Aqueous Chlorine Dioxide Research Articles

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes on stored iceberg lettuce by aqueous chlorine dioxide treatment.

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes in iceberg lettuce by aqueous chlorine dioxide (ClO(2)) treatment was evaluated. Iceberg lettuce samples were inoculated with approximately 7 log CFU/g of E. coli O157:H7, S. typhimurium, and L. monocytogenes. Iceberg lettuce samples were then treated with 0, 5, 10, or 50 ppm ClO(2) solution and stored at 4 degrees C. Aqueous ClO(2) treatment significantly decreased the populations of pathogenic bacteria on shredded lettuce (P < 0.05). In particular, 50 ppm ClO(2) treatment reduced E. coli O157:H7, S. typhimurium, and L. monocytogenes by 1.44, 1.95, and 1.20 log CFU/g, respectively. The D(10)-values of E. coli O157:H7, S. typhimurium, and L. monocytogenes in shredded lettuce were 11, 26, and 42 ppm, respectively. The effect of aqueous ClO(2) treatment on the growth of pathogenic bacteria during storage was evaluated, and a decrease in the population size of these pathogenic bacteria was observed. Additionally, aqueous ClO(2) treatment did not affect the color of lettuce during storage. These results suggest that aqueous ClO(2) treatment can be used to improve the microbial safety of shredded lettuce during storage.

Effects of aqueous chlorine dioxide treatment on browning of fresh-cut lotus root

Effect of aqueous chlorine dioxide (ClO 2) treatment on browning of fresh-cut lotus root (FLR) was investigated to explore the feasibility to apply ClO 2 for browning inhibition of fresh-cut products. Cut lotus roots were treated in ClO 2 solutions at different concentrations (10, 50 and 100 mg/l) for different time (5, 10 and 15 min), followed by chilled storage for 8–10 days at 4 °C. Color parameters ( L ∗, a ∗ and b ∗), polyphenol oxidase (PPO) activity and overall visual quality (OVQ) were measured at one-day interval during storage. Results showed that higher ClO 2 concentration and longer treatment time can provide better inhibitory effects on the browning of FLR. ClO 2 concentration, treatment time and storage time were three significant factors ( P < 0.05) and some significant interactions were observed. PPO activities were largely inhibited by 100 mg/l ClO 2 treatment for 10 min. The 100 mg/l ClO 2 treatment maintained high OVQ scores during 10-day storage; while 50 mg/l ClO 2 treatment was acceptable for maintaining OVQ during 4-day storage. ClO 2 treatment was demonstrated to be a promising alternative approach to control browning and improve OVQ of FLR.

Inactivation of Agrobacterium tumefaciens Inoculated on Fresh Radix Ginseng by Electron Beam Irradiation and Aqueous Chlorine Dioxide Treatment

Inactivation of Agrobacterium tumefaciens was evaluated on the inoculated fresh Radix Ginseng by electron beam irradiation or aqueous chlorine dioxide () treatment. Two groups of fresh ginsengs were prepared and inoculated with A. tumefaciens. One group was then irradiated at 0, 2, and 4 kGy using an electron beam accelerator, and the other group was treated with 0, 50, and 100 ppm of aqueous . Microbiological data indicated that populations of A. tumefaciens significantly decreased with increasing irradiation dose or aqueous concentration. In particular, A. tumefaciens was eliminated by irradiation at 4 kGy, and 100 ppm treatment reduced the populations of A. tumefaciens by 1.44 log CFU/g. These results suggest that electron beam irradiation or aqueous treatment can be useful in improving the microbial safety of fresh ginsengs during storage.

