Preparation And Characterization Of Zein/nano-TiO₂/CS Composite Film

Antibacterial packaging as a representative form functional packaging material has attracted increasing attention in extending shelf life and protecting food from foodborne microbes.Being natural and edible biomacromolecules,zein and chitosan(CS)has good compatibility,but insufficient antibacterial and poor mechanical properties limited its development in industry.In order to improve the mechanical properties and antibacterial properties of the zein/CS films,adding titanium dioxide(TiO2)nanoparticles were added as an effective modification method.Highly dispersible TiO2 nanoparticles were prepared by the hydrolysis of titanium alcohol,and zein/nano-TiO2/CS composite films were successfully prepared by a process involving blending,solution casting and evaporation.Single-factor,response surface methodology was used to optimize the preparation of zein/nano-TiP2/CS composite films.The experimental results showed that the TiO2 concentration was 0.157%,the CS content was 6.86%,and the glycerin content was 13.54%,which was the optimum process conditions for obtaining the mechanical properties of the composite films.The tensile strength(TS),elongation at break(EAB),water contact angle,water vapor permeability(WVP),water absorption and thermal stability(TGA?DSC)were characterized to explore the effects of different nano-TiO2 contents and physicochemical properties of zein/CS/TiO2 films.The changes in the structure of the TiO2 modified materials were investigated by scanning electron microscope(SEM)and fourier transform infrared spectroscopy(FTIR).Methyl orange was used as a degrading simulant to determine the photocatalytic degradation performance of the composite films and the antibacterial capacity was determined by agar disc diffusion method.The results showed that the addition of nano-scale TiO2 has significant effects on improving mechanical properties and thermal stability of the zein/nano-TiO2/CS film.The TS of the zein/nano-TiO2/CS films significantly increased(p<0.05)with the increasing TiO2 loadings in films,reaching a maximum of 28.33 ± 1.53 MPa at 0.15 wt%TiO2 nanoparticles.The photocatalytic effect was optimal when the content of TiO2 of the films was 0.15%.The antibacterial effect of the composite films on Gram-positive bacteria(S.aureus)was more significant than that of Gram-negative bacteria(E.coli and S.enteritidis),and the antibacterial effect of UV light was better than that of dark conditions.In particularly,the diameter of inhibition zone of zein/nano-TiO2/CS(0.15%)film against E.coli,S.enteritidis and S.aureus,under UV light condition were increased by 21.78%,21.45%,26.4%,respectively,compared with the control.The results in this study suggested that adding TiO2 nanoparticles was an effective method in improving mechanical and antimicrobial properties of zein/CS films,which might develop the application in packaging,medical and food industry as an antimicrobial material with preferable functional properties.