Impact of Gas Ultrafine Bubbles on the Efficacy of Commonly Used Food Antimicrobials

Phoebe Marie Unger

doi:10.7273/000006314

Ultrafine bubbles (UFB) technology is a novel tool in food safety with the potential to improve the potency of antimicrobials for the elimination of spoilage and pathogenic microorganisms. Therefore, the first objective of this work was to investigate the impact of incorporating gas UFB [air and carbon dioxide (CO2)] on the efficacy of chlorine (Cl2; 100 and 200 ppm) and peracetic (PAA; 40 and 80 ppm) antimicrobial solutions against Escherichia coli O157:H7 and Listeria monocytogenes on artificially inoculated Gala apples. In brief, apples were dip inoculated with either E. coli or L. monocytogenes and then treated by dipping into Cl2 or PAA solutions with or without UFB for 1 or 2 min. Apples were then transferred directly into Dey-Engley neutralizing broth, hand massaged for 90 s, and microbial enumerations were performed. The incorporation of CO2 UFB in antimicrobial solutions resulted in significantly greater E. coli and L. monocytogenes reductions (2.1 and 2.4 Log CFU/apple, respectively) on apples compared to solutions without UFB (1.4 and 1.9 Log CFU/apple, respectively). However, the incorporation of air UFB resulted in similar log reductions of E. coli O157:H7 and L. monocytogenes (1.9 and 2.2 Log CFU/apple, respectively) on apples compared to antimicrobials with CO2 UFB and without UFB. The second major objective of this research was to evaluate the impact of incorporating gas [air, CO2, and nitrogen (N2)] UFB into Cl2 (50, 100, and 200 ppm) and PAA (20, 40, and 80 ppm) solutions against fresh (3 day) and aged (30 day) single- and multi-species biofilms of non-spore-forming pathogenic Escherichia coli O157:H7 and Listeria monocytogenes, and spore-forming non-pathogenic Bacillus subtilis on polypropylene, silicone, and stainless-steel surfaces. Biofilms were statically grown on polypropylene, silicone, and stainless steel coupons at 25°C for 3 days or 30 days, by immersing in a 3-strain cocktail of the respective bacteria in brain heart infusion (BHI) broth. Then coupons were treated by submerging in antimicrobial solutions with or without UFB for 1 minute, then swabbed into Dey-Engley neutralizing broth and enumerated. The incorporation of CO2 UFB in Cl2 and PAA antimicrobial solutions resulted in significantly greater log reductions of fresh and aged L. monocytogenes, E. coli O157: H7, B. subtilis and multi-species biofilms on all tested surfaces compared to antimicrobial solutions without UFB. This work shows the great potential of UFB in the food industry to enhance food safety.

Impact of Gas Ultrafine Bubbles on the Efficacy of Commonly Used Food Antimicrobials

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