Treatment with chlorine dioxide extends the vase life of selected cut flowers

The accumulation of bacteria in vase water is often associated with premature senescence in many cut flower species. In the present study, we tested the efficacy of aqueous chlorine dioxide (ClO 2) to extend flower display life by preventing the build-up of bacteria in vase solutions. The addition of 2 or 10 μL L −1 ClO 2 to clean deionized water extended the vase life of Alstroemeria peruviana ‘Senna’, Antirrhinum majus ‘Potomic Pink’, Dianthus caryophyllus ‘Pasha’, Gerbera jamesonii ‘Monarch’, Gypsophila paniculata ‘Crystal’ and ‘Perfecta’, Lilium asiaticum ‘Vermeer’, Matthiola incana ‘Ruby Red’ and Rosa hybrida ‘Charlotte’ flowers by 0.9–13.4 d (7–77%) relative to control (i.e. 0 μL L −1 ClO 2) stems. The beneficial effects of ClO 2 treatment were associated with a reduction in the accumulation of aerobic bacteria in vase water and on cut surfaces of flower stems. ClO 2 treatment was also effective in maintaining or extending the vase life of A. majus ‘Potomic Pink’, Dendrathema × grandiflorum ‘Albatron’, G. paniculata ‘Perfecta’ and M. incana ‘Ruby Red’ flowers even when stems were placed into water containing 10 11 CFU L −1 bacteria. The efficacy of 10 μL L −1 ClO 2 in vase water containing 0.2 g L −1 citric acid and 10 g L −1 sucrose to extend the display life of G. jamesonii ‘Lorca’ and ‘Vilassar’ flowers was equal to or greater than other tested biocides (i.e. aluminum sulfate, dichloroisocyanuric acid, 8-hydroxyquinoline sulfate, Physan 20™, sodium hypochlorite). Taken collectively, the results of the present study highlight the potential of aqueous ClO 2 for use as an alternative antibacterial agent in flower vase solutions.

Effect of Aqueous Chlorine Dioxide Treatment on the Microbial Growth and Quality of Chicken Legs during Storage

The effect of aqueous chlorine dioxide (ClO₂) treatment on microbial growth and quality of chicken leg during storage was examined. Chicken leg samples were treated with 0, 50, and 100 ppm of ClO₂ solution and stored at 4℃. Aqueous ClO₂ treatment significantly decreased the populations of total aerobic bacteria, yeast and mold, and coliforms in chicken leg. One hundred ppm ClO₂ treatment reduced the initial populations of total aerobic bacteria, yeast and mold, and coliforms by 0.93, 1.15, and 0.94 log CFU/g, respectively. The pH and volatile basic nitrogen values in the chicken leg decreased with increasing aqueous ClO₂ concentration, while concentrations thiobarbituric acid reactive substances (TBARS) increased during storage regardless of aqueous ClO₂ concentration. Sensory evaluation results revealed that the quality of the chicken leg treated with aqueous ClO₂ during storage was better than that of the control. These results indicate that aqueous ClO₂ treatment can be useful for improving the microbial safety of chicken leg during storage.

Inactivation of Listeria monocytogenes and Campylobacter jejuni in Chicken by Aqueous Chlorine Dioxide Treatment

Aqueous chlorine dioxide (ClO₂) treatment was used for the inactivation of Listeria monocytogenes and Campylobacter jejuni in chicken. Chicken breasts and legs were inoculated with 8~9 log CFU/g of Listeria monocytogenes and Campylobacter jejuni, respectively, and then treated with 0, 50, and 100 ppm of ClO₂ solution. Aqueous ClO₂ treatment decreased the populations of the pathogenic bacteria on the chicken samples. One hundred ppm ClO₂ treatment on the chicken breast and leg reduced the populations of Listeria monocytogenes and Campylobacter jejuni by 0.61~1.93 and 0.99~1.21 log CFU/g, respectively. Aqueous ClO₂ treatment affected the microbial growth during storage at 4oC by decreasing the initial microbial populations. These results clearly suggest that aqueous ClO₂ treatment should be useful in improving the microbial safety of chicken during storage and extending the shelf life.

Aqueous Chlorine Dioxide Treatment Improves the Shelf Life of Panax ginseng C.A. Meyer

Effect of aqueous chlorine dioxide (ClO₂) treatment on the quality change of fresh ginseng during storage was examined. Fresh ginseng samples were treated with 0, 50, and 100 ppm of ClO₂ solution, respectively, and stored at 4℃. Microbiological data of the fresh ginseng after ClO₂ treatment revealed that the populations of total aerobic bacteria, and yeast and mold were significantly reduced with the increase of ClO₂ concentration. In particular, the populations of total aerobic bacteria, and yeast and mold in the fresh ginseng decreased by 2.1 and 1.2 log CFU/g at 100 ppm ClO₂ treatment, respectively. Aqueous ClO₂ treatment improved the color of the fresh ginseng during storage, but there was no significant difference in weight loss during storage among treatments. Sensory evaluation results represented that the qualities of the fresh ginseng treated with aqueous ClO₂ during storage were better than those of the control. These results clearly indicate that aqueous ClO₂ treatment could be useful in decreasing the microbial growth and extending the shelf life of fresh ginseng.

