Research On Preparation, Performance Of Degradable Active Packaging Film And Application In Nondestructive Testing Of Food

In recent years,food quality and safety have become issues of widespread concern in the world.Food packaging and food freshness testing play an important role in food quality regulation and monitoring.In the process of food circulation,traditional packaging films are not degradable,which is easy to cause pollution to the environment.Moreover,the freshness preservation effect is poor,and the shelf life of food is short.The traditional food freshness detection method is subjective and difficult to operate,and the detection needs to destroy the sample and has certain risks.It cannot quickly detect changes in food freshness.Therefore,research on food packaging films with good freshness preservation and real-time monitoring of food freshness have an important impact on food quality assurance.In the research,natural biomaterials and biodegradable film-forming substrates were blended to prepare food packaging films,so as to obtain a biodegradable active packaging film with low cost,good bioactivity and good comprehensive performance.The packaging film made in the laboratory is applied to the detection of food packaging and food freshness.The electronic nose technology is combined with sensory evaluation and traditional physical and chemical index detection methods to comprehensively evaluate the freshness of meat,the aim is to explore a technical method that can detect food freshness in real time,fast,convenient and nondestructive.The main research contents and conclusions are as follows:Starch and chitosan were used as film-forming substrates,and starch/chitosan composite films were prepared by fluidization method.The performance of composite membranes with different content of chitosan was explored by changing the content of chitosan.The results showed that there was a good compatibility between starch and chitosan,the starch/chitosan membrane had a uniform matrix and a complete membrane structure,and the performance of the composite membrane was better than that of the single component membrane.The addition of chitosan increased the tensile strength and elongation at break,decreased the young’s modulus,water vapor transmittance and film opacity.However,with the increase of chitosan content,the density,solubility and water content of the starch/chitosan film increased,the mechanical properties and the brightness of the film decrease,the color difference becomes larger,and the appearance appears darker yellow.In order to improve the comprehensive properties of the membrane,polyvinyl alcohol（PVA）was added to starch and chitosan.The blending film of starch,chitosan and polyvinyl alcohol was prepared by solution blending method,and the concentration of polyvinyl alcohol was changed to explore the change of the properties of blending film.The results show that the three substances have good compatibility,and the blending of substances can enhance the interaction between the polymers,so as to achieve the purpose of complementary advantages.The addition of polyvinyl alcohol enhances the tensile strength and elongation at break of the film（when the concentration of polyvinyl alcohol is 6%,the tensile strength and elongation at break of the blended film are 3.09 and 1.56 times of the CS/CH film）,greatly improves the brightness and transparency of the film,and reduces the color strength of the film.As the content of polyvinyl alcohol increases,the density,water content,swelling degree and solubility of the CS/CH/PVA film gradually decrease,and the water vapor transmittance increased in a certain range.From the analysis results,it can be seen that the addition of polyvinyl alcohol can improve the overall performance of the film and make the film have better applicability.In order to investigate the practical application effect of degradable active packaging film,the starch/chitosan/poly-vinyl alcohol blend film was prepared with the best chitosan content（40%of starch mass）and the best polyvinyl alcohol concentration（6%w/v）.The starch/chitosan/poly-vinyl alcohol blended film was applied to the storage and preservation of meat products,and the ordinary PE film and uncoated meat products were used as the control group.Use sensory evaluation and physical and chemical index detection methods to judge the spoilage cycle of meat in different packaging states.The results showed that:the 3^rd day,3-6 days and 9^th day could be used as the segmentation points of the odor changes of uncoated meat,ordinary PE film meat and active packaging film meat respectively,and the life end point of uncoated meat,ordinary PE film meat and active packaging film meat under the storage condition of 4℃was roughly in the 9th day,the 9th to 12th day and the 15th day.The starch/chitosan/poly-vinyl alcohol blend film has biological activity,which can reduce the degree of food oxidation and inhibit the growth of microorganisms,and delay the process of food spoilage and prolong the storage period of food.In order to improve the efficiency of food freshness testing and achieve non-destructive testing of food freshness,using electronic nose technology combined with Principal Component Analysis（PCA）and Linear Discriminant Analysis（LDA）methods to quickly determine the freshness of meat in different packaging states,and establish a meat freshness discrimination model.The discriminant results are compared with sensory evaluation,ATP detection and pH measurement results.The results show that electronic nose technology can detect the sensitive volatile gas components of the sample,quickly identify the spoilage process of food,and can distinguish different types of samples.The main component contribution rates of the two discriminating methods of PCA and LDA are 99.4%and 100%.The classification effect of LDA is better.Changing the method of extracting the eigenvalues of the analyzed data can also effectively improve the classification accuracy.The electronic nose test results are synchronized in time with the sensory evaluation,ATP test and pH measurement test results and the test results are consistent.Therefore,the electronic nose non-destructive testing technology can be used to monitor the progress of food spoilage and explore the effects of different packaging films in.