Research Of Green Preservation Packaging Film Based On Dietary Fiber From Tomato Peel Pomace

Under the resource pressure caused by plastic materials and the pollution caused by waste,environmental-friendly packaging material has been arousing increasing attention.To be specific,natural polymer materials have become a hot spot on the fields of food and pharmaceutical packaging for their wide range of raw materials,as well as safe,nontoxic and pollution-free characters.However,its products show the general disadvantages of natural bio-based materials such as low mechanical strength and poor water resistance which limit their wide application in the packaging field.Therefore,it is of great significance to focus on the modification and mechanism of natural polymer materials under the guidance of application.In this paper,On the one hand,Tomato soluble dietary fiber(TSDF)and tomato insoluble dietary fiber(TIDF)were separated from tomato peel pomace,and then a new kind of microcrystalline cellulose material(TMCC),which can be used in the performance optimization of natural polymer film,were developed by TIDF acidolysis modification.On the other hand,in order to develop a new application route of tomato dietary fiber in green packaging field,the composite films were prepared for chitosan(CS)and TSDF as matrix and TMCC as additive.The mechanism of action between TMCC and matrix was systematically discussed.Then the formula and properties of material were optimized by statistical methods such as orthogonal and response surface.The main contents and conclusions of this paper are as follows:(1)TSDF and TIDF were separated from tomato peel pomace by ultrasonic-alkali method.The results showed that the main component of TIDF was?-glucose cellulose with a concentrated particle size distribution and large median diameter(249.75?m).However,there was a variety of carbohydrates(e.g.?-uronic acid and furan sugar)contained in TSDF,which led a wider range of particle size distribution and smaller median diameter(186.87?m).The morphology of TIDF and TSDF prepared in this paper was lamellar.The surface of TIDF was rough and filamentous,while the surface of TSDF was smooth due to its orderly crystal.The optimum extraction conditions of dietary fiber,which were obtained by orthogonal analysis,were as follows:when the ratio of material to liquid was 1:25 g:mL,mass fraction of NaOH was 5%wt,reaction time was 50min and reaction temperature was 60 ~oC,the yield of TSDF and TIDF was 25.33%and 59.46%,respectively.(2)Chitosan-dietary fiber composite films(CS-TDF)were prepared by casting method based on CS,TSDF,TIDF and glycerol,and the optimum proportion of composite films were obtained by response surface method as follows:TSDF concentration was 1.6%wt,CS concentration was 4.1%wt,TIDF addition was 21%wt and glycerol addition was 10%wt.The crystal structure of composite film accorded with the characteristics of semi-crystalline polymer.There were strong hydrogen bonds formed between hydroxyl and amide groups in molecular chains of TSDF,TIDF and CS,which made the arrangement regularity of CS molecule increased and the crystallization of composite film improved.(3)Tomato microcrystalline cellulose(TMCC)was prepared from TIDF by ultrasonic synergistic decolorization and acid hydrolysis.The results showed that the decolorization effect of TIDF was improved by ultrasonic cavitation mechanism.And the optimum preparation parameters of TMCC were as follows:HCl concentration was 8%wt,ultrasonic power was 306 w,reaction temperature was 82~oC and reaction time was 62min.The characterization of TMCC showed that acid hydrolysis only acted on the amorphous region of TIDF.TMCC prepared in this paper showed the morphology of short and thick rod(50~70?m)with rough surface accompanied by irregular cracks and gullie.(4)TMCC was added into the mixed solution of CS and TSDF to prepare chitosan-microcrystalline cellulose composite films(CS-TMCC).There showed a good compatibility between TMCC and matrix.In the process of formation,TMCC played the role of heterogeneous nucleation in the matrix,which made the crystallinity of material increased.The mechanical,barrier and thermal sealing properties of composite film were improved by addition of TMCC,and the optimum comprehensive properties were achieved when the content of TMCC was 7%.The mechanism analysis showed that the moisture absorption characteristic of composite film in the range of water activity(a_w=0~0.35)and water activity(a_w=0~0.9)was well simulated by B.E.T model and G.A.B model,respectively.The results of barrier mechanism analysis showed that there was an exponential relationship between oxygen permeability and environmental temperature,the activation energy of the material was20.527 kJ/mol when the addition of TMCC was 7%.While the water permeability was affected by the interaction of temperature and humidity,and the quadratic function relationship was obtained by statistical method.The results of thermal sealing properties analysis showed that he optimum processes of thermal sealing were as follows:Temperature was150~oC,pressure was 0.4MPa,time was 5s.(5)Cherry and Agaricus bisporus were packaged by CS-TMCC in order to investigate the preservation performance of the films.And the biological safety of composite film was preliminarily studied by oral toxicity test of SD rats.The results showed that CS-TMCC film had a good preservation effect in protecting Cherry and Agaricus bisporus by comparing with PE film.The loss of water,decomposition of nutrients and decrease of quality were effectively controlled during the storage.CS-TMCC composite film showed a good biocompatibility.There was no toxic reaction within 14 days after intragastric administration by CS-TMCC film and its main components in SD rats.Dietary fiber in the composite film had a strong water holding capacity and expansion power,which led the intake of food reduced,weight gain of rats controlled,and water content in feces increased at the same time.The results of this paper can provide a valuable theoretical method and reliable data for the functional modification and utilization of dietary fiber from plant waste,which has certain promotion significance for improving the comprehensive properties of composite materials and expanding its wide application in green packaging field.