martes, 8 de julio de 2008

Salmonella can ride water into tomatoes

Washing tomatoes in cold water should be avoided.
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, and maintained at room temperature pathogens have time to multiply.That doesn't mean people shouldn't wash their tomatoes they should, just probably not in cold water.
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. Florida's agriculture department on July 1 begins enforcing so-called "tomato best practices," farming and handling guidelines that leading growers pushed the state to formally adopt, and that many farms voluntarily began following in the past year.
Washing fresh produce under running water is a commonsense consumer defense. "We know you can wash off some Salmonella sp.," 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."Water is an automatic first suspect. Was clean water used to irrigate, mix pesticides sprayed on crops, wash down harvest and processing equipment, and wash field workers' hands?Then in packing houses, tomatoes often go straight into a dump tank, flumes of chlorinated water for a first wash. To guard against Salmonella washed into the water in turn being sucked into the tomatoes, producers often keep wash-water 10 degrees warmer than the incoming crop, says food-safety scientist Keith Schneider of the University of Florida, also part of FDA's tomato initiative.
Beyond packing houses, the industry points to cases where suppliers were shipped unwashed, warm tomatoes and dunked them in ice-water baths to firm them for further processing.
Another question: How often does the water have to be changed? Organic material, dirt, leaves and other sediment reduce the chlorine's effectiveness.Salmonella may be particularly hard to prevent in a variety of crops because birds, reptiles and amphibians carry it the same reason children should wash their hands after handling a turtle, iguana or frog. The tomato industry's guidelines already advise surrounding fields with bare soil "buffer zones" to discourage reptiles.
Aporte: Guillermo Figueroa

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