As it is often not cooked before being eaten, leafy green salad vegetables may be contaminated with harmful bacteria that can even be fatal among vulnerable people.
As soap or other detergents is not recommended, washing with plain water could very easily leave an infectious dose on the crevices in the leaf surface.
The European Union Foods Standards Agency regards bagged salads as the second most frequent cause of food poisoning.
Leafy greens can become contaminated with harmful bacteria, such as E. coli, Salmonella and Listeria, which can occur across various stages.
Contamination can occur from unclean water and dirty runoff in the soil, or from dirty processing equipment and unhygienic food preparation practices.
In a new study, scientists used ultrasonic water streams to clean spinach leaves directly sourced from a field crop and then compared the results with leaves rinsed in plain water.
The results showed the samples cleaned with soundwaves for two minutes “scrubbed” the leaves of microbes and were fresh even after six days compared to those treated without the special treatment.
The acoustic cleaning also caused no damage to the leaves and demonstrated the potential to extend food shelf life.
Professor Timothy Leighton of the University of Southampton, who invented the technology, said: “Our streams of water carry microscopic bubbles and acoustic waves down to the leaf.
“There the sound field sets up echoes at the surface of the leaves, and within the leaf crevices, that attract the bubbles towards the leaf and into the crevices.
“The sound field also causes the walls of the bubbles to ripple very quickly, turning each bubble into a microscopic ‘scrubbing’ machine.
“The rippling bubble wall causes strong currents to move in the water around the bubble, and sweep the microbes off the leaf.
“The bacteria, biofilms, and the bubbles themselves, are then rinsed off the leaf, leaving it clean and free of residues.”
The study was published in the journal Ultrasound in Medicine and Biology.
