• Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.10.1-10.14
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• 2019

Fish skin waste accounts for part of the solid waste generated from seafood processing. Utilization of fish skin by bioconversion into high-grade products would potentially reduce pollution and economic cost associated with treating fish processing waste. Fish skin is an abundant supply of gelatin and collagen which can be hydrolyzed to produce bioactive peptides of 2-20 amino acid sequences. Bioactivity of peptides purified from fish skin includes a range of activities such as antihypertensive, anti-oxidative, antimicrobial, neuroprotection, antihyperglycemic, and anti-aging. Fish skin acts as a physical barrier and chemical barrier through antimicrobial peptide innate immune action and other functional peptides. Small peptides have been demonstrated to possess biological activities which are based on their amino acid composition and sequence. Fish skin-derived peptides contain a high content of hydrophobic amino acids which contribute to the antioxidant and angiotensin-converting enzyme inhibitory activity. The peptide-specific composition and sequence discussed in this review can be potentially utilized in the development of pharmaceutical and nutraceutical products.

• KSBB Journal
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• v.15 no.6
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• pp.635-643
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• 2000

To compare the antioxidative activities of fish skin and bovine skin gelatin hydrolysate, gelatin hydrolysates from Alaska pollack and bovine skin were prepared by various enzymatic hydrolysis methods (1st step, Alcalase; 2nd step, pronase E; 3rd step, collagenase) using a continuous three-step membrane reactor. The molecular weight distributions of the 1st, 2nd and 3rd step hydrolysates were 7∼10 kDa, 2∼5 kDa and 0.7∼0.9 kDa, respectively. The antioxidative activity of fish skin gelatin hydrolysate was stronger than that of bovine skin gelatin hydrolysate, and in particular, both of 2nd step hydrolysates showed more antioxidative activity than hydrolysates of any other step. The optimum antioxidative activity concentration of the 2nd step hydeolysates of fish and boving skin were 1% (w/w) in a linoleic acid water-alcohol emulsion. In cultured cells exposed to t-butyl hydroperoxide (t-BHP), the 2nd step hydrolysate of fish skin gelatin delayed cell death most. These results suggest that the antioxidative activity of fish skin gelatin hydrolysate is higher than that of bovine skin gelatin hydrolysate because of their different amino acid contents.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.4
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• pp.365-370
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• 2013

This study investigated the effect of dietary paprika on the skin coloration of red- and white-colored fancy carp Cyprinus carpio var. koi, in two age groups: 0-age ($7.4{\pm}0.1$ g/fish) and 1-age ($164{\pm}2.9$ g/fish). Three isonitrogenous diets were formulated to contain 0, 5, and 10% paprika (Con, P5 and P10, respectively). Three replicate groups of 0-age fish and two replicate groups of 1-age fish were fed one of the experimental diets for 9 weeks. Survival, weight gain, and feed efficiency were not significantly affected by the dietary paprika level (P>0.05) at both fish sizes. The dietary paprika level influenced the redness ($a^*$), lightness ($L^*$), and yellowness ($b^*$) of fish skin. The $L^*$ value of the skin of the fish fed the P5 and P10 diets tended to decrease with feeding period. The skin $a^*$ value of 0-age fish (small) fed the diets containing paprika increased significantly with feeding period and was higher than that of fish fed the control diet after 3 weeks (P<0.05). However, the $a^*$ value of 1-age fish (large) fed the diets containing paprika tended to increase slightly with feeding period. At the end of the experiment, the skin total carotenoid level was increased significantly in fish of both sizes fed the P5 and P10 diets compared to fish fed the control diet. Therefore, 5% paprika powder in the diet increases the skin redness of red- and white-colored fancy carp, especially in small fish.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.2
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• pp.414-421
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• 2015

