Preparation And Application Of The Edible Films Based On Polysaccharides

Nowadays, more attention is paid to migration of harmful substances for food,white pollution and the shortage of oil resources caused by plastic packagingmaterials, which has resulted in worldwide concern on edible food packagingmaterials. Natural polysaccharides are ideal for edible packaging because of theirabundant resource, renewable, environmental pollution-free. But a single film haspoor mechanical properties and water resistance.This research concerns on the preparation of chitosan and gellan gum ediblecomposite film. Investigating the possible influence of each ingredient on thefunctions of the edible film, then adopting the method of ionic crosslinking modifiedcomposite film, Effect of cross-linking time and pH on the mechanical properties andwater resistance of composite film were investigated. Besides, infraredspectrum（FT-IR）, X-ray diffraction（X-RD）, scanning electron microscopy（SEM） anddifferential scanning calorimetry（DSC） were used to characterize and analyze thetructure and thermal stability of the film. Also research on the preparation of pullulanand gellan gum composite film, through single factor experiment investigate thepossible influence of each ingredient on the functions of the edible film, optimized theingredients through the response surface used the performance parameter water vaporpermeability and water solubility as the indicator. In addition, the applications of twokinds of composite films to package and preserve fresh pork and instant noodlesseasoning were evaluated. The results are as follows:1. Preparation and characterization of chitosan/gellan composite film. Thecomposite film had the best properties under chitosan concentration1.5%, gellanconcentration2.0%, glycerol content0.4%. Composite film cross-linked by4%sodium citrate and2%calcium chloride. The results showed that sodium citrate andcalcium chloride cross-linked composite film, and the cross-linking decreased thecrystallinity of chitosan and gellan, and then improved thermal stability of composite film. The composite film had the best properties under a cross-linking time of5minand pH6.0, tensile strength91.45MPa, water solubility7.28%, swelling ratio416.63%,water vapor permeability0.68×10^-10g/Pa·s·m².2. Optimizing preparation of pullulan/gellan edible film. Optimum preparation ofcomposite film was determined by single factor and response surface analysis: gellanconcentration2.5%, pullulan concentration2.0%, the ratio of pullulan in the blendingsolution45%, glycerol content0.3%, the predicted value of water vapor permeabilitycould be1.01×10^-10g/Pa·s·m², water solubility could be49.31%, actual value are0.96×10^-10g/Pa·s·m²and48.37%. Then, Tensile strength36.78MPa, elongation atbreak14.23%, oxygen barrier0.589g/100g.3. Ionic crosslinking chitosan/gellan composite film used as packaging and palletcover film for pork preservative, the results show that, composite film for packagingmethod can restrain TVB-N and the total number of microbe colonies effectively, butin controlling the water loss and sensory were not ideal. Composite film for palletpacking method was obvious in controlling the water loss, had certain effect inrestrain TVB-N and total number of microbe colonies.4. Pullulan/gellan composite film used for packaging of instant noodlesseasoning, the results show that, composite film for instant noodles seasoning packinghad certain feasibility, but packaging effect couldn’t compared with traditional instantnoodles seasoning packing.