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Abstract

Materials in contact with foodstuffs are various materials that come into contact with food during its production, processing, preparation, and storage. Food contact materials must be safe. The safety of a particular food contact material depends on the type and quantity of constituents released from it into food. Migrated constituents should not endanger human health, cause an unacceptable change in the composition of food, or deteriorate its organoleptic characteristics.
New food contact materials containing nanoparticles have recently been developed. These novel materials are mostly still in the research and development stage, but some have already reached the market or may do so soon. The main risk of consumer exposure to nanoparticles in novel food contact materials arises from their potential migration into food. At present, very little information is available on the actual presence and use of novel food contact materials and the release of nanoparticles from these materials into food.
In this project, commercially available non-stick food contact coatings on pans were selected for characterisation and investigation of possible nanoparticle release. The results of release testing were used to assess potential health risks associated with exposure to released nano-TiO₂ particles. Furthermore, a screening method for detecting nanoparticles in food contact materials was developed and used to detect silver nanoparticles released from food contact paper.
The non-stick food contact coatings were characterised using FTIR, electron and optical microscopy, EDXS, and XRD. The characterisation revealed that the coatings contained submicron and nanosized rutile TiO₂ particles and quartz (SiO₂) embedded in a silicone polymer matrix. To estimate the potential migration of TiO₂ nanoparticles into food, migration tests were performed using deionised water, 3% acetic acid, and citric acid (5 g/L) as food simulants. The tests were conducted for 2 h at 100 °C. In addition, thermal and mechanical degradation of the matrix was investigated for a selected coating.
The simulants that had been in contact with the coatings were analysed by ICP-MS after ultrafiltration and by microwave-assisted digestion. The highest concentration of titanium-containing particles was determined in 3% acetic acid, reaching up to 861 µg/L or 147 µg/dm². Titanium was also present in the simulants in ionic form. The presence of TiO₂ nanoparticles in 3% acetic acid was confirmed by SEM-EDXS analysis.
Thermal stability testing (TG/DSC-MS analysis) showed no degradation of the matrix under foreseeable conditions of use. However, mechanical degradation studies demonstrated the potential release of titanium-containing nanoparticles in microgram quantities during tribological testing. These findings were corroborated by observations of the morphology of coatings of the same type that had actually been used for food preparation. Both surface dissolution and mechanical abrasion resulting from matrix degradation may contribute to nanoparticle release from this type of non-stick food contact coating. The release of nanoparticles from food contact materials due to mechanical degradation had not previously been described in the literature.
The results of migration testing and calculations of potential release from coatings in actual use were considered alongside different food consumption data to assess exposure to TiO₂ nanoparticles. Estimated exposures were compared with derived no-effect levels (DNELs) for neurobehavioural effects and endocrine dysfunction to assess potential health risks associated with exposure to released nano-TiO₂ particles. Based on the available information, a health risk associated with exposure to nano-TiO₂ particles released from the examined quasi-ceramic coating cannot be excluded. However, a more refined assessment using more precise exposure and hazard data is needed to confirm the potential health risk.
In addition, a method for detecting the presence and release of nanoparticles from food contact materials was developed. The method is based on the reaction rate of the redox reaction between sodium borohydride and methylene blue dye, in which nanoparticles act as catalysts. It was used to detect the release of silver nanoparticles from food contact paper bearing a printed radio-frequency identification (RFID) antenna.
Since the rate of decolourisation depends not only on the nanoparticle concentration but also on temperature and various nanoparticle properties, such as size and shape, the method is suitable for screening purposes. If catalytic activity is detected in an extract of a food contact material, more sophisticated material characterisation methods should be applied, including the determination of the concentration and physicochemical properties of the released nanoparticles.
Research on nanoparticle migration from food contact materials and the assessment of potential health risks associated with exposure to released nanoparticles are still in their infancy. Future research should include release testing using real foods, investigations into the persistence of released particles in gastrointestinal fluids during digestion, and the generation of toxicity data for nanoparticles with various physicochemical characteristics.