STORY LEAD:
Food Irradiation and Chlorine Team Up to Kill E. coli O157:H7 and Salmonella
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ARS News Service
Agricultural Research Service, USDA
June 1, 1999
Doris Stanley Lowe, (301) 893-6727, dstanley@asrr.arsusda.gov
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Treating alfalfa seeds and sprouts with a combination of irradiation and
chlorine effectively safeguards them against contamination by E. coli
O157:H7 and Salmonella, Agricultural Research Service scientists report.
ARS scientists Donald W. Thayer, Kathleen T. Rajkowski and William F. Fett
found that a treatment of irradiation and chlorine solution not only killed
both organisms, but extended the shelf life of sprouts from about five days
to more than a week. They conducted the lab studies at the ARS Eastern
Regional Research Center's Food Safety and Plant Science and Technology
Research Units in Wyndmoor, Pennsylvania. The research is part of the effort
by a task force of representatives from several Federal Government agencies
and industry to find ways to control microbial contamination of sprouts .
The finding is good news for sprout growers. Since 1995, raw alfalfa sprouts
have been recognized as a source of foodborne illness in the United States,
with several outbreaks of both E. coli O157:H7 and Salmonella. FDA and the
Centers for Disease Control and Prevention have advised those at high
risk—including children, the elderly, and persons with compromised immune
systems—to avoid eating raw alfalfa sprouts. Since sprouts can't withstand
abrasive physical washing because of their fragility, cleaning the seed has
become the primary focus.
In the tests, the scientists used the irradiation dose approved for
irradiating meat. The U.S. Food and Drug Administration (FDA) has approved
ionizing radiation as a safe and effective food preservation tool.
Along with irradiation, they subjected alfalfa seeds to 2-percent,
2.5-percent, and 3-percent weight-per-volume concentrations of calcium
hypochlorite (a chlorine source). A 3-percent concentration equals about
20,000 parts per million of available chlorine. With a neutral pH of about
7, the 2.5 and 3-percent concentrations reduced E. coli O157:H7 99.99
percent. The pH level is important because at a higher pH level, such as 10,
the chlorine would change to a form that would not be as effective in
killing bacteria.
According to the scientists, the best way to eliminate pathogens would be a
combination of irradiation and sanitation treatments. This is because
sprouts can be contaminated internally, which would prevent a surface
disinfectant from working effectively.
ARS is USDA's chief scientific research agency. More information on this
story appears in the agency's June Agricultural Research magazine, available
at
http://www.ars.usda.gov/is/AR/archive/jun99/food0699.htm
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Scientific contact: Donald W. Thayer, ARS Food Safety Research Unit, Eastern
Regional Research Center, Wyndmoor, PA 19038, phone (215) 233-6582, fax
(215) 233-6406, dthayer@arserrc.gov.
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