# Antimicrobial effects of combined piezoelectric cold plasma, organic acids, and nanoemulsions against Salmonella Typhimurium and Listeria monocytogenes on pork

## TL;DR

This study shows that combining cold plasma with organic acids or nanoemulsions can effectively reduce harmful bacteria on pork, offering a non-thermal food safety solution.

## Contribution

The study introduces a non-thermal antimicrobial strategy using piezoelectric cold plasma in combination with organic acids or nanoemulsions for meat safety.

## Key findings

- CAP treatment alone reduced Salmonella Typhimurium and Listeria monocytogenes on polycarbonate membranes in a time-dependent manner.
- Combining CAP with organic acids at specific concentrations and application sequence significantly enhanced antimicrobial efficacy.
- On pork, CAP combined with antimicrobials reduced pathogens by ~1.5 log CFU/g, showing additive effects.

## Abstract

This study evaluated the antimicrobial efficacy of cold atmospheric plasma (CAP) alone and in combination with nanoemulsions or organic acids against pathogens on polycarbonate membranes and pork meat. CAP was generated via piezoelectric direct discharge technology with ambient air as the working gas. On polycarbonate membranes, CAP treatment alone for 15, 30, and 45 s reduced Salmonella Typhimurium by 0.9, 1.4, and 2.4 log CFU/cm2 and Listeria monocytogenes by 0.7, 1.7, and 2.3 log CFU/cm2, respectively, showing a time-dependent antimicrobial effect. When CAP was applied before lactic or acetic acid (at minimum inhibitory concentrations (MICs)/minimum bactericidal concentrations (MBCs)) on polycarbonate membranes, the combined treatments achieved significantly greater reductions (~ 3.6 log CFU/cm2) than when acids were applied before CAP (~ 2.3 log CFU/cm2), highlighting the importance of application sequence. Overall, CAP treatments on polycarbonate membranes showed additive effects when CAP (applied for 15, 30, or 45 s) was combined with antimicrobials (at MIC/MBC). On pork, CAP treatment for 9 min combined with organic acids or nanoemulsions at 10× MIC produced significant additive effects, enhancing pathogen inactivation (by ~ 1.5 log CFU/g) compared with CAP alone or antimicrobials alone under the same conditions. These findings support the application of CAP–antimicrobial combinations as a non-thermal, sustainable strategy to improve meat safety. Further research should evaluate the impact of treatments on the sensory attributes of meat and support their implementation at an industrial scale.

•Cold atmospheric plasma (CAP) generated via piezoelectric direct discharge significantly reduced pathogens on pork and membranes.

• CAP efficiency against Salmonella Typhimurium and Listeria monocytogenes significantly increased with extended exposure time.

•Applying CAP prior to organic acids, significantly increased antimicrobial efficacy, confirming sequence effects.

•CAP combined with antimicrobials reduced pathogens on pork by ~1.5 log CFU/g.

•CAP–antimicrobial combinations represent a promising strategy for meat safety.