A University of Illinois food science research team has found that adding a high-powered ultrasound to the typical chlorine wash can eliminate up to 99.9% of E.coli in spinach and lettuce, according to News-Gazette and The Salt. That’s a substantial improvement on the effectiveness of the wash alone, which only gets rid of 90% of the bacteria.
Purging leafy greens of bacteria is a delicate process, as the ultrasound must strike the right level of power to kill the bacteria without destroying the vegetable. Hao Feng, the associate Professor of Food Engineering at the university, begins the treatment by submerging spinach in large tanks of water. Jets are use to keep the water swirling so every leaf of spinach is exposed to sound waves, and transducers are used to extend the reach of the waves. The “tiny cavities that pop like bubbles”—produced by the sound waves—”can dislodge and destroy bacteria.”
Feng has had to adjust the process so there are just enough cavities to clean effectively, but not so man that they create pressure that could break the vegetable.