Preparation And Characterization Of Composite Edible Films Based On Collagen And Chitosan

In recent years,food safety,especially the safety of additives,has received extensive attention.It has become hotspot in research of extending food shelf life under the premise of food safety.As a common method for food preservation,coating film preservation has the advantages of convenient operation and high safety,which has attracted extensive attention of researchers.In this dissertation,fish scale collagen and chitosan were selected as the main research objects.We adopted the method of film preservation,based on molecular self-assembly technology and atomic force microscope.We studied the influence of different metal cations on the collagen self-assembly structure,the effects of calcium acetate and chloride salts on the chitosan self-assembly structure,and further explored the preparation conditions of collagen/chitosan complex edible films.The specific findings of this research project are shown as follows:（1）It was studied the special ion effects of four metal cations during collagen self-assembly.K⁺,Na⁺,Mg²⁺,and Ca²⁺four cation salts were used to study the effect of different cationic groups on collagen self-assembly and we gave an explanation on cation interaction mechanism using Hofmeister ion sequence and the Collins model on molecular level.The experiment showed that K⁺can reduce the solubility of collagen and increase the stability of collagen;while Na⁺and Mg²⁺increased the solubility of collagen.And under the condition of 400 mM NaAc,collagen self-assembles into a flat film.At low and medium concentrations of Ca²⁺,the collagen solubility was relatively increased.But in the 400 mM CaAc₂ solution,the collagen solubility decreased,and a short rod-shaped fibrous structure was formed.（2）It was investigated the effects of different metal ions on the structure and properties of self-assembly of chitosan molecules.The effects of different concentrations of calcium acetate and four chlorates on chitosan selfassembly were observed.It was found that chitosan molecules adsorbed on the mica surface and gradually changed from punctate to stub structure and finally formed a mesh-like film at high concentrations.After the calcium ions were added,the chitosan molecules assembled a regular fiber structure by being connected with calcium ions through chelation.In presence of different chlorates,with KCl,NaCl,and MgCl₂concentrations increased,the chitosan molecules gradually breaks down from the porous membrane to a granular structure.After high concentration of CaCl₂ was added,chitosan self-assembled into a flat and smooth porous membrane.（3）We had initial research on the preparation of collagen/chitosan composite membrane and calcium acetate effect on the composite membrane morphology.The collagen and chitosan solutions were thoroughly mixed in different proportions,and the morphology of the composite membrane was observed by atomic force microscopy to select the optimal ratio 1:1.Based on this,different concentrations of calcium acetate were added.It was found that the collagen-chitosan composite membranes were uniform,dense and flat in presence of 5.0mM calcium ions.We hopes this experiment can provide new ideas for the preparation of collagen and chitosan composite membranes and recommendations for food preservation.