Combined Effect of Aqueous Chlorine Dioxide and Modified Atmosphere Packaging on Inhibiting Salmonella Typhimurium and Listeria monocytogenes in Mungbean Sprouts

This study was conducted to investigate the effect of chlorine dioxide (ClO2) combined with modified atmosphere packaging (MAP) on inhibiting total mesophilic microorganisms, Salmonella Typhimurium, and Listeria monocytogenes in mungbean sprouts during refrigerated storage. Mungbean sprouts were packaged using 4 different methods (air, vacuum, CO2 gas, and N2 gas) following treatment with water or 100 ppm ClO2 for 5 min and stored at 5 +/- 2 degrees C. The population of total mesophilic microorganisms in mungbean sprouts was about 8.4-log(10) CFU/g and this level was not significantly reduced by treatment with water or ClO2 (P > 0.05). However, when samples were packaged under vacuum, N2 gas, or CO2 gas following treatment with ClO2, the populations of total mesophilic microorganisms were significantly reduced during storage (P < 0.05). Levels of S. Typhimurium and L. monocytogenes in mungbean sprouts following inoculation were 4.6- and 5.6-log(10) CFU/g and treatment with water followed by different packaging conditions (air, vacuum, N2 gas, and CO2 gas) had no significant effect on population reduction (P > 0.05). However, treatment with ClO2 significantly reduced populations of S. Typhimurium and L. monocytogenes by 3.0- and 1.5-log CFU/g, respectively (P < 0.05), and these reduced cell levels were maintained or decreased in samples packaged under vacuum or in N2 or CO2 gas during storage. These results suggest that the combination of ClO2 treatment and MAP such as CO2 gas packaging may be useful for inhibiting microbial contamination and maintaining quality in mungbean sprouts during storage.

Aqueous Chlorine Dioxide Treatment Decreases Microbial Contamination and Preserves Sensory Properties of Mackerel During Storage

Effect of aqueous chlorine dioxide (ClO₂) treatment on quality change of mackerel during storage was examined. Mackerel treated with 0, 5, 10, and 50 ppm of ClO₂ solution, respectively was stored at 4℃. ClO₂ treatment decreased populations of aerobic bacteria in mackerel during storage. The number of total aerobic bacteria of mackerel treated with 50 ppm ClO₂ increased from 2.45 to 3.44 log CFU/g after 9 days of storage, while that of the control increased from 3.47 to 4.72 log CFU/g. The pH values of mackerel increased during storage, with no significant changes among treatments. Volatile basic nitrogen values of mackerel were decreased by ClO₂ treatment. Quality of mackerel treated with ClO₂ was better than that of the control during storage based on sensory evaluation. These results indicate that aqueous ClO₂ treatment could be useful for improving the microbial safety and qualities of mackerel.

Effect of a simple chlorine dioxide method for controlling five foodborne pathogens, yeasts and molds on blueberries

The effect of aqueous chlorine dioxide (ClO 2) on controlling foodborne pathogens, yeasts, and molds on blueberries was studied. Five pathogens were spot-inoculated on the skin of blueberries. A sachet containing necessary chemicals for generation of ClO 2 was used to provide 320 ppm of ClO 2 in 7.5 l of water. The efficacy of different concentrations (1, 3, 5, 10, and 15 ppm) of ClO 2 and various contact times (10 s; 1, 5, 10, 20, 30 min; and 1 h and 2 h) were studied. ClO 2 was most effective in reducing Listeria monocytogenes (4.88 log cfu/g) as compared to the other pathogens. Pseudomonas aeruginosa was reduced by 2.16 log cfu/g after 5 min when treated with 15 ppm of ClO 2. Relatively short treatment time was more effective in reducing Salmonella Typhimurium than longer treatment time for most concentrations. The highest reduction (4.56 log cfu/g) of Staphylococcus aureus was achieved with 15 ppm of ClO 2 for 30 min. When treated for 2 h with 5 ppm of ClO 2, Yersinia enterocolitica was reduced by 3.49 log cfu/g. Fifteen ppm of ClO 2 reduced natural yeasts and molds by 2.82 log cfu/g after 1 h. Concentrations of ClO 2 decreased over time. When exposed to blueberries, ClO 2 concentrations were further reduced, showing significant degradation.