This study was conducted to investigate the effects of Spirulina level in the diet on growth and skin color of red- and white-colored fancy carp Cyprinus carpio var. koi at different feeding periods. Five experimental diets (designated as Con, S5, S9, S13 and S17) were prepared to contain 0, 5, 9, 13 and 17% Spirulina. Each experimental diet was fed to two replicate groups of fish (6.6 g/fish) to visual satiation three times a day for 12 weeks. Weight gain and feed efficiency of fish were not affected by dietary Spirulina level. The values of redness ($a^*$), lightness ($L^*$) and yellowness ($b^*$) of the fish skin were influenced by dietary Spirulina level at different feeding period. The $L^*$ value of skin in the fish fed S9, S13 and S17 diets tended to decrease with feeding period. The skin $a^*$ value of the fish increased significantly with feeding period and dietary Spirulina level. The skin $a^*$ value of the fish fed the diets containing 5-17% Spirulina was higher than that of fish fed control diet at 6 and 12 weeks of feeding. The skin $a^*$ value and total carotenoids of the fish fed the S17 diet was the highest among groups. Based on the results of this study, it can be concluded that dietary inclusion of Spirulina powder could increase the skin redness of red- and white-colored fancy carp.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.683-689
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• 1994

With a view to utilizing effectively fish skin wastes from marine manufactory, a gelatin solution extracted from yellowfin sole skin was fractionated by precipitation with ethanol, and then the functional and physico-chemical properties for the fractionated gelatin were determined. Ethanol was added up to 50% of ethanol content to a gelatin solution extracted from yellowfin sole skin, then the mixture was left to stand at $0^{\circ}C$ for 12 hours. Finally, the precipitates were dried by hot-air ($40^{\circ}C$). The gel strength and melting point of a 10% gel of gelatin prepared from yellowfin sole skin by precipitation with ethanol has 322.4g and $23.3^{\circ}C$, respectively. The physico-chemical properties of the ethanol treated fish skin gelatin were superior to those of fish skin gelatin prepared without ethanol treatment. Besides, the functional properties of the ethanol treated gelatin were lower in solubility and higher in water holding capacity, oil binding capacity, emulsifying activity, emulsifying stability, foam expansion and foam stability than those of pork skin gelatin sold on market as well as gelatin prepared without ethanol treatment. It may be concluded, from these results, that the fish skin gelatin prepared by precipitation with ethanol can be effectively utilized as a human food by improving the functional properties.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.4
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• pp.337-342
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• 2012

A feeding trial was conducted to investigate effect of three paprika levels (0%, 5% and 10%) with two lipid levels (4% and 10%) in diets on growth performance and skin coloration of red- and white-colored fancy carp, Cyprinus carpio var. koi. Two replicate groups (an average body weight of $4.3{\pm}0.2g$) of fish fed one of eight experimental diets for 8 weeks. Survival, weight gain and feed efficiency of the fish were not significantly affected by both dietary paprika and lipid levels (P>0.05). After 8 weeks feeding period, the values of $a^*$, $L^*$ and $b^*$ of fish skin were significantly changed by dietary paprika level (P<0.05) but not lipid level. The $a^*$ value of fish fed the diets containing paprika was higher than that of fish fed control diet (P<0.05). Additional inclusion of 50-100 ppm canthaxanthin in diets containing 5% and 10% paprika did not improve $a^*$ value of fish skin. Based on the results of this study, it can be concluded that dietary inclusion of 5% paprika powder could increase the redness of red- and white-colored fancy carp fingerling.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.790-795
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• 2014

A feeding trial was conducted to investigate the effects of dietary carotenoids sources on growth and skin color of red- and white-colored fancy carp Cyprinus carpio var. koi. Nine experimental diets (designated as Con, CP, PA, SP, OP, MB, TO, BE and PO) were formulated to contain Carophyll Pink, red paprika, Spirulina, Opuntia, mandarin bark, tomato, beet and Porphyra, respectively. Each experimental diet was fed to two replicate groups of fish (22.9 g/fish) to visual satiation three times a day for 8 weeks. Weight gain and feed efficiency of fish fed the diets containing Spirulina or Opuntia were higher than those of fish fed the control diet (P<0.05). The values of $a^*$, $L^*$ and $b^*$ of fish skin were significantly changed by dietary carotenoids sources (P<0.05). The $a^*$ values of fish fed the diets containing Carophyll Pink, red paprika and Spirulina were higher than those of fish fed other diets (P<0.05). The skin total carotenoids of fish fed the diets containing Spirulina and Opuntia were higher than those of others (P>0.05). Based on the results of this study, it can be concluded that dietary inclusion of red paprika and Spirulina pacifica could increase the skin redness of red- and white-colored fancy carp.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.547-559
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• 1994

