• Applied Biological Chemistry
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• v.36 no.4
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• pp.290-295
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• 1993

In order to utilize effectively fish skin from fish processing, characteristics of the yellowfin sole and dover sole skins were investigated. In the yellowfin sole, the crude protein content and yield of fish skin used for the preparation of gelatin were 22.3% and 11.3%, respectively and in the dover sole, 17.2% and 8.9%, respectively. In the yellowfin sole skin, the soluble and insoluble collagen occupied 66.1% and 33.9%, respectively and in the dover sole skin, 78.8% and 21.1%, respectively. No difference in the amino acid composition between soluble and insoluble collagen was detected. The sum of proline and hydroxyproline content in the collagen extracted from fish skin was lower than that of those from pork skin or bone. The molecular weight of the two major subunits from the soluble collagen in the yellowfin sole skin were found to be 143 KDa and 202 KDa. Those in the dover sole skin were 142 KDa and 207 KDa. The physico-chemical properties such as the melting point and gelling point of yellowfin sole skin gelatin were superior to those of dover sole skin gelatin.

• Applied Biological Chemistry
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• v.36 no.6
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• pp.440-448
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• 1993

To utilize effectively fish skin wasted from fish processing, a dover sole skin gelatin was prepared by alkaline extraction method and the physico-chemical properties were examined. Conditions for the suitable pretreatment, extraction and decolorization for gelatin preparation from dover sole skin are as follows: the skin is limed with 1.0% calcium hydroxide solution at $5^{\circ}C$ for 4 days, washed thoroughly for 2 days with tap water, extracted with 5 volumes of water $(pH\;5.0{\sim}7.0)$ to dehydrated skin for 3 hours at $50^{\circ}C$, and then bleached with 3% activated carbon. Though dover sole skin gelatin was prepared under above conditions, physico-chemical property values such the melting point and gelling point of that were lower than those of yellowfin sole skin gelatin as well as the commercial pork skin gelatin. Therefore, the purified dover sole skin gelatin requires a suitable modification operation for better quality gelatin manufacture.

• Applied Biological Chemistry
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• v.38 no.2
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• pp.129-134
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• 1995

With a view to utilizing effectively fish skin wasted from marine manufactory, an extracted dover sole skin gelatin was fractionated by further ethanol fractional precipitation method, and then the functional and physicochemical properties for the modified gelatin were determined. Ethanol was added to the concentration of 30% in an extracted dover sole skin gelatin solution, and then the mixture was left to stand at $0^{\circ}C$ for 12 hours. Finally, the precipitates were dried by hot-air$(40^{\circ}C)$ blast. The yellowfin sole skin gelatin prepared by further ethanol fractional precipitation has 223.0 g in gel strength, $17.7^{\circ}C$ in the melting point, and $12.0^{\circ}C$ in the gelling point. The physicochemical properties of the ethanol treated fish skin gelatin were superior to those of fish skin gelatin prepared without ethanol adding, whereas inferior to those of animal skin gelatin. The functional properties of the ethanol treated fish skin gelatin were superior to those of fish skin gelatin prepared without ethanol adding, and were more similar to animal skin gelatin. It may be concluded, from these results, that the dover sole skin gelatin prepared by further ethanol fractional precipitation can be effectively utilized as a human food by improving the functional properties.

• Applied Biological Chemistry
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• v.38 no.4
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• pp.330-333
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• 1995

Effects of additives on physical properties of dover sole skin gelatin prepared by fractional precipitation with ethanol were investigated to obtain basic data for utilizing as food protein source. Physical properties such as gel strength, melting point, gelling point and viscosity of both ethanol- and non-treated gelatins were improved as ferric ion, sugar and ethanol were added to gelatin sol, but were deteriorated as sodium hydroxide and acids were added. Insignificant difference in effects of physical properties on additives such as ferric ion, sodium chloride, sugar, acids and ethanol between ethanol- and non-treated gelatins were not observed.

• Applied Biological Chemistry
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• v.38 no.2
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• pp.147-150
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• 1995

Effects of gelation conditions on physical properties of dover sole skin gelatin prepared by fractional precipitation with ethanol were investigated. The physical properties such as gel strength, melting point and gelling point of both ethanol treated and non-ethanoltreated gelatins were improved as concentration of gelatin was increased. The physical property of 10% ethanol treated gelatin sol reached maximum at pH 6.0, whereas non-treated one showed maximum at pH 5.0. Both ethanol treated and non-treated gelatin gel showed the higher gel strength and melting point at lower temperatures and longer period of time. Generally, the physical properties of ethanol treated gelatin gel was better than those of non-ethanol treated gel.