Using Aqueous Chlorine Dioxide To Prevent Contamination of Tomatoes with Salmonella enterica and Erwinia carotovora during Fruit Washing

Chlorine dioxide (ClO2) is an antimicrobial agent recognized for its disinfectant properties. In this study, the sanitizing effects of ClO2 solutions against Salmonella enterica and Erwinia carotovora in water, on tomato surfaces, and between loads of tomatoes were evaluated. In water, ClO2 at 5, 10, and 20 ppm caused a ≥5-log reduction of S. enterica within 6, 4, and 2 s, respectively. Higher lethality was observed with E. carotovora; a 5-log reduction was achieved after only 2 s with 10 ppm ClO2. On fruit surfaces, however, the sanitizing effects were compromised. A full minute of contact with ClO2 at 20 and 10 ppm was required to achieve a 5-log reduction in S. enterica and E. carotovora counts, respectively, on freshly spot-inoculated tomatoes. On inoculated fruit surfaces, populations decreased >3 log CFU/cm2 during desiccation at 24 ± 1°C for 24 h. Populations of air-dried Salmonella and Erwinia were not significantly reduced (P > 0.05) by ClO2 at ≤20 ppm after 1 min. Either wet or dry inoculum of these two pathogens could contaminate immersion water, which in turn can cross-contaminate a subsequent load of clean fruit and water. ClO2 at 5 ppm used for immersion effectively prevented cross-contamination. Pathogen contamination during fruit handling is best prevented with an effective disinfectant. Once a load of fruit is contaminated with pathogens, even a proven disinfectant such as ClO2 cannot completely eliminate such contaminants, particularly when they are in a dehydrated state on fruit.

Effects of aqueous chlorine dioxide treatment on polyphenol oxidases from Golden Delicious apple

Effects of chlorine dioxide (ClO 2) treatment on the activity and characteristics of polyphenol oxidase (PPO) in Golden Delicious apples were studied. The treatment with 50 mg/l ClO 2 for 1 h did not affect some characteristics of the PPO, including its optimum pH value (5.0) and temperature (40 °C) as well as the maximum absorption wavelength (412 nm) of the final products. With increasing ClO 2 concentrations from 0 to 100 mg/l, the V max ′ value reduced and K m ′ value changed irregularly. When the concentration of ClO 2 increased from 0 to 60 mg/l, residual PPO activities significantly decreased, showing a negative linear-correlation with ClO 2 concentration. For 10 and 50 mg/l ClO 2 treatments, partial inhibition of PPO was achieved within 0.5 h and the PPO activities did not significantly decrease after 0.5 h. The inhibition and inactivation of PPO by ClO 2 treatment were observed at processing temperatures (30 and 70 °C) and storing temperatures (20, 0–4, and −18 °C).

POTENTIAL OF CHLORINE DIOXIDE TO EXTEND THE LONGEVITY OF CUT FLOWERS

The postharvest longevity of fresh-cut flowers is often limited by the accumulation of bacteria in vase water and flower stems. Aqueous chlorine dioxide is a strong biocide with potential application for sanitizing cut flower solutions. We evaluated the potential of chlorine dioxide to prevent the build-up of bacteria in vase water and extend the longevity of cut Matthiola incana `Ruby Red', Gypsophila paniculata `Crystal' and Gerbera jamesonii `Monarch' flowers. Fresh-cut flower stems were placed into sterile vases containing deionized water and either 0.0 or 2 μL·L–1 chlorine dioxide. Flower vase life was then judged at 21 ± 0.5 °C and 40% to 60% relative humidity. Inclusion of 2 μL·L–1 chlorine dioxide in vase water extended the longevity of Matthiola, Gypsophila and Gerbera flowers by 2.2, 3.5, and 3.4 days, respectively, relative to control flowers (i.e., 0 μL·L–1). Treatment with 2 μL·L–1 chlorine dioxide reduced the build-up of aerobic bacteria in vase water for 6 to 9 days of vase life. For example, addition of 2 μL·L–1 chlorine dioxide to Gerbera vase water reduced the number of bacteria that grew by 2.4- to 2.8-fold, as compared to control flower water. These results confirm the practical value of chlorine dioxide treatments to reduce the accumulation of bacteria in vase water and extend the display life of cut flowers.

