| Edible film is defined as membrane, which is formed by interacting between different molecules and come from nature and edible material such as polysaccharide, protein, etc., adding plasticizers and crosslinking agents. Edible packaging film can be eaten together with packaged food. It can't bring about environment pollution. So, as a kind of green packaging material, more and more people are aroused interest and attention. People hope that edible packaging film will play a better role in replacing some traditional packaging materials. In recent years, edible packaging film was studied thoroughly by many researchers at home and abroad and gained some positive results. But, because single component films have certain defects in some performance, make their range of application limited. Many components films can improve properties of membranes by simple physical blending. It can meet demands of different food packaging, extending range of application of edible films. So, at present, composite edible films are developing trend in study and application. This thesis mainly studied in two parts, which are cassava starch/chitosan composite films mechanism and composite coating preservation.In part one, mechanisms of cassava starch/chitosan blend films were essentially studied. Cassava starch/chitosan blend films were prepared by cassava starch and chitosan blending at different ratios at 60℃. Meanwhile, concentration of cassava starch was kept variety and concentration of chitosan was kept constant. Then, the effects of cassava starch/chitosan ratios on the physical properties of the composite films were studied, including TS, E, WVP, POV, WSQ, T. Furthermore, the relationship between the microstructures and physical properties of the cassava starch/chitosan composite films was investigated by SEM, X-RD and FTIR. The effects of membrane properties were studied on addition of plasticizer. Antimicrobial activities of membranes were discussed, too. The results showed that the effects of the properties of the composite films were different by different membrane ratios. The good choice of ratio of cassava starch and chitosan was 1 to 1. The two film-forming components were compatible by micro-analysis. With the increase of the added quantum of the chitosan, tense strength and the barrier ability of water vapor permeability became ascending, the barrier ability of oxygen and antimicrobial activity increased, but films flexibility and water solubility decreased. With the increase of concentration of the glycerine, the plasticity and transparency increased, but tense strength and the barrier ability of water vapor permeability decreased. The good glycerine addition was 15%(w/w) of the total solid weight in solution.In part two, coating preservation of cassava starch/chitosan composite films was studied. Firstly, fresh-cut Jackfruits were coated with cassava starch/chitosan composite film, then stored at (3±1)℃. The freshness indexes were examined at regular intervals. To probe the freshness keeping effect of cassava starch/chitosan composite coating, it was compared with that of chitosan film and cassava starch film in the same concentrations. The results suggested coating samples can markedly extend the shelf life of fresh-cut Jackfruits stored at (3±1)℃. In terms of sensory assessment, physiological and biochemical examinations, microbial counts as freshness index, (1)coating treatments could slow down the quality change of sense; (2)coating treatments could control the rates of drop of reducing sugar, starch, and total acid, and the rates of raise of total soluble solids and total sugar, and could prevent from the losses of Vc; (3)bacteria, mildew and microzyme were inhibited by coating treatments; (4)coating treatments could inhibit the activities of enzymes such as cellulase, PG, amylase, POD, PPO and maintain CAT activity; (5)the shelf life of the coating sample A(chitosan), B(cassava starch) and C(cassava starch/chitosan) could be prolonged 6~9 days compared with control experiment. In the three coating samples, coating sample A and C could effectively keep freshness of fresh-cut Jackfruits compared with coating sample B, respectively, prolonging 3~4 days. There was no significant difference between coating sample A and C. But, in view of economic benefits, the two blend coating will have broader development prospects in fruits and vegetables preservation. This study will provide some design parameters and theoretical direction for utilizing cassava starch/chitosan as green food packaging material and as coating film material for preservation.
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