Preparation Of Water-soluble Chitosan-based Transparent Composite Film And Application To CO₂ Response

The intelligent packaging freshness indicator material has the function of monitoring food quality in real time without destroying the food packaging,and has broad development space in the market.Chitosan occupies a place in food packaging due to its unique antibacterial properties,and its application in freshness indicating materials is rarely reported.To expand the application of chitosan and its derivatives in the field of food packing instructions,solve the problem of difficult judgment of edibility of perishable foods,and make up for the shortcomings of opaque and difficult to reuse of current food preservation indicator materials.This paper combined N-succinyl chitosan with hydroxypropyl chitosan,?NSCS with HPCS?the water-soluble chitosan material,loading indicator,prepared CO₂color response NSCS/HPCS transparent composite response film,which successfully realized the CO₂ concentration information visualization,is expected to be used in food preservation field.Water-soluble NSCS with high yield?100%?and high molecular weight?100%?was obtained by freezing and comminution pretreatment and room temperature solvent method.The structure of the product was characterized by FT-IR and HNMR,which prove that the carboxyl group was successfully introduced into the C2 amino group of the chitosan molecule.RXD shows that NSCS has no crystalline structure and is easily soluble in water.UV dissolution performance analysis shows that NSCS can be dissolved in aqueous solutions between p H 1-4 and 7-14,all of which have a wide range of p H dissolution properties.In addition,the contents of carboxyl group and amino group were determined quickly and accurately by an improved conductance titration method.For the first time,two water-soluble chitosan NSCS and HPCS were combined into NSCS/HPCS composite films with a flat surface by the method of film formation.SEM showed that the surface of NSCS/HPCS composite film was flat.The tensile strength of NSCS/HPCS composite membrane is higher than that of NSCS composite membrane.TGA shows that the NSCS/HPCS composite membrane has good thermal stability.UV transmittance analysis shows that the NSCS/HPCS composite film has good light transmittance,and the light transmittance at 600 nm is as high as 85%.The basis of the composite membrane,we added the methyl red-bromothymol blue mixed indicator to the NSCS/HPCS mixed solution to form a uniform indicator mixed solution,and prepared the NSCS/HPCS composite response membrane by the casting method.SEM showed that the surface of the composite response film was flat and uniform in color.We used it as a CO₂ response indicator to show good color response performance,and there is a good linear relationship between the color response of the indicator and the CO₂concentration in different temperature and humidity environments,and the linear correlation coefficients R² are all Above 0.94,it can be used to indicate the freshness of food preservation.