Preperation And Characterization Of Antibacterial Packaging Film By Extrusion

It has been the focus of concern in the food industry to improve the antibacterial propertyof wrapping materials so as to facilitate the food preservation. Up till now, however, only afew researches and reports have studied the preparation of wrapping materials ofsustained-release food, the sustained-release rules and the application effects. The resultsshowed that the inclusion of Allyl isothiocyanate （AITC） with cyclodextrin （CD） could beprepared with co-precipitation method and the antimicrobial packaging films was prepared byextrusion blow molding that was widely used in the industrialized manufacturing. Then theproperties of the films, the role between CD inclusion compound and polylactide （PLA） andthe dispersed pattern of inclusion compound in antibacterial films were studied. Finally therelease rules of AITC in the antimicrobial packaging film was analyzed. These studies providethe theoretical basis for the industrial preparation of sustained-release antimicrobial packagingfilm.The stability of the β-CD_AITCinclusion compound (β-CD_AITCIC) was discussed for thepreparation of the antimicrobial packaging film. Test results showed that the embedding rateof β-CD_AITCIC was85.2%, and the formation of β-CD_AITCIC was confirmed by infraredspectrometer and thermal analysis. By analyzing the heat loss rate of the inclusion compoundwith the method of thermal analysis, the studies discovers that the thermal stability wasimproved after the embedding process and the loss rate dropped from95.76%to75.58%,which indicated that the inclusion compound could preserve AITC well and made itapplicable to extrusion blow molding in high temperature.The material and antibacterial properties of antimicrobial packaging films were studiedfor illustrating the role of inclusion compound. By analyzing parameters, such as tensilestrength and elongation at break of the films, melting temperature （T_m）, crystallizingtemperature （T_c）, degree of crystallinity （X_c） of crystallization properties, as well as theplasticizer eduction rate, the results showed that the higher amount of inclusion compoundaddition （>10%） would lead to the worse mechanical property of antibacterial films, moreeduction amount of plasticizer, decrease in X_c,and a slight increase in T_mand T_c. Puttingseven common food microorganisms as the objects of research, the experiment showed thatthe sustained-release antibacterial films had the excellent bactericidal effect. The studydiscovered that in high-humidity environment （RH is over75%）, the concentration of AITCinside the packaging space was saturated and maintained in a relatively high level （theconcentration is>110ng/mL） after40hours. And the antibacterial films had the most obviousinhibition effect on yeasts （the minimum inhibit concentration is22ng/mL）. The studiesindicated that the film had a good sustained-release effect and bactericidal effect.The films were confirmed by infrared spectrometer，differential scanning calorimetry，X ray diffraction and scanning electron microscope to explain the dispersed patterns ofβ-CD_AITCIC in antimicrobial packaging films. According to the analysis of infrared spectrumresults, there was no distinct change in peak positions and shapes of the characteristic peak ofadded film (the film contained β-CD_AITCIC) and the non-added film （the film only contained AITC）. But the peak of1753cm^-1only moved4cm^-1to the long-wave direction, whichindicated that no covalent bond forms between β-CD_AITCIC and PLA and that weakinteraction existed between CD molecule and PLA molecule. And differential scanningcalorimetry analysis, X ray diffraction analysis and scanning electron microscope analysisshowed that β-CD_AITCIC just mixed and dispersed physically in the packaging films in adisordered state without any new crystal structure, and the β-CD_AITCIC with high additionamount led to destroy the structural integrity and continuity of the film system.The sustained-release rules of AITC in the antimicrobial packaging was analyzed underdifferent environmental conditions. The result indicated that the antimicrobial packaging filmhad the property of sustained-release, and its releasing rate was proportionate to the relativehumidity （50RH%and75RH%） and temperature （10℃,25℃and40℃） and it dependedmuch on RH%. In the accelerated environment （98RH%,40℃）, AITC that had not beenembedded by CD would be depleted after10days while the antibacterial agent that had beenembedded by CD still had amount of10%or so remained after20days. And the film kept thesustained-release condition after a month, which indicated that the antimicrobial packagingfilms prepared by CD inclusion compound could release the bactericide slowly to sterilize in along-term and that this kind of antimicrobial packaging films should be kept in a certainenvironmental temperature and humidity.