The Preparation Of Chitosan Curdlan And Carboxymethyl Cellulose Composite Membranes And Its Application On Strawberry

Edible film is defined as membrane,which is formed by interacting between different molecules and come from nature and edible material such as protein,polysaccharide,cellulose land derivatives,et al.In recent years,edible film as a kind of green packaging materials become a research hotspot because of its safety,environmental protection,et al.At this stage,because single component films have certain defects in some performance,make their range of application limited.Many component films can improve properties of membranes through interaction between polymer by physical blending in certain conditions.Strawberry is a kind of perennial herbaceous plant in the rosaceae family,and its pericarp thin,high moisture content(90%-95%),away delicate tissue,poor storability,extremely apt to rot,can only be placed at room temperature for 2 days.At present,the main methods of preservation of strawberry were heat treatment,low-temperature storage,air-adjustment storing,irradiation treatment,nitrogen treatment and so on,but these conventional nethods are difficult to achieve in the process of storage and transportation,thus limiting their applications.However in recent years research on the field of strawberry preservation because of coated with edible was safe,preservation remarkabled,energy dissipation pollution-free and so on.The present stage is mainly used for the preservation of the edible film of strawberry was chitosan,but its mechanical properties are unideal,low tensile strength,high viscosity,and the effect of bio-film was bad of the chitosan membrane solution,so it's difficult to uniform coating on the surface of strawberry.To cure the above problems,this paper based on chitosan,curdlan,carboxymethyl cellulose to preparation edible film,and applied to the strawberry preservation.The following results were abtained:1.Determining the development of chitosan/curdlan/carboxymethyl cellulose composite membranes.To study the control conditions of pH and temperature in the process of blending between chitosan,curdlan and carboxymethyl cellulose,and determining the development of chitosan/curdlan/carboxymethyl cellulose composite membranes:put the mother liquor of chitosan,curdlan and carboxymethyl cellulose in 55? to preheating and mixed then.At the same time adjust the pH of the mixture in 55? controlled.Add a certain amount of glycerol make its final concentration is 1.4%,stirring,the ultrasonic degassing,pour into the teflon plate(18cm ×18cm),under the condition of 90? for 10min,stripped the membrane after dry 12h in RH25%,30?.Peeling the film and then put into the NaOH(0.25mol/L)for 8min,and then dry 4h in the constant temperature and humidity box(20?,RH50%).Mechanical streng as index,the best technological parameters for composite membrane:The results displayed that the tensile strength(MPa)maximum 10.74±0.89,the fracture elongation(%)was 96.55±6.72,when the content of chitosan,curdlan,carboxymethyl cellulose were 1.10%,0.55,0.45%,the setting temperature for 90?,drying condition for 30?and RH25%,in alkaline soaking time for 8min,so the performance of blend membranes has been improved than single membrane.This part also studied the performance of chitosan/curdlan/carboxymethyl cellulose composite membranes including tensile strength(TS),elongation-at-break(EB),water absorption(WA),water vapour permeability(WR),transparency(T).The micro-structure of the mixed membranes was studied by SEM and FT-IR.And the results show that the three film-forming components were compatible.2.To achieve the applications of chitosan/curdlan/carboxymethyl cellulose composite membranes for strawberry.Strawberry were coated and sealed with chitosan/curdlan/carboxymethyl cellulose composite membranes to study the effect of preservation.And the results show that:Stored at room temperature(21?,RH75%)for 6 days,the freshness indexes were examined at regular intervals.The physiology and biochemistry indicator of strawberry after coated and sealed by composite membranes were better than blank control,effectively reduce the respiration rate in the process of strawberry storage,and delayed the water loss,soluble solids content,electrolyte leakages,organic acid,reducing suger in the rate of change.