| Plastic residue is not easy to biodegrade, which has become a serious environmental problem in the whole world at present. To enhance the attention of environmental protection, and extend the shelf-life and improve the quality of food, edible films become research focuses of food package. Edible films are prepared from inartificial macromolecule material, such as polysaccharides, proteins, lipids along with plasticizers and cross-linking agents. Since the edible films could be eaten together with the food packaged with, they can't bring about environment pollution.Gelatin is the most attractive animal protein. Because of religion and cow disease, the gelatin of bovine or porcine skin and bone is restricted. Since fish gelatin is an abundant and safe protein, and has good filmogenic property, it is a potential film material. Developing edible fish gelatin films is concerned.Walleye pollock (Theragra chalcogramma) skin gelatin as material, along with chitosan, alginate and carrageenan, fish gelatin composite films were prepared, and their properties were studied in this dissertation. In addition, plasticizers and cross-linking agents were added to the composite films, to improve the properties of the fish gelatin films. Meanwhile the structure and application of composite films were systematically studied. The results are as follows:1. The fish gelatin had lower viscosity and gel strength. When the concentration of fish gelatin is 6%, the viscosity was 0.011Pa·s at 25℃, and the gel strength was 3.925gf/mm2 after the fish gelatin was layed for 18h at 4℃. The fish gelatin had good filmogenic property, the transmittancy of film being about 90%. But it had lower mechanical properties. The tensile strength (TS) and elongation at break (E) were 13.65MPa and 1.03% respectively, and the denaturation temperature was 77.15℃. The barrier properties of the fish gelatin film were worse. The water solubility (WS) was 100% stationarily for 24h at room temperature, the hygroscopicity was 22.6% placed open-cased for 72h, and the water vapor permeability(WVP) was 0.34g﹒mm/m2﹒h﹒kPa.2. Three polysaccharides were added into fish gelatin with different ratio to form composite filmogenic solution. The viscosity was all increased after addition of polysaccharides. Chitosan and alginate could decrease the gel strength, but carrageenan could increase it obviously. The transmittancy of composite films was higher than 80%, which suggested that gelatin and the three polysaccharides had good compatibility. The mechanical properties of three composite films were increased highly. The TS and E were increased by 83.12% and 315.17% respectively. The denaturation temperature of gelatin-chitosan composite film and gelatin-alginate composite film were increased by 10℃and 8℃respectively, while the denaturation temperature of gelatin-carrageenan composite film was decreased slightly. The hygroscopicity of gelatin-alginate composite film was lower than gelatin film, but the two other composite films were not improved obviously. The WS and WVP of three composite films were both lower than gelatin film, revealing the barrier properties of composite films much better.3. Adding glycerol into gelatin-chitosan composite-solution, the TS and E of film were increased, but the TS was decreased later with concentration. After the gelatin-alginate composite films and gelatin-carrageenan composite films were cross-linked by CaCl2, the TS was increased evidently, while the E was decreased. So the mechanical properties were increased to a certian extent, after the composite films were modified. Gelatin-chitosan composite films were plasticized by glycerol, the barrier properties had not been improved. But the barrier properties were much improved after the composite films cross-linked by CaCl2. The transmittancy of composite films modified was high, and various molecules had good compatibility. The denaturation temperature of gelatin-carrageen composite films cross-linked by CaCl2 was increased. 4. The gelatin film and composite films of good mechanical properties were evaluated, by Fourier transform infrared (FTIR), X-ray diffraction studies (X-RD) and Scanning electron microscopy (SEM). The results showed that classical bands of gelatin film were Amide I, Amide II and Amide III in the FTIR, and X diffraction peaks were 7.7°and 21.2°. However, in the FTIR and X-RD spectras of composite films, there were several new bands, which suggested that new groups formed in composite films. So it could be concluded that gelatin and three polysaccharides interacted with each other, forming new macromolecule and stable system, not mixed simply. In the SEM photograph, gelatin film and composite films were smooth and homogeneous, without phase separation. Again, the result of SEM here indicated good compatibility in the gelatin and three polysaccharides. The section structure of composite films was more compact, which suggested the mechanical and barrier properties of composite were better than gelatin film.5. Bread was coated with gelatin or composite-solution. Compared with control group, the content of water and specific volume were higher, and the color of bread was better, which suggested that the quality of bread coated with samples was better. Considering several factors, the bread coated with gelatin-chitosan composite films was the most desirable.
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