The Effect Ultrasound and Surfactants on Nanobubbles Efficacy against Listeria innocua and Escherichia coli O157:H7, in Cell Suspension and on Fresh Produce Surfaces

Abstract

Removing foodborne pathogens from food surfaces and inactivating them in wash water are critical steps for reducing the number of foodborne illnesses. In this study we evaluated the impact of surfactants on enhancing nanobubbles’ efficacy on Escherichia coli O157:H7, and Listeria innocua removal from spinach leaves. We evaluated the synergistic impact of nanobubbles and ultrasound on these two pathogens inactivation in the cell suspension. The results indicated that nanobubbles or ultrasound alone could not significantly reduce bacteria in cell suspension after 15 min. However, a combination of nanobubbles and ultrasonication caused more than 6 log cfu/mL reduction after 15 min, and 7 log cfu/mL reduction after 10 min of L. innocua and E. coli, respectively. Nanobubbles also enhanced bacterial removal from spinach surface in combination with ultrasonication. Nanobubbles with ultrasound removed more than 2 and 4 log cfu/cm2 of L. innocua and E. coli, respectively, while ultrasound alone caused 0.5 and 1 log cfu/cm2 of L. innocua and E. coli reduction, respectively. No reduction was observed in the solutions with PBS and nanobubbles. Adding food-grade surfactants (0.1% Sodium dodecyl sulfate-SDS, and 0.1% Tween 20), did not significantly enhance nanobubbles efficacy on bacterial removal from spinach surface.

Use of Nanobubbles to Improve Mass Transfer in Bioprocesses

“…This characteristic is particularly valuable for applications that require stringent environmental compliance [129]. This makes them especially suited for applications such as water treatment and sensitive bioprocesses, where chemical changes can adversely affect microbial communities [136]. Their prolonged presence and ability to improve gas availability mean that fewer external inputs are required, contributing to resource conservation and minimizing environmental impacts.…”

Recent advances in activated water systems for the postharvest management of quality and safety of fresh fruits and vegetables

“…A synergistic study combining pure O 2 ‐nanobubble solution followed by ultrasonication for 5–20 min against an initial count of 6–7 log CFU mL −1 E. coli O157:H7 and L. innocua on spinach leaves was performed; the treatment resulted in >6 log CFU mL −1 reduction of L. innocua after 15 min and 7 log CFU mL −1 reduction for E. coli after 10 min. Nanobubbles in combination with ultrasonication also improved bacterial removal from the surface of spinach leaves, eliminating >2 and 4 log CFU cm −2 of L. innocua and E. coli , respectively (Rafeeq & Ovissipour, 2021). Le Nguyen et al.…”

“…However, extreme internal pressure, temperature, and a rapid collapse are required to support adiabatic compression during MNB collapse to produce ROS. One of the most important ROS generated by oxygen and air MNB is hydroxyl radicals (Rafeeq & Ovissipour, 2021). However, it is still unknown whether MNB‐derived hydroxyl radicals can be produced without applying mechanical and ultrasonic agitation or by lowering pH of the solution (Takahashi et al., 2021; Yasui et al., 2018).…”

Efficacy of Power Ultrasound-Based Hurdle Technology on the Reduction of Bacterial Pathogens on Fresh Produce

“…Several studies have demonstrated the potential of power ultrasound alone or combined with antimicrobial compounds such as chorine, PAA, or organic acids to reduce the bacteria load on the fresh produce surfaces [13,[16][17][18][19][20]. However, many of the studies evaluated washing conditions that were not practical for industry use (e.g., long treatment times).…”