Preparation And Characterization Of BC/cotton Fiber Self-assembly Materials Used In Food Packaging

With people's increasing requirements for food freshness and preservation time,traditional food packaging materials have been unable to meet the needs of today,and the preparation of functional food packaging materials has become a hot topic of current research.Cellulose materials are widely available,easy to obtain,biocompatible and biodegradable,and can be used as food packaging materials instead of plastic products.In this study,bacterial cellulose/cotton(BCF)composites were prepared by in situ modification,physical adsorption,chemical synthesis and other technologies.Then,BCF was used as the substrate to load curcumin and quaternized chitosan,and finally quaternized chitosan/curcumin /BCF composites were prepared.It is found that it has high swelling degree,strong UV barrier,strong antioxidant,strong antibacterial,and has p H color response and can be used as functional food packaging materials.First,BCF material was obtained by co-culture of BC and cotton fiber by in situ modification.The morphology of BCF was observed by scanning electron microscope,and the microstructure was a sandwich structure of BC-cotton-BC.The thermogravimetric test showed that the addition of cotton fiber improved the thermal stability of the composite compared with pure BC,which could be applied to food processing and transportation in high temperature environment.Finally,the optimal conditions for the preparation of BCF were determined by the orthogonal experiment with three factors and three levels.Through the test and analysis,the fracture strength of the prepared BCF material reached 36.40 MPa,the elongation at break was5.23%,the transparency was 32.99%,and the swelling degree reached 360.22%.Compared with pure BC,the addition of cotton fiber effectively improved its mechanical properties and swelling degree,and it could be used as a new type of cellulose base material for food packaging.Secondly,curcumin/BCF composites with different curcumin concentrations were prepared by combining curcumin with BCF material by means of physical adsorption.The effect of curcumin content on the properties of the material was investigated,and its properties were characterized.It was found that compared with pure BC,the addition of cotton fiber increased the elongation at break,water solubility,swelling degree,thermal stability,UV barrier property and antioxidant property.Fourier transform infrared spectroscopy(FT-IR)and X-ray diffraction(XRD)analysis showed that curcumin had been successfully incorporated into the solid supporting film.With the addition of curcumin,the water solubility,tensile strength and swelling degree of the material decreased,while the elongation at break,thermal stability and UV barrier property increased,which is beneficial to the application in food packaging.Under the same concentration of curcumin,the composite based on BCF showed better oxidation resistance and more significant p H color response than the composite based on pure BC.The color of curcumin/BCF changed from bright yellow to brown at p H 7 to 10,and the maximum free radical scavenging efficiency at 2 h was close to 90%.These results indicate that curcumin/ BCF materials can be used for active smart food packaging.Finally,chitosan was grafted onto dehydrating glyceryl trimethylammonium chloride(GTMAC)to prepare quaternized chitosan,and then the quaternized chitosan/curcumin /BCF composites were prepared by combining different concentrations of quaternized chitosan with curcumin /BCF materials in the previous chapter.After vacuum drying,FT-IR and XRD tests showed that the quaternary aminated chitosan had been successfully prepared.Scanning electron microscope observation of its microstructure showed that the quaternary aminated chitosan had been successfully combined with curcumin/BCF material and had a good combination with the material at the molecular level.It was found that the addition of quaternary amine chitosan increased the fracture strength,swelling degree,water solubility,oxidation resistance,UV resistance,and showed strong antibacterial properties.The loading of quaternary amine chitosan can improve the p H color responsiveness,but has little effect on the thermal stability.The antibacterial test showed that the material had strong inhibitory effect on both Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus.The antibacterial rate against Escherichia coli and Staphylococcus aureus reached 98.3%and 94.2% respectively.Therefore,the application of quaternized chitosan/curcumin /BCF as active intelligent food packaging materials with antibacterial,antioxidant and p H color response properties has a wide application prospect.