Purdue Center Aims at Preventing, Detecting Food Contamination
WEST LAFAYETTE, Ind. In an effort to protect the nation's food supply from biological and chemical contaminants, Purdue University and U.S. Department of Agriculture engineers and food scientists have teamed up to develop faster, more exact ways to detect possibly deadly substances.
With research grants and a partnership with the USDA's Agricultural Research Service, Purdue has launched the Center for Food Safety Engineering focused on developing methods to find, identify and eradicate microbes or chemicals.
"The Purdue Center for Food Safety Engineering is utilizing a multidisciplinary team to contribute to the science and technology needed to enhance food safety," said Michael Ladisch, a scientist in the center that includes work by nearly 90 university researchers.
The Centers for Disease Control and Prevention (CDC) estimates that 76 million cases of foodborne illness occur in the United States annually and claim approximately 5,000 lives and cost $7.7 billion or more. Although disease-causing bacteria accidentally can contaminate meat, fruit and vegetables at any stage, from the field through processing and storage, concern over food contamination has heightened since the Sept. 11 terrorist attacks on New York City and the Pentagon.
Ying Chang Han, a Purdue food research scientist, tests a way to sanitize a processing vat. Researchers in the Purdue Center for Food Safety Engineering are finding new ways to eliminate biological and chemical contaminants at all stages of food production.Health officials have long viewed the safety of the country's food as a prime concern, Ladisch said. Foodborne pathogens cause 325,000 hospitalizations yearly, according to the CDC. In fact, the Clinton Administration issued a "no tolerance" edict for Listeria monocytogenes in processed and ready-to-eat foods, such as hot dogs. Listeria is one of the most deadly of the biological food contaminants, with a fatality rate of about 20 percent.
One aspect of the task with which researchers must cope is the difficulty of tracing the source of foodborne illness. In addition, a minuscule amount of some pathogens, such as listeria, can cause illness. So the center's scientists are investigating detection methods that not only are faster and more exact, but also require smaller bacteria-containing food samples to make an analysis.
Food science Associate Professor Richard Linton, as center director, leads the biochemists; molecular biologists; physicists; and biomedical, electrical, computer, agricultural and biological engineers. Their quest is to prevent microbial organisms such as Salmonella enteritidis, Listeria, Escherichia coli (E. coli) O157:H7, Campylobacter and Fusarium from entering the food chain at any point, whether it's the farm gate, the processing plant or the consumer's table. The investigators come from five schools within the university Agriculture, Consumer and Family Sciences, Engineering, Science, and Veterinary Medicine, and team with the USDA Agricultural Research Service scientists.
"The multidisciplinary center provides an important platform for bringing different scientific expertise together," said Linton, a microbiologist. "With this collection of creative minds working together, new and exciting research approaches are being developed and studied. This is an important step for solving complex food safety problems and, most importantly, for protecting the health of consumers."
A five-year, $7 million USDA grant provides funding for cooperative projects between the center and the Agricultural Research Service, while other funding has allowed creation of the center for expansion of the university researchers' work.
"We need long-term research to develop and improve techniques and to engineer methods in systems that are readily usable in the plant and the laboratory," said Ladisch, who also is director of Purdue's Laboratory of Renewable Resources Engineering and a distinguished professor of agricultural and biological engineering and biomedical engineering. "The partnership between the USDA and the university allows us to carry out cooperative research that facilitates achieving results that would be difficult otherwise."
The projects currently under way by Purdue scientists at the Center for Food Safety Engineering focus on the following areas:
- Fusarium is a fungus that infests grains and then produces carcinogenic mycotoxins that can affect both people and animals. It often appears in moldy corn, but also has been found in sorghum, rice, cottonseed meal, legumes, wheat and barley. Maribeth Cousin and Charles Woloshuk are working on a method to detect various Fusarium species in grain and foods. This research may give grain storage operators information enabling them to alter storage conditions in order to prevent Fusarium growth.
- Nanotechnology and magnetic beads are integral to investigations by Arun Bhunia and Mark Morgan to develop more sensitive, less expensive, faster methods of detecting Listeria. This bacterium can contaminate almost any food, from vegetables to ready-to-eat bologna, and even grow in the refrigerator. Listeria is responsible for about 2,500 cases of foodborne diseases each year. In the first of the twostep method, microscopic beads separate Listeria cells from food. Then the researchers use a test called a cytotoxicity assay that differentiates between disease-causing Listeria cells and those that are harmless.
- Molecular biology and tiny chips with electronic signaling and other possible Listeria detecting procedures are being investigated by Rashid Bashir, Bhunia, Paul Robinson, Stephen Badylak, Ladisch and their graduate students. Bashir's group is leading the fabrication and design of microscopic, hair-thin structures that will carry fluid from a food sample across a postage stamp-sized device called a biochip. The chip will electronically detect Listeria and distinguish it from other organisms. Molecules on the chip target and capture Listeria. When the targeted microorganism is captured, an electrical response from the biochip will signal its presence.
- Charles Santerre is developing ways to rapidly and accurately detect PCBs in fish and is investigating a rapid test for predicting the toxicity of PCBs in fish. The full effect of the common environmental contaminant polychlorinated biphyenyls, or PCBs, is unknown, but anecdotal evidence indicates they adversely impact fetal neural and physical development as well as the function of the liver and thyroid, and the immune and reproductive systems. PCBs also likely play a role in some forms of cancer. Humans are most commonly exposed by eating PCBcontaminated fish from rivers, streams and lakes. The contaminants can pass through the placenta or through breast milk at levels that are higher than in the original fishmeal.
- Measuring the characteristics of light scattered across a surface is another possible method to quickly detect and identify biological contaminants and distinguish between virulent and non-virulent bacteria. E. Dan Hirleman and Bhunia are investigating this using an instrument called a scatterometer. This technique may meet one research objective: to detect bacterial pathogens quickly; the scatterometer has found them as early as six to 10 hours after they were introduced into food.
- Fruits and vegetables can carry a number of illnesscausing bacteria including E. coli O157:H7, Salmonella and Listeria. A number of the center's researchers including Linton, Rakesh Singh, Bhunia and Richard Stroshine are testing alternate processes to eliminate these potentially deadly pathogens. Sanitizing methods they are investigating include use of chlorine dioxide, ozonated water and a solution that contains clove, thyme and oregano oils.
- Listeria monocytogenes can invade commercially processed and vacuum-packed ready-to-eat meats from contaminated air, equipment and water, as well as from food handlers in the processing plant. Tim Haley, Bhunia, Osvaldo Campanella, David Gerrard and Linton have designed a post-packaging pasteurization process for sliced bologna. The hightemperature, short-time method is applied to pouches containing one or two meat slices. This extends shelf life for ready-to-eat meat products and may provide food processors and consumers with another weapon in the fight to prevent Listeria-caused illness and death.
- Certain viruses called bacteriophages attack only specific bacteria. Using that knowledge, Bruce Applegate is genetically engineering bacteriophages that detect and identify specific bacterial pathogens. When bacteriophages infect the target pathogen, they cause it to produce a signal compound. The compound triggers a bioluminescent chain reaction in a second type of bacteria causing it to glow. This indicates the presence of pathogens. Eventually this two-component detection system will include use of a hand-held device called a luminometer that would enable those in the field or the plant to test for such bacteria as Salmonella, Campylobacter jejuni, E. coli O157:H7 and Listeria on meat, fruit and vegetables.
Writer: Susan A. Steeves, Department of Agricultural Communication, Purdue University