How Clean Is Your Pre-Washed Spinach? Probably Not As Clean As You'd Like


If you nosh on spinach right out of the bag, you might want to think twice. (Photo: iStock)

Labels like “thoroughly washed” and “triple washed” make us feel comfortable chowing down on pre-washed baby spinach straight from the container. But researchers from the University of California, Riverside, say we might want to rethink that habit.

They discovered that the small peaks and valleys in baby spinach leaves can harbor bacteria — even during the washing process they often undergo in food-processing plants. This, researchers say, could be an important reason why there have been several outbreaks of E. coli and salmonella in pre-washed baby spinach.

The findings were presented Wednesday at the American Chemical Society National Meeting & Exposition.

Pre-washed baby spinach is typically treated using a bleach disinfectant. But, researchers discovered, the shape of the baby spinach leaf means that 15 percent of the leaf’s surface may only see a very small percentage of the disinfectant. That remaining bacteria, which can include E. coli, salmonella, and Listeria monocytogenes, can survive, grow, and spread to the other leaves.

Here’s the freaky part: After researchers rinsed baby spinach leaves under the typical disinfectant, nearly 90 percent of bacteria were still attached to (and alive on) the leaf’s surface.

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While the news is shocking to most people, “this is not a surprise to many of us in the food safety arena,” Mike Doyle, director of the Center for Food Safety at the University of Georgia, tells Yahoo Health.

The danger in this bacteria remaining is that it can cause outbreaks of food-borne illness, which he says are more common than we realize. “There are many outbreaks that go unreported or uninvestigated because the CDC can’t investigate them all,” he says.

The realization that spinach could cause food-borne illness reached national consciousness in 2006, when nearly 200 people from 26 states were infected with a strain of E. coli contracted from fresh spinach. Three people died from that outbreak. Fresh spinach was also involved in an outbreak in 2012 that infected 33 people in five states.

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Unfortunately, washing your pre-washed baby spinach before eating it doesn’t make a difference, says Benjamin Chapman, PhD, an assistant professor and food safety extension specialist at North Carolina State University.

“Rinsing isn’t going to do a whole heck of a lot for food safety,” Chapman tells Yahoo Health — it just may remove dirt or other physical objects that you can see. Cooking the spinach, however, will kill potentially harmful bacteria.

But what about the whole “triple wash” label? Does that make pre-washed spinach safer? Chapman says there’s some confusion about what it means. Companies don’t triple wash spinach to disinfect it, he explains — they do it to reduce the likelihood of cross-contamination from one piece of spinach to another during the washing process.

So, what does this mean for consumers? Experts are mixed. Doyle says he doesn’t eat raw spinach because of the risks, but Chapman eats pre-washed baby spinach out of the bag.

“From a health standpoint, eating fruits and vegetables sometimes outweighs the risk,” Chapman says. However, he says he wouldn’t feed raw spinach to a person who is immunocompromised or elderly, just to be safe.

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