Preparation And Characterization Of Silica-Cinnamaldehyde Antibacterial Microcapsules And Its Degradable Films

Food spoilage can lead to foodborme infections in humans,so it is necessary to find a new,efficient and safe antibacterial agent that prevents food spoilage.Cinnamaldehyde(CA)is the main component of cinnamon essential oil.It has broad-spectrum antibacterial properties and can be used for food seasoning and antisepsis.However,it is limited by the effects of instability such as volatilization and easy degradation.Microcapsule technology can encapsulate cinnamaldehyde inside the wall material to protect it from light,heat and oxygen.In this paper,silica-cinnamaldehyde(Si02-CA)microcapsules were prepared by sol-gel microencapsulation and embedding natural antibacterial agent cinnamaldehyde,and the sustained release law was studied.On this basis,the PBAT/Si02-CA antibacterial film was prepared by automatic coating machine.The research results are as follows:(1)Silica-cinnamaldehyde microcapsules with cinnamaldehyde as core material and silica as wall material were prepared by sol-gel method and oil-in-water method.The optimal preparation process of microcapsules by single factor experiment and orthogonal experiment is:the volume of ethyl orthosilicate is 0.7 mL,the volume ratio of ethanol to water is 0.59,the volume of ammonia water is 1.5 mL,the mass of surfactant is 0.09 g,the volume of cinnamaldehyde is 0.1 mL,the stirring speed is 700 r/min.The microcapsule embedding rate of the optimal process was 58.33%,and the morphology of SiO2-CA microcapsules was regular spherical.The particle size ranged from 540 nm to 760 nm.The"shell-core" structure of SiO2-CA microcapsules was observed by transmission electron microscopy,and the shell thickness was about 40 nm.The inhibition zone experiment of Si02-CA microcapsules showed that the microcapsules were bacteriostatic against Listeria and Escherichia coli,and the inhibition zone of concentration of 90 mg/mL was 13.95 mm and 11.99 mm,respectively.(2)The release of cinnamaldehyde in SiO2-CA microcapsules at different temperatures and different humidity conditions at 15d was studied.The results showed that the final release rates were 87.46%,74.46%and 56.58%at 40?,23? and 4?,respectively.The final release rates were 87.46%,84.4%and 77.87%at 90%RH,70%RH and 50%RH,respectively.The release mechanism of Si02-CA microcapsules was studied by zero-order kinetic model,first-order kinetic model,Higuchi model and Korsmeyer-Peppas model.The results showed that the release of microcapsules under different conditions had a higher correlation coefficient with the first-order kinetic model(R2>0.94).The release of Si02-CA microcapsules at low temperature(4?)and lower humidity(50%RH and 70%RH)also has a higher correlation coefficient with the Korsmeyer-Peppas model(R2>0.92).(3)The PBAT/SiO2-CA antibacterial film was prepared by an automatic coating machine,and the addition amount of Si02-CA microcapsules was 0.5%,2.5%,and 4.5%.The antibacterial rate of PBAT/Si02-CA antibacterial film showed that the inhibition rates of Escherichia coli and Listeria were both>95%.The addition of microcapsules increased the film rigidity and reduced the toughness of the film.When the addition amount of Si02-CA microcapsules was 2.5%,the tensile strength was 13.58 MPa,which reached the maximum value.The moisture barrier properties of PBAT/SiO2-CA antibacterial film showed that the addition of 2.5%Si02-CA microcapsules could improve the moisture barrier properties of the film.The results of atomic force microscopy analysis showed that the addition of 2.5%SiO2-CA microcapsules could reduce the surface roughness of the film.The thermal performance of PBAT/SiO2-CA antibacterial film showed that Si02-CA microcapsules can increase the degree of crystallization and the degree of wafer perfection,further explaining the reasons for the improvement of tensile strength and moisture resistance of the film.