In the United States, calcium phosphate nanoparticles were identified in infant formula extractions, but their presence could not be linked to a specific additive.

The purpose of this research was therefore to find out whether the TCP additive used in Europe was considered a nanomaterial based on the EFSA guidelines.

The researchers systematically characterized 3 samples (from a chemical company and two manufacturers) following the EFSA guidelines. It was found that the additive actually consisted of hydroxyapatite, and the nano nature could be verified for each sample, so they satisfied the definition of nanomaterial according to EFSA.

They also showed that the particles can appear in many shapes (from needle to sphere). The hydroxyapatite nanoparticles are assembled in a simple aqueous medium in unstable agglomerates with a diameter of about 10 micrometers, which take hours to settle. The agglomerates gradually dissolve below pH=6 (in acidic conditions).

The importance of the work is that it provides information about its reactivity in digestive processes. Since it dissolves completely below pH=2, nanoparticles may still be present in the intestinal tract, raising the question of their further fate during digestion.