TiO2 (Nano)Particles Extracted from Sugar-Coated Confectionery

Abstract

As the debate about TiO2 food additive safety is still open, the present study focuses on the extraction and characterisation of TiO2 (nano)particles added as a whitening agent to confectionary products, that is, chewing gum pellets. The aim was to (1) determine the colloidal properties of suspensions mutually containing TiO2 and all other chewing gum ingredients in biologically relevant media (preingestion conditions); (2) characterise the TiO2 (nano)particles extracted from the chewing gum coating (after ingestion); and (3) verify their potential photocatalysis. The particle size distribution, in agreement with the zeta potential results, indicated that a small but significant portion of the particle population retained mean dimensions close to the nanosize range, even in conditions of moderate stability, and in presence of all other ingredients. The dispersibility was enhanced by proteins (i.e., albumin), which acted as surfactants and reduced particle size. The particle extraction methods involved conventional techniques and no harmful chemicals. The presence of TiO2 particles embedded in the sugar-based coating was confirmed, including 17–30% fraction in the nanorange (<100 nm). The decomposition of organics under UV irradiation proved the photocatalytic activity of the extracted (nano)particles. Surprisingly, photocatalysis occurred even in presence of an amorphous SiO2 layer surrounding the TiO2 particles.