Effect of organic acids on the morphology and particle size of titanium dioxide (E171) in processed food.

TiO (E171) is widely used in processed food as a coloring agent. However, growing concerns about the potential health effects of TiO nanoparticles (< 100 nm) have necessitated the need for monitoring the size distribution and cytotoxic properties of food additive TiO present in commercial food. In this study, we employed magnetic separation method to extract food additive TiO from 100 commercial foods. The extracted TiO had a mean particle diameter of 121-143 nm along with the fraction in nanoscale (< 100 nm) ranging from 7.5% to 35.7%, where certain types of food, such as candy and jelly, were shown to contain smaller TiO with higher fraction of nanoscale particles. Assuming that the low pH of the products with high content of organic acid is responsible for the smaller TiO, the effect of three organic acids, such as acetic acid, ascorbic acid, and citric acid, on the physicochemical property of TiO was investigated. The citric acid was shown to reduce the size of TiO along with the generation of fragmented nanoparticles with a size of around 20 nm, whereas the effect of acetic acid and ascorbic acid was negligible. Although TiO treated with citric acid did not exhibit short-term cytotoxicity, this study suggests the importance of fully assessing the potential long-term health effect of food additive TiO whose physicochemical properties were altered in processed food.