| It is a research hotspot in food packaging industry to prepare antibacterial packaging by adding natural antibacterial agents to packaging materials.In this paper,the plant essential oils citral and cinnamaldehyde(CIN)were used as antibacterial substances.Firstly,the essential oils were prepared into ?-cyclodextrin-stabilized oil-in-water Pickering emulsion(PE),and then the emulsion was added into chitosan membrane matrix to prepare antibacterial packaging films of citral and cinnamaldehyde.Then the mechanical properties of chitosan-essential oil antibacterial film were enhanced by sodium tripolyphosphate(STPP)polymerization and polylactic acid(PLA)coating.Furthermore,the appearance,water vapor barrier and mechanical properties of the antibacterial film were tested,and the correlation between relative humidity and the release behavior of antibacterial agent was discussed.The application experiments of the antibacterial film for cherry preservation and meat preservation were carried out.The main results are as follows:(1)Preparation and characterization of citral Pickering emulsions(N-PE)and cinnamaldehyde Pickering emulsions(R-PE): Citral and cinnamaldehyde Pickering emulsions were prepared by high-speed homogenization method using ?-cyclodextrin as emulsifying stabilizer.The preparation conditions were as follows: When ?-cyclodextrin dosage was 30 g/L,homogenizing speed was 11900 RPM and oil-water ratio was 13:7,the emulsification coefficient of the two Pickering emulsions reached 100% and the stability was the best.Among them,the particle size of citral emulsion was about 800 nm,and the particle size of cinnamaldehyde emulsion was about 1000 nm.The two kinds of essential oil emulsion droplets were evenly distributed in spheres.The addition of xanthan gum in external water phase can significantly reduce the particle size of emulsion and enhance the stability of emulsion to a certain extent.The thermal stability of citral Pickering emulsion was higher than that of cinnamaldehyde Pickering emulsion.(2)Preparation and characterization of chitosan emulsion film: Two kinds of ?-cyclodextrin-stabilized oil-in-water Pickering emulsion and chitosan film forming liquid were mixed in a certain proportion,and the essential oil emulsion film was prepared by flow-casting method.It was found that the essential oil in the film was distributed in nanodroplet scale.With the increase of emulsion content,the transparency and water vapor permeability of the film decreased,the elongation at break decreased,but the tensile strength increased obviously.The addition of xanthan gum in the aqueous phase of the emulsion can significantly increase the stability of the emulsion during the film preparation process.Although the water vapor permeability is increased,the transparency and color of the emulsion film are improved,and the mechanical properties of the film are also enhanced.Moreover,the release of citral in the emulsion film was effectively slowed down.(3)Chitosan emulsion films were modified by the polymerization of sodium tripolyphosphate(STPP)and chitosan and by polylactic acid(PLA).The results showed that compared with chitosan emulsion films,the thickness of the two modified emulsion films increased,the transmittance decreased,and the barrier and mechanical properties were enhanced.The sustained release experiment of the film showed that the sustained release behavior of the oil antibacterial film was further strengthened after the emulsion film was modified.(4)Citral and cinnamaldehyde antibacterial essential oil emulsion films showed significant antibacterial properties.Cinnamaldehyde emulsion film is stronger than citral emulsion film in antibacterial activity.The antibacterial properties of the two essential oil emulsion antibacterial films were staphylococcus aureus > Salmonella > Escherichia coli.It was found that citral emulsion film could significantly inhibit the Browning of cherry skin color and enhance the sensory properties of cherry.When cinnamaldehyde emulsion antibacterial film was applied to fresh meat preservation,it was found that the total number of bacteria in chilled meat decreased significantly and the shelf life was prolonged. |
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