Preparation And Properties Of Chitosan/TiO₂/Corn Starch Edible Films

Chitosan/corn starch composite edible thin films were prepared by solution casting with corn starch as raw material and chitosan in the presence of glycerol plasticizer.The structure and microstructure of the films were characterized by infrared spectroscopy(FTIR)and scanning electron microscopy(SEM).The effects of the content of chitosan on the mechanical properties,water vapor permeability,oil resistance and antibacterial properties of the films were investigated.The results show that proper amount of chitosan can improve the mechanical properties of the film,improve the water insulation and oil resistance,and can form hydrogen bond between chitosan and corn starch.The structure of the film is uniform,and the tensile strength is 21.54 MPa,which is 2.52 times that of starch film.The water vapor transmission rate was 4.52×10^-5 g·mm^-1·d^-1,which was 49.3%lower than that of starch film.The film could inhibit the growth of Escherichia coli and Staphylococcus aureus,and the bacteriostasis rates were 43.55%and 32.89%,respectively.Biodegradable composite films have been prepared from corn starch(CS)incorporating chitosan(CH)and nano TiO₂ by a solution casting method and the mechanical,physicochemical and antimicrobial properties of the films were determined.Scanning electron microscopy(SEM)observations demonstrated that the appropriate proportion of components resulted in ideally homogeneous surface of films.Fourier transform infrared(FTIR)spectra analysis revealed that hydrogen bonds were formed between CH and CS and a covalent interaction existed between the nano TiO₂ and the CS and CH.The addition of proper amounts of CH to a CS matrix produced an enhancement of mechanical and antimicrobial properties accompanied by lower water moisture resistance.Incorporation of nano TiO₂ into the CS/CH film increased the tensile strength,moisture resistance and impermeability to oil and achieved significant antimicrobial properties.The tensile strength of the nano TiO₂/CH/CS composition film was 21.12±0.34 MPa which was 6.27 times that of a plasticized CS film,while the antibacterial activity for E.coli reached 94±2%.The mechanical properties,moisture resistance and antimicrobial properties of the films were deteriorated by the incorporation of excessive nano TiO₂ because of self-aggregation of the nanoparticles.By fixing the amount of CS/CH/TiO₂ and changing the amount of different plasticizers and reinforcing agents,the effects of mechanical properties,light transmittance,hygroabsorbability and water vapor transmittance of the film were studied.The results show that various plasticizers can improve the mechanical properties of the films to some extent,among which glycerol is the most obvious.After adding different kinds of plasticizers,the whole film becomes easily hygroscopic,and the influence of different kinds of plasticizers on the transmittance and WVP of the film is not consistent.The strength and hygroscopic properties of the film are improved by adding different reinforcing agents,but the flexibility of the film will be reduced by adding too many reinforcing agents.Both plasticizer and reinforcing agent should be found in a certain range of appropriate concentration,the overall performance of the film can be improved.