Preparation And Characterization Of Cassava Starch/Sodium Carboxymethyl Cellulose Edible Film Loaded With Caffeic Acid@Silica Nanoparticles And The Application In Meat Preservation

Caffeic acid（CA）is a kind of natural phenolic acid compounds that have broad spectrum antibacterial and antioxidant activity as well as anti-cancer,anti-thrombotic,antiviral and anti-tumor activities.In recent years,caffeic acid has been studied in many fields,such as food.It can be used to maintain the color,flavor and nutritional value of food.However,due to the low solubility and stability of caffeic acid in common solvent systems,and the poor effectiveness of natural caffeic acid derivatives,the wide application of caffeic acid in the food industry is limited.In this study,caffeic acid was coated with silica nanoparticles（Si O₂NPs）to improve its solubility and stability,and to characterize it.Then nanoparticles were loaded into the edible film made of sodium carboxymethyl cellulose and tapioca starch,and the properties of the composite edible film were investigated.Finally,the edible film was applied to the preservation effect of fresh meat.The main research contents and conclusions are as follows:（1）Bacteriostatic and antioxidant activities of caffeic acid.The results showed that the minimum inhibitory concentration（MIC）and minimum bactericidal concentration（MBC）of caffeic acid against E.coli O157:H7 were 1.5 mg/m L,and the MIC and MBC against Staphylococcus aureus were 1.5 mg/m L and 3 mg/m L,respectively.Under the conditions of MIC and 2MIC caffeic acid for 8 h and 4 h,respectively,the bactericidal rate of caffeic acid reached 99.99%.The results showed that caffeic acid had good antibacterial activity.In the experiment of antioxidant activity,0.5 mg/m L and 1 mg/m L caffeic acid can clear more than 95%of DPPH and ABTS free radicals.（2）Preparation and characterization of caffeic acid@silica nanoparticles（C@SNPs）.The experimental results showed that when the dosage of caffeic acid was9 mg,the encapsulation rate and dispersibility of the nanoparticles were the highest,and the caffeic acid could be released continuously in the Si O₂NPs for a long time.The experimental results of X-ray diffraction（XRD）and Fourier infrared spectroscopy show that C@SNPs has been successfully prepared.Scanning electron microscope and atomic force microscope were used to observe the morphology of nanoparticles.It was found that the particle size of nanoparticles containing caffeic acid increased significantly,which proved that caffeic acid was successfully contained.In addition,DPPH and ABTS scavenging rates were determined,and the results showed that the antioxidant activity of C@SNPs was proportional to the amount of caffeic acid added.In terms of antibacterial activity,caffeic acid nanoparticles had better antibacterial effect than Si O₂NPs.In order to determine the stability of nanoparticles,the particle size and PDI of nanoparticles were evaluated at different temperatures.The experimental results show that Si O₂NPs can keep stable for a long time at normal temperature,but the particle size changes significantly at 4℃.The C@S₉NPs particle size remained stable at both temperatures.The p H stability experiments showed that the dispersion of the nanoparticles remained good in both acidic and alkaline environments,indicating that caffeic acid could improve the stability of the nanoparticles at low temperature and in a certain amount.Therefore,C@S₉NPs was selected for the subsequent preparation of edible film.（3）Preparation and characterization of edible tapioca starch/sodium carboxymethyl cellulose film loaded with C@SNPs.In this study,C@SNPs edible film was prepared with cassava starch and sodium carboxymethyl cellulose as the base material,supplemented with glycerin as the plasticizer.The experimental results show that C@SNPs can significantly improve the physical properties of edible film.When the volume ratio of distilled water to nanoparticles was 5:1,the tensile strength of the film reached 15.44 MPa,and the permeability of water vapor reached the lowest,0.27 g·mm·m^-2·d^-1·k Pa^-1,indicating the strongest thermal stability.In addition,the antibacterial and antioxidant capacity of the film was also significantly improved.The atomic map shows that the roughness of the nanoparticle film is much lower than that of the pure polysaccharide film,which is more conducive to packaging application.The 45 day storage experiment showed that the edible film loaded with C@SNPs could maintain high mechanical strength and barrier properties for a long time,and maintain stable water solubility and moisture content,so it has great potential for application in the food packaging industry.（4）Application of C@SNPs edible film in meat storage and fresh-keeping.In this study,beef and chicken were taken as experimental subjects to comprehensively evaluate the effects of edible film on the two kinds of meat.The results showed that the edible film had good color preserving effect on both kinds of meat,and could effectively maintain the meat quality and p H stability.The antibacterial experiments showed that the edible film had significant inhibition effect on Staphylococcus aureus and Escherichia coli on the surface of two kinds of meat,and could slow down the lipid oxidation rate of meat.Therefore,the edible film prepared in this study has a broad application prospect in the preservation of meat food.