“It’s probably one of the lowest-cost possibilities to manufacture a nanostructure on a metallic surface,” Dr. Moraru said, noting that low-cost solutions to limiting bacterial attachment is key to nanofood processing applications. “The food industry makes products with low profit margins,” she explained. “Unless a technology is affordable, it doesn’t stand the chance of being practically applied.”
Already widely commercialized are nanocomposites in food packaging to extend product shelf life. These include nano-silver, nanoclay (naturally occurring fine-grained silicates), and nano-zinc, among others. Nanoclays are fabricated into plastic films and coatings to strengthen gas and moisture barriers and to increase strength and toughness. Several large beer and beverage makers, including Miller Brewing Co. and South Korea’s Hite Brewery, have been using nanoclay composites in their plastic bottles to create high-oxygen barrier packaging that keeps beer fresh for six months and longer.
Nano-silver is strongly anti-microbial, capable of killing more than 650 disease-causing pathogens within six minutes of contact time. As such, nano-silver is widely used in medical applications including catheters and for dressing wounds. Nano-silver has also been added to a variety of plastic food packaging and storage containers to inhibit the growth of mold and fungus. In 2014, however, the EPA banned nano-silver from food storage containers because the application had not been properly tested and registered. Nano-silver in food packaging has also been banned in many European countries. Nevertheless, such containers remain commercially available in South Korea, China, Taiwan, and other countries. Other non-food U.S. nano-silver products include socks, sportswear, laundry detergents, and deodorants.
While nano-silver is widely suspected of causing health harms, other nanomaterials, such as nano-titanium dioxide and nano-silica, continue to be used in food. Titanium dioxide is commonly used to increase the whiteness or brighten the color of numerous products including toothpaste, candy, mayonnaise, cheese, cake frostings, and yogurt. While FDA considers conventional titanium dioxide to be safe, the health effects of its nano-sized particles remain unclear. Food companies whose products have been found to contain nano-titanium dioxide deny adding the particles and suggest that they occur naturally. Nano-silica is widely used as an anti-caking agent in powdered food products and in cosmetics and skin care. The European Commission’s Scientific Committee on Consumer Safety found “inadequate and insufficient” evidence to draw any firm conclusion for or against the safety of nano-silica in cosmetics.
Nanosensors to Detect Foodborne Pathogens
Researchers are also developing nanosensors to detect foodborne pathogens and toxins. The USDA’s National Institute of Food and Agriculture (NIFA) last year awarded $3.8 million in grants to support nanofood R&D in food safety, food security, nutrition, and environmental protection. The University of Massachusetts in Amherst received $444,200 to develop a pathogen detection platform based on surface-enhanced Raman scattering, or SERS, mapping. This approach permits bacteria from food samples to be concentrated, identified, and quantified before any food product is shipped. The University of Georgia in Athens received nearly $500,000 to develop bio-nanocomposite-based electrochemical sensors that can detect fungal pathogens in selected crops.
“Advances in nanotechnology help secure a healthy food supply by enabling cost-effective methods for the early detection of insects, diseases, and other contaminants; improve plant and animal breeding; and create high value-added products of nano-biomaterials for food and non-food applications,” says Sonny Ramaswamy, PhD, director at NIFA.
One important goal for nanotech sensors is to detect foodborne pathogens rapidly and inexpensively. Conventional detection methods such as microscopy and nucleic acid- and immunoassay-based techniques can require large samples, long incubation times, or the need to prepare cultures. Newer techniques including polymerase chain reaction, or PCR, and other molecular diagnostic methods require undamaged DNA and reagents and rely on experienced technicians, making the overall cost high enough to limit wide-scale use.