Preparation Of Pullulanase Modified Starch Films And Effects Of Reinforcing Agents, Blocking Agents On Properties Of Films

In recent years, the development and application of starch films was becoming a researchhotspot in the field of scientific research. There were few research about pullulanase modifiedstarch films in our country, and most concentrated on the enzymatic hydrolysis study, whilehow to further enhance the tensile strength and watertightness were ignored. In this study,Basing on corn starch, glycerol as plasticizer, the effects of pullulanase dosage and reactiontemperature on the amylose content and properties of films were studied; Sodium alginate,sodium carboxymethylcellulose, gelatin and these three mixed with the mass ratio of1:1wereadded to make films to further research their effects on the properties of films; Fatty acid andsurfactants（stearic acid, lauric acid mixed with alkyl glycosides, monoglyceride with the massratio of1:1） were added to make the films and their properties （most prominently about thewater resistance） were investigated. The main results were as follows:1. When pullulanase reaction temperature was50℃and pullulanase dosage was0.4u·g^-1starch, the best results was gained. Compared with the native starch films, the filmswith pullulanase showed smoother surface and exhibited enhanced thermal stability; thetensile strength, water vapor permeability and light transmittance increased by74.76percent,16percent and35percent, respectively, the elongation at break decreased by65.6percent.The amylase content of pullulanase modified corn starch was increased. There was a certainliner relation between amylase content and tensile strength of films when amylase contentwas less than36.6%（R²=0.791）.2. When sodium alginate, sodium carboxymethylcellulose, gelatin and these three mixedwith the mass ratio of1:1were added to films, all the films exhibited a certain degree ofimprovement mechanical properties, decreased light transmittance, insignificant change ofwater vapor permeability, weakened heat sealability, and the surface of the films withreinforcing agents became rougher. In conclusion, the films incorporated with sodiumcarboxymethylcellulose, sodium alginate （5%w/w starch and reinforcing agents respectively）showed better properties, On this condition, the film’s tensile strength was8.28MPa,elongation at break was46.54%, water vapor permeability was2.56×10^-12g·cm·cm^-2·s^-1·Pa^-1,light transmittance was84.4%.3. The results of films incorporated with fatty acids and surfactant were all showed decreased tensile strength; increased elongation at break; enhanced water resistance propertiesand light resistance performance, the crystalline types of films were changed from type B totype V. In conclusion, the films incorporated with stearic acid, monoglyceride （3%w/wstarch and reinforcing agents, respectively） showed better properties, On this condition, thefilm’s tensile strength was3.67MPa, elongation at break was59.69%, water vaporpermeability was1.30×10^-12g·cm·cm^-2·s^-1·Pa^-1, light transmittance was10.43%.