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Investigation of a large gap cold plasma reactor for continuous in-package decontamination of fresh strawberries and spinach
2020-01, Ziuzina, Dana, Misra, N. N., Han, L., Bourke, Paula, et al.
The aim of this work was to investigate the efficacy of a large gap atmospheric cold plasma (ACP) generated with an open-air high-voltage dielectric barrier discharge (DBD) pilot-scale reactor, operated in either static (batch) or continuous mode for produce decontamination and quality retention. Significant reductions in the bacterial populations inoculated on the strawberries and spinach were obtained after the static mode of ACP treatment with 2.0 and 2.2 log10 CFU/ml reductions for E. coli and 1.3 and 1.7 log10 CFU/ml reductions for L. innocua, respectively. Continuous treatment was effective against L. innocua inoculated on strawberries, with 3.8 log10 CFU/ml reductions achieved. No significant differences in colour, firmness, pH or total soluble solids (TSS) was observed between control and ACP-treated samples with the effects of treatment retained during the shelf-life period. The pilot-scale atmospheric air plasma reactor retained the strawberry quality characteristics in tandem with useful antimicrobial efficacy. Industrial relevance: This in-package plasma technology approach is a low-power, water-free, non-thermal, post-package treatment. Generating cold plasma discharges inside food packages achieved useful antimicrobial effects on fresh produce. Depending on the bacterial type, produce and mode of ACP treatment significant reductions in the populations of pathogenic microorganisms attached to the fresh produce was achieved within 2.5 min of treatment. The principal technical advantages include contaminant control, quality retention, mitigation of re-contamination and crucially the retention of bactericidal reactive gas molecules in the food package volume, which then revert back to the original gas.
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Controlling microbial safety challenges of meat using high voltage atmospheric cold plasma
2016-06-22, Han, L., Ziuzina, Dana, Heslin, Caitlin, Bourke, Paula, et al.
Atmospheric cold plasma (ACP) is a non-thermal technology, effective against a wide range of pathogenic microorganisms. Inactivation efficacy results from plasma generated reactive species. These may interact with any organic components in a test matrix including the target microorganism, thus food components may exert a protective effect against the antimicrobial mode of action. The effect of an in-package high voltage ACP process applied in conjunction with common meat processing MAP gas compositions as well as bacteria type and meat model media composition have been investigated to determine the applicability of this technology for decontamination of safety challenges associated with meat products. E. coli, L. monocytogenes, and S. aureus in PBS were undetectable after 60 s of treatment at 80 kVRMS in air, while ACP treatment of the contaminated meat model required post-treatment refrigeration to retain antimicrobial effect. The nutritive components in the meat model exerted a protective effect during treatment, where 300 s ACP exposure yielded a maximum reduction of 1.5 log using a high oxygen atmosphere, whilst using air and high nitrogen atmospheres yielded lower antimicrobial efficacy. Furthermore, an ROS assay was performed to understand the protective effects observed using the meat model. This revealed that nutritive components inhibited penetration of ROS into bacterial cells. This knowledge can assist the optimization of meat decontamination using ACP technology where interactions with all components of the food matrix require evaluation.