• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.794-803
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• 1997

Long line suspended culture of oysters has been started commercially in Hansan-Koje Bay since 1969. However, its Annual production has been decreased and culturing periods extended in recent years. So, we investigated environmental parameters and food organisms to identity the causes of poor fatness of oysters in Hansan-Koje Bay from February to November, 1994. As the result, the Water quality of Hansan-Koje Bay was found to be good for culture. For example, the mean concentration of COD was $1.35mg/\ell$, phosphate phosphorus was $0.30{\mu}g-at/\ell$ and dissolved inorganic nitrogen was $4.68{\mu}g-at/\ell$. However, the Hwado island and the inner part of the Hansan-Koje Bay were found to be eutrophicated due to various contaminants transported by land-based activities. But in the central pan of the Hansan-Koje Bay where the oyster farms Have been developed densely, the level of nutrient concentration was very low. During the study period, the dominant species of phytoplankton was Chaetoceros spp. with the percentage of $72.6\%\~87.8\%$ and the mean values of Chlorophyll-a concentration and phytoplankton standing crops were $2.05mg/m^3\;and\;188ind./m\ell$, respectively. The distribution of these parameters also showed similar trends those of nutrients. Especially, chlorophyll-a contents was very low with the concentration of below $0.5mg/m^3$ at central part of the Bay, Juklimpo. The fatness of oysters and the eutrophic index in this area were $18.1\%$ and 0.54, respectively. These values were lower than those of other culturing farms in the southern coastal areas in Korea. Therefore, we estimated that the insufficient food supply due to the low level of nutritional status was the major factors affecting the poor fatness of the Pacific oysters in Hansan-Koje Bay.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.4
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• pp.321-326
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• 1986

Oyster (Crassostrea gigas), arkshell (Anadare(Scapharce) broughtonii) and sea-mussel (Mytilus edulis) were investigated as to their lipid classes. Lipid extracts from shellfishes were fractionated into neutral lipid (NL), glycolipid (GL) and phospho-lipid (PL) by column chromatography with silicic acid. The fatty acid compositions of their lipid classes and lipid fractions were determined by gas liquid chromatography (GLC). Total lipid contents of shellfishes were $3.5\%$ in the oyster, $1.4\%$ in the arkshell, $1.0\%$ in the sea-mussel. The major fatty acids of total lipids were palmitic acid, eicosapentaenoic acid and docosahexaenoic acid in the oyster and the sea-mussel, palmitic acid, oleic acid and eicosapentaenoic acid in the arkshell. The lipid composition of neutral lipid fractions in shellfishes was separated and identified as free sterol, free fatty acid, triglyceride, hydrocarbon and esterified sterol by TLC. Of these classes, triglyceride fraction was most abundant, amounting to 55.6, 77.7 and $60.4\%$ in the three samples mentioned above, respectively. The main fatty acids of glycolipid were palmitic acid, eicosaenoic acid and docosahexaenoic acid in oyster, myristic acid, palmitic acid and palmitoleic acid in the arkshell, docosahexaenoic acid, linolenic acid and palmitic acid in the sea-mussel. The major fatty acids of phospholipid were palmitic acid, eicosapentaenoic acid and docosahexaenoic acid in the oyster and sea-mussel, palmitic acid, eicosapentaenoic acid and erucic acid in the arkshell.

• Journal of fish pathology
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• v.18 no.1
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• pp.39-48
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• 2005

Pathogenicity of Vibrio tapetis, the causative bacterium of 'brown ring disease (BRD)' was evaluated in Manila clams (Ruditapes philippinarumi by artificially 0.1 $m\ell$ infection of $1.0\times10^5$cells and $1.0\times10^8$ cells at 20 $^{\circ}C$. A PCR assay based on 16S rRNA to detect the bacteria in clam tissues was established. Accumulative mortality of clams infected with $1.0\times10^7$cells and $1.0\times10^4$ cells per an individual of the bacteria was 67.5% and 7.5%, respectively. However, the deposit of brown pigment in the inner shells by accumulation of chonchiolin was not found. The bacteria were not be able to re-isolate from the infected clams by the conventional agar plate method but were easily detected by PCR assay established in this experiment. In clams artificially infected with 10 species of Vibrio, a 414bp for V. tapetis was detected in PCR assay. The specific band in the clams infected with $1.0\times10^4$cells per an individual of V. tapetis was detected only in gills one day after the infection but never be found in any tissues including gills three days after the infection. In the case of clams infected with $1.0\times10^8$cells per an individual of V. tapetis the specific band was detected in gills and intestine one day after the infection, in all tissues three days after the infection, and then in gills and adductor muscle nine days after the infection. The PCR assay was applied to detect V. tapetis in manila clam, surf clam (Mactra veneriformis), oyster (Crassostrea gigas) and Thomas' rapa whelk (Rapana venosa) taken from Taean and Gochang from April to July 2004. The infection rates were detected to 23.1% and 9.4% in the oyster and surf clam, while manila clam and Thomas' rapa whelk were not found.

