Preparation Of Chitin-based Food Packaging Materials And Study On Its Antibacterial Activity

The extensive use of non-degradable packaging materials based on petroleum-based raw materials has caused increasingly serious pollution to the global environment.The research and application of biodegradable materials have received extensive attention.Chitin is a natural biopolymer molecule that has a film-forming property,a bacteriostatic property,and can be degraded in a natural environment and is a good choice for preparing a biodegradable material.Paraben,cinnamaldehyde and nano-ZnO particles have antibacterial effect.Adding them to biological materials can improve the antibacterial performance of biodegradable packaging materials.In this dissertation,chitin was used as the main film substrate,and the alkali/urea solution was used as the solvent for low-temperature dissolution of chitin to prepare chitin gels and films.The specific findings are as follows:?1?Different concentrations of chitin solution and gel properties were studied.An increase in chitin concentration can increase solution viscosity and decrease solution clarity;the shear viscosity of the solution decreases rapidly with increasing shear rate(at 0 s^-1-20 s^-1),With the increase of shear rate(20 s^-1-100 s^-1range),the viscosity of solution decreases slowly and eventually decreases to a steady level;The viscosity and modulus values of the solution near70°C change from a gradual decrease to a rapid increase.This temperature is the gelation temperature of the solution.With the increase of chitin concentration,gel color,mechanical properties,modulus and thickness increase,and the water content of the gel decreases;the chemical structure of chitin is stable,and the peak value of chitin from dissolution to gel preparation and functional groups does not change.Deacetylation,high crystallinity of the chitin powder,reduced crystallinity of the gel,the greater the concentration of chitin,the smoother the gel surface,and the tighter the connection between chitin molecule chains.?2?The performance of chitin solution and gel with a mass fraction of 3%was studied.The viscosity of chitin solution decreases with the increase of freezing frequency;the color of chitin gel does not change with the prolongation of storage time;The mechanical properties of the gel were stable within 25 days of storage,and the compressive strength and deformation of gel at this stage are 3 MPa and 80%respectively;With the storage time prolonged gel compression performance weakened,the compressive strength and deformation of the gel measured on the45th day was only 1.2 MPa and 60%;the chemical structure of the gel was stable;ethanol can improve the mechanical properties of the gel.?3?Heat-pressed chitin films were analyzed for the performance of different concentrations of chitin films?2%CT-F,3%CT-F,4%CT-F?.With the increase of chitin concentration,the thickness,color and mechanical properties of chitin film increased,the film swellability changed little,and the film was dark yellow;the chitosan film with mass fraction of 4%had the best mechanical properties and tensile strength.The morphological variables reached 70 MPa and8.5%;the crystallinity,peak value,functional group and water content of chitin film did not change with the chitin concentration;the chitin film had better thermal stability than the chitin powder,and chitin concentration has no effect on the change of thermal degradation curve;the increase of chitin concentration increased the smoothness of the films.The roughness and impurity are reduced.?4?Study on antibacterial properties of chitin films and composite films.Chitin film and three kinds of films added cinnamaldehyde,paraben and nano ZnO particles have no bacteriostatic effect on Bacillus subtilis;chitin films had antibacterial activity against Salmonella and E.coli;3%chitin/cinnamaldehyde films,3%chitin/paraben and 3%chitin/ZnO films have bacteriostatic effect against Staphylococcus aureus,Salmonella and E.coli,and have a better bacteriostatic effect against Salmonella.