An effective sanitizer for fresh produce production:In situplasma activated water treatment inactivates pathogenic bacteria and maintains the quality of cucurbit fruit

Abstract

The effect of plasma activated water (PAW) generated with a dielectric barrier discharge diffusor (DBDD) system on microbial load and organoleptic quality of cucamelons was investigated and compared to the established sanitizer, sodium hypochlorite (NaOCl). Pathogenic serotypes of Escherichia coli, Salmonella enterica, and Listeria monocytogenes were inoculated onto the surface of cucamelons (6.5 log CFU g-1) and into the wash water (6 log CFU mL-1). PAW treatment involved 2 minutes in situ with water activated at 1500 Hz and 120 V, and air as the feed gas; NaOCl treatment was a wash with 100 ppm total chlorine; and the control treatment was a wash with tap water. PAW treatment produced a 3 log CFU g-1reduction of pathogens on the cucamelon surface without negatively impacting quality or shelf life. NaOCl treatment reduced the pathogenic bacteria on the cucamelon surface by 3-4 log CFU g-1, however, this treatment also reduced fruit shelf life and quality. Both systems reduced 6 log CFU ml-1pathogens in the wash water to below detectable limits. The critical role of superoxide anion radical (·O2-) in the antimicrobial power of DBDD-PAW was demonstrated through a scavenger assay, and chemistry modelling confirmed that ·O2-generation readily occurs in DBDD-PAW generated with the employed settings. Modelling of the physical forces produced during plasma treatment showed that bacteria likely experience strong local electric fields and polarization. We hypothesize that these physical effects synergise with reactive chemical species to produce the acute antimicrobial activity seen with the in situ PAW system.

Transcriptional Signatures Associated with the Survival ofEscherichia coliBiofilm During Treatment with Plasma-Activated Water

“…We have previously shown that PAW can enhance the antibiofilm activity of topical chronic wound antiseptics underscoring its clinical application 6 . We have also demonstrated PAW's ability to outcompete bleach as a fresh produce sanitiser in the context of the food industry 7 . More recently, we have generated PAW with differing gas input sources (air, argon, nitrogen and oxygen), finding PAW generated with oxygen as the most effective at eradicating E. coli biofilms that contaminate stainless-steel surfaces 5 .…”

“…PAW contains various RONS crucial for its antimicrobial effectiveness against bacteria such as E. coli, S. aureus and Listeria monocytogenes [5][6][7] . PAW, produced with different gas sources, yields diverse RONS 4,5 .…”

“…The versatility of PAW is attractive and the composition can be further modified dependent on the reactor type, voltage settings, frequency discharge, or by using alternate liquids (e.g., tap water, saline solution and buffers). RONS are widely accepted as the microbicidal component of PAW, with activity against biofilm and planktonic Gram-negative and Gram-positive bacteria, fungi and viruses [5][6][7][8][9] . PAW targets multiple microbial components such as the membrane, proteins, lipids and nucleic acids 4,6,10 .…”

Optimizing chitosan‐enriched salicylic acid coating to extend the shelf‐life of fresh‐cut radishes using response surface methodology

“…Much higher whiteness values were observed in NaClO‐treated samples compared to that in CS–SA. This might due to the bleaching and antioxidant capacity induced by the oxidation of hypochlorite (ClO − ) in NaClO solution (Rothwell Joanna et al, 2023). Furthermore, the interference of coating film color (brown) might cause the lower whiteness values in samples compared to that in NaClO.…”