Preparation And Properties Of Collagen Peptide Chelated Zinc From Fish Bioprocessing By-products

Previous research showed that collagen peptide from fish scale and fish skin has a variety of biological functions, including enhancement of zinc absorption. Research has also proved that collagen peptide chelated with zinc has many biological activities which can promote animal growth, and improve the immunity of animals, etc.This thesis focused on the preparation and biological activity of collagen peptide chelated zinc.Firstly, marine collagen peptide was prepared using puffer fish skin and tilapia fish scale as raw materials. Characterization of collagen peptide showed that the protein content of collagen peptide from puffer fish skin reached as high as 87.3% and the isoelectric point was 7.0. The protein content of collagen peptide from tilapia scale reached 85.4% and the isoelectric point was5.4. Both of them had low apparent viscosity. The molecular weight of collagen peptide was under 1000 Da.Secondly, collagen p eptide chelated zinc was prepared using collagen peptide and zinc acetate as raw materials. The effect of p H, temperature, time and molar ratio of collegan peptide to zinc on the preparation was investigated. Response surface test was used to optimize the chelating process. The results showed that the optimal preparation conditions of puffer fish skin collagen peptide chelated zinc were at p H 5.2, chelating temperature at 70.1°C for 2.9 h and molar ratio of collagen peptide to Zn(CH3COO)2 at 2.1:1. The optimal preparation conditions of tilapia fish scale collagen peptide chelated zinc were p H 3.8, reaction temperature 74.1°C for 2.1h and molar ratio of collagen peptide to Zn(CH3COO)2 at 1.0:1.Pilot scale production was carried out under the optimal condition to prepare collagen peptide chelated zinc. Nanofiltration membranes with different molecular weight cut off(MWCO) were applied to desalination. The results showed that the nanofiltration membrane with MWCO 700 Da could remove free zinc ions and inorganic salt effectively.The morphology of prepared collagen peptide chelated zinc was observed by transmission electron microscope. The results showed that the size of collagen peptide chelated zinc from puffer fish skin ranged from 200 nm to 500 nm and collagen peptide chelated zinc from tilapiafish scale ranged from 100 nm to 200 nm. Both of them were in amorphous structure.Finally, the antioxidant activities of collagen peptide and collagen peptide chelated zinc were evaluated by three kinds of chemical models in vitro(DPPH-radical scavenging activity,hydroxyl-radical scavenging activity and Fe2+ reducing power). Both of them showed excellent antioxidant activity. The antioxidant activity of collagen peptide chelated with zinc was higher than that of collagen peptide.