Study: Irradiation Doesn’t Harm Produce

X-ray technology is effective in killing bacterial pathogens in leafy greens without causing undesirable changes in product quality, say two Michigan State University (MSU) researchers.


Bradley Marks and Sanghyup Jeong, who are both based at MSU, say that X-rays can kill bacterial pathogens such as E. coli 0157:H7 and Salmonella on the most delicate vegetables as well as extending the shelf life of the produce. E. coli 0157:H7 is the strain found on spinach in the fall of 2006 that killed three people.

Irradiation from other sources has been used for years to protect ground meat and other products. The process exposes foods to ionizing radiation that kills insects, moulds, and bacterium, and the technology can kill up to 99% of pathogens.

FDA recently published a final rule allowing the use of irradiation for iceberg lettuce and fresh spinach; the technology can already be used with other foods such as spices, poultry, and shellfish including oysters, clams, and scallops.

The MSU researchers said that they have been applying a higher dose than that used for medical X-ray imaging, but a lesser dose than that used by competing irradiation methods. “That means less protective shielding is necessary, so the equipment is more compact and food companies can install it at their processing plants,” claim the researchers.

The X-ray technology, continued the MSU scientists, is being tested in the university’s biosafety processing facility and is being commercialized by Rayfresh Foods of Ann Arbor, MI.

Peter Schoch, CEO of Rayfresh Foods, says the potential for widespread contamination is compounded by the mingling of greens from different sources in processing plants. He claims that food irradiation based on the use of gamma rays from radioactive material or machine-generated electron beams tends to cause cellular damage and visually degrade food, whereas irradiation using X-rays promise a gentler, more scalable approach.

Schoch says the company has recently won its first contract to build an X-ray machine to treat ground beef for Omaha Steaks, which inspected the prototype at MSU. “The university’s validation work was pivotal in winning that first order,” he adds.