碩士 / 弘光科技大學 / 食品科技所 / 105 / Soft-shelled turtle (Pelodiscus sinensis) is a delicious food since ancient China, it’s not only used for the royal tonic but also be regard as medicine and food homologous. Soft-shelled turtle has the value to be used for the whole body. Numerous scientific studies found that nutritions in the whole turtle body are rich in proteins, amino acids, unsaturated fatty acids (ie. DHA, EPA, α-linolenic acids, minerals, vitamin B group, folic acids…etc ), are helpful human body to improve immunity, metabolism and anti-aging, etc. The turtle fats located inner the abdominal cavity and the four legs, it’s scarcely only 6 % body weight. In this study, four physical and chemical processes, including water bath heating (WBH), decoction (FBH), ethyl acetate extraction (EAE) and n-hexane extraction (HXE) are investigated to compare the characteristics of the soft-shelled turtle oils. These crude oils are stored and evaluated during storage at room temperature, dark and sealed conditions, and Schaal oven test at 63 ℃ are participated for evaluating the acceleration of oxidation. Samples were taken during periods to detect acid value (AV), peroxidation value (POV) and fatty acid changes. The four methods for WBH, FBH, EAE and HXE yields the crude oils are 61.27 %, 63.50 %, 72.31 % and 82.00 %. The initial AVs (mgKOH/g) are 4.6, 5.2, 6.2 and POVs (meq/kg) are 8.5, 7.5, 8.9 and 7.4. In soft-shelled turtle fats, the contents of saturated fatty acids (SFA), mono unsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and others were 28.34 %, 43.19 %, 20.91 % and 7.56 %, respectively. During storage, the AV values of each method are increased, but the POV values are fluctuate. Therefore, it is unreliable by depending the POV values to decide the oxidative rancidity of unrefined oil or marine foods. During room storage and oven acceleration, PUFA presents different degrees of decline.
The total of 18 volatile flavor components from soft-shelled turtle oil were identified by solid phase microextraction (SPME). Among them, there were 2 alcohols, 12 aldehydes, 1 alkane, 1 furan, 1 ketone and 1 pyran. The 18 components accounted for the total volatile content (in terms of integral area) was 83.97 %.
In conclusion, WBH is the prior extracting method for highly unsaturated soft-shelled turtle oil, followed by HXE. Due to long extracting time, high temperature, solvent characteristics and accelerated rancidity, FBH and EAE are the most unsatisfactory process in the four methods.
| Identifer | oai:union.ndltd.org:TW/105HKU00255012 |
| Date | January 2017 |
| Creators | LEE, TZU-MIN, 李子泯 |
| Contributors | LIN, LI-YUN, 林麗雲 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 91 |
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