Study On Preparation And Physicochemical Properties Of Grass Carp Collagen Peptides

The total yield and process of freshwater fish in China are increased rapidly . Due to freshwater fish enterprises are small , and don't have the deep-processing capasity,the processing wastes of freshwater fish are very difficult to get a reasonable treatment not only waste resources but also pollute the environment.Grass Carp scales have richable collagen,the research make full use of collagen,expand the resources of collagen and its peptide,and meanwhile it can avoid the wastes,improve the level of technology and value-added processing of freshwater fish.The research including pretreatment conditions of grass carp scale,collagen enzymatic hydrolysis condition , peptide purification process and its physicochemical properties were studied.The optimal pretreatment conditions of fish scales before enzymatic hydrolysis were investigated through single effecting factors and orthogonal tests by the ratios of fish scales decalcification rate and the contens of collagen.The best HCl concentration,decalcifying time,and the ratio of solid material to liquid material for decalcification were 0.4mol/L,1 to 20,and 6 hours with the decalcification rate 97.8%.And the best condions of taking-off noncollagenous proteins were NaOH 0.15mol/L,1:20,12 h with the taking off noncollagenous proteins'rate 98.3%.The optimal high enzymatic hydrolysis degree conditions of grass carp scale collagen were investigated through single effecting factors and central composite design tests . The best condions of high degree enzymatic hydrolysis were temperature 50℃,pH 9.5,3 h with the hydrolysis degree rate 20.2%.Grass Carp collagen peptides were refined by desalinization and ultrafiltration with MW 3000u.The results showed that 89% of the salts in the hydrolysate were removed effectively by ion exchage resin at a flow rate of 6 m/h,7.5% peptide concentration and 25℃;and the optimal ultrafitration conditions were:5% peptides,pressure 0.125 MPa and temperature 40℃.The total yield of refined collagen peptide (relative to fish scale) was 20%.The physicochemical properties of fish scale collagen peptides were researched,the peptides had a good solubility,the viscosity was relatively low and reduced after ultrafiltration accordingly;when at pH 5,its ability of foaming was the worst,the foaming stability was the best.The distributing of molecular weight (MW) and contents of amino acid for fish scale collagen peptides were determined.The results indicated that the MW of peptides below 1000 Da were to 92.7%, lower than 500 Da up to 71.6%.Compared with fish scale gelatin in amino acid composition,in addition to proline,glycine,most of amino acids were significantly increased,essential amino acid content as high as 19.6%.Glycine,proline,glutamic acid and alanine were the major component of amino acids,the sum of the four up to 59%.Compared with gelatin,the content of hydrophobic amino acid and aromatic amino acids in collagen peptides was raised of 33.6% and 380% respectively,high content of hydrophobic amino acid made peptides much bitter.