Cold plasma and organic acid treatment combination enhances inactivation of salmonella bacteria on tomato stem scar surfaces

Authors: Ukuku, Dike; Niemira, Brendan; Olanya, Modesto; Mukhopadhyay, Sudarsan

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2023
Publication Date: 7/19/2023
Citation: Ukuku, D.O., Niemira, B.A., Olanya, O.M., Mukhopadhyay, S. 2023. Cold plasma and organic acid treatment combination enhances inactivation of salmonella bacteria on tomato stem scar surfaces. In: International Association for Food protection (IAFP) 2023 Program Book, Toronto, Ontario, Canada; July 16-19, 2023. p. 230.

Interpretive Summary: A treatment combination of organic acid solution with cold plasma was investigated for inactivation on Salmonella bacteria inoculated on tomato stem scar surfaces. The tomatoes were spot inoculated or by total submersion in 107 CFU/ml Salmonella inoculum for 3 min to achieve average populations of 5.6 ± 0.14 log CFU/ g and 3.9 ± 0.12 log CFU/g, respectively. Tomato stem scars were surface treated with antimicrobial solution and cold plasma for 30 s, 60 s, 120 s, 180 s and 360 s, and a combination of the two, led to a significant inactivation of bacterial populations. Organic acid and cold plasma treatments for 180 s led to 2.2 and 1.9 log CFU/g inactivation of Salmonella bacteria respectively, 1.9 log CFU/g and 1.6 log CFU/g for aerobic mesophilic bacteria, and a < 0.1 CFU/g for yeast, and mold. Combined treatments for 120 s and above led to a < 0.3 CFU/g reduced populations of aerobic mesophilic bacteria and caused 4.9 log CFU/g reduction of Salmonella bacteria on tomato surfaces suggesting that a combination treatment will lead to improved microbial safety of tomatoes.

Technical Abstract: INTRODUCTION: Produce industry and research institutions are trying to come up with ways to reduce bacterial populations on fruits and vegetables. In this study, we investigated antimicrobial efficacy of organic acid solution combined with cold plasma treatment in reducing aerobic mesophilic bacteria and Salmonella populations inoculated on tomato stem scar surfaces. METHODOLOGY: Tomatoes were spot inoculated or by total submersion in 107 CFU/ml Salmonella inoculum for 3 min to achieve an average of 5.6 ± 0.14 log CFU/ g and 3.9 ± 0.12 log CFU/g, respectively. All inoculated tomatoes were treated separately with antimicrobial solution, cold plasma, and a combination of the two for 30 s, 60 s, 120 s, 180 s and 360 s. RESULTS: Separate treatments of each for 120 s led to a significant inactivation of bacterial populations. Treatments with organic acid alone for 180 s led to 1.9 log CFU/g inactivation of aerobic mesophilic bacteria and 1.6 log CFU/g for cold plasma, while both treatments led to < 0.1 CFU/g for yeast, and mold. Treatment combination for 120 s led to 2.2 and 1.9 log CFU/g inactivation of Salmonella bacteria, respectively on spot and dip inoculated tomatoes and reduced the aerobic mesophilic bacteria populations to < 0.3 CFU/g. CONCLUSION: This result suggests that a combination treatment for = 120 s to = 180 s is recommended for a higher inactivation of Salmonella bacteria on tomato stem scar surfaces to improve the microbial safety.