Effect of sequential dry heat and hydrogen peroxide treatment on inactivation of Salmonella Typhimurium on alfalfa seeds and seeds germination

Hong, Eun-Jeong; Kang, Dong‐Hyun

doi:10.1016/j.fm.2015.08.002

Cited by 33 publications

(21 citation statements)

References 34 publications

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“…In addition, different bacterial strains and attachment conditions were used in the two studies. Higher cell concentrations were also used as inocula in several other studies (30)(31)(32), and as expected, the attachment ratios calculated from these studies were lower than what was observed in the present study.…”

Section: Discussionsupporting

confidence: 71%

Differential Attachment of Salmonella enterica and Enterohemorrhagic Escherichia coli to Alfalfa, Fenugreek, Lettuce, and Tomato Seeds

Cui

Walcott

Chen

2017

Appl Environ Microbiol

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Vegetable seeds have the potential to disseminate and transmit foodborne bacterial pathogens. This study was undertaken to assess the abilities of selected Salmonella and enterohemorrhagic Escherichia coli (EHEC) strains to attach to fungicide-treated versus untreated, and intact versus mechanically damaged, seeds of alfalfa, fenugreek, lettuce, and tomato. Surface-sanitized seeds (2 g) were exposed to four individual strains of Salmonella or EHEC at 20°C for 5 h. Contaminated seeds were rinsed twice, each with 10 ml of sterilized water, before being soaked overnight in 5 ml of phosphate-buffered saline at 4°C. The seeds were then vortexed vigorously for 1 min, and pathogen populations in seed rinse water and soaking buffer were determined using a standard plate count assay. In general, the Salmonella cells had higher attachment ratios than the EHEC cells. Lettuce seeds by unit weight had the highest numbers of attached Salmonella or EHEC cells, followed by tomato, alfalfa, and fenugreek seeds. In contrast, individual fenugreek seeds had more attached pathogen cells, followed by lettuce, alfalfa, and tomato seeds. Significantly more Salmonella and EHEC cells attached to mechanically damaged seeds than to intact seeds (P Ͻ 0.05). Although, on average, significantly more Salmonella and EHEC cells were recovered from untreated than fungicide-treated seeds (P Ͻ 0.05), fungicide treatment did not significantly affect the attachment of individual bacterial strains to vegetable seeds (P Ͼ 0.05), with a few exceptions. This study fills gaps in the current body of literature and helps explain bacterial interactions with vegetable seeds with differing surface characteristics.IMPORTANCE Vegetable seeds, specifically sprout seeds, have the potential to disseminate and transmit foodborne bacterial pathogens. This study investigated the interaction between two important bacterial pathogens, i.e., Salmonella and EHEC, and vegetable seeds with differing surface characteristics. This research helps understand whether seed surface structure, integrity, and fungicide treatment affect the interaction between bacterial cells and vegetable seeds.KEYWORDS alfalfa, attachment, EHEC, fenugreek, lettuce, Salmonella, tomato, vegetable seeds G lobally, fresh produce consumption has increased significantly in the last few decades because of the accrued health benefits (1). Since most fresh produce receives minimal processing and is often eaten raw, it can be a vehicle for transmitting foodborne pathogens (2). It is reported that in the United States, fresh produce was the most common vehicle for transmitting foodborne illness and 19% of the foodborne outbreaks and 24% of the illnesses that took place from 2004 to 2013 were associated with fresh produce (3). In general, enterohemorrhagic Escherichia coli (EHEC) and

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Section: Discussionsupporting

confidence: 71%

Differential Attachment of Salmonella enterica and Enterohemorrhagic Escherichia coli to Alfalfa, Fenugreek, Lettuce, and Tomato Seeds

Cui

Walcott

Chen

2017

Appl Environ Microbiol

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“…Similar results were obtained in this study after treatment with 50 mM and 200 mM hydrogen peroxide (C1, C2). So far, an application of H 2 O 2 effectively increased the vigour, microbiological quality, and phenolics content in lentil [13,25] and alfalfa sprouts [29]. However, the use in this study modification of sprouting did not affect strongly the total phenolics content; an increase in the flavonoids content was clearly visible.…”

Section: Resultscontrasting

confidence: 51%

Hydrogen Peroxide Treatment and the Phenylpropanoid Pathway Precursors Feeding Improve Phenolics and Antioxidant Capacity of Quinoa Sprouts via an Induction of L-Tyrosine and L-Phenylalanine Ammonia-Lyases Activities

Świeca

2016

Journal of Chemistry

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Hydrogen peroxide treatment and the phenylpropanoid pathway precursors feeding affected the antioxidant capacity of quinoa sprouts. Compared to the control, total phenolics content was significantly increased by treatment of control sprouts with 50 mM and 200 mM H2O2—an elevation of about 24% and 28%, respectively. The highest increase of flavonoids content was found for the sprouts treated with 200 mM H2O2obtained from seeds fed with shikimic acid. All the studied modifications increased the antioxidant potential of sprouts (at least by 50% compared to control). The highest reducing power was found for the sprouts treated with 200 mM H2O2obtained by phenylalanine feeding (5.03 mg TE/g DW) and those obtained from the seeds fed with tyrosine (5.26 mg TE/g DW). The activities of L-tyrosine (TAL) and L-phenylalanine (PAL) ammonia-lyases were strongly affected by germination time as well as the applied modification of sprouting. On the 3rd day the highest PAL activity was determined for both untreated and induced with 50 mM H2O2sprouts obtained by phenylalanine feeding. H2O2induced TAL activity; the highest TAL activity was determined for 3-day-old sprouts induced with 200 mM H2O2obtained from seeds fed with phenylalanine.

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“…Furthermore, in a humid environment, bacterial cells are much more susceptible to elevated temperatures compared to dry conditions, where higher temperatures are less detrimental. This is supported by several studies that investigated dry heat inactivation of bacteria (Beuchat and Scouten, 2002; Bang et al, 2011; Choi et al, 2016; Hong and Kang, 2016). Thus, the experimental setup used for the investigation of isolated CAPP components in this study might have caused an increase in the temperature of the liquid suspension that contributed to the inactivation of the bacteria by membrane damage, as suggested by the high number of bacteria showing a positive PI stain.…”

Section: Discussionmentioning

confidence: 57%

Characterization of Efficiency and Mechanisms of Cold Atmospheric Pressure Plasma Decontamination of Seeds for Sprout Production

et al. 2018

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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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Effect of sequential dry heat and hydrogen peroxide treatment on inactivation of Salmonella Typhimurium on alfalfa seeds and seeds germination

Cited by 33 publications

References 34 publications

Differential Attachment of Salmonella enterica and Enterohemorrhagic Escherichia coli to Alfalfa, Fenugreek, Lettuce, and Tomato Seeds

Differential Attachment of Salmonella enterica and Enterohemorrhagic Escherichia coli to Alfalfa, Fenugreek, Lettuce, and Tomato Seeds

Hydrogen Peroxide Treatment and the Phenylpropanoid Pathway Precursors Feeding Improve Phenolics and Antioxidant Capacity of Quinoa Sprouts via an Induction of L-Tyrosine and L-Phenylalanine Ammonia-Lyases Activities

Characterization of Efficiency and Mechanisms of Cold Atmospheric Pressure Plasma Decontamination of Seeds for Sprout Production

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