碩士 / 國立高雄海洋科技大學 / 水產食品科學研究所 / 96 / Part 1.
Tilapia (O. niloticus (♀) × O. aureus (♂)) is one of the most important aquaculture fish in Taiwan. Taiwan has gained worldwide reputation in frozen tilapia fillet processing technology. This study was aimed to investigate the relation of qualities between raw fish and the frozen fillet, in order to found the certification index. At first, tilapia was scarified and the round fish was stored in ice or at 25°C for due time intervals, and then provided for the comparison of changes in freshness and the other quality indices. After the storage, round fish were cut into fillets and vacuum packed, then stored at −20°C for 60 days. Among the quality indices examined, the changes in K value and cooking loss of all the samples of raw fish and the frozen fillet were found to have the similar increasing tendency as storage days increased. It reveals that K value (freshness) and cooking loss (flesh quality) can be used as the certification indices for tilapia as raw fish and frozen fillet. Using CO gas for 90-min treatment, frozen tilapia fillets made from various stored conditions materials had no changes on the flesh quality while the surface color of the fillets was improved apparently.
Secondly, in order to simulate the proper or improper state of storage and transportation, frozen vacuum-packed fillets were stored in 3 conditions; at −5°C for 7 days, thawed in ice for 12 hours and then stored at −20°C for 7 days, or −20°C for 7 days, respectively. Both the former two with improper conditions showed the decreases in quality indices of K value and cooking loss. It reveals that the quality of frozen tilapia fillet was not only affected by the freshness of raw material, but also the conditions of storage during marketing.
Qualities indices of five of commercial frozen tilapia fillets were examined. It showed all the samples had been treated with CO gas, and three of them were good in quality, one was as common, and the other one was of low quality.
In conclusion, the K value and cooking loss can be used as quality certification indices for the raw fish and frozen fillet of tilapia. To maintain the quality, raw fish had better be stored in ice before processing, and frozen fillets were suggested to be stored at −20°C during transportation or market.
Part 2.
White-leg shrimp (Litopenaeus vannamei), is the most commonly consumption aqualcultural shrimp in market. Superior quality product is usually made from fresh raw materials. This study was aimed to investigate the relation of qualities between raw shrimp and the frozen peeled shrimp, in order to found the certification index. At first, white-leg shrimp was covered and sacrificed with crush ice and the round shrimp was then stored in ice or at 25°C for due time intervals, and these shrimp were provided for the comparison of changes in freshness and the other quality indices. After the storage, round shrimp were peeled, frozen and ice-glazed into frozen peeled shrimp and vacuum packed, then stored at −20°C for 60 days. Among the quality indices examined, the increasing changes in K value of all the samples of raw shrimp and the frozen peeled shrimp was found to have the similar tendency as storage days increased, while flesh toughness after cooking decreased. It reveals that K value (freshness) and toughness after cooking (flesh quality) can be used as the certification indices for white-leg shrimp as raw material and frozen peeled shrimp. It is hard to estimate the quality of frozen peeled shrimps from appearance as the products were made from various stored conditions materials.
In order to simulate the proper or improper state of storage and transportation, frozen ice glazed peeled shrimps were stored in 2 conditions; at −5°C or −20°C for 7 days, respectively. The former with improper condition showed the decreases in quality indices of K value. It suggests that the quality of frozen peeled shrimp was not only affected by the freshness of raw material, but also the conditions of storage and transportation.
Qualities indices of three of commercial frozen peeled shrimps were examined. It showed one of them was good in quality, and the other two were as common.
In conclusion, the K value and toughness after cooking can be used as quality certification indices for the raw shrimp and frozen peeled shrimp of white-leg shrimp. To maintain the quality, raw shrimp had better be stored in ice before processing, and frozen products were suggested to be frozen below −20°C during storage.
| Identifer | oai:union.ndltd.org:TW/096NKIM8084013 |
| Date | January 2008 |
| Creators | Yu-Xain Tzeng, 曾裕憲 |
| Contributors | Chau-Jen Chow, 周照仁 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 102 |
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