Assisted ultrasound enhanced the levels of microbial reduction on the surface of the lettuce at concentrations
higher than 0.010% (v/v) of oregano EO. Significant differences were found at 0.018%, 0.022% and 0.025% (v/v)
both in continuous and pulsed US modes when compared with samples treated only with US. Same concentrations
of EO combined with continuous or pulsed mode of US reduced the level of E. coli in water below the
limit of detection. When continuous or pulse mode of US was combined with 0.025% (v/v) of EO of oregano
the resultwas synergetic. Images reported neither structural differences nor damage of the leaves among treated
samples and controls. Concluding, the effectiveness of the assisted ultrasound process was dependent on the
processing time rather than on the different configurations (continuous or on/off) or the total treatment
duration. Furthermore, EO combined with US could work synergistically on enhancing the inactivation of the
tested bacteria.