碩士 / 國立海洋大學 / 食品科學系 / 91 / Abstract
Cobia（Rachycentron canadum）has become one of the main cage
cultured fish. In spite of the increases in processing of cobia fillet
products, cobia liver has not been utilized commercially. Since cobia liver
is high in lipid content, the objective of this study was to develop a cobia
liver oil product and to improve its odor. Body weight and body length of
cobia was significantly correlated, while condition factor, hepatosomatic
index and seasonal changes of cobia was not correlated with body weight
（p＜0.05）.
The cobia liver oil was extracted with chloroform-methanol（Folch
method）, or hexane or wet-rendered at 100℃ for 30 min. The yields
were 41.48、36.39 and 28.29﹪respectively. The wet-rendered cobia liver
oil was higher in polyunsaturated fatty acids, its acid value was lower and
the odor notes of fishy and oxidized odors were stronger than those of the
solvent extracted. The wet-rendered cobia liver oil was treated with
oxirane-immobilized lipoxygenase （LOX） at 25℃ for 2 h, improved its
otherwise undesirable odor.
Treatment of this LOX-modified oil with hydroperoxide lyase
（HPLS）, the desirable odor note increased in intensity. The optimal
reaction condition of HPLS from a green marine macroalgae, Ulva
conglobata, was pH 6.6 and 35℃. The algal HPLS was stable at
temperature below 37℃. Storage at 4 and 26℃ for 24 h, the half-life was
8 and 4 h respectively.
The cobia liver oil modified with LOX and HPLS at their optimal
conditions produced desirable odorous compounds of 5、6、8 and 9
carbons. Using GC-sniffing and GC-MS techniques, higher
concentrations of desirable unsaturated alcohols, aldehydes, that
resembled odors of green, melon, and fruit, were tentatively identified as
E-2-heptenal 、E-2-octenal, 1-octen-3-ol and reduced contents of
undesirable odor compounds including E,E-2,4-heptadienal 、
2,4-heptadienal、2,6,10,14-tetramethyl pentadcane and 2,4-decadienal.
Aroma modification of cobia liver oil using LOX and HPLS at 25℃
for 3 h, maintained 95﹪of the original polyunsaturated fatty acids along
with a significant reduction in fishiness and higher concentration of
fruity- and sweet- odor notes. Small amounts of polyunsaturated fatty
acids were enough for modification of cobia liver oil odor by LOX and
HPLS
| Identifer | oai:union.ndltd.org:TW/091NTOU0253010 |
| Date | January 2003 |
| Creators | An-Chi Lin, 林安琪 |
| Contributors | Bonnie Sun Pan, Liang-Bang Hung, 孫寶年, 洪良邦 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 103 |
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