Rapid detection of TiO₂ (E171) in table sugar using Raman spectroscopy

The potential toxic effects of titanium dioxide (TiO₂) to humans remain debatable despite its broad application as a food additive. Thus, confirmation of the existence of TiO₂ particles in food matrices and subsequently quantifying them are becoming increasingly critical. This study developed a facile, rapid (< 30 min) and highly reliable method to detect and quantify TiO₂ particles (E171) from food products (e.g., table sugar) by Raman spectroscopy. To detect TiO₂ particles from sugar solution, sequential centrifugation and washing procedures were effectively applied to separate and recover 97% of TiO₂ particles from the sugar solution. The peak intensity of TiO₂ sensitively responded to the concentration of TiO₂ with a limit of detection (LOD) of 0.073 mg kg^-1. In the case of sugar granules, a mapping technique was applied to directly estimate the level of TiO₂, which can be potentially used for rapid online monitoring. The plot of averaged intensity to TiO₂ concentration in the sugar granules exhibited a good linear relationship in the wide range of 5-2000 mg kg^-1, with an LOD of 8.46 mg kg^-1. Additionally, we applied Raman spectroscopy to prove the presence of TiO₂ in sugar-coated doughnuts. This study begins to fill in the analytical gaps that exist regarding the rapid detection and quantification of TiO₂ in food, which facilitate the risk assessment of TiO₂ through food exposure.