Studies On The Preparation,Structure And Properties Of Zinc Chelating Collagen Peptides From Sea Bream Fish-Scale And Skin

In the thesis, the red sea bream scale and skin were used as raw materials, and the technologies of biological enzymatic hydrolysis, ultrafiltration separation and ultrasonic synthesis were applied to prepare fish collagen peptide chelating zinc. The structure and properties of the chelates were studied as well.Four kinds of enzymes were used to hydrolyze fish scale and skin protein. The result showed that trypsin was the most suitable enzyme for its highest hydrolysis degree. The best hydrolysis conditions were as follows:reaction temperature 55℃, solid-liquid ratio 1:8, enzyme dosage 950U/g, reaction time 6h and pH 7.0. The result analyzed by HPLC showed that the total amount of 15 kinds of amino acids in enzyme hydrolysis solution was 278.94mg/100mL, and the content of essential amino acids was 132.74mg/100mL.Activated carbon was used to remove fishy smell from the enzyme hydrolysis solution. The best conditions were as follows:concentration of activated carbon 1.0%, adsorption time 35min and temperature 45℃.When the pressure and the temperature were 0.08MPa and 30℃ respectively, the enzyme hydrolysis solution was separated by ultrafiltration to get collagen peptides of less than 3000Da molecular weight.The collagen peptide was chelated with zinc. The optimum conditions of chelation were as follows:concentration of ligand 6%, temperature 70℃, molar ratio of peptide and ZnSO4 4:1, reaction time 30min and reaction pH 5.5., and the chelation rate was 85.97% under the condition. The optimum conditions of chelation assisted with ultrasound were gotten as follows:ultrasonic power 150W, concentration of ligand 5%, temperature 70℃, molar ratio of peptide and ZnSO4 4:1, reaction pH 5.5, and reaction time 5min. Under the above conditions, the chelation rate was 96.07%, The ultrasonically assisted chelation could greatly promote the chelating reaction and shorten the reaction time compared with that of conventional chelating reaction.The product was testified by Fourier transform infrared spectroscopy and UV spectroscopy, and result showed that it belonged to chelates.Through antioxidant activity test, it was proved that both collagen peptide and chelates had a certain scavenging ability on DPPH-,-OH and O2, and the scavenging ability of collagen peptide were stronger than that of chelates.The filter paper method was used to study antibacterial activity of collagen peptide and chelates. The result showed that both collagen peptide and chelates had evident antibacterial activity to Salmonella, Escherichia coli and Bacillus subtilis and the antibacterial activity of chelates was better than collagen peptide. And neither of them had antibacterial activity to Staphylococcus aureus.