Washing fruits and vegetables under cold water does not always remove potentially harmful bacteria off their surface completely because some of them are resistant to the shower and hang on tight, according to experts.
Brendan Niemira of the USDA's Microbial Food Safety Unit in Pennsylvania says that bacteria left on the surface of fruits and vegetables may eventually lead to outbreaks of Salmonella or E. coli in humans.
His statement comes in the wake of an estimated 383 Salmonella cases linked to contaminated tomatoes, which have been reported to date in 30 states in the US since April 10.
Salmonella serotype Saintpaul, an uncommon type of Salmonella that can live in the intestinal tracts of humans and other animals, is said to be the cause of the outbreak.
"As of right now, the FDA hasn't been able to identify exactly where the tomatoes came from," Live Science quoted Niemira as saying.
The researcher, however, added that tomatoes could pick up such a pathogen from contaminated soil, irrigation water, manure, wildlife, or farm workers.
"If you've got bacteria on the surface of fruits and vegetables, and you give them a wash with cold water, it removes some of what's on the surface. Unfortunately, it (cold water rinsing) doesn't remove all of them, and that's a problem. If things are well attached or living in a tight-knit community called a biofilm, that's going to be hard to get rid of," Niemira said.
The researcher pointed out that fruits and vegetables like cantaloupes and spinach have rough surfaces, which provided lots of nooks and crannies in which bacteria could hide out.
Although tomatoes are much smoother, said Niemira, their surfaces do contain tiny pores where bacteria could hide.
Even washing the rougher-surfaced fruit might not work because it could bruise or tear the protective layer covering tomatoes and other fruits and vegetables, the researcher cautioned.
Niemira said that any damage to the produce could lead to spoilage, and the associated "spoilage bacteria".
"The spoilage bacteria don't hurt people; they start to digest the tomatoes and you get a little bit of spoilage and weeping. That releases sugars and other things that can support the growth of pathogens. If you do have some pathogens on there, and you do have some spoilage, that can lead to an outgrowth (of the pathogens)," said the researcher.
Neimira further said that handling the produce with care to minimise bruising, washing it in cold water, drying off any excess water, keeping the produce in refrigerator, getting rid of rotten fruits and vegetables, etc. are some of the tips that may help keep the produce safe.