Abstract: The migration behavior of thymol from polylactic acid (PLA) film to different food stimulants was studied by soaking the film in distilled water, 4% acetic acid (V/V), n-hexane and 10% ethanol (V/V) at 4, 10, 20 and 30 ℃, respectively. The migration amount of thymol to food simulants was determined by UV spectrophotometry. The effects of temperature and food simulants on the migration of thymol were analyzed. Based on the obtained experimental data, a model for thymol migration was established by the Piringer equation and its rationality was analyzed. Results showed that the thymol content increased gradually until reaching equilibrium with increasing migration temperature and time in both simulants. The migration of thymol to four food simulants was in the decreasing order of n-hexane > 10% ethanol > 4% acetic acid > distilled water. According to the power law model, the mechanism of thymol diffusion through PLA films was in line with Fick’s law. The diffusion coefficient increased with migration temperature while the opposite was observed for the partition coefficient. Thus, the Piringer equation could describe the migration behavior of thymol. The mathematical equation developed in this study can provide a useful tool for prediction of the migration of thymol from PLA food packaging materials to foodstuffs.

Key words: thymol, polylactic acid, packaging, food simulant, mathematical model for migration