
Safer Salad In The BagBy Doris Stanley
Lowe February 10, 1999Irradiating bagged salads after
washing the vegetables in a chlorine solution reduces harmful and non-harmful
microorganisms without affecting quality, scientists with
USDAs
Agricultural Research Service report.
Thats good news for health-conscious consumers who are eating more
salads. Sales of packaged lettuce alone were more than $1.2 billion in the
United States in 1997. From a food safety perspective, salads are considered to be among the safest
foods. However, some segments of the population often exclude salads and other
uncooked fruits and vegetables from their diets. These foods have the potential
to be a food safety risk for the young, old, pregnant or immunocompromised,
because of the presence of human pathogens. These groups cant risk
exposure to microorganisms that, for the general population, may not be a major
concern. Although the food industry uses chlorine to control microbes on fresh-cut
lettuce, chlorine doesnt eliminate all the organisms that can be present,
like Shigella and E. coli O157:H7. In lab experiments at the U.S.
Citrus and Subtropical Products Research Laboratory, Winter Haven, FL, ARS
scientists found that irradiation significantly reduced the microbial and yeast
populations on cut iceberg lettuce. Eight days after zapping chlorine-washed
lettuce with only 0.2 kilogray (kGy) of irradiation, microbial counts were 290
colony-forming units (CFU) and 60 CFU of yeast. Control samples showed
microbial counts of 220,000 CFU and 1,400 CFU of yeast. (The
U.S. Food and Drug Administration has
approved up to 1 kGy of irradiation for fresh produce.) Irradiated lettuce had about the same shelf life as untreated samples.
Manufacturers of salads for retail sales claim normal shelf life of 14 to 16
days from packaging date. Scientists also irradiated chlorine-washed, shredded carrots in
modified-atmosphere packaging. Nine days after irradiation, on the expiration
date, microbial count was 1,300, compared with 87,000 for nonirradiated,
chlorinated control samples. This combination treatment could help fresh-cut salads to be included in
diets of people who otherwise cant enjoy them because of a potential
microbiological health risk. Scientific contact: Robert D. Hagenmaier, ARS Citrus and Subtropical
Products Research Laboratory, Winter Haven, FL; phone (941) 293-4133, X123, fax
(941) 299-8678, email [email protected] U.S. Department of Agriculture | |