Characterization of silicium dioxide (SiO2) nanoparticles in E 551-containing instant coffee products by Scanning Electron Microscopy (SEM) combined with Energy-dispersive X-ray spectroscopy (EDX)

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 coffee instant products 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, there are only very few E 551-containing foods on the market with nano-labelling of E 551 on the ingredient list. The analysed instant coffee products had no such nano-labelling. 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. However, these aggregates consist of nanoscaled constituent particles (also called “primary particles”). This dataset contains SEM images showing the morphology of SiO2 aggregates in three commercially available instant coffee products containing E 551. In the high magnification images (100.000x) the constituent nanoparticles can be visualised. Basic information about the SEM setup and the sample preparation can be found in the attached txt-file (“Instant coffee_SEM analysis_Equipment_Sample info_Sample preparation.txt”). All in all, the obtained SEM results show, that E 551 in all three instant coffee products is present in aggregated form and is deposited on the other food components, fulfilling its purpose as anti-caking agent. The primary particle sizes of SiO2 particles within the aggregates are in the size range of ca. 30 – 60 nm.