Pre-Harvest Treatment Can Reduce Foodborne Pathogens

New research from the Center for Food Safety at the University of Georgia suggests that farmers can reduce foodborne pathogens by applying sanitizers to produce while it is still in the ground. Modern practices for the reduction of foodborne pathogens on produce typically focus on post-harvest washing; however, even though tremendous efforts are performed, outbreaks of foodborne pathogens in this produce still occur.

The researchers examined the bactericidal effects of a food-grade sanitizer and found that it could kill inoculated foodborne pathogens on tomato plants. Additionally, pre-harvest treatment reduced coliform and total bacterial population.

“There was no Listeria detected on all collected tomatoes,” says Tong Zhao, PhD, an associate research scientist at the university and co-author of the study.

According to Dr. Zhao, pre-harvest application of bactericides is not a common practice among vegetable growers. Originally, the researchers planned to study the use of a nonchlorine-based sanitizer made of two FDA-approved food additives—levulinic acid and sodium dodecyl sulfate—as a post-harvest wash solution. However, with advice from Bill Brim, president of Lewis Taylor Farms in Tifton, Ga., the researchers used the solution in a pre-harvest spray instead.

The researchers examined both laboratory and field tests, spraying tomato plants with a solution containing five strains of E. coli, five strains of Salmonella, and five strains of Listeria specially grown in a lab. The plants were then separated into three equal groups and sprayed with the bacteria solution comprised of commercial product Fit-L. One group was treated with acidified chlorine as the positive control, another with a treatment solution containing levulinic acid and sodium dodecyl sulfate, and a third was treated with tap water only as the negative control.

The outcome of the study showed that the combination of levulinic acid and sodium dodecyl was effective in reducing foodborne pathogens on tomato plants contaminated with Salmonella, Shiga toxin-producing E. coli, and Listeria monocytogenes.

“The results reveal that pre-harvest intervention by Fit-L is a practical, easy-to-use, labor-cost-effective, and environmentally friendly approach for control and reduction of foodborne pathogens that may contaminate the surface of the produce and total surface bacterial population at pre-harvest stage,” Zhao says. “Its application at pre-harvest plus post-harvest washing will provide a warranty to secure the safety of fresh produce.”