FDA-Approved Food Additives Could Kill Microbes on Tomatoes without Chlorine: Study
Wed, April 21, 2021

FDA-Approved Food Additives Could Kill Microbes on Tomatoes without Chlorine: Study


A new method to make tomatoes safer to eat has been revealed by a group of researchers. The method could reduce the growth of pathogens that cause foodborne illnesses without using chlorine.

The new method for reducing foodborne illness-causing pathogens was presented by researchers at the University of Georgia (UGA), a US public research university. Their method uses FDA-approved food additives to control bacterial growth on tomatoes. The food additives could control bacterial growth without decreasing the quality of the crop. These additives are not based on chlorine. They published their findings in the journal Food Control.

US Foodborne Illnesses by Cases and Preparation

Foodborne illnesses are irritation or infection of the gastrointestinal tract induced by contaminated food or drink. The contamination is caused by bacteria, parasites, viruses, or harmful substances. When a person has a foodborne illness, they usually develop symptoms like stomach pain, vomiting, diarrhea, and fever. If the infection is serious, the symptoms will become severe. They will need immediate medical attention to prevent complications.

According to Statista, a German portal for statistics, there were several cases of foodborne illnesses in different food categories in 2017 in the US. Some of the food categories with high cases of foodborne illnesses were mollusks at 279 cases, fish at 144 cases, beef at 329 cases, pork at 376 cases, chicken at 487 cases, turkey at 609 cases, vegetable row crops at 351 cases, and fruits at 521 cases. Food categories with less than 100 cases included crustaceans at 37, dairy at 85, eggs at 81, sprouts at 62, grains and beans at 73, and herbs at 20.



In the same year, the prevalence of foodborne illnesses based on food preparation in the US was determined by available data. Both the sit-down dining and banquet or catering facility had the highest distribution of foodborne illnesses at 30% and 29%, respectively. Other distribution rates of cases include private home at 8%, jail or prison at 6%, unknown restaurant type at 5%, fast food restaurant at 4%, and school at 2%.

Foodborne illnesses can be prevented by following proper food preparation and storage practices. Proper handwashing before and after preparing food, cleaning utensils and kitchen areas, cooking food at the right temperatures, and chilling leftovers correctly are some of the steps to prevent food poisoning.



Making Tomatoes Safer to Eat

Tomatoes are one of the most common ingredients in dishes. As a fruit, it can be eaten raw but many add tomatoes to make dishes more flavorful. Sometimes, its color adds beauty to the overall look of various dishes. However, like other crops, tomatoes can harbor pathogens that cause foodborne illnesses. These pathogens can enter the digestive tract if tomatoes are not cleaned or cooked properly.

At UGA, researchers devised a new way to reduce the growth of common pathogens, such as salmonella, Shiga toxin-producing Escherichia coli, and Listeria monocytogenes. These three have been associated with numerous cases of food poisoning worldwide, especially in cases involving raw food. Their new method utilized food additives approved by the US FDA. They initially planned to study the effectiveness of these additives as a postharvest wash. But a suggestion changed the study's objective: would the additives be effective as a preharvest wash?

"This method can easily be adopted using equipment that most farms are already using. Preharvest treatment is very effective, efficient and easy considering the amount of labor needed for postharvest washing," said Tong Zhao, the first author of the study and associate research scientist with the Center for Food Safety at UGA.

The suggestion came from Bill Brim of Lewis Taylor Farms in Georgia. Normally, farmers would wash harvested crops using chlorine-based disinfectants, like chlorine gas or chlorine dioxide. Farmers would rarely conduct preharvest wash of crops to reduce the presence of microbes. The difference in the timing of applying bactericides motivated researchers to investigate preharvest wash.

In the study, the research team noted that previous studies of levulinic acid and sodium dodecyl sulfate found the effectiveness of the chemicals in reducing E. coli and salmonella. The effectiveness was determined in experiments performed on romaine lettuce. The two chemicals could decrease bacterial growth and maintain the quality of the lettuce. This led them to test the chemicals on tomatoes.



Two sets of tests were prepared to demonstrate the effectiveness of levulinic acid and sodium dodecyl sulfate on tomatoes. One set was done in the laboratory and the other was performed on the field. Tomato plants would be completely sprayed with a solution containing five strains of E. coli, salmonella, and Listeria, which totaled 15 strains of pathogens. The strains were grown in the lab.

For the lab tests, tomato plants were assigned into three equal groups. Next, researchers sprayed the solution with bacterial strains. The first group was treated with acidified chlorine to serve as positive control. The second group was treated with levulinic acid and sodium dodecyl sulfate to serve as subject. The third group was treated with tap water to serve as negative control.

For the field tests, the two groups of tomato plants served as positive and negative control groups, which were treated the same way as with lab tomato plants. The subject group was treated with a commercial product diluted according to the manufacturer's instructions. Before the field test, the product was tested in two concentrations for safety on tomato seedlings.

Results from the tested showed that the use of levulinic acid and sodium dodecyl sulfate, as preventative or treatment, reduced the numbers of the five strains of each pathogen. The reduction in bacterial growth was on par with postharvest wash. This could decrease labor costs for producers who do not need workers to perform the washing and drying before packaging. Also, the findings supported the use of the two chemicals as an alternative to chlorine-based disinfectants.

In agriculture, disinfectants without chlorine are often easily neutralized by organic material. Chlorine is usually mixed with inorganic compounds to make an effective disinfectant. But the study shows that certain non-chlorine-based solutions can be effective as well in killing microbes on fresh produce.