipid, Crude lipid and nucleotide-related compounds showed no difference in groups. Group with dietary lipid level of 16% had the highest fatty acid content. The ash content were 1.22~1.54% and pH value were 6.23~6.42 in cultured fish. The moisture, crude protein, crude lipid and ash in the muscle of wild fish were 77.04~79.19%, 18.32~20.25%, 0.25~1.01% and 1.25~1.37%, respectively. Wild fish had a lower level of crude lipid than cultured fish.
The major nucleotide-related compound in the muscle was inosine monophosphate (IMP). IMP content showed no difference in muscle of cultured fish. The bigger wild fish had lower IMP content. The predominant free amino acid (FAA) in the muscle of cultured fish were taurine (Tau), glutamic acid (Glu), glycine (Gly), alanine (Ala), lysine (Lys), and wild fish was Tau. Wild fish had a lower level of FAA content than cultured fish. Dipetides, carnosine (Car) and anserine (Ans), were not detected. The dominant fatty acids were palmitic acid and oleic acid in the muscle of cultured and wild fish. The content of DHA was higher than EPA. Cultured fish had more unsaturated fatty acid than saturated fatty acid. Cultured fish had more fatty acid content, but less n-3/n-6 proportion than wild fish.
The perceptible decomposed odor occurred after rock porgy stored at 7℃ for 9 days and 25℃ for 16 hours. The pH value of the muscle increased and then decreased with storage time, and ammonia content increased. The total plate count exceeded the limited value of 3 × 106 CFU/g at 7℃ and 25℃ for 9 days and 24 hours. The amount of volatile basic nitrogen (VBN) exceeded the limited value (25 mg/100 g) at 7℃and 25℃ for 9 days and 48 hours, respectively. Trimethylamine (TMA) increased with storage time. The degradation of IMP to hypoxanthine (Hx) was found after storing at 7℃ for 6 days. Hx further increased with storage time at 25℃. When stored at 7℃and 25℃,K value exceeded 60% at storage time of 9 days and 16 hours. According the results, the shelf-life of rock porgy was 6 days and 16 hours during storage at 7℃and 25℃, respectively.
| Identifer | oai:union.ndltd.org:TW/101NTOU5253057 |
| Date | January 2013 |
| Creators | Hui-Chu Zheng, 鄭惠珠 |
| Contributors | Chyuan-Yuan Shiau, Tai-Yuan Chen, 蕭泉源, 陳泰源 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 69 |
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