Comprehensive Development And Utilization Of Silver Carp Scraps

China is the biggest freshwater fish framing country in the world. In freshwater fish processing process produces a large number of residues, including skin, bones, innards, etc. At present most of the enterprises bury directly, or product the low value-added products, such as fish meal and feed, which not only pollute the environment, but also waste the protein resources. The thesis utilize fish scrap, including fish skin and fishbone, as materia, through the low temperature enzymatic preparation acquiring highly active collagen oligopeptide, and studying on its physical and chemical properties, which provides the new ideas with comprehensive processing and utilization for freshwater fish enterprises.Silver carp scrap is skin and bones in the main, there is a small amount of the flesh of fish. Silver carp scrap contains56.5percents fishbone,35.1percents fish skin, and8.4percents ground meat. Fishbone contain46.56percents crude protein (dry basis),32.59percents collagen,44.12percents ash; while fishskin include79.34percents crude protein and79.34percents collagen. So using cleaning to remove most of the fish first, then through miscellaneous protein and degreasing process, gets relatively pure collagen. Skin’s natural collagen structure close and bone’s collagen combining with calcium together lead to enzymolysis is not good. Choosing calcium lactate swelling skin and hydrochloric acid removing calcium in bones with together, make the fish scrap are easy to protease hydrolysis. The result indicated that the best process condition of lactic acid treatment is total acid concentration0.2mol/L, hydrochloric acid and lactic acid mole ratio of1:1.5, solid to liquid1:5, time3h, temperature25℃, the hydrolysis degree was as high as42.8%.Selecting suitable protease by means of different protease enzyme hydrolyzes silver carp scrap after acid treatment.. Passing on the single factor and orthogonal experiment, the optimum technological conditions were determined as follows:alcalase was target enzyme, substrate protein concentration3%, and enzyme dosage10%(the substrate protein), pH9.0, hydrolysis temperature50℃, enzyme hydrolysis time6h. After enzyme deactivation and filtering, degree of hydrolysis could reach45.2%, and peptide yield was88.6%.The enzyme solution of silver carp scrap contained a lot of pigment, salt and molecular weight in inhomogenous size, with some large proteins existed, first decolorization and deodorization with powdered activated carbon, ultrafiltration with UF-3ultrafiltration membrane after microfiltration, removed molecular weight greater than3000. The optimum conditions for ultrafiltration were optimized by single factor and orthogonal experiment, with Membrane flux and peptides transmittance as indexes. On this basis, the enzyme solution was desalted using NF-1812type nanofiltration membrane. The best conditions for nanofiltration were optimized with desalination rate and peptides yield as indexes. The results showed that the optimal conditions for ultrafiltration were pressure0.25MPa, pH7, temperature20, polypeptide concentration of2%and polypeptide transmittance can reach75%; the optimal conditions for nanofiltration were pressure0.5MPa, temperature15, polypeptide concentration of3%, by nanofiltration100minutes on this condition,the desalination rate can reach95.2%and short peptide recovery rate can reach as high as90%.The enzymolysis liquid after ultrafiltration, nanofiltration, reduced pressure concentration and freeze drying, got pure silver carp scrap low residue collagen peptide. It was detected whiteness80, protein content94.21%, ash0.08%. The peptide’s molecule weight ranged from1000to500Da was22.02%,500to180Da was55.32%and under180Da was 20.23%. Main amino acid in the peptide powder were as follows:Gly,Glu, Ala, Pro, Arg and Hyp, et al. Among them,the essential amino acid content was as high as20.71%, hydroxyproline content was6.08%.