Preparation And Properties Of Fish Gelatin Base Multielement Composite Film

Traditional petroleum base plastic packaging film materials cause serious environmental pollution.With the enhancement of people's awareness of green environmental protection,it has become a new development trend in the field of food packaging to use natural green,pollution-free,renewable and degradable natural polymer materials instead of traditional film materials.Especially in the field of food packaging,green,safe and pollution-free natural degradable packaging film material has become a research hotspot.Fish gelatin(FG)has been widely used in research and application due to its unique film-forming,biocompatibility and biodegradability.However,the application of pure FG film in the field of food packaging is limited due to its strong hydrophilicity and poor mechanical properties.In this dissertation,FG was modified by natural polymer chitosan(CS),plasticizer(glycerin(GE)and sorbitol(SR)),hydrophobic zein(Zein),and crosslinker(tannic acid(TA)and glutaraldehyde(GTA);scanning electron microscope(SEM)and Fourier transform infrared spectroscopy(FTIR)were used and other test methods were used to explore the microstructure of the multi-component FG based composite film;the mechanical properties,water resistance and optical properties of the composite films were studied.The experimental results are as follows:(1)The introduction of CS can improve the flexibility of FG film;compared with Sr,GE as a plasticizer has a more significant effect on the plasticity and toughness of FG/CS composite film.When GE content is 30%,the maximum elongation at break is 33.23%,which is 4.7 times higher than that of pure FG film(7.05%),while the maximum elongation at break of SR plasticized composite film is 11.28%.Compared with pure FG films,the improvement effect is not obvious;in the aspect of water resistance of composite film,both two plasticizers have multiple hydroxyl hydrophilic groups,which aggravates the hydrophilicity of composite films to a certain extent;SEM and FTIR results show that CS and FG have good compatibility.At the same time,the overall transmittance of the all films can be maintained above 85%.The addition of plasticizer and CS does not affect the optical properties of the composite film.Considering the mechanical properties and water resistance,the plasticizing effect of Ge is better than that of Sr.(2)Zein particles were introduced into the FG/CS matrix by in-situ formation method.Because Zein macromolecular chain contains a large number of hydroxyl groups,it can form hydrogen bonds with the hydroxyl and amino groups contained in the FG/CS matrix,strengthen the matrix structure,hinder the diffusion of water molecules,and improve the water resistance.In addition,the hydrophobic end of Zein exposed to the outside will also improve the water resistance.A proper amount of Zein particles can form a stable network structure with FG/CS composite matrix through electrostatic interaction,which hinders the movement of molecular chains and improves the tensile strength of the membrane.However,excessive Zein particles are easy to agglomerate due to their hydrophobic properties,which has adverse effects on the mechanical properties.Protein itself contains a large number of aromatic amino acids that can absorb ultraviolet light,and FG/CS/Zein composite films has good mechanical properties The outer region shows excellent UV barrier performance,while the visible region can still maintain more than 80% high transparency.(3)The mechanical properties and water resistance of the FG/CS/Zein/TA Composite films crosslinked by TA were improved obviously.The addition of TA improves the compatibility of Zein and FG/CS matrix,reduces the size of Zein particles and facilitates the stress transfer.The results show that the tensile strength of Zein-6% composite film increases from 19.85 MPa to 28.81 MPa when the content of TA is 6%,which is about 45%.By comparing Zein-6% composite film with Zein-9% composite film,it can be found that the maximum TS value of Zein-6% composite film is 28.81 MPa.When the content of TA is 2%,while the TS value of Zein-9% composite film is 28.87 MPa,and the maximum TS value of Zein-9% composite film is 29.97 MPa.In the aspect of water resistance,amphiphilic TA forms a close three-dimensional network structure by combining with hydrophobic Zein and hydrophilic matrix,which hinders the diffusion of water molecules to FG matrix and improves the water resistance of the membrane.FG/CS/Zein/TA composite film is light brown due to the addition of TA,and the overall transmittance has decreased.However,it has unique advantages in the field of UV resistant and antioxidant packaging film because it contains a large number of aromatic amino acids that can absorb UV.(4)The mechanical properties of GTA crosslinked composite films were improved obviously.The tensile strength increased from 18.85 MPa to 38.76 MPa However,excessive GTA will lead to over crosslinking,destroy the peptide bonds in the crosslinked gelatin molecules,weaken the intermolecular force and decrease the tensile strength of gelatin.GTA can improve the water resistance of FG/CS/Zein/GTA composite films.The aldehyde group of GTA reacts with the free amino group of polypeptide chain in the matrix to form a Schiff base structure,which hinders the movement of polymer molecular chain and limits the availability of free hydroxyl and hydrophilic water point in the membrane matrix.The C = N group in the Schiff base structure formed in the cross-linking reaction of the composite film can inhibit lipid oxidation,which makes it show excellent ultraviolet barrier performance in the ultraviolet region.It has a broad application prospect in the field of antioxidant food packaging.