To Foil Salmonella, Cook Your Tomatoes

Why doesn't washing tomatoes make them safe to eat? That's Question No. 1 as restaurants and supermarkets dump fresh tomatoes, and federal inspectors race to pinpoint the source of a salmonella outbreak in fresh tomatoes that has spread to 17 states, sickening at least 167 people.

FDA's southwest regional research lab in Irvine, Calif., where microbiologists are working to trace the source of the outbreak.

Tomatoes are suspected to be responsible for salmonella related illnesses in at least 17 states.

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The unpleasant answer: Bad bugs like salmonella don't just lie on the surface of plants. They may also enter in, where they can’t be washed away or killed by sterilizing solutions commonly used in produce processing. Some state and local health departments, as well as news media, have reported that it's OK to eat tomatoes as long as they’ve been washed. Not so, says Doug Powell, a plant pathologist and director of the International Food Safety Network at Kansas State University. Tomatoes and canteloupes, which both have soft, porous skin, can absorb water during processing, and also may absorb pathogens in irrigation water. It's not known if that happened in this case, Powell says. But that's all the more reason to shun tomatoes. "In these situations, it's important to say that washing's not enough. You gotta cook it."

The bugs-in-hiding problem surfaced in September 2006, when e. coli contamination in fresh spinach sickened at least 200 people and killed several. The strain was traced to cattle in nearby fields, as well as a wild boar. But that was just the most visible of dozens of instances in which spinach or other fresh greens had become contaminated. Since 1995, there have been at least 20 outbreaks associated with leafy greens, according to the Food and Drug Administration. Nonleafy produce has its problems, too. This February, canteloupes sold in California were recalled because they were tainted with salmonella. Powell's blog, with the wonderful name of barfblog, is a great source for solid scientific advice on food safety.

The FDA has listed tomato-producing states that aren't implicated in the outbreak so far, but in many cases it's impossible to figure out where supermarket tomatoes come from.

Buying organic doesn't guarantee that fruits and veggies are pathogen-free; neither does buying produce in a farmer's market, since in some markets farmers can sell products they've bought from wholesalers. Growing your own would be good, but hurry; the tomato plants are all but gone at most local garden stores. The safest bet: Cooked tomatoes. Canned is fine. So are fresh tomatoes that have been cooked to the boiling point, since heating past 160 degrees kills pathogens.