The Modification And Application Of Room Temperature Gelatinized Starch

The important role of native starch on people's table cannot be overestimated.Based on the advantages such as wide sources,low-cost,and environmental protection,the investigations of starch in non-food fields has attracted even more attention.However,direct applications of native starch suffer from the drawbacks of poor water solubility,resistance,retrogradation,etc.Through oxidation,crosslinking and grafting,a variety of starch derivatives can be produced and enrich their functions.Starch-based materials are green and environmentally friendly.They owing the advantages such as abundance,innocuity,biodegradability can make up for the shortcomings of traditional fossil energy which are limited,easy-contamination and hardly degradable.However,there are problems such as complication,strictness,high energy consumption,secondary pollution in many existing chemical modification methods.As a result,the concern about green and convenient starch modification methods has been increased.Therefore,based on the principle of environmental friendliness,urea,polyvinyl alcohol,and borax were used to modify starch.On the basis of natural advantages such as high biocompatibility and environmental protection,some new materials,including composite films and composite hydrogels were prepared.Then,their composition and structure were characterized by FT-IR,S EM and XRD.At the same time,its mechanical properties,swelling capacity and solubility were tested and analyzed.Furthermore,the strengthening mechanism of the modified material was studied.This article may expand new ideas for starch materials in the fields of biology,food,medicine and so on.The main content is summarized as follows:Urea modified starch under microwave irradiation for and its enhancement research for chitosan composite filmsIn this part,at first,the starch and urea were mixed and stirred at room temperature for 30 min to translucent gel,to prepare room temperature gelatinized starch,then dried and grinded.Without solvent and initiator,the powder was directly reacted under microwave irradiation,to modify starch with urea.Then,it was characterized by FT-IR,XRD,SEM and element analyzer.The results of FT-IR and element analysis showedCONH2 group was successfully introduced into the modified starch(u-starch).In addition,the effects of the mass ratio of urea and starch,the power of microwave irradiation and the time of microwave irradiation on the grafting rate were studied:the starch and urea with mass ratio of 1:2 was irradiated by microwave for 4 minutes at 616W power.Subsequently,the u-starch particles prepared under the optimal condition were added to the chitosan solution.The chitosan composite films enhanced by modified starch was prepared by casting and regenerating.The results of FT-IR showed that there was strong hydrogen bond interaction between u-starch and chitosan.When adding 1 wt%u-starch,it can be uniform in chitosan matrix and the tensile strength,Young's modulus and fracture energy of the composite films were 1.4,2.1,1.2 times than that of the pure chitosan films,respectively,with the transparency only decreasing slightly.However,with the increase of u-starch,the modified starch will agglomerate,resulting in the decrease of tensile strength.In conclusion,through room temperature gelatinized starch and its modification,we succeeded to prepared the composite films with enhanced mechanical properties and good light transmittance,which has certain application potential in the field of packaging.The application of room temperature gelatinized starch in the preparation and research of composite hydrogelsIn this part,at first,the room temperature gelatinized starch was mixed with polyvinyl alcohol(PVA)and natural plant polyphenol tannic acid(TA)in different ratios.Then,the two-component or three-component composite hydrogels was prepared by freeze-thaw.The microstructure of the composite hydrogels was characterized by FT-IR and SEM.What's more,its compression,DMA,swelling and resilience performance were tested and analyzed.It indicated that the network structure is formed by hydrogen bonding of different components.In addition,the adding of TA can effectively enhance the crosslinking of the PVA+Starch hydrogels.Moreover,in the compression and swelling property test,it was found that the structure of hydrogen bonding network formed by starch and TA can be rebuilt at room temperature,resulting in better resilience and the release of free TA.The composited hydrogels showed potential in biological antibacterial and food application.The application of room temperature gelatinized starch in the preparation and research of films materialsIn this part,the starch and urea were mixed at room temperature to prepare room temperature gelatinized starch,firstly.Subsequently,it was mixed with 10 wt%polyvinyl alcohol solution.Then,the mixture was casting,heating and immersing it in borax solution.to prepare the composite films.FT-IR,XRD,SEM were used to characterize the composite films,and the mechanical properties,light transmittance,swelling behavior and water solubility of the composite films were also tested.It suggested that the boric acid ions formed by borax in water can effectively crosslink between the hydroxyl groups to form a complex rigid network.When the amount of concentration of borax was low,the system can form a uniform crosslinking.However,when it is excessive,the crosslinking would reduce because of the excessive crosslinking and the electrostatic repulsion between excessive boric acid ions and the crosslinking.Therefore,with appropriate amount of boric acid,the tensile strength and Young's modulus of the composite films could be improved to a certain extent.When the concentration of borax is 6 wt%,the tensile strength and Young's modulus of the composite films are 1.6 times of without borax.In addition,the water absorption rate and water retention capacity of the composite films have been improved to a certain extent,showing certain prospects in the fields of packaging and agricultural cover films.