The 2019 North American outbreak of E. coli contamination in romaine lettuce doubtless got many people thinking about how to most effectively wash their leafy veggies. Well, a new study suggests that using ultrasonic water may be the best way to go.
First of all, plain ol' tap water can't necessarily dislodge all of the bacteria from leafy vegetables, yet the use of cleansers such as soap or disinfectants also isn't recommended. Not only is it difficult to completely rinse the chemicals out of all the leaves' nooks and crannies, but bacteria deep within those same crevices may get missed by the cleansers.
Instead, researchers at Britain's University of Southampton tried using a continuous stream of water that carried microscopic bubbles and acoustic waves down from an upstream source onto contaminated leafy vegetables.
"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," says the lead scientist, Prof. Timothy Leighton. "The sound field also causes the walls of the bubbles to ripple very quickly, turning them into microscopic 'scrubbing' machines. The rippling bubble wall causes strong currents to move in the water around the bubble, and sweep the microbes off the leaf."
It was found that six days after receiving a 2-minute ultrasonic water treatment, microbial loads on contaminated spinach leaves were "significantly lower" than those on leaves rinsed with plain water at the same velocity, for the same amount if time. And importantly, the scrubbing micro-bubbles appeared to cause no damage to the leaves.
While it's unlikely that our household taps will be equipped with ultrasound transducers anytime soon, the technology could be utilized by produce suppliers such as Vitacress, which funded the study.
A paper on the research was recently published in the journal Ultrasound in Medicine and Biology.
Source: University of Southampton
