Preparation And Application Of Chitosan Grafted Bacterial Cellulose Active Composite Film

With the enhancement of people’s awareness of environmental protection,environmental and food safety issues caused by traditional petroleum-based packaging materials have received more and more attention.Therefore,there is an urgent need to develop non-toxic,harmless,pollution-free and degradable green natural bio-based packaging film materials to replace traditional petroleum-based packaging materials.However,compared with traditional petroleum-based materials,natural bio-based packaging materials still have certain defects in mechanical properties and barrier properties,which cannot meet the needs of consumers.By compounding natural biomacromolecules with different structural and functional properties,natural biobased composite packaging film materials with synergistic properties can be developed.In addition,by adding an appropriate amount of active substances to the bio-based packaging film material,food spoilage can be delayed and bacterial contamination can be reduced.Therefore,in this work,chitosan（CS）was used as the base material and bacterial cellulose（BC）was used as the strengthening agent.The effects of different composite methods of chitosan and bacterial cellulose on the film-forming effect,mechanical properties and barrier properties of composite films were studied.At the same time,different concentrations of curcumin were added to the composite film as an active substance to explore the effect of curcumin dosage on the comprehensive performance and antioxidant properties of the composite film.Finally,the application of the antioxidant properties of the composite film in the storage of edible oil was studied.The main results are as follows:Firstly,the dispersion stability of bacterial cellulose was discussed in detail.Bacterial cellulose was treated by ultrasonic cavitation of a high-speed dispersive machine,cell crusher,and chitosan grafting reaction,and the dispersion effect was evaluated by Zeta potential,particle size,and so on.The results show that the dispersion effect of BC was better with the increase of revolution after high-speed homogenization,and the dispersion effect was the best when the speed was 25000 rpm.After homogenization,the ultrasonic power was 60%and the time was 25 min.The absolute value of Zeta potential was 49.19±0.45 m V,and PDI decreased to 0.37±0.02.After grafting with bacterial cellulose and chitosan,the whole system became more uniform and stable.The absolute value of Zeta potential increased to 55.79±2.94 m V,and the PDI decreased to 0.22±0.02.Standing for 24 h,the dispersion reached 98%.Subsequently,the effects of the uniform dispersion stability of bacterial cellulose-chitosan film solution and the molecular weight of chitosan on the film-forming effect were systematically studied.By compounding chitosan with different molecular weights and bacterial cellulose,on the basis of the optimal dispersion parameters,CSn-OBC composite films were prepared and compared with a single physical mixing method to obtain the optimal parameters for film formation.The results show that the CSn-OBC dispersion system was fine,continuous,uniform and stable,the Zeta potential was generally higher than that of the CSn-BC dispersion,and the medium molecular weight chitosan（CS₄=850 k Da）was more conducive to the dispersion of fibers.The SEM results show that the surface of CSn-OBC films presents a smoother and denser microstructure.The measurement results of mechanical properties and barrier properties show that chitosan with a molecular weight of 850 k Da can comprehensively improve the comprehensive properties of the composite membrane.Finally,the effects of adding different concentrations of curcumin on the comprehensive properties and antioxidant activity of CSn-OBC composite membranes were investigated.Different concentrations of curcumin were added to the bio-based composite membranes prepared by the optimal film-forming parameters（CS₄-OBC）.The results showed that the films exhibited excellent oxygen barrier properties,water vapor barrier properties,hydrophobicity,mechanical properties and antioxidant activity when the curcumin concentration was 0.5%.When the active composite film was in the simulated fat system,the time for the release of polyphenols in the film to reach a dynamic equilibrium was about 6 h.Finally,after applying the active film to the antioxidant experiment of edible oil,it was found that the peroxide value of the edible oil sample sealed with CS₄-OBC-Cur active composite film remained at the standard level after one month.However,both the untreated oil samples and the oil samples sealed with PE film showed the phenomenon of excessive peroxide value,which proves that the active composite film has an ideal effect in delaying the oxidation of oil.