Preparation, Properties And Application Of Chitosan Based Composite Films

Chitosan, a natural macromolecule copolymer yielded from deacetylation of chitin, is the second largest biological resources to cellulose. Due to its good properties of film-forming, biocompatible, biodegradable, antibacterial, non-toxic and side-effect free, chitosan has a great prospect for applications in new food packaging film materials. Although chitosan is a promising biopolymer, it has weak mechanical strength, poor water vapor barrier performance, poor antioxidant activity and narrow bacteriostatic spectrum, these weaknesses as packaging film limit its applications in food packaging.In this thesis, chitosan was used as substrate, gelatin as blending, glycerol as plasticizer, chitosan-gelatin composite films were prepared firstly aiming at enhancing the mechanical properties of chitosan films. Then chitosan oligosaccharide(COS), tea polyphenols(TP) and Nisin were used as functional additives, chitosan-gelatin-COS ternary composite films, chitosan-gelatin-TP ternary composite films, chitosan-gelatin-Nisin ternary composite films were prepared through solution blending method aiming at enhancing the antioxidant activity and antibacterial activity of chitosan-gelatin composite film. The properties related to food packaging of the prepared chitosan based films were characterized at the same time. The effects of additive content on the performance of the films were studied. The prepared chitosan based films were applied to storages of beef to investigate their actual effectiveness through the determination of physical and chemical indexes and microbial indexes during the storage.With chitosan and gelatin as material, glycerin as plasticizer, chitosan-gelatin composite films were prepared, the effects of gelatin concentration and glycerol content on the property of the films were studied. The results showed that gelatin solution concentration was 7%, chitosan solution and gelatin solution volume ratio of 2:1, glycerin dosage of 0.75 m L, the composite film had good properties.Chitosan-gelatin-COS ternary composite films were prepared with the addition of COS on the basis of chitosan-gelatin composite films. The results showed that the antioxidant activity and antibacterial activity of the chitosan-gelatin-COS ternary composite films were significantly increased with increasing of COS concentration. With the addition of proper content COS(≤20%), the mechanical properties and water vapor barrier properties of composite films were improved. With increasing of COS concentration, the transparence of the chitosan-gelatin-COS ternary composite films decreased, while swelling ratio and solubility increased.Chitosan-gelatin-TP ternary composite films incorporated with different amounts of TP were prepared. The results showed that the mechanical properties and water vapor barrier properties of composite films were significantly increased with increasing of TP concentration. While it failed to improve the antioxidant property and antibacterial activity of the composite films with the addition of TP. With increasing of TP concentration, the transparence of the chitosan-gelatin-TP ternary composite films decreased, swelling ratio and solubility decreased as well.Chitosan-gelatin-Nisin ternary composite films were prepared with the addition of Nisin. The results showed that the antibacterial activities of chitosan-gelatin-Nisin ternary composite films were significantly improved compared with chitosan-gelatin composite films. It had no obvious effects on antioxidant property of composite films with addition of Nisin. With increasing of Nisin concentration, the mechanical properties of the chitosan-gelatin-Nisin ternary composite films decreased, the transparence declined, while swelling ratio and solubility increased.The performances of chitosan based films were compared when the content of COS, TP, Nisin was 20% respectively. Moreover, the chitosan based films were used for beef storage to investigate effectiveness of preserving. The results showed that, chitosan-gelatin-TP ternary composite films showed the best mechanical properties and water vapor barrier properties, chitosan-gelatin-COS ternary composite films showed the best antioxidant activities, and chitosan-gelatin-Nisin ternary composite films showed the best antibacterial activities. It was found that as for beef wrapped with chitosan based composite films, the rises of p H value, TVB-N value, and TBARS value were delayed, the microorganisms were inhibited effectively, the deterioration process was delayed during storage. In the inhibition of unsaturated fatty acids oxidation, chitosan-gelatin-COS ternary composite films played a good role. Chitosan-gelatin-Nisin ternary composite films had good performance in inhibition of the growth of bacterias.