Particle size measurement of SiO2 nanoparticles in the food additive E 551 (SiO2) and E551-containing food products based on Scanning Electron Microscopy (SEM) imaging

Silicon dioxide (SiO2, amorphous silica) is a food additive approved in the EU with the designation number E 551. It is mainly used in powdered foods as a separating agent or anti-caking agent. Silicon dioxide as a food additive is under public discussion due to controversial views on the declaration obligation of the substance as an engineered nanomaterial. According to the Food Information Regulation (EU) No. 1169/2011, all food ingredients that are present in a food in the form of engineered nanomaterials must be clearly listed in the list of ingredients. The name of such ingredients must be followed by the word "nano" in brackets. So far, there are only very few E 551-containing foods on the market with nano-labelling of E 551 on the ingredient list. For all analysed samples, the outlines of the constituent SiO2 nanoparticles could be visualized within the SiO2-aggregates in high magnification SEM images (100.000x). Using the image analysis software ImageJ (v1.52p), at least 100 randomly selected particles were measured manually. The median minimum Feret diameter (Fmin) was defined as relevant measurand, based on the EU nano-definition recommendation and the EFSA -"Guidance on technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles”. This data set contains the chosen SEM images of all samples, showing the outlines (in green or yellow) of all measured particles. The Fmin sizes of each measured particle is added in the attached Excel file.