A screening method for detection of TiO2 in food based on Raman spectroscopy and its applicability in a regulatory context

Abstract

Starting from August 7, 2022, with the publication of the European Regulation EU 2022/63, the European Commission has prohibited the use of titanium dioxide (TiO2) (E 171) as a food additive within the European Union (EU). As the food industry has the obligation to adapt the formulation of their products accordingly, it is now crucial for EU member states' competent authorities and official control laboratories to have adequate analytical methods to ensure compliance with this new regulation. The existing literature predominantly focuses on quantitatively determining the elemental titanium (Ti) concentration by ICP-based techniques after complete digestion of the analyte and the food matrix. Compared to this approach, Raman spectroscopy would offer the possibility of a more rapid albeit qualitative screening by identifying the insoluble fraction of titanium dioxide after removing the food matrix. It is also important to note that compliance with the EU ban requires determining the presence of TiO2 in particulate form, an information that Raman spectroscopy can easily deliver. As a further advantage, an analytical approach based on Raman spectroscopy eliminates the need for using particularly harmful acids, which are necessary for the complete digestion of TiO2, when ICP-based analytical methods are employed. In the present study, the aim was first to gather information on the commonly occurring total Ti levels in food and, second, to discuss the potential of a newly developed Raman procedure based on TiO2 extraction by mild acid digestion of the food product as a rapid, safer albeit qualitative screening method. To evaluate the effectiveness of the Raman procedure in verifying compliance with the European Regulation, the qualitative results obtained using a macro-Raman instrument were compared with those obtained through ICP-based techniques on the same food samples, used as benchmark. In total 22 food-samples belonging to 6 different food categories were analysed. The sampling was conducted in the Italian, Belgian, and French markets both before and after the EU ban on E 171 entered into force. The limit of detection, qualitatively established, was 50 mg kg−1, which effectively encompasses the majority of food items containing E 171, as supported by the extensive literature review. The results obtained with the Raman screening method were found to align well with information reported on product labels and benchmark quantitative data.