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with Elaine Magee, MPH, RD

Elaine Magee's blog has now been retired. We appreciate all the wisdom and support she has brought to the WebMD community throughout the years.

Wednesday, February 3, 2010

Bagged Salad and Bacteria: What YOU Can Do

Pretty much the last thing you want on your salad greens is bacteria that tends to reside in human feces. Many people, including me, buy the pre-washed spinach and romaine lettuce in bags expecting them to be clean and bacteria-free.

Well, Consumer Reports pretty much blew this belief out of the water. According to their recent tests, 39 percent of packaged salad green samples exceeded the level for total coliforms considered acceptable and 23 percent exceeded this level for enterococcus bacteria…bacteria that Consumer Reports describes as “better indicators of fecal contamination.” Shocked and concerned? I know I am. The first question that pops into my mind is what type of feces are we talking about – animal or human (not that any type of fecal bacteria is more desirable than another)?

What did researchers look for?

  • Total coliforms: Water is commonly tested for total coliforms to indicate the general quality of the water and the likelihood the water is fecally contaminated. According to the US Environmental Protection Agency (EPA), “Coliforms are a group of bacteria, most of which are harmless. At first glance, it might seem strange that a harmless group of bacteria such as coliforms could cause such commotion. But like police tape and chalk outlines, coliform bacteria are often found at the scene of a crime even though they are not themselves criminals.
  • Enterococcus: One of the bacteria they tested for is enterococcus. If this refers to enterococcus faecalis then we are talking about an extremely durable bacterium that normally lives in the gastro-intestinal tracts of humans. How durable are we talking about? It can survive 77 days on dirt. Food technologists from the Agricultural Research Service Produce Quality and Safety Laboratory discovered recently that bacteria can actually become hardier and more likely to survive exposure to stomach acid when the bacteria are sitting in air-starved containers/bags while in the presence of nutrients, which are coming from the cut leaves of lettuce.

What are the symptoms?
What types of symptoms can someone expect from bacteria contamination in their salad greens? It all depends on the bacteria. If it’s enterococcus faecalis, someone might experience fever, confusion, urinary tract infection with painful urination and blood in urine. The bacteria responsible for the food poisoning outbreak with raw spinach in previous years, E. coli, can cause severe stomach cramps and diarrhea, nausea and vomiting.

What can we do to decrease our risk of consuming high amounts of bacteria on salad greens (bagged or otherwise)?

  • Buy bags of salads greens from the back of the shelf and as far from their use-by date as you can get your hands on. Consumer Reports found in their tests that the packages one to five days from their use-by date were more likely to have higher bacteria levels.
  • In light of this new information about washed and packaged lettuce, particularly spinach, is it better to buy a head of lettuce? It seems like it might be better to buy it as a head since the bags, due to the low oxygen environment in the bag (which encourages the lettuce to stay fresh) seems to encourage bacteria growth if they are improperly stored (unrefrigerated for an extended period).
  • Try to buy ready-to-eat salads and salad green from stores where they appear to be properly stored at cold temperatures and keep them at cold temperatures when you are storing them at home.
  • Wash your greens yourself when you bring them home from the store, even the prewashed or triple-washed ones. Rinse them well in clean, running water and pat them dry or use a salad spinner to remove excess water. If you aren’t using them immediately, you can put the salad greens in a clean bag, not the same bag you bought them in. The longer the greens sit in the bags and the closer to their use-by date, the more chance the bacteria has to multiply.

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Posted by: Elaine Magee, RD at 6:57 am

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