Studies On The Preparation And Properties Of Chitosan/Mint Extraction Composite Film

In this paper, fresh mint as raw material was extracted by distilled water. Through the determination of the total phenolic and flavonoid content, antioxidant activity, iron chelating capacity and reduction capacity, the antioxidation of mint extract was investigated. Using the agar diffusion disc method, the antibacterial circle diameter was measured, therefore, the antibacterial effect by mint extract including bacterial, yeast and mould could be compared. The chitosan/mint extract composite film was blended by chitosan and mint extract solution. The composite films were tested by single factor experiment, and the factors were as follows:solvent type, solvent concentration, chitosan concentration, peppermint extract content and glycerol content. The films were studied by thickness, tensile strength, elongation rate, water vapor permeability, opacity, swelling ratio and acid resistance indexes, characterized by scanning electron microscope, in order to find out the optimum process conditions. The antioxidation of chitosan/mint extract composite film and mint extract was compared, while the bacteria inhibition effect of chitosan solution and chitosan/mint extract compound solution was tested. The effect of chilled meat preservation test by different concentration of chitosan composite solution was compared with determination of the targets about total bacteria, TVB-N, loss rate of juice, TBARS and pH. The results showed that:1.The mint extract had certain antioxidant, and the antioxidant was positively correlated with solution concentration. The total phenolic content of mint extract was19.38±2.81mg GAE/g DW, and the flavonoid was10.13±1.03mg GAE/g DW. In the reaction system, when the concentration was50μg/mL, the DPPH removal rate of mint extract was78.07%, closed to94.41%BHT; when the concentration was5mg/mL, the chelating ability of mint extract was36.58%, nothing more than51.14%EDTA;when the concentration was1000μg/mL, the reducing capacity of mint extract was equivalent to376μg/mL Vc. The mint extract had a certain effect on bacteria, yeasts and mould, the bacteriostatic ring average diameters by100%extracts of Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Saccharomyyces cerevisiae, Aspergillus niger and Rhizopus stolonifer were respectively8.90mm,10.27mm,9.74mm,9.23mm,15.12mm,15.31mm and13.37mm.2.The optimum process conditions of chitosan/mint extract composite film were:2%acetic acid,1.5%chitosan,5%mint extract,0.45%glycerol, and drying temperature of50℃. At this point, the film was the thickness of0.0074mm, tensile strength of21.23kN/m, elongation at break of8.71%, water vapor transmission rate of13.71%, opacity of1.288, swelling rate of55.12%, and it had good resistance to acid. The surface and internal structure of chitosan single film and chitosan/mint extract composite film, which characterized by SEM were suggested that mint extract had good dispersion in chitosan solution.3.Chitosan/mint extract composite film had higher DPPH clearance rate and reduction capacity than mint extract, and the antioxidant showed some linear connection with solution concentration. In the reaction system, when the concentration was50μg/mL, the DPPH removal rate of composite film was88.05%, relatively improved by9.98%relative to mint extract. Added mint extract to chitosan, the inhibition rate of film against bacteria, yeast and mould was improved. The bacteriostatic rate of Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Saccharomyyces cerevisiae, Aspergillus niger and Rhizopus stolonifer were respectively increased6.50%,22.34%,16.84%,17.19%,36.49%,28.96%and30.81%. Therefore, the composite film, which could not only improve the mint extracts antioxidant activity, but also could improve the single chitosan antibacterial.4.The chilled meat preservation test showed that the composite film could effectively reduce the total bacteria count and TVB-N, control the climb of pH, and slightly enhance preservation effect by increasing mint extract concentration. Storage to the21d, compared with the control group, chitosan/mint extract composite film could prolong the shelf life about6days, therefore, it had a good preservation effect on chilled meat.