Fabrication Of Cinnamaldehyde Active Nanofiber Film By Electrospinning And Its Application In Chilled Meat Preservation

In recent years,with the continuous advance and development of nanotechnology,nanofiber materials fabricated by electrospinning technique have attracted more and more attention of researchers in the food industry.In the field of food packaging,the preparation of green,safe,and biodegradable novel nano-packaging materials has been a research hotspot.Pullulan is an extracellular polysaccharide produced by Aureobasidium pullulans.It possessed excellent properties including safty,nontoxicity,adhesion,and good film-forming ability.However,the strong water solubility and poor water stability of pullulan nanofiber film seriously limited the applications in food packaging.In this study,the ethyl cellulose with high water stability was selected to improve the water stability of pullulan nanofiber film by electrospinning process.The polysaccharide based composite nanofiber materials were prepared by blending ethyl cellulose with pullulan.Meanwhile,in order to enhance the practicability of pullulan/ethyl cellulose nanofiber film in the field of food packaging,cinnamaldehyde was encapsulated in the fiber film to fabricate the active composite nanofiber film with good release performance and antibacterial activity.Finally,chilled pork was selected as the research object,and the active composite nanofiber film was combined with the modified atmosphere packaging technology as combination preservation method to explore the practical application of active composite nanofiber film in meat storage and preservation.The main research contents and results are shown as follows:(1)Fabrication and characterization of pullulan/ethyl cellulose nanofiber filmNanofiber materials with tunable physical properties were fabricated by blending electrospinning of pullulan and ethyl cellulose(w/w).The results showed that the addition of ethyl cellulose reduced the viscosity and conductivity of pullulan/ethyl cellulose polysaccharide solution,and the average diameter of composite fiber was decreased from 302.1 to 167.7 nm.Fourier transform infrared spectroscopy(FTIR)analysis confirmed that hydrogen bond interaction existed between pullulan and ethyl cellulose molecules.X-ray diffraction analysis indicated that pullulan was a typical amorphous substance,while ethyl cellulose had a semi-crystalline structure,and the crystallization process of polysaccharide molecules was greatly hindered during electrospinning.Thermal analysis showed that compared with pure pullulan nanofiber film,the composite nanofiber films had higher melting point and thermal degradation temperature,indicating improved thermal stability.The water contact angle and water stability tests proved that the water contact angle of composite nanofiber films was ranged from 94.6 ° to 120.1°,suggesting adjustable surface wettability.Besides,the water stability of composite nanofiber films was significantly enhanced(P < 0.05).The mechanical properties test showed that the tensile strength of the composite nanofiber films was improved due to the interaction of hydrogen bonds between polysaccharide molecules,especially for pullulan to ethyl cellulose ratio of 1:1 which had the highest tensile strength.Therefore,through the comprehensive analysis,the pullulan/ethyl cellulose nanofiber film with the ratio of 1:1 was selected as the carrier material of bioactive compounds for subsequent experiments.(2)Fabrication and characterization of pullulan/ethyl cellulose-cinnamaldehyde active composite nanofiber filmsActive composite nanofiber films with good physical performances,release properties,and antibacterial activity were prepared by blending different concentrations of cinnamaldehyde(0%,2%,4%,8%,v/v)with pullulan/ethyl cellulose solution(1:1,w/w)for electrospinning.The results indicated that the viscosity and conductivity of the complex solution were decreased with the addition of cinnamaldehyde,which reduced the average diameter of the composite fiber from231.9 to 203.4 nm.Meanwhile,the SEM observation showed that the composite nanofiber films loaded with cinnamaldehyde had regular and smooth morphologies,which indicated that cinnamaldehyde was compatible and well dispersed in the fiber films.FTIR analysis confirmed that cinnamaldehyde was successfully encapsulated and loaded in the nanofiber films.The encapsulation rate result indicated that the encapsulation rates of cinnamaldehyde slightly decreased with the increasing concentration of cinnamaldehyde(P < 0.05),but all the encapsulation rates were greater than 40% suggested a high efficiency encapsulation of nanofiber film.The water contact angle test indicated that the addition of cinnamaldehyde in a certain range of concentration could enhance the surface hydrophobicity of composite nanofiber films.The mechanical properties analysis showed that the addition of cinnamaldehyde decreased the elastic modulus and tensile strength of the nanofiber films,while increased the flexibility.The release properties results indicated that the release of cinnamaldehyde was driven by the concentration.Meanwhile,the release amount and release rate were positively associated with the concentration of cinnamaldehyde,and the release kinetics followed Fickian diffusion mechanism.In addition,the results of antibacterial assays suggested that the antibacterial activity of the active nanofiber films was positively correlated with the concentration of cinnamaldehyde,and the fiber films loaded with 4% and 8% cinnamaldehyde exhibited a strong inhibitory effect on the growth of Escherichia coli and Staphylococcus aureus.(3)Application of active composite nanofiber filmsChilled pork and active nanofiber films were placed in the modified atmosphere boxes and stored at 4 ?.The physicochemical indexes of pork were determined regularly to research the application of active fiber film in food non-contact preservation.The results showed that in the same storage time,there was no significant difference(P > 0.05)between the nanofiber film loaded with low concentration of cinnamaldehyde(2%)treatment group and the control group,indicating that nanofiber film loaded with 2% cinnamaldehyde could not realize the antibacterial and preservation effect.Compared with the control group and 2% cinnamaldehyde loaded nanofiber film group,the total viable count,total volatile base-nitrogen and p H value of chilled pork treated with nanofiber films loaded with higher concentration of cinnamaldehyde(4% and 8%)were significantly lower(P < 0.05),and the thiobarbituric acid reactive substances value,cooking loss and shear force value increased slowly,which indicated that the quality of pork was maintained to a certain extent.On the 9th day,the pork in the control group and 2%cinnamaldehyde loaded nanofiber film were spoiled,while the pork treated with 4% and 8%cinnamaldehyde loaded nanofiber films remained fresh(it spoiled on the 12 th day).Therefore,4%and 8% cinnamaldehyde loaded nanofiber films extended the shelf life of chilled pork by about 3days.