Aging Studies on Food Packaging Films Containing β-Cyclodextrin-Grafted TiO2 Nanoparticles

TiO2 is a common food additive recognised as safe by US FDA [1]. Upon irradiation with light TiO2 forms reactive oxygen species (ROS) which degrade cell components of microorganisms and act as antimicrobial agents. Incorporating TiO2 into polymer matrix provides antimicrobial activity against bacteria, yeasts and molds and accelerates the self-degradation of the polymer using a renewable energy such as the sun [2,3]. Also, a recent study on the evaluation of the migration of TiO₂ from chitosan films into food revealed that most of the titanium remained in the polymer matrix after migration tests. Only a negligible amount of titanium migrated into the food (<5.44 × 10⁻⁴% of the total titanium in the chitosan matrix). Indeed, the potential risk of TiO₂ migration can be excluded [4]. The addition of CD to the TiO₂ NP surface, using a linker as hexamethylene diisocyanate (HMDI), produces a useful nanocarrier system. HMDI is one of the isocyanates approved for food-contact applications. Even though isocyanates are known to be quite toxic, they are used in very low amounts (<0.5%) and all unbonded HMDI chains are removed during the modification process. This system can be incorporated into thermoplastic polymers to obtain films with applications in food packaging. Also, food preservatives can be loaded in the CD cavity. This fact can provide protection against loss and heat decomposition during preparation of the packages, and is also intended to reinforce the TiO₂ intrinsic antibacterial activity. A previous work reported the loading capacity and further release of different food preservatives from the CD-grafted TiO₂ NPs [5]. The controlled release of these active molecules from the cavity of the macrocycles may extend the inhibitory effect of the NPs on microbial growth [6].

In this work, films containing composites of EVOH and PVA and different % TiO₂− and βCD-grafted NPs were prepared and characterized [7]. Films were treated in a temperature and humidity stability chamber and under different UV light intensities in order to study the influence of TiO₂ NPs regarding polymer degradation. The system changes were monitored by the color variation of the films (CIELAB) and FTIR characterization. The presence of βCD seemed to slightly favor the degradation of the PVA polymeric matrix at the higher temperature studied (80 °C), in contrast to EVOH, which underwent greater oxidation with unmodified TiO₂ NPs under thermo- and photo-oxidative conditions.

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7. Goñi-Ciaurriz, L.; Senosiain-Nicolay, M.; Vélaz, I. Aging Studies on Food Packaging Films Containing β-Cyclodextrin-Grafted TiO₂ Nanoparticles. Int. J. Mol. Sci. 2021, 22, 2257. https://doi.org/10.3390/ijms22052257