Study On The Preparation Of Fish Oil And Peptide-Selenium Chelates From Fed Sea Bream Head

During the processing of red sea bream, large amount of byproduct are produced. The head which is rich in protein and fat was the main byproduct. In this thesis, peptide and fish oil were prepared from head by enzymatic hydrolysis and peptide-selenium chelates were synthesized by peptides of molecular weight less than 3000 Da and selenium salt. This research was expected to provide technical support for the development and utilization of red sea bream head.The results of different enzyme hydrolysis showed that trypsin was selected for further research. The optimum conditions were gotten by orthogonal experiment as follows: enzyme dosage of 950 U/g, hydrolyzing at 55℃ with pH 7, solid/liquid ratio at 1:4 and reaction time at 6 h. Under above conditions, the DH was 61.15% and the oil yield reached 82.09%.The hydrolyzate analyzed by HPLC showed that the amount of its 15 kinds of amino acid was 419.09 mg/100mL and the amount of essential amino acid was 241.24 mg/100mL.Activated carbon was used to remove fishy of hydrolyzate and the result showed that the optimum deodorization conditions were gotten as follows:activated carbon concentration at 0.5%, adsorption time at 35 min and 45℃, smell values and the loss rate of peptides were 2.25 and 4.09% respectively.Twenty-three kinds of fatty acids were identified in crude fish oil by using GC-MS and C13-C22 fatty acids occupied the majority. Unsaturated fatty acids totaled 71.45% and the content of EPA and DHA was 19.52%.The optimum ultrafiltration conditions of hydrolysis were gotten as follows:pressure at 0.08 MPa and temperature at 30℃. The peptide hydrolyzate of molecular weight less than 3000 Da was collected.The optimum chelating reaction conditions were gotten by orthogonal experiment as follows:the concentration of peptide 3%, temperature at 80℃, mass ratio (peptide to selenium salt) 3:1, PH8.5 and time at 40 minutes.The chelation rate and yield rate were 42.26% and 36.19% respectively under above conditions. UV and IR analysis results showed that the product was peptide-selenium chelates.The results of antioxidant properties in vitro showed that:peptide and. peptide-selenium chelates had a certain scavenging ability on DPPH·radical,·OH radical and O2-·radical.Salmonella, Staphylococcus aureus, Escherichia coli and Bacillus subtilis were taken as research object to study antibacterial activity of peptide and chelates. In the concentration range of sample, the antibacterial test of peptide showed that it had inhibitory effects on both Salmonella and Bacillus subtilis, while the peptide-selenium chelates showed inhibition to Salmonella.