Inactivation of Escherichia coli O157:H7 on Radish Seeds by Sequential Treatments with Chlorine Dioxide, Drying, and Dry Heat without Loss of Seed Viability

Abstract

We developed and validated a treatment to inactivate Escherichia coli O157:H7 on radish seeds without decreasing seed viability. Treatments with aqueous ClO 2 followed by drying and dry-heat treatments were evaluated for efficacy to inactivate the pathogen. Conditions to dry radish seeds after treatment with water (control) or ClO 2 were established. When treated seeds with high water activity (a w ) (>0.99) were stored at 45°C and 23% relative humidity (RH), the a w decreased to <0.30 within 24 h. Drying high-a w seeds before exposing them to dry-heat treatment (>60°C) was essential to preserve seed viability. The germination rate of radish seeds which had been immersed in water for 5 min, dried at 45°C and 23% RH for 24 h, and heated at 70°C for 48 h or at 80°C for 24 h was not significantly decreased (P < 0.05) compared to that of untreated radish seeds. Sequential treatments with ClO 2 (500 g/ml, 5 min), drying (45°C, 23% RH, 24 h), and dry heating (70°C, 23% RH, 48 h) eliminated E. coli O157:H7 (5.9 log CFU/g) on radish seeds and, consequently, sprouts produced from them without decreasing the germination rate. These sequential treatments are recommended for application to radish seeds intended for sprout production.

Seasonal and Growth‐Dependent Dynamics of Bacterial Community in Radish Sprouts

“…To date, no methods can completely decontaminate bacteria residing in plant seeds, and combined physical and/or chemical treatments are currently used to efficiently reduce bacterial contamination (MAFF 2003;Bang et al 2011;Ding et al 2013). Our data demonstrating the predominance of Halospirulina spp.…”

Development of an antimicrobial sachet containing encapsulated allyl isothiocyanate to inactivate Escherichia coli O157:H7 on spinach leaves

“…This may indicate that the resistance of MY to environmental stresses is greater than that of E. coli O157:H7 because they had colonized on the surface of spinach leaves for a longer period of time. Bang et al (2011bBang et al ( , 2011c reported that E. coli O157:H7 was more sensitive than mesophilic aerobic microorganisms or MY to environmental stresses on radish seeds. It was suggested that these microorganisms and MY were already established on the seeds prior to treatment, making them more resistant than E. coli O157:H7, which was artificially inoculated onto seeds.…”

Reduction of Salmonella enterica on the surface of eggshells by sequential treatment with aqueous chlorine dioxide and drying

“…Treatment with either water or NaOCl followed by drying caused A C C E P T E D M A N U S C R I P T Although reports on the synergistic lethal effect of ClO 2 and drying on S. enterica have not appeared to date, reports on other foodborne pathogens exposed to these sequential treatments have been published. For example, it was found that treatment with ClO 2 followed by drying or dry heat exerted a synergistic lethal effect on E. coli O157:H7 on radish seeds (Bang et al 2011a(Bang et al , 2011b(Bang et al , 2011cKim et al, 2010). Kreske et al (2006) found that planktonic B. cereus spores exposed to ClO 2 were more sensitive to wet heat than those exposed to chlorine.…”

“…Studies in our laboratories have indicated that sequential treatment with ClO 2 and other stressors results in synergistic lethal effects against foodborne pathogens. Cells of Escherichia coli O157:H7 exposed to ClO 2 were more sensitive to desiccation (Bang et al, 2014;Kim et al, 2010) and dryheat (Bang et al, 2011a(Bang et al, , 2011b(Bang et al, , 2011c. Kreske et al (2006) reported that spores of Bacillus cereus or B. thuringiensis treated with ClO 2 had decreased tolerance to wet-heat.…”