ε-Caprolactam migration from irradiated PA-6 food packaging: kinetic simulation and measurement

Migration of low molecular mass compounds (LMMC), such as monomers and additives, from plastic packaging into food simulants is a very important issue, concerning public health and chemical contamination of foods. Sterilization of food packaging materials with ionizing radiation is considered an alternative to other sterilization methods, but when polymers are irradiated, LMMC may be formed, as radiolysis products. According to the Brazilian legislation, specific migration tests, such as those of LMMC from packaging into simulants, should be carried out at certain temperature and time, depending on the real conditions of contact. In this work, multilayer flexible films with polyamide 6 (PA-6), used for meat foodstuffs, were studied. The ε-caprolactam (PA-6 monomer) specific migration into acetic acid 3% simulant at 40 deg C during 10 days and at 100 deg C during 30 minutes was performed. The initial monomer level in the irradiated and non irradiated PA-6 films was quantified by high resolution gas chromatography (HRGC). Radiation doses were 3 and 7 kGy. ε-caprolactam specific migration was carried out only with non irradiated films. The results showed that radiation causes a significant change in the monomer level, up or down, depending on the multilayer film type. The kinetic of the ε-caprolactam migration at both temperatures, 40 and 100 deg C was clearly explained by the numerical simulation, combining an Arrhenius equation with the Fick's second law, although this kinetic was not experimentally studied. This simulation allowed to predict diffusion parameters estimates, like diffusion coefficients and activation energies of ε-caprolactam in the films or simulant. (author)