• Korean Journal of Food Science and Technology
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• v.41 no.4
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• pp.458-463
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• 2009

To establish and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the rapid and accurate quantitation of diarrhetic shellfish poisoning (DSP) toxins, we compared the results from different mobile phases and columns used for their analysis and collision energies for MS/MS experiments. Clear peaks of okadaic acid (OA) and dinophysistoxin-1 (DTX1) were obtained by using a mobile phase comprising aqueous acetonitrile containing 2 mM ammonium formate and 50 mM formic acid. The collision energies were optimized to facilitate the most sensitive detection for each toxin, namely, OA, DTX1, pectenotoxin-2 (PTX2), or yessotoxin (YTX). Further, the maximum ion response was obtained at a collision energy of 48 V for OA and DTX1. We compared the analytical performance of $C_8$ and $C_{18}$ columns. A wide range of toxins namely, OA, DTX1, PTX2, and YTX, except DTX3, were detected by both the columns. Although DTX3 was only detected by the $C_8$ column, we found that the $C_{18}$ column was also suitable for the quantitation of OA and DTX1 the toxins responsible for inducing diarrhea. The limit of detection of OA and DTX1 by the established LC-MS/MS conditions was 1 ng/g, and the limit of quantitation of the toxins under the same conditions was 3 ng/g. The process efficiencies were 91-118% for oysters (Crassostrea gigas) and 96-117% for mussels (Mytilus galloprovincialis) further, we observed no significant effect of matrix during the ionization process in LC-MS/MS. The comparison between mouse bioassay (MBA) and LC-MS/MS yielded varying results because low concentrations of OA and DTX1 were detected by LC-MS/MS in some shellfish samples, which provided positive results on MBA for DSP. The analysis time required by MBA for DSP analysis can be reduced by LC-MS/MS.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.7
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• pp.935-939
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• 2006

Raw oyster (Crassostrea gigas) was inoculated with Vibrio parahaemolyticus and Escherichia coli, treated with high hydrostatic pressure and evaluated for microbial counts. Cell death of V. parahaemolyticus (Vp) increased with the increase of applied pressure. Vp starting inoculum of $3.8{\times}10^5\;CFU/mL$ was totally eliminated after exposure to 200 MPa for 10 min at $22^{\circ}C$ Viable cell of Vp decreased with the increase in treatment time and dropped below the detection limit with treament of 25 min at $22^{\circ}C/150\;MPa$. The number of Vp by treatment of $0^{\circ}C$ and $10^{\circ}C$ for 20 and 25 mon at 100 MPa, respectively. For E. coli, there was an initial lag up to 250 MPa gollowed by a rapid decline. Treatment at 325 MPa/$22^{\circ}C$ for 15 min caused 5-log reduction, while that at 375 MPa resulted in total reduction of starting inoculum of $4.0{\times}10^7\;CFU/mL$. Lower treatment temperature showed higher killing effect of E. coli at the same treatment pressure and time. Viable cell of E. coli decreased with the increase in treatment time, and 4-log reduction was achieved with treatment of 5 min at $10^{\circ}C$/350 MPa and then total reduction was achieved after treatment of 15 mon. Higher pressure, lower temperature and longer time were more effective in sterilizing V. parahaemolyticus and E. coli.

