Direct non-thermal plasma treatment for the sanitation of fresh corn salad leaves: Evaluation of physical and physiological effects and antimicrobial efficacy |
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Affiliation: | 1. Leibniz Institute for Agricultural Engineering, Max-Eyth-Allee 100, 14469 Potsdam-Bornim, Germany;2. Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Straße 2, 17489 Greifswald, Germany;3. Department of Food Biotechnology and Food Process Engineering, Berlin University of Technology, Königin-Luise-Straße 22, 14195 Berlin, Germany;1. Centre for Innovation Competence plasmatis, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany;2. Leibniz Institute for Plasma Science and Technology, INP Greifswald e.V., Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany;3. Greifswald School of Medicine, Institute for Hygiene and Environmental Health, Walter-Rathenau-Str. 49A, 17475 Greifswald, Germany;1. Department of Food Science and Technology, Seoul Women''s University, Seoul, 139-774, Republic of Korea;2. Department of Food Science and Engineering, Ewha Womans University, Seoul, 120-750, Republic of Korea |
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Abstract: | Current problems with outbreaks of serious infections caused by human pathogens on fresh-cut greens highlight the need for new, optimized postharvest sanitation treatments to effectively meet recent food safety standards. In contrast to various chemical treatments, non-thermal plasma (NTP) has a high potential as a gentle target sanitation technique. However, possible interactions between NTP and the physiology of treated fresh products have not been investigated in detail. Here, chlorophyll fluorescence image analysis (CFIA) was used to study the potential impacts of non-thermal plasma on the photosynthetic activity of highly perishable corn salad leaves as a model produce. For this purpose, an atmospheric pressure plasma jet, driven at radio frequency, and transforming argon with flow rates of 20 L min−1 into non-thermal plasma at 10, 20, 30, and 40 W generator power was applied for various times to the surface of corn salad leaves. Thermographic measurements indicated maximum temperatures of 39.0 °C, 44.4 °C, 60.1 °C, and 66.0 °C, respectively, on treated leaf surfaces. CFIA revealed that treatment at moderate generator power of 20 W for up to 1 min was the maximum setting for quality retention. Furthermore, the microbial inactivation efficiency of the plasma jet system at these operating parameters was successfully tested on Escherichia coli bacteria, inoculated on corn salad surface at 107 cfu cm−2 and 104 cfu cm−2. At 20 W, bacteria with lower initial load could be inactivated by 3.6 (±0.6) log-cycles within 15 s of treatment duration; whereas at the higher initial load of 107 cfu cm−2, bacteria were reduced by 2.1 (±0.2) log-cycles after 30 s. |
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Keywords: | Chlorophyll fluorescence imaging Fresh produce Physical sanitation treatment Postharvest quality Noninvasive methods |
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