The New York Times is reporting tonight that the produce industry — rocked by several major recalls in recent years linked to outbreaks of salmonella, E. coli and other bacteria — has been searching for a better way to wash the lettuce, spinach and other greens it bags and sells in grocery stores and to restaurants.

Now, the nation’s leading producer of bagged salad greens, Fresh Express, says that washing them in a mild acid solution accomplishes the task.

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.

Mike Burness, vice president of global quality and food safety at Chiquita Brands International, which owns Fresh Express, said,

“We do believe it provides a much higher level of effectiveness versus the chlorine sanitizers in use today. 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.

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.