Integrating intermittent ultrasound with micro-nanobubbles for enhanced reduction of pathogenic bacteria during fresh-cut lotus root sanitation.

Abstract

Fresh-cut lotus roots require highly efficient and sustainable sanitation approaches to ensure high food quality and low microbial safety risks. In this study, we investigated the efficacy of micro-nanobubble (MNB) filled with ambient air (approximately 78% N₂, 21% O₂) or carbon dioxide (CO₂), in combination with ultrasound and hydrogen peroxide (H₂O₂) for decontaminating Escherichia coli O157:H7 and Listeria monocytogenes on fresh-cut lotus roots. Findings revealed that CO₂ MNB combined with 1% H₂O₂ and intermittent ultrasound (15 s on / 60 s off, US-3) achieved a reduction of E. coli O157:H7 on the surface of lotus root slices by 3.91 ± 0.39 log CFU/slice in 10 min, significantly higher (p < 0.05) than individual or other combined treatments. The enhanced sanitation efficacy may be attributed to combined oxidative, acidic, and mechanical stresses generated by H₂O₂, dissolved CO₂, US, or MNB-US interactions, which may accelerate bacterial inactivation or detachment. Additionally, air MNB + H₂O₂ and CO₂ MNB + H₂O₂ + US-3 maintained the number of indigenous microorganisms below 5 log CFU/g on fresh-cut lotus roots during the initial 4 days of storage at 4 °C, and showed lower browning indexes at the end of the 16-day compared to water and individual MNB washes. The findings of this research provide valuable insights into developing highly efficient and safe sanitation approaches for the fresh produce industry.