
Food Irradiation and Chlorine Team Up to
Kill E. coli O157:H7 and SalmonellaBy Doris Stanley
Lowe June 1, 1999Treating 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 Centers 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 riskincluding children, the
elderly, and persons with compromised immune systemsto avoid eating raw
alfalfa sprouts. Since sprouts cant 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 USDAs chief scientific research agency. More information on
this story appears in the agencys June Agricultural Research magazine,
available at: http://www.ars.usda.gov/is/AR/archive/jun99/food0699.htm 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, [email protected]. U.S. Department of Agriculture | |