Effect of gas ultrafine bubbles on the potency of antimicrobials against Escherichia coli O157:H7 biofilms on various food processing surfaces

This study investigated the impact of incorporating gas [air, carbon dioxide (CO₂), and nitrogen (N₂)] UFB on the potency of chlorine (Cl₂; 50, 100, and 200 ppm) and peracetic acid (PAA; 20, 40, and 80 ppm) antimicrobial (AM) solutions against fresh (3 days) and aged (30 days) E. coli O157:H7 biofilms on polypropylene, silicone, and stainless-steel surfaces. The biofilms were statically grown on polypropylene, silicone, and stainless-steel coupons (7.62 × 2.54 cm) at 25°C for 3 or 30 days by immersing in a 3-strain cocktail of E. coli. The incorporation of air, CO₂, and N₂ UFB in AM solutions resulted in significantly increased log reductions (2.1–3.7 logs) in fresh and aged E. coli biofilms on all surfaces compared to solutions without UFB, except for N₂ UFB on aged stainless-steel biofilms and air UFB on aged polypropylene biofilms, which resulted in similar log reductions as solutions without UFB (1.5–2.1 logs).