213: Evaluation of Cold Atmospheric Argon Plasma Jet for Inactivation of Listeria Monocytogenes and Preservation of Physicochemical Properties in Strawberries During Refrigerated Storage

Introduction

Cold plasma, a partially ionized gas maintained at low temperatures, is an emerging non-thermal food processing technology. While the CAAP has been extensively studied in biomedical applications, its use for sterilizing fresh produce remains limited. This study aims to evaluate the effect of a cold atmospheric argon plasma jet on the inactivation of Listeria monocytogenes and the physicochemical properties of strawberries during refrigerated storage.

Methods

A 2×2 factorial design was employed with plasma treatment time and frequency as factors. Fresh strawberries were spot-inoculated with 100 µL of concentrated Listeria innocua (8–9 log CFU/mL), air-dried for 1 hour, and subjected to four cold atmospheric argon plasma (CAAP) treatment groups: S1 (1,000 Hz, 1 min), S2 (1,000 Hz, 2 min), S3 (2,000 Hz, 1 min), and S4 (2,000 Hz, 2 min). The CAAP jet treatment was conducted at 3 kV, 55 duty cycles, and a 10 mm probe-to-sample distance. Control groups included uninoculated untreated (control 1) and inoculated untreated (control 2). Treated samples were stored at 4°C and analyzed for L. innocua, aerobic counts, and yeast and mold growth over six days. Additionally, pH, titratable acidity (TA), moisture content, color, total soluble solids, and volatile compounds were evaluated over 12 days. Statistical significance was assessed at α = 0.05.

Results

CAAP treatments significantly reduced (p < 0.05) Listeria innocua in all treatment groups compared to control 2 (3.17 ± 0.54 log CFU/g). The S3 treatment group exhibited the lowest count (0.76 ± 0.86 log CFU/g) among treatments. By day 3, L. innocua was entirely inactivated in all CAAP-treated groups, while control 2 retained 3.27 ± 0.61 log CFU/g. Total aerobic and yeast and mold counts were relatively lower in CAAP-treated samples on day 0 compared to controls, although no significant differences were observed. Physicochemical parameters showed no significant differences between treated and control groups throughout the storage period. These findings demonstrate CAAP's potential to inactivate pathogens on strawberries without affecting their physicochemical properties.

Significance

This study demonstrates that CAAP is a promising and sustainable technology for inactivating pathogenic microbes on fresh produce while maintaining their sensory and physicochemical properties.

Authors: Mariel Benigno, Kaushalya Wickramasinghe, Tharindu Trishan, Mario Melendez, Chien-I Hsu