Although E. coli is primarily found on meat, it has recently shown up in apple juice, sprouts, and lettuce. Outbreaks of food poisoning from Shigella on iceberg lettuce have occurred in Sweden, England, and Wales. Robert D. Hagenmaier, an Agricultural Research Service chemist at the U.S. Citrus and Subtropical Products Laboratory in Winter Haven, Florida, has found a way to reduce these and other pathogenic and nonpathogenic microorganisms. He combines an ionizing irradiation treatment with the chlorine wash. Technician Kelly Alger assists with the research.
Ionizing radiation passes through food in the form of radiant energy, without leaving any residue.
It does not make food radioactive. In lab experiments, he found that irradiation significantly reduced the microbial and yeast populations on cut iceberg lettuce. Irradiated lettuce had about the same shelf life as untreated samples. Normal shelf life claimed by manufacturers for retail sales of salads is between 14 and 16 days from the packaging date. Nine days after irradiation, on the expiration date, the microbial count was 1,300 compared to 87,000 for nonirradiated, chlorinated controls, he says, and texture and appearance were unchanged.