| Chitosan/montmorillonite composite film was prepared by intercalation method, and three factors, drying temperature, chitosan concentration and montmorillonite content, were explored on the chitosan film. Mechanical properties, water vapor permeability and water solubility were tested. And using scanning electron microscopy to measure surface and inner structure of the composite film. Choosing glycerol, polyethylene glycol 400 and sorbitol as plasticizers to study the effect of properties on chitosan/montmorillonite composite film. Antibacterial activity of single chitosan solution and chitosan composite solution to several common food bacteria, yeasts and molds was compared. Carried out loquat fresh coating test at room temperature, and during storage of loquat measured the changes of weight loss rate, hardness, good fruit rate, titrable acidity, total sugar, Vc, POD activity, soluble solids content, respiration rate, and other indicators. Compared loquat fresh effect with chitosan coating solution and chitosan composite coating solution.The results showed that:1 The optimum condition for chitosan/montmorillonite composite film was drying temperature 50℃, chitosan solution 1.5%w/v concentration and the montmorillonite content of 5%w/w chitosan. By measuring the properties, chitosan composite film was found that it could effectively improve the tensile strength, elongation-at-break, water vapor permeability and water solubility. The composite film separately increased the tensile strength and elongation-at-break by 33.05% and 82.78%, reduced the water vapor permeability and water solubility by 34.69% and 13.33%, compared to single chitosan film. And the result of scanning electron microscopy analysis showed that chitosan had good compatibility with montmorillonite.2 Experiment showed that three plasticizers to some extent played plasticization, increased the flexibility of composite film, plasticized with glycerol had the best effect. And the addition of plasticizers had increased water vapor permeability and water absorption, reduced light transmittance. Glycerol and sorbitol did not have significant effect on light transmittance of chitosan composite film, but polyethylene glycol 400 led light transmittance decreased significantly.3 The single chitosan solution and chitosan composite solution had relatively good inhibitory effect on the bacteria, yeasts and molds. They had the best antibacterial activity for bacteria, antibacterial rates could reach 80% or more, especially for Staphylococcus aureus, the antibacterial rate of chitosan composite solution can reach 100%. The antibacterial activities of yeasts and molds were enhanced by adding nano-montmorillonite to chitosan. The antibacterial rate of chitosan/ montmorillonite composite solution to Saccharomyces cerevisiae, Penicillium sp, Rhizopus stolonifer and Aspergillus niger were separately increased 24.70%,40.89%,44.36% and 19.35%, compared with the single chitosan solution.4 Loquat fresh coating test showed that, during the loquat storage time, chitosan/ montmorillonite composite film significantly reduced the weight loss and decay rate, after 16 days storage, the weight loss and decay rate of chitosan composite coating group were 71.85% and 176.88% to that of black control group separately. The total sugar content of chitosan composite coating group and chitosan coating group were 1.47 and 1.28 times than that of black control group separately, so reduced the extent of damage. And chitosan composite coating film inhibited the loquat PPO and POD activity, after 16 days storage, the PPO and POD activity of chitosan composite coating group were 82.68% and 84.12% to that of black control group separately, and delayed the reduce of Vc content, reduced the extent of browning, controled the decreasing of fruit hardness, titrable acidity, soluble solids content and other index effectively, so that the quality of loquat got better maintained, the preservation effect was improved and the shelf life was extended. |
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