Double Whammy for Ecoli and Salmonella

Double Whammy for E. coli and Salmonella
Food& Nutrition Research Briefs, July 1999

Treating alfalfa seeds and sprouts with a combination ofirradiation and chlorine effectively safeguards them against E. coliO157:H7 and Salmonella, researchers found. Not only did the dualtreatment kill both organisms, it extended the shelf life of sprouts from aboutfive days to more than a week. This is good news for sprout growers. Since 1995,raw alfalfa sprouts have been recognized as a source of foodborne illness in theUnited States, with several outbreaks of both E. coli O157:H7 and Salmonella.Since sprouts can’t withstand abrasive physical washing because of theirfragility, cleaning the seed has become the primary focus.


Along with irradiation, the researchers subjected alfalfa seeds tothree concentrations of calcium hypochlorite-a chlorine source. A 3-percentweight-per-volume concentration equals about 20,000 parts per million ofavailable chlorine. When the pH is neutral, the 2.5- and 3-percentconcentrations reduced E. coli O157:H7 by 99.99 percent. The pH level isimportant because when the solution is more alkaline, such as pH 10, thechlorine would change to a form that would be less effective against bacteria.


According to the scientists, the best way to eliminate pathogenswould be a combination of irradiation and sanitation treatments. That’s becausesprouts and seeds may be contaminated internally, which would prevent a surfacedisinfectant from working effectively. In the tests, the scientists used theirradiation dose approved for meat. The U.S. Food and Drug Administration hasapproved ionizing radiation as a safe and effective food preservation tool. Theresearch is part of an effort by a task force of representatives from severalfederal agencies and industry to find ways to control microbial contamination ofsprouts .


For more information, contact Donald W. Thayer on irradiation,(215) 233-6582 and William F. Fett on chlorination, (215) 233-6418, EasternRegional Research Center, Wyndmoor, PA