Nano Materials' Slow Ascent

Adoption of new technology usually inches along. In the case of nanotechnology in food, the timeline is measured in even smaller increments.

By Kevin T. Higgins, Managing Editor

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A catchy phrase can catapult manufacturing issues to buzz status — think Internet of Things or Six Sigma — but like yesterday’s news, their shelf life is limited.

Nanotechnology enjoyed buzz status not too many years ago, but its star power has lost some luster. Partly, that’s a consequence of the vagueness of the term and the different definitions attributed to it.

Food scientists focus on possible improvements in bioavailability, but they recognize that advocacy would pose a public relations minefield. Microbiologists are pursuing “lab on a chip” detection of foodborne pathogens, although commercial development is still years away.

In a sense, nanotech didn’t go away, it just went underground.

Take, for example, Owlstone, a British firm that is a pioneer in field asymmetric ion mobility spectrometry, a technology that miniaturizes ion spectrometry for detection of chemical signatures such as diacetyl, a flavor indicator in fermenting beer and wine. When Owlstone began developing electronic noses for food & beverage products a decade ago, it happily wrapped itself in a nanotech cloak.

Today, not so much. “I’d steer away from defining what we do as ‘nanotechnology,’” the firm’s communications director wrote in an email. “The presence of the word in our web domain is (mostly) a historical accident.”

Nano particles in packaging materials are potential game-changers. Three years ago, Nanox Tecnologia S/A received approval from the Brazilian government to include nanoscale silver ions in a polyethylene matrix for packaging. According to Gustavo Simoes, CEO of the São Carlos, Brazil, firm, the silver particles measure about 0.2 microns, a tenth of the size of the particles in other manufacturers’ antimicrobial silver ions but just as effective.

The silver coats silica particles measuring about 7 microns, and the powder then is added to preforms prior to blowmolding or injection molding. The silica carrier helps stabilize the color and transparency of the plastic, while the silver causes bacterial plate counts to gradually go down. “It’s a physical process,” says Simoes.

Most milk sold in Brazil is UHT processed and shelf stable for four months. Fresh milk is minimally pasteurized and usually only good for a few days. A handful of Brazilian dairies are using Nanox’s particles in high-density polyethylene containers and flexible pouches, boosting refrigerated shelf life to 10 days from four.

“It’s usually very difficult to show consumers the benefits of auto-sterilant containers,” Simoes acknowledges, but extended freshness is easily understood.

Nanox is a spinoff of the Multidisciplinary Center for the Development of Ceramic Materials, a government research initiative. Migration tests on the silica and silver composite determined that it is below the threshold set by Brazilian health authorities. The material is registered with the FDA, but winning EPA approval for an antimicrobial often is a lengthy and expensive process. Simoes says the firm is trying to attract U.S. investors to fund the petition process.

Slippery when wet

Nanoscale coatings for food contact surfaces are among the more active development areas, and although the food safety benefits of preventing biofouling usually drive the work, the benefits in a production environment go beyond safety.

Researchers at the University of Massachusetts have used an electroless nickel plating process to co-deposit fluorinated nanoparticles on the interior of stainless steel plates of a heat exchanger. Five layers of the polymeric coating measure less than 100 nanometers and reduce the need for machine shutdowns to address fouling caused by biofilms.

A similar benefit is delivered with slippery liquid-infused porous surfaces (SLIPS), a surface chemistry from Harvard University’s School of Engineering and Applied Sciences. SLIPS is a fluorinated oil that is immobilized on a surface and resists attachment by anything, giving rise to the term “omniphobicity” to distinguish it from nanostructured superhydrophobic surfaces that biofilm can adhere to.

Low cost is part of SLIPS’ attraction, and economic feasibility is a prerequisite for any metal coating that might be used on food equipment and contact surfaces, points out John Dutcher, director of the nanoscience program at University of Guelph in Guelph, Ontario. “Nanotoxicology is a real concern,” he adds, and extensive research is ongoing to understand what occurs at a molecular level when engineered nanoscale materials enter the environment or the human body.

Coatings for equipment that does not come into contact with food are less contentious. Energy losses from steam pipes and condensate lines, ovens, bottle washers and other equipment drive up production costs, but insulating them with rock wool usually isn’t an option in a food plant, where moisture will turn the insulation into a bacteria incubator.

An epoxy coating from Industrial Nanotech Inc. relies on porous tunnels to trap heat in microscopic layers. A typical application involves six coats with a total thickness of 300 microns, or 0.3 mm.

A project involving a European soft drink manufacturer began with six coats of the firm’s EPX-4 epoxy, followed by two layers of Translucent GP coating, a water-based acrylic that is registered with NSF International for incidental food contact. According to Francesca Crolley, vice president-business development at the Naples, Fla., firm, the bottler realized a 13-month ROI on the project.

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