The company plans to announce on Friday that it is abandoning the standard industry practice of washing leafy greens with chlorine and has begun using the acid mixture, which it claims is many times more effective in killing bacteria. The new wash solution, called FreshRinse, contains organic acids commonly used in the food industry, including lactic acid, a compound found in milk.
“We do believe it provides a much higher level of effectiveness versus the chlorine sanitizers in use today,” said Mike Burness, vice president of global quality and food safety at Chiquita Brands International, which owns Fresh Express. “This technology was developed to raise the bar.”
Mr. Burness said the breakthrough came when researchers at the company combined lactic acid with another organic acid, peracetic acid. The two together, he said, worked much better than either one separately and also achieved markedly better results than chlorine.
He said that the company had already begun using the acid mixture, diluted in water, to wash produce at one of its processing plants. He said the company’s four other plants would be converted to use the mixture by early next year.
Scientists not involved in the Fresh Express project and industry executives said that while they were not familiar with the company’s research, if its claims were borne out, the new wash mixture could be a significant improvement.
“The holy grail of fresh-cut produce is finding a wash step that’s going to be more effective than chlorine at reaching those bacteria that chlorine can’t quite reach,” said David Gombas, senior vice president of food safety and technology at the United Fresh Produce Association, a trade group. “If they’ve achieved that, that would be a significant advance in ensuring the safety of fresh-cut vegetables.”
Fresh Express is a member of the produce association, but Mr. Gombas said that he was not aware of the company’s plans or the results of its research.
The leafy greens industry was forced to confront its food safety shortfalls after a deadly E. coli outbreak in 2006 caused by spinach produced at a California farm. Since then, there have been numerous outbreaks and recalls involving leafy greens. Earlier this year, romaine lettuce grown in Arizona caused a major E. coli outbreak.
Fresh Express issued three separate recalls this year of packaged salad greens after random testing found salmonella, E. coli and listeria in bags of its products.
Fresh Express said that its new cleaning mixture was 750 times as effective as chlorine in killing bacteria suspended in wash water. It is also at least nine times as effective as chlorine in killing bacteria that has become attached to the leaves of produce.
Mr. Burness said that lettuce and other greens were cut up in the company’s plants, washed in water containing the acid mixture, typically for 20 to 40 seconds, then rinsed, dried and bagged. He said another advantage is that the acid wash did not bleach the greens, making them pale in color, as chlorine can.
The company said that it planned to license the mixture for use by other producers.
Fresh Express has not published its research, so food safety experts said on Thursday that they were unable to adequately evaluate the company’s claims.
Fresh Express said that it had informed the F.D.A. about its use of the acid wash mixture, but that it was not required to get approval for the switch because the ingredients were already approved for use in the food industry.