碩士 / 國立海洋大學 / 食品科學系 / 89 / The chemical, nutritional and taste components of newly cultured fish including yellowfin seabream, blackfin seabream, Japanese seabass, red drum, threadfin fish, grey snapper, malabar grouper, yellow grouper, snubnose pompano, American eel, European eel, and Japanese eel were analyzed for the improvement of fish quality and utilization. The chemical changes of American eel and European eel during storage at different temperatures were also studied to investigate how different in the degradation of carnosine between two eels.
The pH value of twelve fresh cultured fish was ranged from 6.32 to 6.70, ammonia was between 6 to 19 mg/100g, and urea between 2.11 to 2.44 mg/100g. Protein and ash showed no significant difference among fish. Threadfin fish was proposed as a high level of protein and middle fat fish; American eel, European eel, and Japanese eel were high protein and high fat fish; and others were high protein and low fat fish.
The composition of free amino acid (FAA) was similar to that of dermersal fish, and the quantity was between 181~528 mg/100g. Carnosine (Car), a dipeptide, present in high levels (272-425 mg/100g) in American eel, European eel, and Japanese eel. Among the ATP-related compounds, inosine monophosphate (IMP) was the most predominant compound.
The proportion of unsaturated fatty acid was much higher than that of saturated fatty acid, in which C16:0, C16:1, C18:1, C18:2, C18:3, C20:0, C20:5 (EPA) and C22:6 (DHA) were the major fatty acid. American eel and European eel contained a large amount of vitamin A. In other fish, water-soluble nicecin was the major vitamin, and vitamine E "α-type" was the second abundant one.
When European eel meat was stored at 5, 15, 25 and 35℃, a perceptible decomposed odor was observed at the 16th day, 2nd day, 18th hours and 12th hours, respectively. The pH value decreased frist and then increased during storage. Ammonia increased rapidly at the stage of the initial decomposition. The amount of urea was low, and it changed little during storage. As the initial decomposition occurred, the VBN value reach 16 mg/100g, which was lower than 25 mg/100g in other fish.
The amount of FAA, s-Ala and His changed significantly at the initial stage of the storage. Tau, the other abundant FAA, had a little change during storage. However, Car decreased obviously at the initial stage of different storage temperatures. This result showed that Car in European eel was easy to be decomposed into s-Ala and His by carnosinase. The change of the FAA in eel meat during storage was significantly affected by the degraded products of Car, s-Ala and His. The ATP-related compounds changed rapidly after the eel died. IMP was the major compound at the initial stage of storage. If the K value 50﹪was proposed as the index of freshness quality, the period reached the value during storage at four temperatures was 12, 6, 3 and 2 hour, respectively. Consequently, the eel was subject to decomposition.
The perciptable decomposed odor was found in Japanese eel meat at the 3rd day, 24th hour, 18th hour, and 12th hour during storage at 5, 15, 25 and 35℃, respectively. The duration reached the initial decomposition was shorter than that of European eel. The pH value decreased first and then increased during storage. Japanese eel contained more ammonia than European eel. Ammonia and urea had a little change during storage. The change of VBN was similar to that of European eel, which was low as the initial decomposition ocurred. The VBN change was not correlated well with the storage of both eels; therefore, VBN was not suitable for the indicator of freshness.
The storage change of FAA in Japanese eel was different from that of European eel. The FAA in Japanese eel remained unchanged during storage until the fish was spoiled. Tau, Gly, and Ala were the major FAA, which also showed no remarkabe change during storage. Japanese eel contained a higher level of Car than European eel. The degradation of Car was also different between two species of eel. The Car in Japanese eel showed no significant change during storage. However, Car in European eel rapidly degraded to s-Ala and His. The activity of carnosinase in the latter might be much higher than that of the former.
| Identifer | oai:union.ndltd.org:TW/089NTOU0253022 |
| Date | January 2001 |
| Creators | Lin Rong Ru, 林容如 |
| Contributors | Shiau Chyuan Yuan, 蕭泉源 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 109 |
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