To effectively utilize fish skin wastes from marine manufactory, the optimal extraction conditions to prepare gelatin from fish skins of Alaska pollack, cod and yellowfin sole were investigated. In addition, the physical properties of the fish skin gelatins prepared under the optimal extraction conditions were compared with the commercial animal skin gelatin. The conditions for extraction of gelatins from fish skins were as follows ; The skins were limed with 1.0~1.5%(w/v) calcium hydroxide solution. The fish skin gelatins were extracted with 6~7 volumes of water(pH 6.0~7.0) for 5hrs at $40{\sim}50^{\circ}C$, and the yield of Alaska pollack skin gelatin extracted under the above conditions was higher than those of cod and yellowfin sole skins. The heavy metal contents, jelly strength and electric conductivities of fish skin gelatins were lower than those of a commercial gelatin(bovine skin), but the viscosity and isoelectric point were higher. The amount of amino acid in fish skin, such as gelatin, glutamic acid, serine, threonine, methionine and cysteine, were higher than those in pig and ox skin. However, the contents of hydroxyproline and proline were lower.

• Applied Biological Chemistry
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• v.39 no.2
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• pp.134-139
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• 1996

In order to effectively utilize marine animal skin wastes in marine processing manufacture, conger eel skin, file fish skin and arrow squid skin as raw material of edible gelatin were screened. Conger eel skin was the highest in the collagen content, followed by Ole fish skin and arrow squid skin, in the order named. In the fish skins, the soluble and insoluble collagens occupied $67.4%{\sim}72.3%\;and\;27.7{\sim}32.6%$, respectively, and in the arrow squid skin, 30.4ft and 69.6ft, respectively. No difference in the amino acid composition between soluble and insoluble collagens was detected. Collagen from the marine animal skin catched in coasted and offshore water in Korea consisted ${\alpha}$ chain and ${\beta}$ chain, and ${\alpha}$ chain were hetero type. The sum of proline and hydroxyproline contents in conger eel skin collagen was higher than that in the other skin collagens, while was lower than that pork skin collagen. Conger eel skin collagen exhibited a higher denaturation temperature in solution and a higher degree of proline hydroxylation, compared with skin collagen of the respective species. The physical properties such as gel strength, melting point and gelling point of conger eel skin gelatin were superior to those of file fish skin and arrow squid skin gelatins.

• Journal of fish pathology
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• v.5 no.2
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• pp.159-164
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• 1992

The skin of fishes is also the important external barrier against a variety of the environmental detrimental agents, allowing normal internal physiological function, so its condition is very important in many disease processes. Since fishes are aquatic, morphologically and physiologically they posses specific characteristics lacking in terrestial animals. Thus, it is necessary to keep in mind various specific histologic characteristics for a precise interpretation of the histopathological lesions. In the normal environment the fish skin is more subtly adapted for its physiological requirements as a limiting barrier than the skin of higher terrestial vertebrates. However, its delicacy makes it high vulnerable to damage in fish culture facilities or polluted waters. Although changes in the skin of fish such as discoloration, ulcerative lesions, are the the most readily observed clinical features of fish, there is a wide variety of possible responses, which are best considered in terms of their site within the skin. Up to now, there are relatively few sytematically described information on the histological structure of the teleost skin as well as integrated reviews of the range of pathological processes that can occur in teleost skin. Therefore it was tried in this article to rearrange the information already described by other investigators on the histological structure and histopathological changes of teleost skin.