Smoothies Reduce the "Bioaccessibility" of TiO <subscript>2</subscript> (E 171) in the Model of the In Vitro Gastrointestinal Tract.

The food colorant E171 (TiO 2 ) containing nano fractions can cause potential health problems. In the presented work, we used a "gastrointestinal tract" model (oral→large intestine) to "digest" a fruit smoothie in the presence of TiO 2 nanoparticles and the Lactiplantibacillus plantarum B strain. The TiO 2 migration was measured using the microfiltration membrane (0.2 µm; model of "TiO 2 bioacessability"). We observed that the addition of the smoothie reduced the Ti content in the microfiltrate (reduced "bioacessability") at the "mouth", "stomach" and "large intestine" stages, probably due to the entrapment of Ti by the smoothie components. A significant decrease in Ti "bioaccessibility" at the "gastric" stage may have resulted from the agglomeration of nanoparticles at a low pH. Additionally, the presence of bacterial cells reduced the "bioaccessibility" at the "large intestine" stage. Microscopic imaging (SEM) revealed clear morphological changes to the bacterial cells in the presence of TiO 2 (altered topography, shrunk-deformed cells with collapsed walls due to leakage of the content, indentations). Additionally, TiO 2 significantly reduced the growth of the tested bacteria. It can be stated that the interactions (most probably entrapment) of TiO 2 in the food matrix can occur during the digestion. This can influence the physicochemical properties, bioavailability and in vivo effect of TiO 2 . Research aimed at understanding the interactions between TiO 2 and food components is in progress.