Researchers say common packinghouse practices for fresh spinach are not sufficient to avoid outbreaks of salmonella-related illnesses and recently showed that irradiation eliminated almost all cross contamination from field and packing operations.
Scientists at Texas A&M University and Pusan National University in South Korea set out to develop a quantitative risk assessment model to evaluate microbial hazards during the processing of baby spinach leaves, according to their abstract recently published with their results in the journal “ScienceDirect.”
Cross contamination is the most probable scenario for the contamination of an entire day’s production of the leafy green, according to the abstract.
Even if initial contamination was low, the researchers found that cross contamination after washing at the packing facility could reach more than 84% of the entire lot.
However, when the spinach was treated with ionizing radiation at only 1kGy, the contamination rate dropped to one-tenth of 1%.
The scientists concluded that spinach growers and packers “can deliver a highly safe product in a cross-contamination scenario — on the field or packing shed — if the produce is harvested at 20°C (about 63 degrees F), stored for at least 5 hours, washed with water and chlorine at 220 ppm, and exposed to irradiation treatment with a dose of 1 kGy.”
FDA requires foods that have been irradiated to bear this radura logo and a statement declaring the food has been treated with radiation or irradiation. Many growers, however, remain reluctant to irradiate leafy greens. Some have concerns about consumer perception because government rules require irradiated produce to carry a statement that says it has been treated with radiation.
Also, regulations prohibit the irradiation of organic produce.
Will Daniels, senior vice president of operations and organic integrity at Earthbound Farm, San Juan Bastista, Calif., said there is also concern about the impact of irradiation on the produce itself, as well as the logistics of such treatments.
“While irradiation may be effective at eradicating pathogens, there are questions about the practicality of irradiation large quantities of any leafy greens — how would they pass through the machine?” Daniels said.
Daniels “Right now, since there is no irradiation facility adjacent to growing and processing regions, how much time would the transportation and process subtract from the shelf-life of a highly perishable product? Importantly, how does irradiation affect the flavor and texture of leafy greens? These are important questions that we haven’t seen the answers to yet.”
In 2008 the Food and Drug Administration published a final rule allowing irradiation of iceberg lettuce and fresh spinach, saying the treatment makes the leafy greens safer and extends shelf life.
The FDA also stated that the nutrient value of the leafy greens was not decreased by irradiation.
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