Study On Preparation, Modification By Chitosan And Composite Film Of Cynoglossus Semilaevis Fish Skin Gelatin

With the rapid development of fishery,fish skin and other by-products have caused serious environmental pollution and resource waste.Developing fish skin gelatin is one of the effective means to solve this problem.There are some common scientific problems in the development of fish skin gelatin.The physical and chemical properties of cynoglossus semilaevis fish skin gelatin（CSG）,process optimization,blending modification of chitosan（Ch）and composite packaging film of cynoglossus semilaevis were studied.The main research contents are as follows:Firstly,the physicochemical characteristics of fish skin gelatin were analyzed by SDS-PAGE,FTIR and second derivative spectroscopy.It was found that the content of CSG amino acids,the proportion of large molecular weight protein,the proportion ofβ-folding andα-helix secondary structure were higher.These are the main reasons why the physicochemical properties of CSG are close to that of commercial mammalian gelatin.This part of research is an attempt to excavate the source of commercial gelatin.To solve the problem of low extraction rate of CSG,the response surface method was used to optimize the hot water extraction process of CSG,and the effective response surface model equation was established.The optimal parameters of the hot water extraction method were determined as follows:the concentration of Na OH was1.63 mol/L;Hot water extraction temperature 62.49℃;The hot water extraction time is 4.74h,and the prediction effect of each response model equation is proved to be better.By means of DMA,XRD and DSC,it was found that the optimized process improved the thermal stability by increasing the proportion of high molecular weight protein andα-helix secondary structure.This part of content supplements the theoretical basis of CSG industrial production process optimization.In order to further solve the problems of poor barrier and low mechanical strength of CSG,chitosan was used to modify CSG,and turbidimetric titration method proved that CSG and Ch polymer molecules formed soluble or insoluble complex mainly through electrostatic interaction.In addition,the flow behavior of CSG/Ch composite solution is pseudoplastic non-Newtonian liquid through steady state rheological analysis and DMA,which can be well fitted by Herschel-Bulkley and Cross models.The rheological parameters（ε_a,η₀）,dynamic parameters of cementation(K_gel,G’_Pl)and dynamic viscoelastic parameters（G’,LVR,Tanδ,K_f,T_G,T_m,etc.）of CSG-based complex increased from 0.1%to 0.6%.When the concentration of Ch was more than 0.6%,the opposite change occurred.This part of the research provides a systematic theoretical basis for Ch blending modification of CSG.On the basis of above,CSG/Ch/OEO composite packaging film was prepared with orange peel essential oil（OEO）as modifier.Through the analysis of DTG,mechanical mechanics and DSC,it was found that OEO could change the microstructure and mechanical properties of the composite membrane by destroying the intermolecular interaction of the composite membrane,thus improving the water resistance,light transmission,antioxidant and antibacterial activities of the composite membrane,showing a good preservation effect.The research content of this part is a development of the application prospect of CSG/Ch composite membrane.