Purdue University Develops Two Technologies to Eliminate Food-borne Pathogens

12/10/06 Purdue University researchers are developing two technologies that may be able to prevent future food-borne illness, such as the recent outbreak of E. coli in contaminated spinach. Together, these technologies rapidly detect and eradicate food-borne pathogens.

The first method uses a laser to detect and identify many types of bacteria, and is about three times faster and one-tenth as expensive as current technology.

"A second innovation uses chlorine dioxide gas to kill pathogens on produce, fresh fruits and vegetables. This would be a large step up from current technologies, which mainly involve washing and scrubbing, and cannot completely rid a product of a pathogen like E. coli," said Richard Linton, a professor of food science.

"We can use the laser technology to detect problems more quickly, determine exactly what the pathogen is and where it came from," Linton said."As for using this gas as a disinfectant, I would say that in my 13 years of doing research, it is 10,000 to 100,000 times more effective than any process I have seen."

While different in nature, the methods have the common goal of keeping food safe and preventing people from getting sick, and have each progressed to the point where they could be commercialized, Linton said. Patents are pending on both technologies, and the laser technology is available for licensing.

Arun Bhunia, also a professor of food science, leads the team that developed the laser-based technology, called"Bacteria Rapid Detection Using Optical Scattering Technology." The process works by shining a laser though a petri dish containing bacterial colonies. A computer program determines the type of bacteria by analyzing how light is refracted—a unique"scatter pattern."

Bhunia has shown his technology is capable of recognizing Listeria monocytogenes, a microbial pathogen that is the leading cause of food-borne illness. The pathogen has a high mortality rate—one in five—and kills about 500 people each year. E. coli, which has the second highest mortality rate, kills less than 1 percent of those infected.

Industry has shown interest in Bhunia's technology, as well as the chlorine dioxide work done by Linton and the project's co-leader, Mark Morgan, a professor of food science.

"We are currently working on an industrial tunnel system to apply the gas to produce," Morgan said. His team is also investigating using the gas to sterilize processing equipment."This would be very helpful, as it could speed up the sterilization process and eliminate the heat energy currently used for such processes."

Previous results have shown the gas to be highly effective at killing microbial pathogens. The largest obstacle remaining is optimizing the system to dispense the appropriate amount of chlorine dioxide, Morgan said. Enough of the gas must be deployed to kill the pathogens, but too much can cause a decrease of quality in the product, such as browning of leafy greens.

"If the product is safe, but nobody will eat it, that's not what we want," Linton said."We are always thinking in terms of, "Will this work for industry?' In this case, I believe the answer is yes. I would like to see this technology used regularly by industry in a couple years from now."

Both technologies have the potential to help prevent food-borne illness, Linton said, but he also noted that following proper agricultural practices is as important, if not more important, for food safety.

Since E. coli, or Escherichia coli, is found in the intestines of warm-blooded animals, it does not naturally contaminate most produce. Therefore, following more stringent sanitary policies, as well as practicing better manure and water management, can go a long way to help prevent future outbreaks, Linton said.

E. coli is especially problematic because it only takes as few as 10 cells to infect humans. Other pathogens, like salmonella, need thousands or millions of cells to cause infection.

Bhunia's technology is further described in an article published this summer in the Journal of Biomedical Optics. Linton and Morgan have been working with chlorine dioxide for years, and have several published studies, one of which appeared in the Journal of Food Protection in 2004.