Securing the Safety of the Food Supply
Most of us take for granted that the food on our plate—from packaged snacks to fresh greens at a salad bar to a meal served at a restaurant—is safe to eat. That is, until something goes wrong, and we wake up in the middle of the night sick to our stomachs.
Unless it's grown in a backyard garden, our food generally goes through a complex production chain—from production and processing to distribution and preparation—with multiple opportunities along the way for mishandling and contamination.
Our food system is indeed very vulnerable.
Every year, approximately 179 million cases of food-borne illness occur in the United States, including nearly 500,000 hospitalizations and over 6,000 deaths, according to Centers for Disease Control and Prevention estimates. Norovirus and salmonella are the top two pathogens causing domestically acquired food-borne illness, as well as the top two that send people to the hospital. Food can also be contaminated by chemicals and engineered nanomaterials, an emerging threat resulting from the rapid development of nanotechnology.
As Lili He, UMass Amherst professor in food science and director of the graduate program, put it, “Our food system is indeed very vulnerable.”
He is one of several members of the Food Safety Group in UMass Amherst’s top-ranked Department of Food Science. From examining cleaning and disinfection practices at food processing facilities to improving our capacity to detect the source of outbreaks, these researchers are working to improve the safety of our food supply.
Before food reaches our table, most of it is processed in some way. For fresh produce, this may be as simple as washing, drying, and sorting before packaging it for sale, while other types of food are slaughtered, pasteurized, cooked, chopped, and combined in countless ways.
The federal Food Safety Modernization Act (FSMA) enacted in 2011 seeks to prevent contamination of the food supply through regulations. One focus within these regulations centers around maintaining clean and hygienic facilities for food processing. While important for safety, compliance with these regulations may prove challenging for small producers and processors with limited resources.
Amanda Kinchla, UMass Amherst Extension associate professor of food science and co-director of the USDA-funded Northeast Center to Advance Food Safety, is leading research to support small farmers in New England who grow leafy greens. Through her extension work, Kinchla became aware that many small producers and processors of leafy greens were using the spin cycle on retrofitted household washing machines—rather than expensive commercial dryers—to dry greens after triple washing them.
Kinchla and Pragathi Kamarasu, PhD candidate, together with food science colleagues, are studying the safety of this novel practice and investigating best practices to minimize the risks of contamination. According to Kinchla, leafy greens have been implicated in outbreaks of Listeria, E. coli and Salmonella in the past. “Good Agricultural Practices (GAP) are critical for food safety with produce, and cleaning and sanitizing is one of those pillars,” she said.
For their study, the researchers are deliberately inoculating leafy greens with Listeria, then putting them through a triple wash and drying them in a retrofitted washing machine designed by colleagues at the University of Vermont Extension. The retrofitted washing machine uses a separate basket inside the washing machine—similar to a hand-operated kitchen salad spinner—which reduces direct contact between the greens and the barrel of the washing machine, and which can be removed for cleaning and sanitizing. After drying the greens, the researchers swab them to track the transfer of Listeria to understand the contamination transfer within the process.
Through this work, Kinchla and her colleagues aim to identify best practices for cleaning the retrofitted washing machines, and to transfer this knowledge to producers and processors. “We hope to find solutions that are practical for small farmers, and to help them defend their practices to regulators while reducing contamination risks,” she said.
Some types of facilities pose sticky challenges. If you’ve ever cooked with peanut butter or chocolate, you know how challenging it can be to clean up. Now imagine this on an industrial level.
Recent recalls and outbreaks of salmonella linked to chocolate and peanut butter processing facilities show the failures that can occur without proper cleaning and sanitizing. “Cleanup with water at peanut butter and chocolate manufacturing plants is very challenging,” explained Lynne McLandsborough, professor, and department head in food science, “and liquid can even promote the growth and survival of microorganisms in low-moisture environments.” Currently, water-based cleaning requires plant shutdowns of nearly a week and is rarely performed.
With UMass PhD students Shihyu Chuang in food science and Mrinalini Ghoshal in microbiology, as well as a collaborator at the University of Shanghai for Science and Technology, McLandsborough recently published a paper in Applied and Environmental Microbiology describing a novel, water-free method for cleaning machinery used for processing peanut butter and chocolate. The research was funded with USDA’s National Institute of Food and Agriculture food safety and defense grant.
