Abstract:Antimicrobial films are widely used in fruit and vegetable preservation due to their excellent preservation performance. However，the elevation of endogenous pectin methylesterase activity and the infestation of exogenous microorganisms during the storage process of fruits and vegetables can interfere with the migration and diffusion of antimicrobial agents in antimicrobial films. The mass transfer and migration of antimicrobial agents in the films determine whether the antimicrobial films can perform their expected roles. Therefore，in this work，the enzyme - responsive migration behavior of thyme essential oil in nanocomposite antimicrobial films was investigated，and a release kinetic model was developed. The swelling rate and scanning electron microscopy（SEM）results of nanocomposite antimicrobial films showed that the antimicrobial films exhibited noticeable swelling behavior in the food simulation solution with pectin methyl esterase activity of 0-2.5 U/mL.As the enzyme activity increased，the microstructure of the film cross-section gradually changed from dense to loose，and even holes or slits appeared. The results of the release kinetics of thyme essential oil showed that the essential oil release curve tended to be linear when the diffusion ratio of the early stage of the release，Mt/M∞<2/3. Simulation analysis using the short-time release model and power law model revealed that the release mechanism of thyme essential oil shifted from irregular diffusion to Fick's law with the increase of enzyme activity. The entire process of the diffusive release of thyme essential oil followed the diffusion-solubilization superposition mechanism，which was consistent with the self-fitted negative exponential growth regression model（R2>0.95）.