| Chitosan(CS)is a natural biomacromolecular material with great potential for application in the field of food active packaging.However,the mechanical properties and antibacterial activity of pure CS film are not outstanding enough,which greatly limits its application in food active packaging.Silver nanoparticles(AgNPs)are widely used as a broadspectrum antimicrobial agent to enhance the antimicrobial activity of CS.However,AgNPs tend to agglomerate in the CS matrix,their antibacterial effect significantly reduced.Therefore,the search for green and efficient carriers for immobilizing AgNPs and the development of new AgNPs composite antimicrobial agents are the urgent problems to be solved.In this paper,COFs-AgNPs were prepared by in-situ growth method,and CS/COFs-AgNPs nanocomposite films with excellent physical properties and efficient antibacterial activity were constructed by flow-delaying method,and their applications in the field of food active packaging were discussed.The main research contents and results of this paper are as follows.1.COFs-AgNPs were synthesized by in-situ growth method using COF-SCU1 as a carrier and glucose as a reducing agent,and their antibacterial properties and inhibition mechanism were investigated.The COFs-AgNPs were characterized by Transmission electron microscopy(TEM),elemental analysis,X-ray diffraction(XRD),and Fourier transform infrared spectrometer(FT-IR),and the results showed that COFSCU1 immobilized AgNPs through electrostatic interaction,and the distribution of AgNPs in COFs-AgNPs was uniform and the particle size was homogeneous.The results of the inhibition experiments showed that the COFs-AgNPs had excellent antibacterial activity.The minimum inhibitory concentration(MIC)of COFs-AgNPs was 60 μg/m L and the minimum bactericidal concentration(MBC)was 120 μg/m L against S.aureus as well as E.coli.2.CS/COFs-AgNPs nanocomposite films were prepared by flowdelaying method using CS and COFs-AgNPs as raw materials,and the physical properties and antibacterial activity of CS/COFs-AgNPs nanocomposite films were investigated.The rheological results of CS/COFs-AgNPs composite film solution showed that the viscosity of the film solution increased with the increase of COFs-AgNPs content.The addition of COFs-AgNPs addition significantly enhanced the tensile strength and UV-Vis barrier properties of the composite films,while significantly reducing their water solubility,swelling and water vapor permeability(WVP).The results of the effect of CS/COFs-AgNPs nanocomposite films on the growth curves of S.aureus and E.coli showed that the growth lag period of S.aureus and E.coli was successfully extended from 1 h to 5 h when the content of COFs-AgNPs was increased from 0 to 5%,indicating that the CS/COFs-AgNPs nanocomposite films had effective antibacterial activity.3.The application of CS/COFs-AgNPs nanocomposite films for the preservation of white crucian carp meat was investigated.From the results,it was found that the parameters of p H,weight loss,aerobic plate count,thiobarbituric acid value(TBA)and total volatile basic nitrogen value(TVB-N)in the CS/COFs-AgNPs nanocomposite film group were significantly lower than those in the control and pure CS film groups,and the CS/COFs-AgNPs nanocomposite film successfully extended the shelf life of fish meat by 8 days(4 ℃).Furthermore,the cumulative content of Agfrom fish extract solution was only 10.53 μg/L at the 12 th day of storage.The above results provide a theoretical basis for exploring the application of CS/COFs-AgNPs composite films in food preservation. |
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