Antibacterial mechanism of ultrasound combined with oregano essential oil nano-emulsion on Escherichia coli O157:H7 and application in cherry tomatoes storage

Escherichia coli ( E. coli ) O157:H7 on the surfaces of fruits and vegetables poses significant risks to human health. This study assessed the bactericidal mechanisms of ultrasound (US) and oregano essential oil nanoemulsion (OEON) against E. coli , as well as their application in storage preservation of cherry tomatoes. The results showed that US + OEON treatment exhibited markedly superior inactivation effect on E. coli compared to their individual treatments. OEON (2 %) combined with ultrasonic treatment (375 W) for 4 min reduced the viable E. coli count by 5.06 ± 0.22 log CFU/mL. This performance markedly exceeded that of single treatments, with US achieving 1.15 ± 0.10 log CFU/mL reduction and OEON 1.04 ± 0.18 log CFU/mL reduction. The synergistic treatment intensified lipid peroxidation of bacterial cell membranes and enhanced membrane permeability. Furthermore, in preservation applications on cherry tomatoes, US + OEON effectively suppressed total viable counts, achieving a 1.44 ± 0.19 log CFU/mL reduction after 4-min treatment with 2 % OEON combined with 375 W US. This approach induced no adverse effects on cherry tomato color, texture, nutritional composition, or antioxidant properties. In summary, compared to US or OEON treatment alone, US + OEON treatment exhibits superior antibacterial effect and improves the storage quality of cherry tomatoes.