Preparation,Characterization And Preservation Of Chitosan Films With Different Molecular Weights

In recent years,chitosan-based film,new biodegradable packaging material has provided new ideas for the storage and preservation of agricultural products because of its advantages of non-toxicity,sackless,green and environmental protection,and low price.In this study,high,medium,and low molecular weight of chitosan were used as raw materials,glycerol as the plasticizer to prepare a series of films by controlling the content of chitosan and glycerol,and their mechanical properties,light transmittance,water vapor permeability（WVP）,oxygen transmittance（OP）,morphology and antibacterial properties were characterized as well.At the same time,the fresh-keeping property of picked strawberry was evaluated by chitosan film.The main contents and results as follow:1.The mechanical properties,morphology,and antibacterial properties of chitosan films prepared under different conditions were investigated.The light transmittance,tensile strength（TS,MPa）,elongation at break（EAB,%）,water vapor transmittance（WVP）,oxygen transmittance（OP）,morphology（SEM）and antibacterial performance（Escherichia coli,Staphylococcus aureus,Aspergillus Niger）of27 groups film（C1-C27）have been characterized.The results showed that all films had film-forming properties.Among them,the optimal group was the C16 group with high molecular weight,high content of chitosan,50%glycerin/chitosan（w/w）,which showed high transparency（91.2%）,EAB（28.948%）,TS（77.963 MPa）,WVP(1.46×10^-12 gcm/cm²·s Pa).The film has smooth surface,compact cross section structure,and certain antibacterial properties.2.Evaluation of the preservation properties of chitosan films under different preparation conditions.27 groups of chitosan film（C1-C27）wrap freshly picked strawberries,under the condition of normal temperature preservation under 9 days and the condition of low temperature for the preservation of 16 days,compare and contrast the PE plastic film,commercial strawberry preservation was detected in the physical and chemical indicators（weightlessness rate,total soluble solids,titratable acidity,total ascorbic acid,and color difference）.The results showed that almost all of the 27 groups studied had better preservation effect than the commercially available PE film,and the C16 film with high molecular weight,high content of chitosan and 50%glycerol/chitosan（w/w）had the best preservation effect.It maintained the physical and chemical parameters（weight loss ratio,total soluble solids,titratable acidity,total ascorbic acid,and color change）of strawberry most obviously.