Initially researchers were going to study the use of a nonchlorine-based sanitizer made of two food additives approved by the U.S. Food and Drug Administration – levulinic acid and sodium dodecyl sulfate – as a postharvest wash solution.
At the suggestion of a producer involved in the study – Bill Brim of Lewis Taylor Farms in Tifton, Georgia – they designed the study using the solution in a preharvest spray, said Tong Zhao, associate research scientist with the Center for Food Safety on the UGA Griffin campus.
In the field studies, the spray treatment significantly reduced the total bacterial population on the surface of tomatoes, determining that this preharvest treatment is a practical, labor-cost effective and environmentally friendly approach for the control and reduction of foodborne pathogens.
“This combination of chemicals had never been used for preharvest treatment,” said Zhao, who studied the combination 10 years ago as an alternative to chlorine treatment as a postharvest wash.
To test the effectiveness of the chemicals in the lab as a preventive and as a treatment, tomato plants were separated into three equal groups then sprayed with the bacteria solution.
The first group was treated with acidified chlorine as the positive control, the second with a treatment solution containing levulinic acid and sodium dodecyl sulfate as the test group, and the third treated with tap water only as the negative control.
For the three plots used for farm application testing, the positive and negative control groups were treated the same way, and a commercial product – Fit-L – was diluted according to the manufacturer’s description and used as the treatment solution.
Before treatment studies on the farm, two concentrations of the treatment solution were tested for safety on tomato seedlings in the greenhouse.
Results from the studies showed that the application, used either as a preventive or as a treatment, significantly reduced the populations of inoculated Shiga toxin-producing E. coli, salmonella and L. monocytogenes on tomato plants.
In addition to being effective and affordable, preharvest treatment with levulinic acid and sodium dodecyl sulfate to reduce pathogens also saves labor costs for producers who need workers to perform postharvest washing and drying of produce before packaging.