• Journal of agriculture & life science
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• v.46 no.6
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• pp.105-115
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• 2012

The detailed proximate, fatty/amino acid, mineral composition, texture, color, chemical and taste compounds of six oysters (four kinds of cultured oysters and two kinds of wild oysters) in Korea were investigated. Length and weight of the shell removed cultured and wild oysters were 4.7~5.1 and 3.0~4.2 cm, and 5.9~9.1 and 2.6~5.5 g, respectively. The proximate compositions were not significantly different between cultured and wild oysters. Amino nitrogen and volatile basic nitrogen content of these ones were 232.8~258.2 and 160.5~213.9 mg/100 g, 9.5~12.0 and 7.8~9.5 mg/100 g, respectively. As a texture characteristic of muscle, shearing force were 95~114 and 105~132 g. Amounts of total amino acids of cultured and wild oysters were 9,004~10,198 and 8,165~8,942 mg/100 g, respectively. Major amino acids and inorganic ions were aspartic acid, glutamic acid, proline, alanine, leucine, phenylalanine, lysine, arginine and K, Na, Ca, Fe, S, P, Zn. Major fatty acids of these ones were 16:0, 18:0, 16:1n-9, 18:1n-9, 22:1n-9, 16:4n-3, 20:5n-3 and 22:6n-3, and there was little difference between the two groups. Amounts of free amino acids of cultured and wild oysters extracts were 1,444~1,620 and 1,017~1,277 mg/100 g, respectively, and major ones were taurine, glutamic acid, glycine, alanine, tryptophan, ornithine and lysine. There is a little difference in glycine, tryptophan, ornithine and arginine contents, but TMAO and TMA contents were low in amount, and were not significantly different between the two groups.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.4
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• pp.407-419
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• 1983

In this study, the lipid components of three species of shellfish included oyster(Crassostrea gigas), top shell(Turbo cornutus) representing salt water shellfish and corb shell(Corbicula fluminea producta) representing flesh water shellfish were analysed and nutriontional significances were discussed. Analysed the total lipid composition, and the fatty acid and sterol composition of total lipid were determined. The lipid was fractionated into three lipid classes neutral, glyco and phospholipid by column chromatography. The fatty acid composition of each lipid class and sterols were determined by gas liquid chromatography. The lipid components of total lipid and neutral lipid were estimated by thin layer chromatography and TLC scanner. The results were as follows: Total lipid contents of shellfish were 1.8% in oyster, 0.4% in top shell and 4.0% in corb shell. The contents of total fatty acid in total lipid were 80.7, 71.2 and 73.2%; and the contents of unsaponifiable matters were 15.4, 18.1 and 23.1% respectively. Total lipids were mainly composed of triglycerides, polar lipid-pigments and sterols as major component, and hydrocarbon-esterified sterols were determined in each sample. The major fatty acids in total lipid were palmitic(37.0%), eicosapentaenoic(13.5%) and linoleic acid(11.2%) in oyster, Octadecatetraenoic(15.8%), palmitic(11.2%), oleic(8.6%) and linoleic acid(8.1%) in top shell, but palmitic(34.0%), linoleic(12.3%) and paimitoleic acid(9.8%) in corb shell. Particularly, the contents of eicosapentaenoic acid of oyster and top shell were higher than those of corb shell. Sterol composition from three species of shellfish were mainly consisted of cholesterol (42.7~64.0%), brassicasterol(15.6~24.7%) and 24-methylenecholesterol (4.7~21.9%). But sitosterol (5.3%) was detected only in oyster and 22-dehydrocholesterol(12.9%) was only in top shell. The contents of fractionated neutral lipid was commonly higher than that of polar lipid in each sample. Glycolipid and phospholipid in polar lipid showed similar in quantity. The neutral lipids were composed of triglycerides(33.0~36.7%), free sterols(25.7~31.2%), esterified sterol(12.4~23.7%) and free fatty acids(5.1~11.7%). The contents of triglycerides and free sterols were higher than those of free fatty acids and esterified sterols. The major fatty acids in neutral lipid were palmitic(28.4~26.4%) eicosapentaenoic(18.6~21.9%) and linoleic acid(9.0~5.4%) in oyster and corb shell but octadecatetraenoic(14.5%), eicosapentaenoic (13.5%) and palmitic acid(12.3%) in top shell. The major fatty acids in glycolipid were eicosenoic(10.2%), palmitic(12.1%) and linolenic acid (10.2%) in oyster, Eicosenoic(26.0%), octadecatetraenoic(14.6.%) and eicosadienoic acid(12.9%) in top shell. But eicosadienoic(21.4%) stearic(14.6%), octadecatetraenoic(8.5%) and eicosenoic acid(8.5%) in corb shell. The major fatty acids in phospholipid were myristic(16.0%), stearic(10.6%), eicosenoic(10.5%) and palmitic acid(10.3%) in oyster, Oleic(22.2%), stearic(20.7%) and linolenic acid (11.8%) in top shell but eicosapentaenoic(25.1%), myristic(8.7%) and arachidonic acid(8.3%) in corb shell.