Criteria to define a more relevant reference sample of titanium dioxide in the context of food: a multiscale approach

Abstract

Titanium dioxide (TiO) is a transition metal oxide widely used as a white pigment in various applications, including food. Due to the classification of TiO nanoparticles by the International Agency for Research on Cancer as potentially harmful for humans by inhalation, the presence of nanoparticles in food products needed to be confirmed by a set of independent studies. Seven samples of food-grade TiO (E171) were extensively characterised for their size distribution, crystallinity and surface properties by the currently recommended methods. All investigated E171 samples contained a fraction of nanoparticles, however, below the threshold defining the labelling of nanomaterial. On the basis of these results and a statistical analysis, E171 food-grade TiO totally differs from the reference material P25, confirming the few published data on this kind of particle. Therefore, the reference material P25 does not appear to be the most suitable model to study the fate of food-grade TiO in the gastrointestinal tract. The criteria currently to obtain a representative food-grade sample of TiO are the following: (1) crystalline-phase anatase, (2) a powder with an isoelectric point very close to 4.1, (3) a fraction of nanoparticles comprised between 15% and 45%, and (4) a low specific surface area around 10 m g.

Nanoscience and nanotechnologies for biobased materials, packaging and food applications: New opportunities and concerns

“…Analysis of the TEM images (Fig. 11) showed the presence of 34% TiO2 nanoparticles in the sweet coating, which is consistent with values found in native E171 powders or food products (Weir, Westerhoff et al 2012;Chen, Cheng et al 2013;Dudefoi, Terrisse et al 2017). This amount is below the cut-off threshold (50%) above which the labelling of nanomaterial is required in accordance with the current definition of nanomaterial.…”

“…Moreover, exposure is significantly different between countries due to a significant difference in consumption habits, for example between the US and the UK (Weir, Westerhoff et al 2012). Furthermore, ICP devices are expected to gain sensitivity and food composition is expected to change, and we have experienced these trends ourselves: i) TiO2 was not previously found in Wrigley-brand chewing gums (Lomer, Thompson et al 2000) yet recently found in work performed at our lab and elsewhere (Athinarayanan, Alshatwi et al 2015;Dudefoi, Terrisse et al 2017)); ii) TiO2 is no longer found in Smarties, based on work by us on the listed ingredients and a previous review (Rydström Lundin 2012).…”

“…Investigating titanium dioxide makes it easier, as it is usually at the surface of confectionery and gives a strong signal by Raman spectroscopy when in anatase form. By chance, this form is widely used in food additives (Peters, van Bemmel et al 2014;Yang, Doudrick et al 2014;Dudefoi, Terrisse et al 2017). We thus used this method to discriminate food products containing TiO2.…”

“…The presence of Al, Si and Mg were confirmed by ICP-AES measurements, at 9.15, 72.78 and 35.14 mg/g of washed coating, respectively. The presence of P seems typical of food-grade forms of TiO2 and was identified as a phosphate species (Dudefoi, Terrisse et al 2017). Table 1.…”

“…The size and percentage of nanoparticles contained in the washed coating were determined by TEM in the same conditions as in a previous study performed in our lab (Dudefoi, Terrisse et al 2017). Analysis of the TEM images (Fig.…”