Characterization of nanoparticles in silicon dioxide food additive

Abstract

Silicon dioxide (SiO₂), in its amorphous form, is an approved direct food additive in the United States and has been used as an anticaking agent in powdered food products and as a stabilizer in the production of beer. While SiO₂ has been used in food for many years, there is limited information regarding its particle size and size distribution. In recent years, the use of SiO₂ food additive has raised attention because of the possible presence of nanoparticles. Characterization of SiO₂ food additive and understanding their physicochemical properties utilizing modern analytical tools are important in the safety evaluation of this additive. Herein, we present analytical techniques to characterize some SiO₂ food additives, which were obtained directly from manufacturers and distributors. Characterization of these additives was performed using dynamic light scattering (DLS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and single-particle inductively coupled plasma mass spectrometry (spICP-MS) after the food additive materials underwent different experimental conditions. The data obtained from DLS, spICP-MS, and electron microscopy confirmed the presence of nanosized (1–100 nm) primary particles, as well as aggregates and agglomerates of aggregates with sizes greater than 100 nm. SEM images demonstrated that most of the SiO₂ food additives procured from different distributors showed similar morphology. The results provide a foundation for evaluating the nanomaterial content of regulated food additives and will help the FDA address current knowledge gaps in analyzing nanosized particles in commercial food additives.

Keywords:

• Food additive
• silicon dioxide
• nanosized particles
• particle size distribution
• dynamic light scattering (DLS) assay
• transmission electron microscopy (TEM) field effect scanning electron microscopy (FE-SEM)
• single-particle inductively coupled plasma mass spectrometry (spICP-MS)

Acknowledgements

The authors would like to dedicate this work to the memory of Timothy R. Croley and Savelas A. Rabb. The authors would like to acknowledge the FDA White Oak Advanced Characterization Facility (ACF) for instrument use, scientific and technical assistance. The authors would also like to thank Jiwen Zheng for scientific discussion and help with the ACF.

Disclosure statement

No potential conflict of interest was reported by the author(s). Certain commercial equipment, instruments, and materials are identified in this paper to specify an experimental procedure as completely as possible. In no case does the identification of any particular equipment or materials imply a recommendation or endorsement by the National Institute of Standards and Technology nor does it imply that the materials, instruments, or equipment are necessarily the best available for the purpose.

Additional information

Funding

This project was supported in part by an appointment to the Research Fellowship Program at the Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and FDA.