Aqueous Chlorine Dioxide Research Articles

A multicenter, randomized, open-label, placebo-controlled clinical trial of the effect of cetylpyridinium chloride (CPC) mouthwash and on-demand aqueous chlorine dioxide mouthwash on SARS-CoV-2 viral titer in patients with mild COVID-19

ObjectivesThe established effect of cetylpyridinium chloride (CPC) mouthwash on SARS-CoV-2 viral titers is unclear. No clinical trial has examined the impact of on-demand aqueous chlorine dioxide mouthwash on SARS-CoV-2 viral titer. MethodsIn this multicenter, three-armed, randomized, open-label, placebo-controlled clinical trial involving mildly symptomatic COVID-19 patients, we randomly assigned them to receive 20 mL of 0.05% CPC, 10 mL of 0.01% on-demand aqueous chlorine dioxide, or 20 mL of purified water as a placebo mouthwash in a 1:1:1 ratio. The primary measurement was the SARS-CoV-2 viral titer in saliva, evaluated by a mixed-effects linear regression model. Results49 patients received CPC mouthwash (n=16), on-demand aqueous chlorine dioxide mouthwash (n=16), and placebo (n=17) between January 14, 2024, and February 20, 2024. 0.05% CPC mouthwash significantly reduced salivary viral titer at 10 minutes post-use (-0.97 log10 PFU/mL; 95% CI, -1.64 to -0.30; P=0.004), while no such effect was observed at 30 minutes (difference vs. placebo, -0.26 log10 PFU/mL; 95% CI, -0.92 to 0.40; P=0.435) or 60 minutes (difference vs. placebo, -0.05 log10 PFU/mL; 95% CI, -0.68 to 0.58; P=0.877). 0.01% on-demand chlorine dioxide mouthwash did not reduce salivary viral titer at 10 min, 30 min, or 60 min compared to placebo. Conclusions10 minutes after using a 0.05% CPC mouthwash, the salivary viral titer of SARS-CoV-2 decreased compared to placebo. 0.01% on-demand aqueous chlorine dioxide mouthwash and placebo had no significant difference in SARS-CoV-2 viral titers. Trial RegistrationJapan Registry of Clinical Trials (jRCT): jRCTs031230566.

Oral mouthwashes for asymptomatic to mildly symptomatic adults with COVID-19 and salivary viral load: a randomized, placebo-controlled, open-label clinical trial

BackgroundRecent randomized clinical trials suggest that the effect of using cetylpyridinium chloride (CPC) mouthwashes on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load in COVID-19 patients has been inconsistent. Additionally, no clinical study has investigated the effectiveness of on-demand aqueous chlorine dioxide mouthwash against COVID-19.MethodsWe performed a randomized, placebo-controlled, open-label clinical trial to assess for any effects of using mouthwash on the salivary SARS-CoV-2 viral load among asymptomatic to mildly symptomatic adult COVID-19-positive patients. Patients were randomized to receive either 20 mL of 0.05% CPC, 10 mL of 0.01% on-demand aqueous chlorine dioxide, or 20 mL of placebo mouthwash (purified water) in a 1:1:1 ratio. The primary endpoint was the cycle threshold (Ct) values employed for SARS-CoV-2 salivary viral load estimation. We used linear mixed-effects models to assess for any effect of the mouthwashes on SARS-CoV-2 salivary viral load.ResultsOf a total of 96 eligible participants enrolled from November 7, 2022, to January 19, 2023, 90 were accepted for the primary analysis. The use of 0.05% CPC mouthwash was not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.640; 95% confidence interval [CI], -1.425 to 2.706; P = 0.543); 2 h (difference vs. placebo, 1.158; 95% CI, -0.797 to 3.112; P = 0.246); 4 h (difference vs. placebo, 1.283; 95% CI, -0.719 to 3.285; P = 0.209); 10 h (difference vs. placebo, 0.304; 95% CI, -1.777 to 2.385; P = 0.775); or 24 h (difference vs. placebo, 0.782; 95% CI, -1.195 to 2.759; P = 0.438). The use of 0.01% on-demand aqueous chlorine dioxide mouthwash was also not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.905; 95% CI, -1.079 to 2.888; P = 0.371); 2 h (difference vs. placebo, 0.709; 95% CI, -1.275 to 2.693; P = 0.483); 4 h (difference vs. placebo, 0.220; 95% CI, -1.787 to 2.226; P = 0.830); 10 h (difference vs. placebo, 0.198; 95% CI, -1.901 to 2.296; P = 0.854); or 24 h (difference vs. placebo, 0.784; 95% CI, -1.236 to 2.804; P = 0.447).ConclusionsIn asymptomatic to mildly symptomatic adults with COVID-19, compared to placebo, the use of 0.05% CPC and 0.01% on-demand aqueous chlorine dioxide mouthwash did not lead to a significant reduction in SARS-CoV-2 salivary viral load. Future studies of the efficacy of CPC and on-demand aqueous chlorine dioxide mouthwash on the viral viability of SARS-CoV-2 should be conducted using different specimen types and in multiple populations and settings.

