Taking aim at bacteria
From private corporations and public-funded institutions, the research takes on added urgency with the September 2011 listeria outbreak traced to Colorado-grown cantaloupe continuing to be in the headlines. According to the last update from the Centers for Disease Control, 150 people in 28 states were infected, and 32 people were killed, along with one woman who reported a miscarriage.
The 3M Company is focusing on solutions that detect the presence of pathogens, said Niki Montgomery, global marketing manager for 3M Food Safety. The company’s newest technology is the 3M Molecular Detection System, designed for pathogen testing of food and beverages.
The system includes individual pathogen-specific test kits, computer software and a compact USB-compatible instrument that can accommodate between one and 96 samples in color-coded tubes, said Montgomery. The system tests for pathogens by combining two technologies – isothermal DNA amplification and bioluminescence detection to identify the presence of specific pathogens.
“It targets, amplifies and assesses genetic material in enriched samples and then uses light technology to measure the results in real time,” Montgomery explained.
Where 3M focuses on detection, Wisconsin-based BioIonix has placed its emphasis on disinfection of water used in processing. Its food safety disinfection system “uses catalysts to create a complementary combination of disinfectants directly in the flume water stream itself,” said Jim Tretheway, company president and CEO.
The process draws on oxygen and chlorine-based disinfectants similar to those of more expensive chemicals, “but without the cost of dispensing complications associated with such supplies,” he said.
University researchers are engaged in the battle against bacteria on a variety of fronts. In December, Michigan State University was awarded three USDA grants of nearly $3 million to help fund the work of the newly formed MSU Food Safety Group. One of the grants is targeted at reducing contamination from E. coli, listeria and salmonella in processed produce. The UC-Davis Center for Produce Safety and the National Center for Food Safety and Technology at the Illinois Institute of Technology are both extremely active in researching food safety through the growing and processing chain.
At the University of Georgia’s Center for Food Safety, Director Michael Doyle and researchers are working with a process that uses a wash combining levulinic acid and sodium dodecyl sulfate. The goal is to identify a substance that kills bacteria without affecting produce appearance.
Achieving that desired combination of safety and appearance is a challenge, said Doyle. That’s especially true in seeking a substitute for chlorine in wash water while considering the specific needs of fresh-cut produce.
“Most disinfectants that are chemically based don’t work very well when you get down to refrigeration temperatures,” said Doyle. “The fresh-cut process takes place at close to freezing – 34 degrees or less. Our experience has been that about 8 degrees Celsius, which is about 46 degrees Fahrenheit, is the cut-off where we see any of these chemical disinfectants stop working very well.”
The nature of fresh cut produce poses other obstacles to sanitation. Disinfecting flume water is relatively easy, but providing microbial control on the produce itself is a tougher chore.
“One of the biggest challenges to disinfecting fresh-cut produce is the very high organic loads that are released by the cutting process,” Tretheway said. “Chopped lettuce isn’t a major problem, but products like diced cabbage and onion, with their high cut area-to-volume ratio, are real challenges. These organics preferentially use up most disinfecting agents, so little of their (agents’) power remains for disinfection itself.”
Exhibit A just happens to be the source of last fall’s contamination outbreak: cantaloupe, which is conducive to the growth of listeria microbes.
“The pH of cantaloupe is close to neutral, somewhere between 6 and 7,” said Doyle. “There is not anything in the cantaloupe that would prevent listeria from growing. If it gets inside the cantaloupe, it can grow very well, especially if it’s listeria monocytogenes. It grows at refrigeration temperature and will grow at close to 32 degrees.”
What breakthroughs are on the horizon? Irradiation may be technically feasible, but so far has not been accepted by consumers. 3M plans to release an individual pathogen-specific test for listeria in 2012. BioIonix is branching out to work on control of spoilage organisms, particularly mold and yeast. Other priorities include reducing the level of harmful bacteria in nature, particularly E. coli in ruminant animals.
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–By Lee Dean, Fresh Cut Contributor
Technology photos: Courtesy 3M