Simultaneous removal of SO 2 and NO by wet scrubbing using aqueous chlorine dioxide solution

The present study attempts to generate chlorine dioxide (ClO 2) gas continuously by chlorate–chloride process and to utilize it further to clean up SO 2 and NO x gases simultaneously from the flue gas in the lab-scale bubbling reactor. Experiments were carried out to examine the effect of various operating parameters like input SO 2 concentration, input NO concentration, pH of the reaction medium, and ClO 2 feeding rate on the SO 2 and NO x removal efficiencies at 45 °C. Complete oxidation of NO into NO 2 occurred on passing sufficient ClO 2 gas into the scrubbing solution. SO 2 removal efficiency of about 100% and NO x removal efficiency of 66–72% were achieved under optimized conditions. NO x removal efficiency decreased slightly with increasing pH and NO concentration. Input SO 2 concentration had marginal catalytic effect on NO 2 absorption. No improvement in the NO x removal efficiency was observed on passing excess of chlorine dioxide in the scrubbing solution.

(39) Chlorine Dioxide Treatment Extends Longevity of Cut Gerbera Flowers

The vase life of many cut flowers is often limited by bacterial occlusion of stem bases. In this study, we tested the efficacy of a novel antimicrobial agent, aqueous chlorine dioxide (ClO2), to extend the longevity of cut Gerbera flowers by reducing the number of bacteria in vase water. Commercially mature and freshly cut Gerbera jamesonii `Monarck' flowers were placed into clean vases containing deionized water and 0, 2, 5, 10, 20, and 50 μL·L-1 ClO2. Stems were then maintained in solutions at 21 ± 0.5 °C and 42 ± 11% relative humidity until the end of vase life. Inclusion of 2, 5, and 10 μL·L-1 ClO2 in vase water had beneficial effects on flower longevity. For instance, treatment with 5 and 10 μL·L-1 ClO2 extended flower longevity by 1.4-fold or 3.7 days, as compared to control flowers (0 μL·L-1 ClO2). In contrast, exposure to the higher concentrations of 20 and 50 μL·L-1 ClO2 did not extend flower vase life. Relative to control flowers, treatment with 10 μL·L-1 ClO2 delayed the onset of detectable bacterial colonization of vase solutions from day 3 to day 6 of vase life. However, this ClO2 treatment did not reduce the number of bacteria that subsequently accumulated in vase water as compared to control flowers. Treatment with 10 μL·L-1 ClO2 also increased rates of solution uptake by stems and reduced the loss of flower fresh weight over time. These results highlight the potential use of ClO2 treatments to extend the postharvest longevity of Gerbera flowers.

Remediation ofBacillus anthracisContamination in the U.S. Department of Justice Mail Facility

The U.S. Department of Justice (DOJ) mail facility in Landover, Maryland, was contaminated with Bacillus anthracis spores as a result of the 2001 anthrax bioterrorism attacks through the U.S. postal system. Surface environmental sampling within the facility indicated that the contamination was due to receipt of mail that had come in contact with Bacillus anthracis spores from the source letters at the Brentwood postal facility in Washington, DC. The DOJ adopted a two-pronged approach for remediating the facility, using aqueous chlorine dioxide to decontaminate hard, nonporous surfaces and paraformaldehyde to fumigate two pieces of mail equipment. Before the start of the remediation activities, all porous materials were removed from the mail area. Since all postremediation environmental samples were negative for growth of Bacillus anthracis spores, the remediation was judged to be effective. The facility remained closed for almost 4(1/2) months. The cleanup activities took about 2(1/2) months, with source reduction activities being the most time-consuming. Of the seven facilities that performed fumigations to remediate Bacillus anthracis contamination, the DOJ mail facility was the second building to be reopened.

Time resolved infrared absorption studies of geminate recombination and vibrational relaxation in OClO photochemistry.

Ultrafast time-resolved infrared absorption studies of aqueous chlorine dioxide (OClO) photochemistry are reported. Following photoexcitation at 401 nm, the evolution in optical density at frequencies between 1000 to 1100 cm(-1) is monitored to investigate vibrational energy deposition and relaxation along the asymmetric-stretch coordinate following the reformation of ground-state OClO via geminate recombination of the primary photofragments. The measured kinetics are compared to two proposed models for the vibrational-relaxation dynamics along the asymmetric-stretch coordinate. This comparison demonstrates that the perturbation model derived from molecular dynamics studies is capable of qualitatively reproducing the observed kinetics, where the collisional model employed in previous UV-pump, visible probe experiments demonstrates poor agreement with experiment. The ability of the perturbation model to reproduce the optical-density evolution observed in these studies demonstrates that for aqueous OClO, frequency dependence of the solvent-solute coupling is important in defining the level-dependent vibrational relaxation rates along the asymmetric-stretch coordinate. The absence of optical-density evolution corresponding to the population of higher vibrational levels (n>8) along the asymmetric-stretch coordinate suggests that following geminate recombination, energy is initially deposited into a local Cl-O stretch, with the relaxation of vibrational energy from this coordinate providing for delayed vibrational excitation of the asymmetric- and symmetric-stretch coordinates relative to geminate recombination, as previously observed.

