Is Food Nanotech Withering on the Vine?

When queried about their work with nanotechnology in emulsions, however, Nestlé spokeswoman Hilary Green responded, “Nestlé does not do research in the field of nanotechnology. Although we are not doing our own research, and we are not working with other laboratories in the field of nanotechnology, we do recognize the potential nanotechnology has in the longer term to improve the properties of food and food packaging.”

Part of the problem may be a matter of ontology. The most common definition of a nanoparticle is a particle between 1 and 100 nanometers (nm). However, some of the particles appearing in foods and packaging, and some of those being studied for toxic effects, are larger than 100 nm but still too small to be called microparticles. These particles, of 300, 400, or even 700 nms, may have different properties than the bulk materials from which they are made, and yet they do not fall under the authority of a narrow regulatory definition limited to particles smaller than 100 nm.

One area of open and active innovation in nanotechnology is the packaging of foods. The U.S. Army Natick Soldier Research, Development and Engineering Center is trying out new nanomaterials in the packaging for its Meals, Ready to Eat. The nanocomposite material offers some significant potential benefits, including lighter weight and increased shelf life for the product inside. The optimized formulation consists of melt-processed low-density polyethylene and 7.5% montmorillonite-layered silicate nanoparticles of 6 mil thickness total (six one-thousandths of an inch). Its performance as a barrier to air and heat was significantly better than the standard meal bag, which is made of 11 mil thick low-density polyethylene.

Risks of Nanotechnology

The risks of nanomaterials in food or food packaging are not well characterized. Some foods naturally contain nanoparticles. For example, milk contains casein protein, which falls into the nanoparticle size range. Those natural nanoparticles are not associated with any increased risk in food. However, some studies suggest that nanoparticles may be more chemically reactive and more bioavailable than larger particles because of their increased surface area.

A 2006 publication in Environmental Science and Technology by scientists from the Institute for Chemical and Bioengineering in Zurich, Switzerland, suggested a nanoparticle-specific cytotoxic mechanism of uncoated iron oxide.² And in the same year in Nano Letters, another group of Swiss scientists studied the toxicity of carbon-based nanoparticles to lung cells and found a size-dependent toxicity.³

Other studies show relatively benign effects of nanoparticles. In a recent study published by Liu and colleagues in Biomaterials, Chinese scientists found that mesoporous hollow silica nanoparticles had very low toxicity.⁴

One nanomaterial that is appearing in many consumer products, including some that are food-related, is nanosilver. Ionic silver is known to be toxic to bacterial cells in culture. Nanosilver is a very potent form of ionic silver, whose attributes are likely due in part to its nanoparticle size. Nanosilver has found its way into food packaging, containers, kitchen tools like cutting boards, and even health supplements.

Nanosilver, sold as colloidal silver, is a highly sought after cure-all in the alternative medicine community, although it has been found to have high toxicity to certain rat and mouse cells in vitro. While it has not been shown to have the same toxicity to humans, it can cause an unsightly graying of the skin called argyria. Consumer advocacy groups argue that under a precautionary principle of public health, products such as nanosilver should not be used in human foods or in surfaces that contact food until in vitro toxicity studies are reconciled with thorough human health studies, including studies of the effects of long-term exposure.

The Power of Perception

It’s fair to say that the actual risks of nanotechnology in foods have yet to be defined. However, another set of risks frames the public discourse on nanotechnology: perceived risks. To some consumers, the prospects of nanotech beverages that change flavors to suit the drinker, or tiny nanotech bloodhounds to sniff out spoilage, are not so appealing. Consumer groups have challenged companies on their nanotech research and petitioned the U.S. Food and Drug Administration (FDA) and other government agencies to look more closely at nanomaterials in the food supply.