A new method may make tomatoes safer to eat
FDA-approved food additives prove effective at controlling bacteria on tomatoes preharvest

Date:
September 8, 2020
Source:
University of Georgia
Summary:
When vegetable farmers harvest crops, they often rely on postharvest
washing to reduce any foodborne pathogens, but a new study shows
promise in reducing these pathogens -- as well as lowering labor
costs -- by applying sanitizers to produce while it is still in
the fields.



FULL STORY ==========================================================================
When vegetable farmers harvest crops, they often rely on postharvest
washing to reduce any foodborne pathogens, but a new University of
Georgia study shows promise in reducing these pathogens -- as well as
lowering labor costs -- by applying sanitizers to produce while it is
still in the fields.


========================================================================== Salmonella, Shiga toxin-producing E. coli and Listeria monocytogenes are
major causes of foodborne diseases and of public health concern in the
U.S. Tomato- associated Salmonella outbreaks reported to the Centers for Disease Control and Prevention have increased in frequency and magnitude
in recent years, and fresh produce accounted for 21% of E. coli outbreaks reported to the CDC over a 20- year span.

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. However, 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.

While producers commonly use chlorine-based disinfectants -- including
chlorine gas, sodium hypochlorite, calcium hypochlorite and chlorine
dioxide -- to treat produce postharvest, the preharvest application of bactericides is not a common practice, Zhao said.

Building on previous studies of levulinic acid and sodium dodecyl sulfate
that showed the combination substantially reduces both Salmonella and
E. coli on romaine lettuce without adversely affecting lettuce quality,
Zhao hoped to prove the combination's effectiveness on reducing
foodborne pathogens on tomato plants contaminated with Salmonella,
Shiga toxin-producing E. coli and Listeria monocytogenes.

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. The study was recently published in the journal
Food Control.



========================================================================== "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. "Free chlorine
is easily neutralized by organic material, which is a big problem when
you are using it to reduce pathogens." In both laboratory and field
tests, tomato plants were sprayed all over with a solution containing
five strains of E. coli, five strains of Salmonella and five strains of Listeria specially grown for the study in the lab.

To test the effectiveness of the chemicals in the lab as a preventative
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 preventative or as a treatment, significantly reduced the populations of inoculated Shiga toxin-producing E. coli, Salmonella and L. monocytogenes
on tomato plants.

"I have to express appreciation to the Georgia Fruit and Vegetable
Association for funding this and other research that is of benefit to agricultural producers in the state," Zhao said.

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.

"This method can easily be adopted using equipment that most farms
are already using," Zhao said. "Preharvest treatment is very effective, efficient and easy considering the amount of labor needed for postharvest washing."

========================================================================== Story Source: Materials provided by University_of_Georgia. Original
written by Maria Lameiras. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Tong Zhao, Pingsheng Ji, Govindaraj Dev Kumar. Pre-harvest
treatment for
reduction of foodborne pathogens and microbial load
on tomatoes. Food Control, 2021; 119: 107469 DOI:
10.1016/j.foodcont.2020.107469 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908170533.htm

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