Protocol for a Randomized, Open-Label Clinical Trial on the Effect of Mouthwash on Salivary SARS-CoV-2 Load.

Mouthwashes containing cetylpyridinium chloride (CPC) or on-demand aqueous chlorine dioxide (ACD) have potential to reduce the salivary severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) load in individuals with SARS-CoV-2 infection. This study will evaluate the effect of CPC and on-demand ACD mouthwashes on salivary SARS-CoV-2 levels in individuals with acute asymptomatic or mild SARS-CoV-2 infection (COVID-19) staying in a residential recuperation facility in Osaka, Japan. This randomized, open-label clinical trial will include three equal-sized groups (CPC mouthwash, on-demand ACD mouthwash, and placebo), with 30 participants per group. A stratified replacement block method will be used to ensure balanced allocation based on symptom presence and days since symptom onset. Participants will use mouthwash at set times for 7 days or until the end of recuperation. Saliva samples will be collected at multiple time points and tested for SARS-CoV-2 using quantitative reverse transcription polymerase chain reaction. The primary outcome will be changes in salivary SARS-CoV-2 viral load 2 h after the first mouthwash use compared with the pre-mouthwash level. Secondary outcomes will include changes in salivary viral load and clinical parameters at different time points. This study was registered with the Japan Registry of Clinical Trials on 18 October 2022 (jRCTs051220107).

Evaluation of oral care using MA-T gel for high-risk patients: a pilot study

BackgroundOral care with gel is a common method for preventing aspiration in high-risk patients. An oral care gel is used to clean and moisturize the oral cavity. However, the effects of gel care on the oral bacteria remain unclear. In this pilot study, we described a matching transformation system (MA-T) for elderly high-risk patients. MA-T is an on-demand aqueous chlorine dioxide solution that provides excellent safety and has various antimicrobial activities, even in the presence of abundant organic compounds. This study investigated the effects of MA-T gel in patients requiring nursing care.Materials and methodsPatients who were hospitalized for nursing care were included in this study. No drugs and foods were administered orally. Oral bacteria and intraoral humidity were examined by daily care using MA-T gel. Moreover, oral membranous substances were analyzed and material from the oral cavity was cultured on selective media for identifying opportunistic organisms.ResultsMembranous substances were present in the oral cavities of all patients. The number of bacteria decreased, and oral moisture improved, after treatment with MA-T gel. Moreover, oral humidity was also controlled with the continued use of MA-T gel. MA-T gels should be used not only for professional care but also on a daily basis for better oral care. Furthermore, the results of bacterial cultures showed that MA-T controls the propagation of opportunistic bacterial infections.ConclusionMembranous substances may be observed in the oral cavity of individuals requiring nursing care for tube feeding. The results of this pilot study suggest that MA-T, a novel disinfectant, can be used for oral care in the elderly to reduce the risk of aspiration-pneumonia.

Behaviors of Salmonella enterica serovar Typhimurium and Listeria monocytogenes on whole avocado during storage at 21 or 7°C and their reduction by aqueous chlorine dioxide and peroxyacetic acid

The microbiological safety of avocado is concerning in light of associated foodborne illness outbreaks. Avocados were inoculated with 7 log CFU/fruit of Salmonella enterica serovar Typhimurium or Listeria monocytogenes and stored at 21 °C for 10 days and 7 °C for 14 days. S. Typhimurium level increased by 0.71 log CFU/fruit at 21 °C and decreased by 0.93 log CFU at 7 °C (P < 0.05). L. monocytogenes remained stable at 6.95–7.27 log CFU/fruit at both temperatures. In the sanitation experiment, avocados were inoculated with 8 log CFU/fruit of the bacteria and treated with chlorine dioxide (ClO2) produced with HCl or malic acid (10, 15, 20 ppm) and peroxyacetic acid (PAA; 60, 80, 100 ppm) for 5 min. Fifteen and twenty ppm malic-acid-produced ClO2 and 100 ppm PAA reduced S. Typhimurium to an undetectable level. Twenty ppm ClO2 produced with malic acid showed the highest L. monocytogenes reduction of 6.93 log CFU. This study revealed the potential survival and growth of pathogenic bacteria on fresh avocado stored under household conditions. ClO2 or PAA showed potential to serve as alternative sanitizers in avocado washing, although further confirmation in the industrial settings and the evaluation of their impact on avocado sensory properties are warranted.

