Published on 11/11/98

Risky Diet: Eating Raw Sprouts Can Cause Illness

Larry Beuchat rarely eats raw sprouts. And nothing he has seen in his lab encourages him to eat more.

"There's certainly a risk," said Beuchat, a food microbiologist with the University of Georgia College of Agricultural and Environmental Sciences.

Raw sprouts are popular in salads, sandwiches and other foods. They're also cooked as an ingredient in a number of foods, particularly stir-fried and sauteed dishes.

The cooked sprouts don't worry Beuchat. But eating them raw, he says, poses a risk of food-borne illness. His research at the UGA Center for Food Safety and Quality Enhancement in Griffin, Ga., is at the heart of his concerns.

"We've done quite a lot of work with both the alfalfa seeds and mature sprouts," he said.

The U.S. Food and Drug Administration has concerns about raw sprouts as a source of food-borne illness. Several outbreaks of Salmonella and E. coli have been connected to raw sprouts.

Beuchat and his graduate students have scrutinized sprouts throughout conditions normally used to grow and market them.

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E.coli O157:H7

They've looked for ways to control pathogens, such as Salmonella and E. coli 0157:H7, that cause food-borne illness. They've tried all kinds of sanitizers -- chlorine, chlorine dioxide, hydrogen peroxide, diluted ethanol and commercial products -- to ensure raw-sprout safety.

"We haven't been successful in killing the organisms to the degree we'd like," Beuchat said. "All of the sanitizers have some effect on the pathogens, but none eliminates them."

The problem with anything short of complete success in eliminating pathogens from seeds is the potential for a bacterial explosion as the sprouts grow.

"If you miss only one or two pathogenic bacteria on the seeds, they can multiply to very high numbers," Beuchat said. "You can have pathogen numbers of 1 million to 10 million per gram of sprouts during the three to four days of production."

Beuchat has mainly studied alfalfa sprouts, the kind most commonly used in salads and sandwiches. Mung bean and soybean sprouts are mostly used for cooked dishes. The many other kinds of sprouts include broccoli, clover, onion, radish and sunflower.

To grow sprouts, seeds are kept constantly wet and at room temperature (65 to 75 degrees) for three to four days. Those same conditions are ideal for bacterial growth.

Beuchat said the seeds can become contaminated with a pathogen anywhere in a long trail.

"We can't completely control the environment in the field," he said. "Birds can carry Salmonella. Animals, including deer, can carry E. coli. Manure that hasn't been properly composted can be contaminated."

Harmful organisms can get onto the seeds after they leave the field, too. "Anywhere along the way -- in the handling, transportation, contact with human hands -- the seeds can become contaminated," he said.

The real problem starts then.

"A pathogen on a dry seed is just there. It's not growing," Beuchat said. "But once you hydrate it and put it in the sprout production process, the organism is going to reproduce during that entire time. It has all it needs -- plenty of moisture, adequate temperature and nutrients from the sprouts."

Once the sprouts are mature, they're washed, packaged and distributed to stores and restaurants. They're often refrigerated during that time, which limits further bacterial growth.

But if pathogens were there to start with, the sprouts will already be unsafe. "Without heat, we have no effective intervention step to kill the pathogens," Beuchat said.

"Sprouts are nutritious," said Judy Harrison, an Extension Service foods specialist with the UGA College of Family and Consumer Sciences. "But given the safety concerns, eating them raw is something to be very cautious of."

Children, older people and those with compromised immune systems are especially at risk for food-borne illnesses with serious and even life- threatening complications. "Those people should probably avoid eating raw sprouts," Harrison said.

Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.