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Study On Preparation And Characterization Of Collagen Peptide From Fish Scales Of Grass Carp

Posted on:2010-04-14Degree:MasterType:Thesis
Country:ChinaCandidate:F ShenFull Text:PDF
GTID:2121360302955174Subject:Food Science
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Fisheries and fish processing create large amount of by-products,such as fish scale, fish skin and fish bone,and there are approximately 650,000 tons fish scales every year in china,most of them are discarded except that some are utilized and exported.As known, fish scales contain abundant collagen which can be used to prepare valuable collagen peptide.However,little work has been done on preparation of collagen peptide from fish scales of grass carp and evaluation of its characterizations.In order to offer foundation for preparing valuable collagen peptide,the aim of this work was to study the hydrolyzing effects of proteases types and hydrolyzing conditions on the hydrolysates of grass carp scales,the optimization of hydrolyzing process,and the characterization of scale collagen peptide.The main results are summarized as follows.(1) The effects of protease types on hydrolysis of grass carp scales.The results showed that there was a significant difference among pepsin,protamex,papain and alcalase.Among the four proteases,the hydrolysates of papain had the highest hydrolyzing degree(7.54%) and nitrogen recovery(79.44%),while the pepsin hydrolysates had a high nitrogen recovery and could form gel in low temperature. According to the sensory evaluation to pepsin,papain,alcalase and protamex hydrolysates of grass carp scales,they were milky,yellowish,yellowish and yellow respectively,the first two hydrolysates tasted plain,the alcalase hydrolysate tasted bitter lowly,while the protamex hydrolysate tasted bitter strongly.(2) The effects of hydrolyzing conditions on the enzymatic hydrolysis of grass carp scales with pepsin and the hydrolyzing process optimized by orthogonal experiment were studied.There was a significant effect of hydrolyzing temperature,initial pH value, substrate concentration,and pepsin dosage on the hydrolyzing degree,nitrogen recovery and gel strength of pepsin hydrolysates(p<0.05).Hydrolyzing temperature of 65℃,initial pH value 4.0,substrate concentration 5%(w/v),pepsin dosage of 140 U/g Pro,and a hydrolysis time of 120 min were found to be the optimum conditions to obtain a higher gel strength and nitrogen recovery,and the hydrolyzing degree,nitrogen recovery,gel strength of pepsin hydrolysates were 1.46%,64.38%and 2051g,respectively.(3) The effects of hydrolyzing conditions on the enzymatic hydrolysis of grass carp scales with papain and the hydrolyzing process optimized by orthogonal experiment were studied.There was a significant effect of hydrolyzing temperature,initial pH value, substrate concentration,and papain dosage on the hydrolyzing degree and nitrogen recovery of papain hydrolysates(p<0.05).Hydrolyzing temperature of 60℃,initial pH value 5.0,papain dosage of 3000U/g Pro,substrate concentration 5%(w/v),and a hydrolysis time of 120 min were found to be the optimum conditions to obtain a higher nitrogen recovery and hydrolyzing degree,and the hydrolyzing degree and nitrogen recovery of papain hydrolysates were 12.68%and 89.42%,respectively.(4) Composition and functional properties of scale collagen peptide were studied. The amino acid composition of the scale collagen peptide preparing using the optimized conditions revealed that there were large amount of glycine,proline,hydroxyproline, glutamic acid and alanine.Compared with collagen peptide prepared with papain,the collagen peptide prepared with pepsin had larger average molecular weight,less fractions. Two fractions of collagen peptide prepared with pepsin were obtained through Sephadex G-100 gel filtration chromatography.As the hydrolyzing time prolonged,the larger molecular weight fractions of pepsin hydrolysate decreased and the smaller molecular weight fractions increased gradually.The collagen peptide prepared with pepsin obtained better emulsifying property,foaming property and higher viscosity,while the collagen peptide prepared with papain had better solubility,poorer emulsifying property,foaming property and lower viscosity.The collagen peptide prepared with pepsin from grass carp scales had good gel properties,the gelling point and melting point of 2.5%(w/v) collagen peptide were 9.12℃and 11.80℃respectively.The gel strength of collagen peptide prepared with pepsin increased with the increase of concentration,and had higher gel strength at pH 6 or 8.The gel strength of collagen peptide increased with proper addition of transglutaminase,while the gel strength decreased with the addition of NaCl.The gel strength,hardness, cohesiveness and elasticity of silivi carp surimi had a tendency to reduce with addition of scale collagen peptide,collagen peptide was not suitable to be added to silver carp surimi,but the scale collagen peptide have potential application as colloid stabilizer or emulsifier,since the scale collagen peptide have good gelation and emulsification properties.
Keywords/Search Tags:Grass carp scales, Collagen peptide, Enzymatic hydrolysis, Functional properties
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