NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
October 14, 1999
Food scientists at North Dakota State University are studying eight household products in an ongoing research effort aimed at making fresh produce safer for consumers. In test-tube trials, they've determined the minimum concentrations needed for those products to kill four major strains of E. coli bacteria. Now, they're trying to mimic a household setting to see how the diluted solutions work at containing the most resistant of the E. coli strains.
"With these eight solutions, what we're trying to get at are the bacteria that aren't easily removed by simple washing," says Charlene Hall, an assistant professor in the food and nutrition department at NDSU. Working with Hall on this project is Chitra Vijayakumar, an NDSU graduate student.
The NDSU researchers are studying apple cider vinegar and white vinegar (5 percent acidities), baking soda, chlorine bleach, hydrogen peroxide, reconstituted lemon and lime juice, and a fruit protector (Fruit Fresh). The produce being washed in the diluted solutions are broccoli, whole cantaloupe and iceberg lettuce. In the test-tube trial, hydrogen peroxide proved to be the most effective at killing E. coli, but the results may vary in phase two of the study, Hall says.
Researchers have known for about 100 years that raw fruits and vegetables can serve as vehicles for human disease, Hall says. Yet the Food and Drug Administration reports that fresh fruits and vegetables are not generally subjected to many of the steps designed to reduce or eliminate bacteria that other processed foods receive. During the 1990s, several outbreaks of foodborne illnesses have been linked to the consumption of fresh fruits and vegetables. Montana, Maine and Massachusetts are among the states where these types of outbreaks have occurred.
Prior to washing their produce, the NDSU researchers are "spiking" each piece with the most resistant strain of E. coli, as determined by their test-tube trials, Hall explains. The inoculated food items then sit overnight in refrigerated storage (about 40 F).
The produce is being completely immersed in solution during each washing procedure, which will involve one wash in a diluted solution followed by two rinses in distilled water. Halls says washing will be done at temperatures of about 40 F, 75 F and 140 F and at intervals of five, 10 and 15 minutes. Another factor the researchers are comparing is motion--a static soak versus agitation.
After washing, the NDSU researchers will measure how much E. coli remains to determine each solution's effectiveness. Produce inoculated and washed in distilled water will serve as the check. The researchers will re-examine the washed produce after about two hours to detect any changes, such as in color, texture or odor, compared to the untreated produce.
"Our expectation is that this will probably be an inexpensive way of washing fruits and vegetables in the home," Hall concludes, "and depending on the results we get, it might even be more effective than some commercial processes now in use."
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Source: Charlene Hall (701) 231-6387
Editor: Dean Hulse (701) 231-6136