Characterization of silicium dioxide (SiO2) particles in an E 551-containing spice mixture by Scanning Electron Microscopy (SEM) combined with Energy-dispersive X-ray spectroscopy (EDX)

Max Rubner-Institut (MRI), Federal Research Institute of Nutrition and Food, Department of Food Technology and Bioprocess Engineering, Germany
Hetzer, Birgit

Silicon dioxide (SiO2, amorphous silica) is a food additive approved in the EU with defined purity criteria and bears the designation number E 551. In spices and other types of powdered food products, E 551 is mainly used 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, this spice mixture is one of only very few food products on the market with nano-labelled E 551.
The food additive is an industrially manufactured material, consisting of amorphous agglomerated and aggregated granules whose particle sizes are mainly in the microscale size range.
This dataset contains SEM images showing the morphology of SiO2 aggregates in a commercially available instant meal product containing E 551. In the high magnification images (50.000x - 100.000x) the outline of individual constituent nanoparticles was only partly visible. Basic information about the SEM setup and the sample preparation can be found in the attached txt-file. All in all, the obtained SEM results show, that E551 in this product is present in aggregated form and is deposited on the other food components, fulfilling its purpose as anti-caking agent.
Besides SiO2 aggregates also (unwanted) other solid food matrix components were present in the prepared samples. Therefore, qualitative elemental analysis was carried out by energy-dispersive x-ray spectroscopy (EDX) on the food samples in parallel to SEM imaging. Via EDX-mapping, showing the spatial distribution of the target elements (Si and O), the SiO2 particles/aggregates could easily be identified. Corresponding EDX element analysis data for this product (representative example) can be found in the data folder “Spice_mixture_EDX_element_mapping”.


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