Preparation And Properties Of Controlled Release Antibacterial Chitosan Essential Oil Composite Film And Application In Peach

Plant essential oil has a strong antibacterial activity.Adding essential oil to chitosan film can delay the release of essential oil and achieve the purpose of controlled-release active packaging.In order to further delay the volatilization of essential oil and clarify the mechanism of release,chitosan-essential oil composite films were prepared by casting method by adding emulsifiers with different HLB values or polysaccharide interaction.And the effects of different HLB emulsifiers and other polysaccharides on the physical properties,antimicrobial and antioxidant properties,microstructure and chemical structure of chitosan-essential oil composite films and the release of polysaccharide essential oil film in food simulant were investigated.Furthermore,the composite film was applied to the preservation of peach fruit to verify its bacteriostasis.The main results are as follows:(1)Emulsifiers with different HLB values included the diacetyl tartaric acid ester of mono glycerides(DATEM,HLB 8-9.2),Tween 85(HLB 11),Tween 80(HLB 15)and Tween 20(HLB 16.7)were used to prepare composite films.The results showed that the particle size of the essential oil in the film forming solution decreased with the increase of emulsifier HLB value.Fluorescence microscopy and scanning electron microscope reflected that the particle size of thyme essential oil in composite films depended on HLB of emulsifier.The addition of emulsifier also decreased the water vapor permeability and tensile strength of films.However,the physical properties,the release of essential oil from films and antimicrobial activity of films were not closely related to the HLB of emulsifier,which depended on the solvent type,microbial species and the interaction between emulsifier and film matrix.Lower water vapor permeability(compared with the control film),higher elongation at break and antimicrobial activity(E.coli)were found in Tween 85 composite films,which could be optimal choice to produce active chitosan-essential oil composite films.(2)The microbial polysaccharides(xanthan,pullulan)and plant derived polysaccharides(gum tragacanth,arabic gum)were used to prepare the chitosan-thyme essential oil composite films.The results showed that the addition of four polysaccharides reduced the tensile strength and swelling degree,but increased solubility of the film.The addition of arabic gum and pullulan delayed the release rate of essential oil from composite films in 95%ethanol,but not in 50%ethanol and distilled water.The film swelling was inconsistent with the release of essential oil in different food simulants.Moreover,the expansion of the composite film in the food simulant was not consistent with the release of essential oil.Differential scanning calorimetry and SEM analysis implied that the addition of four kinds of polysaccharides decreased the thermal stability of the film,which led to the change of the microstructure of the film.FTIR showed that there was a strong interaction between chitosan and polysaccharide,the interaction between polysaccharides affected the stability of chitosan essential oil composite film and could regulate the release of essential oil.(3)The inhibition of chitosan composite film on brown rot was studied by film fumigation and film solution coating in vitro and in vivo to verify the application value of chitosan essential oil composite film.The results showed that the film solution with better emulsification had better antibacterial effect in vitro.Research on peaches found that the film solution coating with Tween emulsifier had better antibacterial effect,but the inhibition effect of DATEM film fumigation was the best,and the effect of coating and fumigation was different in the emulsifier composite films.In the chitosan essential oil composite film with polysaccharides,the arabic gum composite film had the best inhibition effect on the peach brown-rot fungus,the smallest plaque diameter,and the same inhibition effect as in vitro.The antibacterial effect of fumigation of active components in the film is consistent with the release of essential oil in 95%ethanol.The slower the release rate in 95%ethanol,the better the antibacterial effect of the composite film.