Rapid Detection of Titanium Dioxide in Food Products using X-Ray Fluorescence Spectroscopy
Creators: name: Sankaranarayanan, Prarthanaa
Publisher: name: University of Massachusetts Amherst
Year: 2024

Titanium dioxide (TiO2) is a white, odorless, and tasteless powder used as the colorant E171 in candies, pudding, coffee creamers, etc. The potential toxicity of E171 led to its ban as a food additive in the EU starting 2022, when the European Food Safety Authority (EFSA) declared E171 as no longer considered to be safe when as a food additive, as they could not exclude genotoxicity concerns after consumption of titanium dioxide particles. However, the current regulations imposed by the US FDA only restrict the amount of TiO2 used in food, which is set at 1% by weight of the food and it is not required to be explicitly listed on the label. There are large knowledge gaps about the amount of titanium dioxide being used in food products in the US and how much of the population is being exposed to it. This study investigates the use of X-ray Fluorescence (XRF) to fill these gaps by developing a rapid and effective method to detect the presence of E171 in various food products and quantify the concentration by weight.  This method will help to obtain exposure and concentration data to enable regulatory bodies to facilitate a reliable risk assessment.  Since existing methods for detection such as Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) are expensive, require lengthy sample preparation and utilize dangerous chemicals such as hydrofluoric acid, there is a dire need for a more rapid and cost-effective way to detect and quantify TiO2 in food. A standard curve with standards from 0.005% to 2% for quantifying the mass concentration of TiO2 was established by using a mixture of E171 with either sucrose or starch as a filling material. Sucrose yielded an excellent linear curve with r2 = 0.9962 and showed limit of detection (LOD) of 0.00059% and limit of quantitation (LOQ) of 0.00197%. A total of 40 food samples in the powder matrix were purchased from the market with and without E171 label claim and tested using XRF. Results showed the presence of E171 in 30 samples, with 16 samples having explicit label claim and 14 samples without. The concentrations ranged from 0.003% to 0.486% TiO2 with the highest category being coffee creamers and the lowest TiO2 content in seasonings. The method was validated by running the samples on ICP-MS which yielded similar results. Recovery tests were also run giving percent recovery in the range of 70%-100%.  This method was also adapted to include other matrices that food products exist in, such as solid, semi-solid and liquid. Several sample preparation methods were tested for semi-solid samples. An emulsion was developed to create a standard curve with concentrations from 0.005% to 2%, which showed great linearity with r2 = 0.9959 and LOD = 0.000054% and LOQ = 0.00018%. This showed optimal results and was used for analysis of all products in this matrix. The highest concentration was found in a Queso Blanco with 0.739% TiO2. Other matrices such as solid included hard candy products, which could be quantified using the previous standard curve. This proves the ability of XRF to perform elemental analysis in a wide range of products. However, some limitations of the method include samples such as jellies and certain confectionery items which require a more specific and extensive preparation method to be used with XRF. Recovery tests were used for validation and percent recovery values from 80%-100% show that this can be a great semi-quantitative method, which is capable of screening a large number of food products for E171 in a rapid and efficient manner. An exposure assessment was also performed by considering the population consumption data from national surveys and amount of titanium dioxide present in each product. Estimated daily intake was obtained as 0.795 mg/kg bw.  Overall, this study has proposed a valuable tool to rapidly and effectively detect and quantify or semi-quantify TiO2 in food and filled the existing gaps about population exposure to this additive.