The Produce Marketing Association recommends washing fruits and vegetables at home under the tap. The items are cleaned by the abrasive action of the water. Soaking isn't recommended, and chemical scrubs aren't necessary, the group says.
But according to new research, described today at the 235th national meeting of the American Chemical Society, washing alone just isn't enough. But irradiation is.
The Los Angeles Times quoted Brendan Niemira, a microbiologist at the USDA's Eastern Regional Research Center in Pennsylvania who led the research: "Irradiation kills E. coli where chlorine doesn't. 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."
Irradiation exposes food to a source of electron beams, creating positive and negative charges. It disrupts the genetic material of living cells, inactivating parasites and destroying pathogens and insects in food, including E. coli and Salmonella, as described in a press release from the American Chemical Society.
Although some hamburger meat, poultry and spices are irradiated to kill bacteria in the U.S, producers are not allowed to irradiate fruits and vegetables for food safety.
The practice has its critics. Foods cannot be certified organic if they are irradiated. The LA Times article said food safety researchers are concerned that high doses of irradiation will not only kill pathogens but also cause cell damage.
For the research, E. coli bacteria was pushed into the leaves of spinach and lettuce with a vacuum process. The leaves were then treated with either a three-minute water wash, a three-minute chemical treatment or irradiation. The study showed that washing with plain water was not effective at reducing the levels of the pathogen on either spinach or lettuce. The chemical treatment, a sodium hypochlorite solution, did not result in significant reductions of E. coli cells in spinach leaves, and ionizing radiation significantly reduced the pathogens in both the spinach and the lettuce leaves.
There was no mention of methods to try and prevent the contamination in the first place.
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