| Under the background of serious white pollution caused by petroleum based plastic films,degradable films have attracted extensive attention.Polysaccharides and proteins were used to produce high safety films,which have degradability,barrier and mechanical properties,and with the development of food industry,the films will become the main food packaging materials.However,there is no systematic study on the properties of degradable packaging films prepared in different environments.Therefore,in the present work,the film was prepared combination with the temperature and relative humidity of the actual food preservation environments,carboxymethyl cellulose and gelatin as the film matrix,the assembly behavior and film-forming characteristics under different environmental conditions of carboxymethyl cellulose with calcium ion and gelatin were explored from the microstructure.At the same time,biomaterials matrix is a kind of good carrier,which can be used to load functional active substances.And the antibacterial / antioxidant bioactive composite films were also prepared and characterized to reveal the incorporation mechanism of antioxidant of bamboo leaves / ε-polylysine into the membrane matrix,all of which could provide a reference basis for the development and application of carboxymethyl cellulose-gelatin film in food packaging industry.The main research contents and results are as follows:(1)Effects of the environmental temperature and relative humidity of drying conditions on the surface ultrastructure of carboxymethyl cellulose(CMC)films were investigated,and the mechanical and water vapor barrier properties of the films were also evaluated.The results showed that CMC molecules self-assembled into a uniform network at the solution of 5%calcium chloride.And continuous structure was formed of composite mixture with the CMC/gelatin ratio in 1:1.The CMC/Gel film forming solution was respectively dried at 2-8℃,23℃,50℃ and 23℃ with ventilation to obtain films.The size and numbers of holes on the films surface were affected by the temperature and relative humidity.Correspondingly,the mechanical properties and water vapor permeability were altered with the films structure.Moreover,the surface structure of the composite films was changed by the infiltration and delivery of water vapor when films were stored at 2-8℃ and-20℃ for 3、6、9、12days.(2)In this study,functional film enrichment with antioxidant of bamboo leaves(AOB)was prepared based on carboxymethyl cellulose-gelatin(CMC-Gel)mixture using casting method.Microstructures of the films were performed on atomic force microscope,Fourier transform infrared spectrometer,and X-ray diffraction(XRD).The physical properties,including the viscosity of film forming solutions,the water vapor permeability,mechanical properties,thermodynamics and transparence of CMC-Gel films were determined.The results showed that addition of AOB had not induced notable change on the surface structure features.The good compatibility among AOB,CMC and gelatin was illustrated by XRD for that the crystallization disappeared of gelatin in CMC-Gel composite film and no diffraction peaks in functionalized films.Viscosity and glass transition temperature of the film with 0.2% AOB were 779.2 ± 26.2 m Pa·s and 83.24℃,respectively,which were higher than those of all other samples.The water vapor permeation resistance and elongation at break of the films significantly decreased when the concentration of AOB exceeded 0.2%.The light barrier properties and scavenging rate of DPPH radicals were enhanced with the increasing of AOB content.Consequently,this antioxidant films utilized for food packaging could protect food quality from the destruction of heat,mechanical force,light,and oxidative free radicals.(3)Antibacterial composite films were produced from carboxymethyl cellulose-gelatin(CMC-Gel)blend with different concentration of ε-polylysine(ε-PL),and their physical and chemical properties were characterized.Compared with the control CMC-Gel film,the functionalized films had almost indistinguishable crystalline type,thickness,tensile strength,and elongation at break,however,poor water vapor barrier properties.The results showed that the ε-PL was well incorporated into CMC-Gel matrix by electrostatic interaction,as the changes of absorption peaks in the Fourier transform infrared spectrometer and the increase of glass transition temperature in differential scanning calorimeter.The films containing ε-PL showed excellent antibacterial activity against S.aureus,B.subtilis,E.coli and P.aeruginosa.In the composting experiment,the films become degraded on the seventh day,and further degraded with the growth of molds over time.The present results showed that the active films could be a potential material for food packaging.(4)The aim of this study was to produce bioactive packaging films based on carboxymethyl cellulose-gelatin(CMC-Gel)incorporated with antioxidant of bamboo leaves(AOB)and ε-polylysine(ε-PL)with preservation effect on food.Structural and physical properties including water vapor permeability,mechanical properties,thermal stability,color and transparence of the films were explored.As a result,the water vapor barrier property and tensile strength of the bioactive films were improved.Correspondingly,the elongation at break of CMC-Gel film was significantly decreased to 32.72 ± 1.75% and 10.48 ± 1.90% for the films containing 15% AOB and ε-PL in 0.05% and 0.10%.Moreover,the barrier properties against ultraviolet and visible light of bioactive films were enhanced,which was primarily influenced by AOB.The increase of total number of colonies and thiobarbituric acid value of beef samples coated with bioactive films were slowed down in the preservation,and the chromaticity of the fresh cut apple slices was well preserved.This bioactive film used in food preservation would present good preservation effect.According to the self-assembly behavior and film-forming characteristics of carboxymethyl cellulose-gelatin,as well as the structure changes and performance parameters of the films loaded with AOB or ε-polylysine,which providing a reference for the preparation of food active packaging film.Therefore,this kind of bioactive films could be a potential material in the application of food packaging industry. |
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