McLandsborough explained that as an alternative to water-based cleaning, factories typically push hot oil through their systems. However, these treatments are not antimicrobial, and Salmonella can persist in the dry environment. The UMass researchers found that using peanut oil mixed with acetic acid at a concentration about half that of household vinegar plus the application of heat was highly effective against Salmonella.
They are now experimenting with adding small amounts of water to form a water-in-oil emulsion. This has shown promise as an even more effective antimicrobial, said McLandsborough.
Finding the Source of Outbreaks
When outbreaks of food-borne illness occur, it’s crucial to be able to detect the specific pathogen and its subtype responsible in order to stop its spread. Yet, too often, this doesn’t happen. In part, that's because most food safety outbreak monitoring systems today rely on whole genome sequencing, which is expensive, time-consuming, and requires a large amount of the pathogen and a centralized testing facility.
Matthew Moore, assistant professor in food science, studies food safety microbiology with a focus on food-borne viruses—particularly human noroviruses, which are the leading cause of foodborne illness in the U.S. and globally. Noroviruses can spread person-to-person or through foods, typically transmitted when an infected person handles the food improperly. According to Moore, many outbreaks are traced to restaurants or other food-service settings, where detecting noroviruses with currently available methods is challenging.
Moore and colleagues are working to develop portable, rapid tests for such viruses—along with bacteria and mycotoxins—that could be deployed in places where food is processed, prepared, and served, as well as in clinical settings. An ideal testing device would be portable and able to detect virus in under an hour. Critically, according to Moore, these tests must incorporate a mechanism to concentrate viruses from food and environmental samples because viral contamination in food is typically very low, while still able to make people sick. Further, an ideal test would be able to not only identify a pathogen, but would provide information about what subtype of the pathogen is present.
“A very important element of detecting infectious disease outbreaks is being able to subtype,” Moore explained. “A wide range of norovirus strains circulates in the population, so being able to identify which strain is making people sick can allow us to clump people into clusters of likely outbreaks. Then, similarities in food and eating events can allow for investigation to identify the source of an outbreak."
Moore and colleagues have received funding from the USDA’s Agriculture and Food Research Initiative to support research to develop such a test. In addition, earlier this year, an international research team led by Moore was awarded a $750,000 USDA National Institute of Food and Agriculture (NIFA) partnership grant.
Detecting a Range of Threats
The risks to food safety extend beyond pathogens like bacteria and viruses. Food also can be contaminated by chemicals, including pesticides and antibiotics, as well as engineered nanomaterials (ENMs), such as silver, titanium oxide, and micro-nano plastics, which can enter the food system through applications including food additives and food packaging. Researcher Lili He said ENMs are an emerging threat, and much is still unknown about their effects on human health, but “there’s growing evidence showing that certain nanomaterials, such as titanium dioxide, may pose a toxic threat to human beings.” Titanium dioxide, a whitening agent sometimes found in sugar, coffee creamer, and white powder on donuts, was recently banned in France to reduce public exposure, but is still permitted in the United States, according to He.
Currently, no single method exists to detect all these different kinds of contaminants, making it difficult to ensure the safety of food. He is seeking to change that through her research on surface enhanced Raman spectroscopy (SERS), a versatile technique which she says has the unique potential to detect all three contaminant classes. In this technique, a laser is shot at a sample, and the scattered light is collected. The molecular vibrations are measured, yielding a chemical signature of the sample, which indicates the presence of any chemical, biological, or ENM contamination.
He is conducting both fundamental research—exploring the capabilities and limitations of this technique in different scenarios—and applied research, helping companies to solve analytical problems using the new technique. For example, He’s lab has conducted pesticide analysis with companies including BASF and Syngenta, and has worked with PepsiCo to study a natural sweetener used in food.
He also collaborates with John Marshall Clark, professor of environmental toxicology and chemistry in UMass Veterinary and Animal Sciences and director of the Massachusetts Pesticide Analysis Lab. They have received two grants from the United States Department of Agriculture (USDA) totaling $1 million in support of research on pesticides.
He is also working to extend the availability of Raman, IRF, and XRF spectroscopy to other research applications beyond her lab. In 2019, she established the Raman, IR, and XRF Spectroscopy Core Facility with support from the UMass Institute for Applied Life Sciences (IALS).
“These instruments have proven to be very powerful in our research,” she said. “Through the core facility, I hope to make them available as resources to other faculty and students on campus, as well as researchers at outside companies, to help solve real-world problems.”
This story was originally published in October 2022.