Pick a tomato in the blazing sun and plunge it straight into cold water. If that happened on the way to market, it might be contaminated.
Too big of a temperature difference can make a tomato literally suck water inside the fruit through the scar where its stem used to be. If salmonella happens to be lurking on the skin, that's one way it can penetrate and, if the tomato isn't eaten right away, have time to multiply.
That doesn't mean people shouldn't wash their tomatoes -- they should, just probably not in cold water.
But as the Food and Drug Administration investigates the nation's outbreak of salmonella from tomatoes, the example shows the farm isn't the only place contamination can occur -- and checking things like water quality and temperature control in packing houses and other supply stops is one key to safety.
Raw fruits and vegetables are crucial to a healthy diet. But they're also the culprits in a growing list of nasty outbreaks: E. coli in spinach and lettuce. Hepatitis A in green onions. Cyclospora in raspberries. Salmonella in cantaloupe. Shigella in parsley.
This newest salmonella outbreak is the 14th blamed on tomatoes since 1990.
Preventing future illnesses depends on learning how salmonella sneaks onto and inside tomatoes, which might seem to be pretty well protected by their smooth waxy skin. Yet scientists have few answers, prompting the FDA last year to begin a Tomato Safety Initiative that is studying industry practices in Virginia and Florida, origin of several previous outbreaks.
The FDA likewise wants the authority to set mandatory safe-handling rules, what it calls "preventive controls," for growers and suppliers of foods linked to repeated outbreaks of serious illness, such as tomatoes and leafy greens. Congress hasn't yet acted on that request.
Further complicating the picture, budget woes mean the FDA's inspections of food-producing facilities have plummeted by 56 percent between 2003 and last year.
There are some common themes when fresh produce sickens, either from salmonella -- bacteria that live in the intestinal tracts of humans and numerous animals -- or other microbes: Water sources, worker hygiene and wildlife or domestic animals near fields are frequent culprits because they involve points where safety systems can easily break down.
Washing fresh produce under running water is a commonsense consumer defense.
"We know you can wash off some salmonella," says Virginia Tech food microbiologist Robert Williams, who accompanied FDA scientists to Virginia farms as part of the tomato initiative. But, "nobody's ever shown it washes off all salmonella."
Print this story
E-mail this story
