Before bagged leafy greens wind up on your plate, they are washed, often three times, in a potent chlorine bath. But new research shows the steps that California companies rely on to protect consumers do not kill dangerous bacteria inside the leaves, whereas zapping them with radiation wipes them out.
The debate over how to protect consumers from E. coli and other potentially deadly microbes has intensified since the fall of 2006, when at least 200 people across the nation became ill and three died after eating tainted spinach grown in San Benito County.
Irradiation, which involves bombarding food with high-energy gamma or electron beams to disrupt the DNA of pathogens, has its supporters and critics. But the new research suggests that it may be the only way to penetrate leafy greens and kill bacteria hiding inside.
Although some hamburger meat, poultry and spices are irradiated to kill bacteria, its use on fruits and vegetables to enhance food safety is not permitted in the U.S. Some produce is irradiated for insect control and shelf-life extension. The Food and Drug Administration is considering whether to allow the practice for killing pathogens, which would make it much more widespread.
No health problems have been associated with eating irradiated food. But some consumer groups say its safety is unproven, and have raised concerns about radioactive waste and accidental radiation releases.
Presenting their findings Thursday at the American Chemical Society's annual conference, U.S. Department of Agriculture scientists said irradiation could be key to destroying pathogens in hard-to-reach places inside and on the surface of fruits and vegetables.
"Irradiation kills E. coli where chlorine doesn't," said Brendan Niemira, a microbiologist at the USDA's Eastern Regional Research Center in Pennsylvania who led the research. "We used pretty aggressive levels of chlorine and found they weren't very effective at all. But when you have E. coli inside a leaf, and you irradiate it, the E. coli dies."
Every year, 1 in 4 Americans suffers a food-borne illness. About 14% of cases are linked to fresh produce, and spinach and lettuce are the biggest known culprits, causing 23 outbreaks since 1995. Most of those outbreaks were traced to California, the leading producer of greens.
Some food safety experts say that the ionizing radiation could damage leaves and that consumers won't buy bags of spinach with a radiation logo on the label. Irradiation also could increase processing and handling times.
