Research And Application Of Fish Gelatin/carboxymethyl Chitosan Composite Film

In order to solve the problems of non-renewable resource exhaustion and environmental pollution caused by traditional petroleum-based plastic products,the development of green degradable composite film packaging has become a research hotspot and development direction.Fish gelatin(FG)derived from aquatic by-products can meet the needs of religious people.Carboxymethyl chitosan(CMCS)is a water-soluble derivative of chitosan also extracted from aquatic by-products.CMCS improved solubility expands the application range.Under the action of Transglutaminase(TGase),carboxymethyl chitosan as an acyl receptor can cross-link with proteins,which can better improve the performance of fish gelatin-based composite membrane.In this paper,fish gelatin and carboxymethyl chitosan were used as raw materials to prepare the composite film by solvent stretching method,and TGase cross-linking was used to improve the barrier and mechanical properties of the composite film.Subsequently,the heat sealing characteristics and storage stability of the composite film were studied,which enriched the application of aquatic by-products in the field of packaging materials.The main studies were as follows:(1)Fish gelatin/carboxymethyl chitosan composite film was prepared by solvent stretching method.Taking the concentration of film forming solution,mass ratio of fish gelatin to carboxymethyl chitosan,p H,plasticizer ratio,plasticizer concentration,heating temperature and heating time as the main factors,and taking tensile strength and elongation at break as the optimization indexes.The orthogonal test was designed to obtain the best preparation conditions of the composite film.The results showed that,the concentration of film forming solution was 5%,the mass ratio of fish gelatin to carboxymethyl chitosan was8:2,p H7.9,plasticizer ratio was 1:1,plasticizer concentration was 40%,heating temperature was 60℃and heating time was 80 min,the fish gelatin/carboxymethyl chitosan composite film had the best tensile strength and elongation at break.At the same time,they reached22.83±0.80 MPa and 138.36%±1.53%,respectively.(2)The interaction between the matrix of the composite film was reaseached.The physical properties and thermal properties of the composite film were studied.The rheological properties showed that the compositefilm-forming solution was non-Newtonian fluid,and the light transmittance of the composite film was above 86.00%.The addition of carboxymethyl chitosan enhanced the ability of the composite film to resist ultraviolet rays.FTIR analysis showed that there was a strong hydrogen bond interaction between fish gelatin and carboxymethyl chitosan,and the two had good compatibility.With the increase of carboxymethyl chitosan,the crystallinity of the composite film decreased,and the water contact angle showed a trend of first increasing and then decreasing.Compared with the pure fish gelatin film,the water vapor permeability of the FG8/CMCS2 composite film decreased to 0.8069±0.055 g·mm/m~2·h·k Pa,and the thermogravimetry analysis showed that the thermal stability of the composite film was improved.(3)By controlling the amount of TGase added,the film-forming solution with different enzyme activities(5 U/g,10 U/g,and 15 U/g)was obtained,and the composite film was prepared to explore the cross-linking modification effect of TGase on the composite film.The results showed that the average particle size of the composite film-forming solution increased from 359.96 nm to 1161.02 nm.With the addition of TGase,the degree of grafting of the film-forming solution increased,the content of free amino group decreased,and the viscosity increased significantly.TGase induced cross-linking between fish gelatin and carboxymethyl chitosan to form macromolecular substances.The tensile strength of TGase modified composite film increased to 27.32±1.21 MPa,but the elongation at break decreased.The water contact angle of TG10-FG/CMCS composite film was increased to 84.6°,and the water vapor barrier ability was increased by 22.84%.The results of FTIR and thermogravimetric analysis showed that TGase promoted the cross-linking interaction between fish gelatin and carboxymethyl chitosan,and the formation of higher molecular weight aggregates improved the thermal stability of the composite film.(4)Fish gelatin/carboxymethyl chitosan composite film modified by TGase crosslinking was studied for heat sealing properties and storage stability.Through the response surface design test,the optimal heat sealing process conditions were obtained as follows,heat sealing voltage 24 V,vacuum time 4.6 s,heat sealing time 3.2 s,cooling time2.9 s,the composite film heat sealing strength was 12.11±0.43 N/15mm.The drop test and pressure test showed that the composite film had good packing effect.With the extension of storage time,the mechanical properties of the composite film and the quality of the packaging contents were studied under different storage temperatures(25℃,4℃)and humidity(RH43%,RH65%).The results showed that the mechanical properties of the composite film were mainly affected by ambient humidity.The packaging effect of the composite film was good within 60 days of storage,and it was suitable for use in ambient conditions with low humidity and room temperature or below.