• 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.37 no.2
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• pp.85-93
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• 1994

The fish skin gelatin hydrolysates were produced using a continuous two-stage membrane (MWCO 10,000, MWCO 5,000) reactor, and molecular weights, amino acids and functional properties of the hydrolysates were investigated. The major molecular weights distribution of the major fractions were $8{\sim}10\;KDa$ and $4.5{\sim}6.5\;KDa$ in the 1st-step hydrolysates, $2{\sim}6\;KDa$ and $0.5{\sim}2\;KDa$ in the 2nd-step hydrolysates. Among the amino acids in the hydrolysates, glycine, proline, serine, alanine, hydroxyproline, glutamic acid and aspartic acid having sweet taste were responsible for $68{\sim}72%$ of the total amino acids. But valine, methionine, isoleucine, leucine, phenylalanine and histidine having a bitter taste were only $23{\sim}25%$ Taste evaluations show that the gelatin hydrolysates have a brothy and sweet taste, 2nd-step hydrolysate have more a favorable taste than 1st-step hydrolysate. The hydrolysates were completely soluble and clear over the entire pH range. Moisture sorption at intermediate water activities of the 2nd-step hydrolysate was much higher than the unmodified fish skin gelatin, but foaming and emulsification properties were poor. Buffer capacity of the 2nd-step hydrolysate was higher than the fish skin gelatin and 1st-step hydrolysate, while viscosities of the hydrolysates were lower than the fish skin gelatin.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.999-1005
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• 2007

An oil-in-water (O/W) emulsion [20 wt% com oil, 0.5-6.0 wt% fish gelatin (FG), pH 3.0] was produced by high pressure homogenization, and the influence of pH, protein concentration, and homogenization condition on the formation of FG-stabilized emulsions was assessed by measuring particle size distribution, electrical charge, creaming stability, microstructure, and free FG concentration in the emulsions. Optical microscopy indicated that there were some large droplets ($d>10\;{\mu}m$) in all FG-emulsions, nevertheless, the amount of large droplets tended to decrease with increasing FG concentration. More than 90% of FG was present free in the continuous phase of the emulsions. To facilitate droplet disruption and prevent droplet coalescence within the homogenizer, homogenization time was adjusted in O/W emulsions stabilized by 2.0 or 4.0 wt% FG. However, the increase in the number of pass rather promoted droplet coalescence. This study has shown that the FG may have some limited use as a protein emulsifier in O/W emulsions.

• Fisheries and Aquatic Sciences
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• v.14 no.1
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• pp.1-10
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• 2011

This study was conducted to obtain hydrolysates with potent antioxidative activity from rockfish skin gelatin. Gelatin was extracted under high temperature/high pressure using a two-step enzymatic hydrolysis with commercial enzymes such as Alcalase, Flavourzyme, Neutrase, and Protamex. The second rockfish-skin gelatin hydrolysate (SRSGH) was prepared by further incubating the first gelatin hydrolysate (FRSGH), which had been hydrolyzed with Alcalase for 1-h (FRSGH-A1), with Flavourzyme for 2-h (SRSGH-F2). The second gelatin hydrolysate showed higher antioxidative activity of 3.72 as measured by a Metrohm Rancimat and superior angiotensin I-converting enzyme (ACE) inhibiting activity of 0.82 mg/mL. Compared with the gelatin, the relative proportion in SRSGH-F2 was markedly decreased in the 100-kDa peak, whereas it was increased in that less than 100-kDa. The amino acid composition of SRSGH-F2 was rich in glycine (25.9%), proline (10.8%), alanine (9.1%), and glutamic acid (9.1%). In contrast, it was poor in cystine (not detected), methionine (1.6%), tyrosine (0.4%), hydroxylysine (0.9%), and histidine (0.9%). In recent years, demand for natural functional foods has been increasing, and SRSGH-F2 can be used as a functional food ingredient in the food industries. However, further detailed studies on SRSGH-F2 with regard to its antioxidant activity in vivo and the various antioxidant mechanisms are needed.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.483-486
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• 1995

With a view to increase utility of ethanol fractionated fish skin gelatin as a food source, the effect of gelation condition on physical properties of the gelatin was investigated. The physical properties of gelatins treated with or without ethanol were improved with a concentration of gelatin increased. The properties such as gel strength, melting point and gelling point of 10% gelatin sol or gel were reached to maximum at pH 6.0 in ethanol treated gelatin and pH 5.0 in non treated one, respectively. Gel strength and melting point of both gelatin gels chilled for long time at low temperature were superior to those of both gelatin gels chilled for short time at high temperature. Gel strength, melting point and gelling point of ethanol treated gelatin gel or sol prepared under optimized gelation conditioning were superior to those of non treated one.

• Journal of fish pathology
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• v.10 no.1
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• pp.31-38
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• 1997

Aeromonas hydrophila isolated from the intestine of carp produced several kinds of proteases into the medium. Inhibitor assay with the culture supernatant of A. hydrophila showed that there were major metalloproteases and minor serine proteases. Gelatin SDS-PAGE showed two proteolytic bands. One broad protease band was inhibited by metalloprotease specific inhibitor, EDTA, indicating a metalloprotease. The other was inhibited by serine protease specific inhibitor, PMSF, suggesting a serine protease. The proteolytic activities of both extracellular proteases remained on Gelatin SDS-PAGE after heating at $70^{\circ}C$ for 30 min. However, the major metalloprotease was separated into two proteolytic bands on Gelatin PAGE by gel filtration chromatography on Sephadex G-75.

• Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.299-304
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• 2014

The objective of this study was to elucidate the physicochemical characteristics of gelatin extracted from jellyfish Rhopilema hispidum. We investigated the proximate composition, amino acids, gel strength, gelling/melting points, dynamic viscoelastic properties, and viscosity of jellyfish gelatin. Jellyfish gelatin contained 12.2% moisture, 1.5% lipid, 2.1% ash, and 84.8% protein. Glycine, hydroxyproline, proline, and alanine were the predominant amino acids. The gelatin showed a gel strength of 31.2 kPa, a gelling point of $18.0^{\circ}C$, and melting point of $22.3^{\circ}C$. The gelatin was composed of ${\alpha}_1$-chain, ${\alpha}_2$-chain, ${\beta}$-chain, and ${\gamma}$-chain. During cooling and heating process, jellyfish gelatin showed lower elastic modulus (G') and loss modulus (G") values than mammalian gelatin. Jellyfish gelatin did not show superior rheological properties to mammalian gelatin, like other fish gelatin; however, it can be used in various food and cosmetic products not requiring high gel strength.

• 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.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.716-723
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• 1993

To utilize effectively fish skin wasted from fish processing, a yellowfin sole skin gelatin was prepared by alkaline extraction method and the physico-chemical properties were examined. Conditions for the suitable extraction and decolorization for gelatin preparation from yellowfin sole skin are as follows: the skin is limed with 1.5% calcium hydroxide solution at $5^{\circ}C$ for 5 days, washed throughly with tap water, extracted with 6 volumes of water ($pH5.0{\sim}7.0$) to dehydrated skin for 3 hours at $50^{\circ}C$, and then bleached with 3% activated carbon. Though yellowfin sole skin gelatin was prepared under above condition, the physico-chemical property values such the melting point and gelling point of that were lower than those of pork skin gelatin. Therefore, the purified yellowfin sole skin gelatin requires a suitable modification operation for more a good quality gelatin manufacture.

• 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.