Study On Formation And Application Characteirstics Of Complexly Modified Corn Starch Films

Plastic products were widely used in food packaging and preservation. But with the finitude of oil raw materials and the serious "white pollution" the products caused, the development was limited. Starch was a renewable natural polymer material with low price and wide production. Starch series packaging films were considered one of the most promising biodegradable packaging materials. The films formed from cross-linked and esterified modified corn starch were applied to fruits preservation for a kink of efficient and environmental preservation method, epichlorohydrin as the cross linker and succinic anhydride as the esterifying agent.The effect of different amylose content, glycerol concentration, stirring rates and drying humidity on the mechanical properties, light transmittance and water vapor permeability were studied in this paper firstly. The results showed that, the preferable comprehensive performance of films were with the amylose content25%, glycerol concentration20%(dry-basis content of starch), stirring speed100r/min and drying humidity50%.The mechanical and light transmittance properties of corn starch-based films formed from cross-linked, esterified and complexly modified starch were concerned in this paper, epichlorohydrin as the cross linker and succinic anhydride as the esterifying agent. The key research content was the related law between films properties and the degree as well as the order difference of compound modification. The results showed that with the increase of crosslinking degree, tensile strength (TS) and water vapor permeability (WVP) of the films were enhanced, elongation at break (E) and light transmittance were declined. With the increase of esterifying degree, E, WVP and light transmittance were improved while TS were reduced. Complex modifying was in favor of combining the advantages of cross-linking and esterifying as to improve the application performance of films. The first way of modifying was influential to the subsequent way to some extent, the modified effect and molecular structure were obviously influenced by the order of compound modification, and embodied different properties of films. The mechanical properties of films were observably influenced by the first step of compound modifying; the WVP of films could be obviously increased when the esterification was the last step; the light transmittance was significantly improved after esterification, and was not relevant to the modifying order or degree.FT-IR analysis showed that the absorption peak near1735cm-1was the telescopic vibration characteristic peak of C=O in the ester. Crosslinking esterification starch characteristic peak was more effective than the esterification crosslinking starch; the characteristic peak of film was weaker than the peak of corresponding starch. The X-ray diffraction analysis showed that the relative crystallinity of starches were increased after crosslinking and esterification through improving the proportion of crystallization area in the particles, for the performance of intensively increasing diffraction peak. The relative crystallinity of films was lower than the corresponding starches. Scanning electron microscopy analysis showed that, the particles morphology of starch was basically not influenced by crosslinking and esterification. The surface of films were connected closer through crosslinking, while the surface morphology of film were markedly improved through esterification to be more smooth, layer was formed on the fracture.The compound films had the effect on the preservation of three varieties litchi(Feizixiao, Nuomici, Guiwei) and clausena lansium, but the influence in the three varieties was not significant, the effect of preservation through the esterified crosslinked films(ECF) were better than the crosslinked esterified films(CEF).