Avoiding E. ColiPosted: November 17, 2011
After the recent E. coli food poisoning scare in Europe, a coworker told me that she was washing her raw fruits and vegetables in a diluted bleach solution to guard against foodborne illnesses. When I found this dubious advice echoed online, alarms went off in my head. This is where the Internet can actually be a dangerous source of information—since unvetted ideas get presented as fact.
I called Christine M. Bruhn, PhD, director of the Center for Consumer Research at the University of California, Davis, to discuss this latest ill-founded advice. She said emphatically, “Never use bleach on food! To be effective and safe, you would have to measure a bleach solution exactly. Yet we have found that people guess instead—so bleach amounts wind up too low to be effective at killing pathogens or, worse, too high to be safe for human consumption.” Even if you think that you’re rinsing off the bleach afterward, fruits and vegetables are porous—so they can absorb bleach.
What to use instead: Simple running water. Dr. Bruhn explained that running water alone removes the dirt and about 90% of the bacteria and other microbes from produce. Given the irregular, dimpled, porous nature of fruit and vegetable skins, there is no real way to remove 100% of potential contaminants, she noted—but getting most of it off certainly reduces your risk.
Tempted to use soap or dish detergent? Don’t. These are not meant to be consumed, Dr. Bruhn said, and the FDA has not evaluated the safety of residues that soap and detergent can leave behind. Some people rinse produce in vinegar but, while not unsafe, this no more effective than plain running water and can impart an unpleasant taste and smell. As for commercial produce-washing products, some studies show that they remove slightly more bacteria than water alone, but results are inconsistent—so Dr. Bruhn suggested skipping them and saving your money. Soaking produce in a bowlful of water is not recommended, either, because it basically allows produce to take a bath in its own dirt and bacteria… and if the container used for soaking isn’t completely clean, cross-contamination can occur.
More self-defense strategies: The following food-handling guidelines may not be new to you (though they were to my coworker), but given the potentially serious consequences of consuming contaminated produce, the information is well worth reviewing.
Before handling raw fruits and vegetables…
- Wash your hands in warm, soapy water for at least 20 seconds. (Surprisingly, one of Dr. Bruhn’s studies showed that nearly half of survey respondents did not always do this before handling fresh produce!)
- For chopping, use a cutting board and knife dedicated only to fruits and veggies. Keep a separate board and knife for cutting meat.
- Prior to each use, sanitize your kitchenware—cutting board, knife, colander and/or scrub brush—by running them through the dishwasher or placing them in boiling water for 20 seconds. Or—provided you measure carefully!—you can rinse the kitchenware with a solution of one teaspoon of bleach mixed with four cups of water, followed by a very thorough plain-water rinse.
How to wash…
- Remove and discard outer green leaves from lettuce, cabbage and cauliflower before washing.
- Wash produce just prior to using—washing it before storing promotes spoilage.
- Thoroughly wash all produce, including produce that has been organically grown, purchased from a farmer’s market or even from your own garden. What about fruits and vegetables with tough rinds or skins that you won’t end up eating? Wash those, too—otherwise, bacteria can transfer from the food’s surface to the knife and into the flesh upon slicing, Dr. Bruhn explained.
- Prewashed, bagged and sealed produce generally is safe to eat without further washing if it has been kept refrigerated and is consumed prior to the “use by” date—though of course you can wash it again if you wish, following the same guidelines as for other produce. Precut or prewashed produce sold in open containers or bags, including those bags with tiny holes, should always be washed again.
- Don’t plop fruits and veggies in the sink while you wash them. Better: Hold produce in your hands or place it in a colander.
- Wash produce under running water—it doesn’t matter if it is hot or cold. How long you should wash depends (for instance, on the size of what you’re washing), but the point is to be thorough. Rub briskly with your hands to help remove dirt and surface microorganisms… for produce that has a firm skin or a rind, such as squash or melon, scrub with a brush under running water. (When I asked Dr. Bruhn if scrubbing these with baking soda would help remove bacteria, she said that it might but she hadn’t seen it tested.)
- Trim hulls and stems from items such as strawberries, tomatoes and peppers after washing.
- Dry your freshly washed produce with a fresh, clean towel or paper towels—not with a dishtowel that has already been used to dry off anything else.
Christine M. Bruhn, PhD, is the director of the Center for Consumer Research at the University of California, Davis, and coauthor of the consumer publication Safe Handling of Fruits and Vegetables (for a free download, visit http://anrCatalog.ucDavis.edu/foodsafetypreservation/8121.aspx). Dr. Bruhn’s research focuses on consumer issues in food safety and quality.