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How clean is bagged salad?

Last updated: March 2010

You might think that "pre­washed" and "triple-washed" salad greens sold in plastic clamshells or bags are squeaky clean. But our recent tests found room for improvement.

No, we didn't find pathogens such as E. coli O157:H7, listeria, or salmonella. With our small sample size—208 containers representing 16 brands purchased at stores in Connecticut, New Jersey, and New York—we didn't expect to. (The Department of Agriculture, in a test of more than 4,000 samples of loose and packaged salad in 2008, found salmonella in two of them. All of our tests included packaged greens.)

But in our samples, all of which were within their use-by date, we did find bacteria that are common indicators of poor sanitation and fecal contamination—in some cases, at rather high levels.

We tested for total coliforms and for other bacteria, including enterococcus, that are better indicators of fecal contamination. Federal action limits exist for indicator organisms in water, raw meat, milk, and some processed foods, but not produce. Those organisms are typically used to gauge possible pathogen contamination.

Several industry experts we consulted suggested that for leafy greens, an unacceptable level of total coliforms or enterococcus is 10,000 or more colony forming units per gram (CFU/g) or a comparable estimate. In our tests, 39 percent of samples exceeded that level for total coliforms and 23 percent for enterococcus.

Results varied widely among samples, even within the same brand, from undetectable levels of those bacteria to more than 1 million CFU/g. Packages with higher bacteria levels had similarities. Many contained spinach and were one to five days from their use-by date. Packages six to eight days from their use-by date fared better. Whether the greens came in a clamshell or bag, included "baby" greens, or were organic made no difference.

Brands for which we had more than four samples, including national brands Dole, Earthbound Farm Organic, and Fresh Express, plus regional and store brands, had at least one package with relatively high levels of total coliforms or enterococcus. Our tests were conducted at an outside lab over two weeks in August and September with financial support from the Pew Health Group, which is working to improve food safety.

Consumers Union supports Senate Bill 510, the Food Safety Modernization Act, that would, among other things, require the Food and Drug Administration to set stronger produce safety standards. Those should include performance standards for indicators of fecal contamination, such as generic E. coli and enterococcus.

What you can do

  • Buy packages as far from their use-by date as you can find.
  • Even if the bag says "prewashed" or "triple-washed," wash the greens yourself. Rinsing won't remove all bacteria but may remove residual soil.
  • Prevent cross contamination by keeping greens away from raw meat.

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