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Waskow A, Butscher D, Oberbossel G, Klöti D, Rudolf von Rohr P, Büttner-Mainik A, Drissner D, Schuppler M. Low-energy electron beam has severe impact on seedling development compared to cold atmospheric pressure plasma. Sci Rep 2021; 11:16373. [PMID: 34385534 PMCID: PMC8360967 DOI: 10.1038/s41598-021-95767-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 07/20/2021] [Indexed: 02/07/2023] Open
Abstract
Sprouts are germinated seeds that are often consumed due to their high nutritional content and health benefits. However, the conditions for germination strongly support the proliferation of present bacteria, including foodborne pathogens. Since sprouts are consumed raw or minimally processed, they are frequently linked to cases of food poisoning. Therefore, a seed decontamination method that provides efficient inactivation of microbial pathogens, while maintaining the germination capacity and quality of the seeds is in high demand. This study aimed to investigate and compare seed decontamination by cold atmospheric-pressure plasma and low-energy electron beam with respect to their impact on seed and seedling quality. The results show that both technologies provide great potential for inactivation of microorganisms on seeds, while cold plasma yielded a higher efficiency with 5 log units compared to a maximum of 3 log units after electron beam treatment. Both techniques accelerated seed germination, defined by the percentage of hypocotyl and leaf emergence at 3 days, with short plasma treatment (< 120 s) and all applied doses of electron beam treatment (8-60 kGy). However, even the lowest dose of electron beam treatment at 8 kGy in this study caused root abnormalities in seedlings, suggesting a detrimental effect on the seed tissue. Seeds treated with cold plasma had an eroded seed coat and increased seed wettability compared to electron beam treated seeds. However, these effects cannot explain the increase in the germination capacity of seeds as this was observed for both techniques. Future studies should focus on the investigation of the mechanisms causing accelerated seed germination and root abnormalities by characterizing the molecular and physiological impact of cold plasma and electron beam on seed tissue.
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Affiliation(s)
- A Waskow
- Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092, Zurich, Switzerland
- Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - D Butscher
- Institute of Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092, Zurich, Switzerland
- BASF Personal Care and Nutrition GmbH, Illertissen, Germany
| | - G Oberbossel
- Institute of Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092, Zurich, Switzerland
| | - D Klöti
- Competence Division for Plants and Plant Products, Seed Quality, Agroscope, Reckenholzstrasse 191, 8046, Zurich, Switzerland
| | - P Rudolf von Rohr
- Institute of Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092, Zurich, Switzerland
| | - A Büttner-Mainik
- Competence Division for Plants and Plant Products, Seed Quality, Agroscope, Reckenholzstrasse 191, 8046, Zurich, Switzerland
| | - D Drissner
- Department of Life Sciences, Albstadt-Sigmaringen University, Anton-Günther-Strasse 51, 72488, Sigmaringen, Germany
| | - M Schuppler
- Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092, Zurich, Switzerland.
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Waskow A, Betschart J, Butscher D, Oberbossel G, Klöti D, Büttner-Mainik A, Adamcik J, von Rohr PR, Schuppler M. Characterization of Efficiency and Mechanisms of Cold Atmospheric Pressure Plasma Decontamination of Seeds for Sprout Production. Front Microbiol 2018; 9:3164. [PMID: 30619223 PMCID: PMC6305722 DOI: 10.3389/fmicb.2018.03164] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Accepted: 12/06/2018] [Indexed: 11/17/2022] Open
Abstract
The consumption of fresh fruit and vegetable products has strongly increased during the past few decades. However, inherent to all minimally processed products is the short shelf life, and the risk of foodborne diseases, which have been increasingly related to such products in many parts of the world. Because of the favorable conditions for the growth of bacteria during the germination of seeds, sprouts are a frequent source for pathogenic bacteria, thus highlighting the need for seed decontamination to reduce the risk of foodborne illness. Consequently, this study focused on cold atmospheric pressure plasma (CAPP) treatment of artificially inoculated seeds in a diffuse coplanar surface barrier discharge to determine the inactivation efficiency for relevant foodborne pathogens and fungal spores. Plasma treatment of seeds resulted in a highly efficient reduction of microorganisms on the seed surface, while preserving the germination properties of seeds, at least for moderate treatment times. To characterize the mechanisms that contribute to microbial inactivation during plasma treatment, an experimental setup was developed to separate ultraviolet light (UV) and other plasma components. The combination of bacterial viability staining with confocal laser scanning microscopy was used to investigate the impact of ozone and other reactive species on the bacterial cells in comparison to UV. Further characterization of the effect of CAPP on bacterial cells by atomic force microscopy imaging of the same Escherichia coli cells before and after treatment revealed an increase in the surface roughness of treated E. coli cells and a decrease in the average height of the cells, which suggests physical damage to the cell envelope. In conclusion, CAPP shows potential for use as a decontamination technology in the production process of sprouts, which may contribute to food safety and prolonged shelf life of the product.
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Affiliation(s)
- Alexandra Waskow
- Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland
| | - Julian Betschart
- Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland
| | - Denis Butscher
- Institute of Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Gina Oberbossel
- Institute of Process Engineering, ETH Zurich, Zurich, Switzerland
| | | | | | - Jozef Adamcik
- Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland
| | | | - Markus Schuppler
- Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland
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Butscher D, Van Loon H, Waskow A, Rudolf von Rohr P, Schuppler M. Plasma inactivation of microorganisms on sprout seeds in a dielectric barrier discharge. Int J Food Microbiol 2016; 238:222-232. [PMID: 27668570 DOI: 10.1016/j.ijfoodmicro.2016.09.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 08/31/2016] [Accepted: 09/11/2016] [Indexed: 11/29/2022]
Abstract
Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties.
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Affiliation(s)
- Denis Butscher
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland
| | - Hanne Van Loon
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland; ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland
| | - Alexandra Waskow
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland; ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland
| | | | - Markus Schuppler
- ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
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Butscher D, Zimmermann D, Schuppler M, Rudolf von Rohr P. Plasma inactivation of bacterial endospores on wheat grains and polymeric model substrates in a dielectric barrier discharge. Food Control 2016. [DOI: 10.1016/j.foodcont.2015.09.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Butscher D, Schlup T, Roth C, Müller-Fischer N, Gantenbein-Demarchi C, Rudolf von Rohr P. Inactivation of microorganisms on granular materials: Reduction of Bacillus amyloliquefaciens endospores on wheat grains in a low pressure plasma circulating fluidized bed reactor. J FOOD ENG 2015. [DOI: 10.1016/j.jfoodeng.2015.03.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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