Kinetics and mechanism of the oxidation of iron(II) ion by chlorine dioxide in aqueous solution

AbstractThe mechanism by which an excess of iron(II) ion reacts with aqueous chlorine dioxide to produce iron(III) ion and chloride ion has been determined. The reaction proceeds via the formation of chlorite ion, which in turn reacts with additional iron(II) to produce the observed products. The first step of the process, the reduction of chlorine dioxide to chlorite ion, is fast compared to the subsequent reduction of chlorite by iron(II). The overall stoichiometry is equation image The rate is independent of pH over the range from 3.5 to 7.5, but the reaction is assisted by the presence of acetate ion. Thus the rate law is given by equation image At an ionic strength of 2.0 M and at 25°C, ku = (3.9 ± 0.1) × 103 L mol−1 s−1 and kc = (6 ± 1) × 104 L mol−1 s−1. The formation constant for the acetatoiron(II) complex, Kf, at an ionic strength of 2.0 M and 25°C was found to be (4.8 ± 0.8) × 10−2 L mol−1. The activation parameters for the reaction were determined and compared to those for iron(II) ion reacting directly with chlorite ion. At 0.1 M ionic strength, the activation parameters for the two reactions were found to be identical within experimental error. The values of ΔH‡ and ΔS‡ are 64 ± 3 kJ mol−1 and + 40 ± 10 J K−1 mol−1 respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 554–565, 2004

Molecular dynamics study of aqueous solvation dynamics following OClO photoexcitation

The solvation dynamics following photoexcitation of aqueous chlorine dioxide (OClO) are investigated by classical molecular dynamics. A total of four OClO/water models are employed, including standard and customized OClO models together with SPC/F and TIP3P water. The simulation results are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed. The simulations demonstrate that the solvation dynamics of aqueous OClO are dominated by the short-ranged mechanical solute–solvent interactions. When compared to the aqueous solvation of spherical solutes, the solvation dynamics of OClO exhibit a novel effect. The role of the faster translational and librational water motions is suppressed in the dielectric component of the response, but is emphasized in the mechanical response, in stark contrast to the results for other spherical systems. The faster translational motions appear in the mechanical response due to the noncentrosymmetric nature of the OClO–water interaction, enhanced by OClO–water hydrogen bonding.

Sequential disinfection of Escherichia coli O157:H7 inoculated alfalfa seeds before and during sprouting using aqueous chlorine dioxide, ozonated water, and thyme essential oil

Several outbreaks of human illness have been documented in the United States associated with alfalfa sprouts. This study was done to evaluate the efficacy of aqueous chlorine dioxide (ClO 2) (10, 25, and 50 mg/L), ozonated water (4.60, 9.27, and 14.3 mg/L) and thyme oil (1.0, 2.5, and 5.0 mL/L), for 3, 5, and 10 min, respectively, alone or their sequential washing (thyme oil followed by ozonated water and aqueous ClO 2) for eliminating Escherichia coli O157:H7 from alfalfa seeds prior and during sprouting. Alfalfa seeds were inoculated with a three-strain E. coli O157:H7 mixture and dried to attain approximately 10 6 cfu/g of seed. No single washing treatment was able to ensure complete elimination of E. coli O157:H7 from alfalfa seeds. Germination of seeds was not adversely affected by any of the treatments. A membrane-transferring surface-plating method was evaluated to recover uninjured and injured E. coli O157:H7. Direct surface-plating on selective media, Sorbitol MacConkey-cefixime-tellurite (SMac-CT) showed significantly ( P⩽0.05) low populations recovered, thus indicating a large population of injured cells for each washing treatments in comparison to membrane-transferring surface-plating method tryptic soy agar/membrane/Sorbitol-MacConkey agar-cefixime-tellurite (TSA/M/SMac-CT). Regardless of different washing treatments, populations of E. coli O157:H7 increased to 7.8–8.2log 10 cfu/g after sprouting (72 h). Results of this study also showed that sequential washing treatments (as irrigation water) during sprouting process have greater lethality than other sanitizer treatments alone.