Extraction of E171 or E172 food additives from sugar-based or lipid-based complex matrices for primary particles identification by electron microscopy

<ns4:p>Measurement of primary particle size distributions is fundamental to determining if a material should be classified as a nanomaterial according to the European Commission recommended definition. This is of particular relevance to alimentary products, where current regulation requires that any additives containing nanoforms be explicitly declared as such in the ingredients’ list. Currently, Electron Microscopy is the only instrumental technique able to reliably classify materials as nanomaterials. To verify the nanostatus of a material using this technique, it is essential to firstly extract the additives from the matrix in which they are dispersed, and then measure a wide size distribution while avoiding artefacts from the food matrix. In this operating procedure, extraction protocols, developed and applied for sugar-based or lipid-based food, are described. In particular, case studies for titanium dioxide E171 and iron oxide/iron hydroxide based materials such as E172 are considered. The protocols are based on gentle extraction of the additive materials and could, in principle, be used for other nanomaterials provided they are not soluble in water or ethanol and are resistant to enzymatic reactions. The size distribution of the extracted material can then be determined from images acquired using scanning and/or transmission electron microscopy.</ns4:p>