碩士 / 國立高雄海洋科技大學 / 水產食品科學研究所 / 93 / This study was aimed to investigate the characteristics and the feasibility of juvenile milkfish in 15 cm length as material for food processing that included frozen, dried, retorted and battered products.
Juvenile milkfish were sampled from ponds at Cigu, Mituo and Linbian and transported to laboratory in ice or liquid nitrogen. After thawing and removing scale, head and viscera, samples were stored at 4 or -20°C, respectively, and the changes in quality of flesh were investigated at certain time interval during storage. The flesh in juvenile milkfish was about 52.9% to the whole body weight and contains almost the same amount of moisture and protein in dorsal and belly portion, which was 75 and 21% respectively. Belly flesh contained 4.2% lipid, which was higher than 2.0% in dorsal flesh. Dorsal flesh contained more ash than belly, which was 1.5 and 1.3% respectively. There were no significant changes in pH value and VBN content, while K value and TBARS value increased significantly during the 8-day storage at 4°C. It revealed that K value and TBARS value are proper parameter to evaluate the quality changes of juvenile milkfish as storing at 4°C. In addition, no significant difference was found in quality changes during the subsequently storage between the samples transported in ice or liquid nitrogen after harvest. The determinations of K value, VBN content, TBARS value and thawing expressible drip of sample flesh showed that the quality could maintain during the 6-month storage at -20°C. To sum up, the shelf life of juvenile milkfish in 15 cm length would be about one week at 4°C and 6 months at -20°C.
According to the characteristics of juvenile milkfish in 15 cm length, dried fillet product was developed. Dehydrating fish fillet to lose 71% of the total weight, the water activity was found about 0.6. Quality of products that were dried in the oven at 60, 75, 100, of 120 or 150°C was compared. The fillet being dried in 150°C oven yield the better sensory scores in flavor, texture and surface color than those prepared under another temperature. Moreover, roasting samples under 150°C takes the shorter processing time to reduce the moisture content to the same level as the others.
Retort product of juvenile milkfish in 15 cm length was developed. Retorting fish, in can, under pressure of 15 pounds, 121°C, for 60 min could soften the backbone and fins and resulted in good texture.
The in vitro protein digestibility of juvenile milkfish flesh was determined. The digestibility of those being steamed, retorted or fried was above 90%. Though the protein content of dried flesh was 68%, higher than the others owing to the loss of moisture, its protein digestibility was about 80%, the poorest among all the samples. Through the process of retorting or roast drying, in vitro soluble calcium of backbone increased by 50% than that of steamed fish.
| Identifer | oai:union.ndltd.org:TW/093NKIMT084008 |
| Date | January 2005 |
| Creators | Chien-Ting Chen, 陳建廷 |
| 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 | 89 |
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