Abstract
A wide variety of foods manufactured by nanotechnology are commercially available on the market and labeled as nanoproducts. However, it is challenging to determine the presence of nanoparticles (NPs) in complex food matrices and processed foods. In this study, top-down-approach-produced (TD)-NP products and nanobubble waters (NBWs) were chosen as representative powdered and liquid nanoproducts, respectively. The characterization and determination of NPs in TD-NP products and NBWs were carried out by measuring constituent particle sizes, hydrodynamic diameters, zeta potentials, and surface chemistry. The results show that most NBWs had different characteristics compared with those of conventional sparkling waters, but nanobubbles were unstable during storage. On the other hand, powdered TD-NP products were found to be highly aggregated, and the constituent particle sizes less than 100 nm were remarkably observed after dispersion compared with counterpart conventional bulk-sized products by scanning electron microscopy at low acceleration voltage and cryogenic transmission electron microscopy. The differences in chemical composition and chemical state between TD-NPs and their counterpart conventional bulk products were also found by X-ray photoelectron spectroscopy. These findings will provide basic information about the presence of NPs in nano-labeled products and be useful to understand and predict the potential toxicity of NPs applied to the food industry.
Highlights
Nanotechnology has been applied to a wide range of foods in the food industry to improve the stability, shelf-life, process convenience, quality, and nutritional values of processed foods [1,2,3]
In the European Commission (EC), nanomaterials are defined as materials consisting of more than 50% of constituent particles in the size range of 1 to 100 nm based on number size distribution, including agglomerates or aggregates whenever the constituent particles belong to 1–100 nm [6]
The results show that the average sizes of constituent particles of all TD-NPs were smaller than those observed by scanning electron microscopy (SEM) (Figure 1), showing ~20 to 40 nm (Figure 2)
Summary
Nanotechnology has been applied to a wide range of foods in the food industry to improve the stability, shelf-life, process convenience, quality, and nutritional values of processed foods [1,2,3]. Nanomaterials can be manufactured by two different methods, top-down and bottom-up approaches, and added as food additives, ingredients, and raw materials [4,5]. NPs can be decomposed into small molecules/ionic forms or form large aggregates with other molecules present in foods or biological systems, and NPs may not be further present in commercial products and in the body [2,16]. In this case, the toxicity evaluation of NPs can be followed according to relevant guidance for conventional materials [16]. The determination of the presence and fate of NPs in commercial processed foods is of importance to understand and predict their potential toxicity
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