Winter 2017

Spoilage alert

Scientists from the U are using nanotechnology to improve food safety


There’s a verse in the Bible that declares wisdom’s superiority over gold. In the field of nanotechnology, however, gold actually provides the wisdom—at least in the work being done by Snober Ahmed and John Brockgreitens, graduate research assistants in the University of Minnesota’s Biosensors and Bionanotechnology Laboratory.

If successful, their work could lead to a more glittering bottom line for the food industry and improved safety for the U.S. food supply.

“In the field of nanotechnology, there’s a lot of medical research being done,” says Brockgreitens, who began working in the lab as an undergrad. “And while that’s important, nobody has really started to explore it in other sectors where nanotechnology and biology intersect, namely food.”

For the past year, he and Ahmed have been working to address a challenge facing the industry: the fact that many of the current food-safety tests required by the U.S. Department of Agriculture (USDA) are costly, clunky, and time-consuming—sometimes taking up to 48 hours—not to mention inaccurate.

That means that while waiting for a batch of peanut butter to pass muster, for example, the manufacturer must store all of that spread—and storage costs money. Or if a test reveals a batch of yogurt is contaminated and has already shipped, the company must recall the product—a costly, logistical, and reputation-damaging nightmare.

In 2015 alone, 21 million pounds of food were recalled in the United States. In fact, the USDA’s Economic Research Service suggests about one-third of our food supply goes to waste, a significant percentage of which is because of recalls.

What the food industry needs is super-fast, highly sensitive, inexpensive technology that detects pathogens before products are stored or shipped. And that’s where Ahmed and Brockgreitens come in.

The USDA’s Economic Research Service suggests about one-third of our food supply goes to waste, a significant percentage of which is because of recalls.


This inventive duo is developing new technology that detects contamination, creating glass devices layered in gold nanoparticles that capture cells from a food solution moving through a channelized system. The researchers then harvest the captured cells and analyze them for pathogens using UV absorption and chemiluminescence (emission of light caused by a chemical reaction). If the interaction between the gold nanoparticles and the captured cells turns the nanoparticles from red to blue, they know foodborne pathogens are present.

“In the medical industry, you’re concerned with finding the culprit and then quantifying it,” Brockgreitens says. “In the food industry, typically, there’s no need to quantify. If it’s there, it’s bad. That’s our advantage.”

The “holy grail” for the food industry, he says, would be pathogen detection in less than two hours—a tremendous improvement over today’s sluggish processes.

Although competitors are researching similar solutions, their techniques are imprecise. “We are working to improve the sensitivity of our processes,” Ahmed says, “so that we can detect fewer bacteria or fungi.” Success would mean foods containing just a few pathogens would be flagged, preventing a manufacturer from green-lighting them for consumption.

Both industry and government are supporting Ahmed’s and Brockgreitens’ work, some of which is being done at the U of M’s Midwest Dairy Foods Research Center. Entities funding their research include MnDrive Global Food Ventures, the Midwest Dairy Association, Schwan Food Company, National Science Foundation, and General Mills. “This funding is very important as we explore uncharted territory in terms of food-safety sensing that could have a real impact on human health,” Brockgreitens says.


In addition to their pathogen-testing technology, Ahmed and Brockgreitens are working on several other food-safety projects. One involves placing sensors that use signal-inducing chemical species or food-grade polymers in packaging. In a milk-carton prototype, a blue sensor that turns red indicates the milk is no longer fit for consumption. (Yes, that’s the opposite of the color change in the gold project.) Although this idea holds great promise, it needs to become more cost-effective before it appears in grocery stores.

In another project, Ahmed is using selenium/gold-particle sensor chips to test drinking water and wastewater for mercury and other pollutants.

Both Ahmed and Brockgreitens have garnered not only international patents for various aspects of their work but also awards of merit from the American Society of Mechanical Engineering’s Global Congress on NanoEngineering for Medicine and Biology. Both were selected in 2015 as finalists for the Dow Sustainability Innovation Student Challenge Award.

“When we have a problem, we try to figure out how it happens in nature,” says Ahmed, explaining how nanotechnology led her to select selenium for its natural ability to act as a magnet for mercury. “That gives us a pretty good clue on where we should start. And we try to apply nanotechnology to make it work.”

Karin B. Miller is a Minneapolis writer and editor.