Characterisation of food contact non-stick coatings containing TiO₂ nanoparticles and study of their possible release into food

Novel nanoparticles containing non-stick coatings have been developed for food contact applications such as frying pans. Possible release of nanoparticles from such coatings into food is not known. In this paper, the characterisation of commercially available non-stick coatings was performed by use of FTIR, electron and optical microscopy, EDXS and XRD analysis. Characterisation revealed that the coatings contained micron- and nanosized rutile TiO₂ particles, and quartz SiO₂ embedded in a silicone polymer matrix. In order to estimate possible migration of TiO₂ nanoparticles from coatings into food, migration tests into simulants (deionised water, 3% acetic acid and 5 g l^–1 citric acid) were performed (2 h at 100°C), and thermal and mechanical degradation of the matrix was studied. Simulants were analysed by ICP-MS after ultrafiltration and by microwave-assisted digestion. The concentration of titanium-containing particles that migrated into simulants was up to 861 µg l^–1 (147 µg dm^–2). Titanium was present in simulants in ionic form as well. The presence of TiO₂ nanoparticles in 3% acetic acid was confirmed by SEM-EDXS analysis. Thermal stability study (TG/DSC MS analysis) did not show degradation of the matrix under foreseeable conditions of use, but mechanical degradation studies (scratch and tribological testing) showed possible release (microgram quantities per punched sample) of titanium-containing nanoparticles. The matrix degradation results were confirmed by observations of the morphology of the same type of coatings actually used for food preparation. Dissolution from the surface and matrix degradation can both contribute to nanoparticles release from this type of non-stick food contact coatings.