Development Of Gelatin/Chitosan/Curcumin Antibacterial Composite Film Based On Photodynamic Technology And Its Effect On The Quality Of Shrimps

In order to develop a new type of degradable antibacterial film to replace petroleum-based food packaging materials to reduce energy consumption and prolong food shelf life,an efficient curcumin-mediated photodynamic technology was established in this study,and applied to food packaging.Photodynamic inactivation（PDI）is a novel non-thermal sterilization technology that utilizes visible light combined with photosensitizers to produce biological activity against food-borne pathogens.Edible composite films were prepared by adding natural food pigment Cur with gelatin（GEL）and chitosan（CS）as film-forming materials.According to research results,it can be concluded that the incorporation of Cur into the biopolymer-based film delivery system with the PDI is a promising new idea for the preparation of food packaging films,which has huge application potential in microbial control in the food packaging industry.The specific research conclusions are as follows:（1）In the second chapter of this study,GEL and CS were used as film-forming materials,and edible GEL/CS composite films were prepared by solution casting method,and the process optimization of the composite films was carried out using orthogonal experiments.The internal microstructure and surface morphology of the composite films of the optimal process group were characterized by Fourier transform infrared（FTIR）spectroscopy,X-ray diffraction（XRD）and Scanning electron microscopy（SEM）.Through the orthogonal test,when the concentration of GEL was1.5%,the concentration of CS was 1%,the concentration of GEL:CS was 4:6,and 0.3%glycerol was added as a plasticizer,it was obtained with good mechanical properties（tensile strength was 14.12 k Pa,elongation at break was 53.19%）and lower water vapor transmission rate(0.3089 g·mm·m^-2·h^-1·k Pa^-1)edible composite film with the best performance.The internal microstructure and surface morphology of the GEL/CS composite film were analyzed,and it was found that there was a strong interaction between the GEL and CS molecules,and they had good compatibility.（2）In the third chapter of this research,GEL/CS/Cur functional films with PDI potency were prepared.The properties of GEL/CS/Cur（0.025,0.05,0.1,0.2 mmol/L）films were investigated by evaluating the surface morphology,chemical structure,light transmittance,mechanical properties,as well as photochemical and thermal stability.The results showed a strong interaction and good compatibility between the molecules present in the GEL/CS/Cur films.The addition of Cur improved different film characteristics including thickness,mechanical properties,and solubility.More importantly,when Cur was present at a concentration of 0.1 m M,the curcumin-mediated PDI inactivated>4.5 Log₁₀ CFU/m L（>99.99%）of Listeria monocytogenes,Escherichia coli and Shewanella putrefaciens after 70 min（18.62 J/cm²）of irradiation with blue LED（455±5）nm.Moreover,Listeria monocytogenes and Shewanella putrefaciens were completely inactivated after 70 min of light exposure when Cur concentration was 0.2 m M.In contrast,the highest inactivation effect was observed in Vibrio parahaemolyticus.This study showed that the inclusion of Cur in the biopolymer-based film transport system in combination with photodynamic activation,represented a promising option for the preparation of food packaging films.（3）In order to evaluate the effect of PDI technology in the preservation of aquatic products,GEL/CS/Cur composite film was used to coat shrimps in this study,and the color,texture properties,p H,TVB-N,etc.of shrimps under PE packaging and GEL/CS/Cur film packaging（L+and L-treatments）were analyzed.The results showed that PDI treatment inhibited the growth of microorganisms in shrimp.When the Cur concentration of the GEL/CS/Cur composite film was 0.2 m M and the irradiation time was 1.5 h（20.52 J/cm²）,Listeria monocytogenes,Vibrio parahaemolyticus and Shewanella putrefaciens could not be detected,the number of E.coli cells decreased to1.04 Log₁₀ CFU/g.PDI treatment played a crucial role in the quality assurance of shrimp.During the storage period of shrimp,the color difference,water loss and tissue texture of the shrimp in the PDI treatment group were smaller than those in the other two treatment groups;it had a significant inhibitory effect on the reduction of p H value and the production of volatile base nitrogen（TVB-N）.The sensory scores also proved that the GEL/CS/Cur composite film based on PDI technology could guarantee the freshness of food.