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Food by VICE

Why You Should Still Rinse That Pre-Washed Lettuce

You may feel safe going to town on "triple-washed" greens without a second rinse. But here's why that could land you a nasty case of food poisoning.

by Hilary Pollack
Aug 20 2015, 3:11pm

Foto von frangrit via Flickr

To wash, or not to wash? That is the question.

All of these sort of amorphous concepts about germs and pathogens are hard to make sense of when you're staring down at a selection of ripe produce and wondering whether it's really worth the effort to give it that extra rinse. After all, it's not like anything you put in your mouth is truly sterile. And sure, there was that whole E. coli outbreak in spinach in 2006 that killed a few people, and that little aftershock in 2012, but those were mere blips on our cultural radar.

Then you realize that you've already dumped salad dressing all over your spring mix without giving them a rinse in the ol' colander, and it's too late. Oh well. In "pre-washed" labels we trust. And what was that thing your aunt used to say? "God made dirt, so dirt don't hurt?"

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Unfortunately, you may have to tell Auntie Ethel that dirt can hurt. And that dirt loves hiding in your package of baby spinach.

According to new research from the University of California, Riverside, pre-washing and triple-washing are nice ideas, but are not going to save you from a particularly nasty bout of food poisoning when it really comes down to it.

The fatal flaw is in the nooks and valleys found in leafy greens, which are particularly hospitable for little bits of crud to collect in. When companies pre-wash their greens, they use tiny amounts of bleach in the water used to rinse the lettuces, but don't actually apply disinfectant to the surface of each leaf. As a result, researchers found, the unique topography of each piece of spinach can leave about 15 percent of the lot insufficiently cleaned.

Photo via Flickr user nettsu

Photo via Flickr user nettsu

And after the rinsing process, the nasty bacteria that has escaped certain death can continue to grow and spread to other leaves—and to equipment in the processing plant.

Here's the extra-alarming bit: after being pre-washed, 90 percent or more of "adhered bacteria" survived on the baby spinach that researchers observed. It was this very pre-washing, then, that could cause the larger contamination of entire product batches.

"In a sense the leaf is protecting the bacteria and allowing it to spread," said Nichola M. Kinsinger, a post-doctoral researcher who co-headed the project, in a statement. "It was surprising to discover how the leaf surface formed micro-environments that reduce the bleach concentration, and in this case, the very disinfection processes intended to clean, remove, and prevent contamination was found to be the potential pathway to amplifying foodborne outbreaks."

With large-scale outbreaks such as the 2006 event that sickened nearly 200 people in 26 states and killed three, compounded with the rise of antibiotic-resistant superbugs, this new understanding of how pre-washing might not be a problem-solver could be crucial to curbing incidences of food poisoning. Particularly because about one out of five foodborne illness outbreaks occurs in leafy greens.

Thankfully, the answer is simple in this case: rinse 'em. Rinse 'em good.