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Pre-Washed Spinach Is Still Covered In Bacteria

08/31/2015 02:24 EDT | Updated 08/31/2015 02:59 EDT

If you're used to ripping open a bag of greens and pouring them into a bowl like cereal, you might want to stop and take them to the sink instead.

Researchers at the University of California, Riverside say the peaks and valleys on baby spinach leaves make industrial pre-washing ineffective.

Using the same cleaning solution processing plants use, with 50 to 200 parts per million of bleach to the water, the researchers washed batches of baby spinach leaves and found 90 per cent of bacteria remained on the leaves' surface, Medical Daily reports.

Due to the naturally deep bumps and ridges on spinach leaves, the bleach-based disinfectant fails to fully cover the leaf's surface, regardless of how many times it is washed in a plant.

“In a sense the leaf is protecting the bacteria and allowing it to spread,” said Nichola M. Kinsinger, a post-doctoral researcher who worked on the study.

Kinsinger and University of California professor, Sharon Walker, are working on a product designed to help kill remaining bacteria on spinach greens at the time of processing. The Boston Globe reports the material will be added to rinse water or as a costing on the processing machines.

Earlier this year, three organic food companies recalled spinach products in Canada and the United States over listeria concerns. And the Toronto Star reports that 92 Canadians suffered from intestinal illnesses between May and August of this year, though the Public Health Agency of Canada has not revealed the cause of the illness.

On their site, Health Canada warns Canadians about previously contaminated produce, including iceberg lettuce, pre-cut ready-to-eat salads and spinach greens. Still, they say ready-to-eat, bagged, pre-washed leafy greens do not need to be washed again.

Spinach is high in folate, vitamin K, iron and lutein. Eating just a cup of raw spinach a day can even help slow the effects of an aging brain.

So you definitely want to eat spinach, but whether you pick it yourself or buy the bagged version, it couldn't hurt to give your greens a good rub and rinse before you eat them raw. Or, better yet, cook them. It only takes 15 seconds at 160°F to kill all the bacteria found in a bunch of greens, the experts at Eating Well say.

Do you eat salad greens straight out of the bag or do you rinse them before serving? Let us know in the comments below.

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