How to best extract silica particles to determine their possible nanoparticles' content in food products?

JRC scientists have systematically assessed whether microwave-assisted acidic digestion is a suitable method for the extraction of silica particles from food matrices.

Results demonstrate that this procedure commonly used is not ideal as it alters the number-size distribution, i.e. having an impact on the evaluation of whether a material is a nanomaterial or not according to the recommended definition of the European Commission.

Silicon dioxide is being used in food processing due to its property as a flavour carrier and anti-caking agent. It is an authorised food additive in the EU (E551) and must be labelled according to the provision of Regulation (EU) No 1169/2011 on food information to consumers.

If present also in the form of engineered nanomaterials, according to article 18(3) of this Regulation, this shall be clearly indicated in the list of ingredients. In this case, the name of the ingredient shall be followed by the word ‘nano’ in brackets. To implement and enforce such a regulation, analytical methods to extract, detect, characterise and quantify engineered nanoparticles (ENPs) are required.

Engineered nanoparticles in foodstuffs are usually suspended or embedded in complex organic matrices and can therefore not be directly measured without prior removal of the matrix components. Therefore, the isolation of nanoparticles from the matrix is the first step towards their comprehensive characterisation.

Due to its complexity, matrix removal is frequently not trivial and may cause modification of the number-size distribution of the silica particles. The isolation of silica nanoparticles by removal of the matrix with microwave-assisted acidic digestion is demonstrated methodologically in this study.

Results of a systematic study performed by the JRC demonstrate that microwave-assisted acidic digestion is unsuitable for the removal of organic matrices when the unaltered number-size distribution is required. A milder process of matrix elimination, such as enzymatic or UV treatment, should in this case be preferred.

Read more in:
Geiss, O., Bianchi, I., Senaldi, C., Barrero. J. Challenges in isolating silica particles from organic food matrices with microwave-assisted acidic digestion. Analytical and Bioanalytical Chemistry, Volume 411, Issue 22, pp 5817-5831.

DOI: 10.1007/s00216-019-01964-2

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Challenges in isolating silica particles from organic food matrices with microwave-assisted acidic digestion