Washing fruits and vegetables with water is not enough to remove common bacteria that can cause severe illness, a new report says.
The researchers injected food-borne bacteria such as E. coli and salmonella into vegetables and then tried various common ways to clean them, including water and a sodium hypochlorite treatment.
Both the water and the chemical solution did not significantly reduce the bacteria levels. Only irradiation killed 99.9 per cent of harmful bacteria. Irradiation is an electron beam that alters a cell's genetic material, thereby killing harmful parasites, germs and insects.
The research, conducted by scientists at the U.S. Department of Agriculture, said that bacteria can sometimes be hard to wash away.
"When bacteria are protected -- whether they're inside a leaf or inside a biofilm -- they're not going to be as easy to kill," Brendan A. Niemira, the study director and a microbiologist with the USDA's Agricultural Research Service, said in a statement.
"This is the first study to look at the use of irradiation on bacteria that reside inside the inner spaces of a leaf or buried within a biofilm."
However, irradiation is not yet approved by the U.S. Food and Drug Administration, and there is some concern that it compromises nutritional values.
But advocates say that using irradiation on fresh fruits and vegetables could help reduce incidence rates of food-borne illnesses. Salmonella and E. coli can cause severe vomiting and diarrhea.
Fruits and vegetables can become contaminated because they are usually grown outdoors, where they can be exposed to germs from animals, soil, manure and irrigation water.
The study was presented Thursday at an American Chemical Society meeting in New Orleans.
Abstract:
With the microbial safety of fresh produce of increasing concern, conventional sanitizing treatments need to be supplemented with effective new interventions to inactivate human pathogens. Our research group investigates physical and chemical treatments such as hot water pasteurization, gaseous chlorine dioxide, cold plasma and irradiation. Research in biological controls deals with the use of single or multiple isolates of antagonistic bacteria for inhibiting the outgrowth of bacterial human pathogens. Related research in microbial ecology determines how pathogen biofilm formation and interactions with native microflora may alter the efficacy of applied treatments and interventions. This presentation will summarize the advances made in these areas, as well as research results on the process of scaling up effective interventions from laboratory scale to pilot plant scale, including the critical process of evaluating the effects of the various interventions on sensory and nutritional quality attributes, yield, physiology, and shelf-life.
