Atmospheric pressure plasma jet inactivation of Pseudomonas aeruginosa biofilms on stainless steel surfaces

• Attachment rates were greatest on the rougher steel surface finishes.
• Stainless steel type did not influence attachment rates.
• Inactivation by plasma was greatest on smoother surfaces.
• Inactivation was greatest if allowed to be accompanied with rapid heating.

This study established the efficacy of atmospheric pressure plasma jet on Pseudomonas aeruginosa on stainless steel types 316 and 304; with different finishes namely, mirror (MR), hairline (HL) and 2B surfaces. A cocktail of four strains of P. aeruginosa in the mid-stationary growth phase were allowed to attach on the test surfaces, and subjected to atmospheric pressure plasma jet treatment with an air injection rate of 5 l/min, output power of 360 W at 4.22 cm source-to-surface distance. Attachment rates were significantly affected by surface finish, rather than by stainless steel type. The D-values on the 316 stainless steel type ranged from 2.53 s (MR) to 3.16 s (2B); while those on the 304 type ranged from 1.95 s (HL) to 3.27 s (2B). Variations in D-values were observed between surface finishes within a specific stainless steel type. However, significant variations were not observed between the same surface finish of different steel types. The observed antimicrobial efficacy was attributed to the generation of reactive oxygen species, ultraviolet-C rays, and rapid temperature increase (final temperature of 143.42 °C to 174.05 °C) within 15 s of treatment. In the absence of heating, the D-value increased to 16.45 s, but a 5-log (99.999%) reduction in the population was observed in a relatively short treatment time of 90 s.Industrial relevanceThe results obtained in this work demonstrated the potential of using atmospheric pressure plasma jet technology as a non-chemical, non-thermal, and thermal stainless steel food contact surface decontamination against Pseudomonas aeruginosa, a common biofilm-producing bacterium. Such a technology shall help the industry address the challenge of cross contamination in the food manufacturing and food service settings.