A research team at the University of Massachusetts Amherst has received almost $500,000 to develop faster methods for detecting and separating microbial contamination from food.
The researchers, led by food scientist Sam Nugen, received the $495,950 grant from the US Department of Agriculture's National Institute of Food and Agriculture (NIFA).
They will create beads made of magnetically charged cobalt nanoparticles coupled with microbe-specific phages, or viruses, which bind to specific bacteria such as Listeria, E. coli or Salmonella.
Nugen said the magnetic virus-bacteria beads can then be quickly removed from liquid samples with a magnet.
“The cobalt nanoparticle beads bind to the phages much more strongly than antibodies, and cobalt is very strongly magnetic so the method works quickly, much faster than other magnetic nanoparticles such as iron, for example.
“Using the iron in the retrieval process might take overnight, but the cobalt works in 30 seconds.”
Unpasteurized whole milk testing
The UMass Amherst researchers have shown that their methods work in non-food liquids; the NIFA grant will allow them to begin testing in food samples such as unpasteurized whole milk.
The group will be inoculating spinach leaves with E. coli and determining how efficiently the bacteria can be separated from the sample.
Techniques should help food manufacturers avoid costly waiting for safety tests before products can be sold, said the team.
Nugen said current techniques can take several days to a week before they identify possible bacteria.
"The current method of testing a batch of chocolate pudding, for example, means collecting a sample, sending it to a lab where a broth is prepared and any bacteria found are plated and grown.
“Meanwhile, the company has to warehouse its pudding during the testing period. We're working on separating bacteria from a food sample much more quickly, in minutes, so technologies that already exist for testing a clean sample can be used.
“It should break the bottleneck in the system and save considerable time and expense."
About 46% of foodborne illness outbreaks come from fresh fruit and vegetables, which can't be held for days of testing without losing freshness and nutritional quality, added Nugen.
Work in cereals and grains
The researchers are also working on detecting disease-causing microbes in dry food samples such as cereals and grains by sampling air sucked from spaces between individual bits as they pass by on a conveyor belt.
Particles collected will be pulled into a "wetted cyclone" filter from which a clean sample can be prepared for microbial testing.
Nugen, food scientists Amanda Kinchla, doctoral student Juhong Chen, with nanochemist Vincent Rotello, will run a pilot air-sampling project for separating microbes from dry cereals at Holliston Technologies in Owensboro, Kentucky.
They hope this method will allow manufacturers to check a truckload of nuts as they arrive from the fields or prepared cereal bits as they move by on a conveyor belt.
"So if I develop a technique for detecting the signature of a replicated virus that had been growing in E. coli, I can also tell whether there ever was E. coli in that sample," said Nugen.
"This study is all about separation but we're setting it up so that this strategy of rapid detection can be an end product of our research."