Edible Films Based On Corn Anionic Starch

The thesis mainly studied the edible packaging material for flavoring powderand soy powder, which was parts of the project "The Foundational Study of NewType Edible Biopolymer"that subsidized by Innovation Fund of Jilin University.The development of edible film is one of the research foci of food packageindustry, and has widely come to attention in some countries. Edible film can beused to substitute the plastic as the internal packaging of food or drug that can beeaten without tearing off. It is convenient, healthy, and free of rejectamentapollution. The edible films studied in the thesis are based on corn modified starchfor wrapping flavoring powder and soy powder, in order to resolve currentproblems of edible films.The author studied the synergic function of the mixed additives on theproperties of the edible films and put forward the best compounding by theoptimized orthogonal experiments. Besides those, there had made the attempt touse ultrasonic technique during the manipulation process. Finally the authorinvestigated the sealing properties of edible films and obtained the appropriatesealing conditions.The main contents and conclusions are as follows:1) Edible films based on acid modified corn starch, oxidation corn starch andanionic corn starch were investigated respectively. According to the contrast test,the film based on corn anionic starch showed better sense characters, mechanicalproperties. The appropriate density of corn anionic starch to form film wasobtained.2) To starch-based edible films, only adding one kind of intensifier and plasti-cizer can not solve the problem of poor flexibility effectively. In order to improvethe flexibility and transparency of starch-based edible film, experimental study onthe synergic function between corn starch and edible intensifier and plasticizerwas discussed. Results showed that in the solution of corn starch film,carboxymethyl cellulose and alginate constituted parts of framework of the film,combining with starch molecular. As a result, the structure of the film becamemore compact, tensile strength of the film became higher. Tensile strength was10.53MPa, elongation was 25.63%, and diaphaneity was 70.4%.Increasing intensifier density could go with the exaltation of tensile strengthbut reduce elongation. When the intensifier density exceeded 0.8%, the film wasfragile, the flexibility and transparency of film were poor, and tensile strengthdecreased.3) Adding glycerol and sorbitol as mixed plasticizing agent could increase thefluidity and stability of the solution, and carry out a kind of film that was smooth,glassy, flexile, resistant to break and easy to solute. Elongation was 29.38%, anddiaphaneity was 73.0%.Increasing mixed plasticizer density could go with the exaltation ofelongation and diaphaneity, but reduce tensile strength. When the plasticizerdensity exceeded 1.0%, the film was flexible but hygroscopic.4) The effects of mixed intensifier and plasticizer on starch film's oxygenpermeability were studied by the orthogonal L9(34) using 3% modified starch asraw material. The optimized experiments chose carboxymethyl cellulose density,alginate density, glycerol volume density and sorbital density as four factors, eachof them adopting three levels. The optimum conditions that summarized byvariance analysis presented that 0.4% carboxymethyl cellulose, 0.3% alginatesodium, 0.5% glycerol and 0.5% sorbitol could decrease the oxygen permeabilityobviously. The oxygen permeability was 1.29cm3/m2·24h·0.1 MPa.5) The attempt to apply ultrasonic technique during the proceeding expressedthe disposed films got higher tensile strength, lower elongation and oxygenpermeability. The results suggested we could obtain films which held onintensified certain property. The properties of film lied on the size, the structureand the construction of molecule in the solutions, as the network of film lied onthe noncovalent bond between molecules.Ultrasonic treatment could destroy the structure of the starch grain, shorten themolecule chain, break the branched starch, and increase the amylase content.Ultrasonic treatment also exposed out more polar groups, broke more hydrogenbonds and hydrophobic combining poles inside liquid, and made macromoleculeto recombine into a variety of nonpolar bonds. Under the appropriate power andtime, the film could get good properties because of fine network construction. Theflatness and particularity of ultrasonic treated films suggested that the treatmentdelivered more excellent quality to the films.Under the conditions as ultrasonic treatment power 80W, treatment time50min, the oxygen permeability decreased 55.0% compared with the untreatedfilms.6) The microstructures of the edible films were investigated by microscope.Compared with the untreated films, the films based on forming solution whichwere treated by ultrasonic showed better structure, more flat, smooth, andcompact. The surface homogeneity was improved.7) The author put forward sealing properties evaluation method of edible film,according to the appropriate adjustment and the generalization to the contents ofthe evaluation system of plastic, which included several aspects such as sealingstrength, sealing state, compression resistance property, airproof property andinstant ratio in hot water.8) The heat sealing mechanism and characteristic were discussed as well asthe internal relation between heat sealing temperature and time, the effects of filmthickness and water content on sealing strength.When sealing the film only at hot temperature, the sealing strength was verylow. After the temperature was over 160℃, each film became crisp and rigid thatslight touching would cause breaking into pieces immediately going with badcapability of instant solution in water.9) The adhering mechanism was discussed and the appropriate adhesive andadhering methods were investigated. The effect factors such as sealingtemperature, sealing time, adhesive layer thickness and sealing breadth on sealingstrength were analyzed.The author studied the adhering methods for the corn starch film. The suitableone was that sealed the films at hot temperature cooperating with the relevantsolution of film as the adhesive. It took long dry time and contraction at seal areawhen using the adhesive alone. In contrary, the method that sealed the films at hottemperature cooperating with adhesive revealed higher sealing strength, morequickly in drying and neater at seal area. At the same time, the highest sealingstrength was obtained by using the right solution of relevant film as adhesive.Increasing sealing temperature and time could go with the exaltation ofsealing strength but reduce instant ratio in hot water.To edible film based on corn anionic starch, when the film thickness was0.06mm, the adhesive layer thickness was 0.05mm, the sealing breadth was 6mm,choosing sealing temperature 130℃,lasting 3.5s, the higher sealing strength...