Safety evaluation of MA-T after ingestion in mice

MA-T (Matching Transformation System®) is a proprietary chemical mixture for on-demand production of aqueous chlorine dioxide that is used for the treatment of oral malodor. MA-T is also an effective disinfectant against at least 39 pathological microorganisms, including severe acute respiratory syndrome coronavirus 2, and therefore may be useful as a disinfectant mouthwash to prevent the spread of infection. Accidental ingestion is the putative worst hazard scenario associated with mouthwash use; therefore, here we investigated the safety of MA-T ingestion in mice. Mice were provided drinking water containing 0–3000 μg/ml MA-T for 7 days followed by non-spiked drinking water for an additional 14 days. At day 7, mice ingesting 1000 or 3000 μg/ml MA-T showed significantly decreased body weight and significantly increased liver, kidney, and heart tissue injury biomarkers compared with control. However, at 14 days after stopping MA-T ingestion, body weight and tissue injury biomarkers had returned to normal. Histological analysis revealed that MA-T–induced injuries in liver, kidney, spleen, stomach, duodenum, colon, and rectum had also recovered at 14 days after stopping MA-T ingestion; however, mild vascular endothelial injuries remained in heart, jejunum, and ileum in the worst-case scenario. Taken together, MA-T may be potentially safety for further development as a disinfectant mouthwash by risk management, such as placing a caution of the label and adding a distinctive flavor.

Chlorine dioxide fumigation: An effective technology with industrial application potential for lowering aflatoxin content in peanuts and peanut products

This study aimed to investigate the influence of gaseous or aqueous chlorine dioxide (ClO 2 , 0.025%–90% relative to dry matter) on the detoxification and physicochemical properties of aflatoxin (AF)-contaminated peanuts and their derivative products (≈13–204 μg AFB 1 /kg sample). Chlorine dioxide fumigation lowered AF levels in peanuts by >72% even to an undetectable level. The detoxification effects remained relatively stable in subsequent storage. AFB 1 or total AFs in oil and meal obtained after pressing was effectively decreased by fumigating whole peanut kernels. Moreover, the iodine value, acid value, and fatty acid composition of the crude oil from fumigated peanuts did not change significantly except that a higher level of hydroperoxides was observed. In addition, fumigation induced increased moisture content in peanuts and oil yield, and after aqueous ClO 2 treatment at lower fumigant dose, a post-heating treatment caused an increase of AFB 1 level. The findings suggest that ClO 2 fumigation is a potential detoxification method for oilseed storage or oil processing industry. • Chlorine dioxide fumigation effectively lowered aflatoxin (AF) levels in peanuts. • Crude oil and meal made from fumigated peanut (FP) showed notably lowered total AFs. • Most chemical quality parameters of crude oil from FP did not change except for PV. • Fumigation induced increased moisture content in peanuts and cold-pressed oil yield. • Grinding or post-heating treatment could impair the detoxification effect of ClO 2 .

The Bactericidal Effect of MA-T for Factitiously Contaminated and Used Masks.

Matching transformation system (MA-T), an on-demand aqueous chlorine dioxide solution, is an excellent safety disinfectant, because chlorine dioxide is not detected during storage or before use. The production of chlorine dioxide in MA-T is induced by a catalytic reaction in the presence of target microorganisms. In this study, we investigated MA-T disinfection of masks as a reuse method to eliminate mask shortages. After spraying Escherichia coli on sterilized surgical mask, samples (factitiously contaminated masks) were treated with MA-T spraying or immersion, and the bactericidal efficacy was assessed by culturing. Used surgical masks were also sprayed with MA-T or were immersed in MA-T, and then were cultured to verify the bactericidal effect. The performance of N95 masks was assessed before and after application of MA-T. After spraying with MA-T, the numbers of bacteria of factitiously contaminated masks and used masks were drastically reduced compared with control samples (not applicable and p = 0.002, respectively). After MA-T immersion, the bacterial counts of both masks (factitiously contaminated masks and used masks) were significantly reduced (both p = 0.002). Taken together, the disinfection test on factitiously contaminated with E. coli and used surgical masks showed that masks can be disinfected by MA-T spray and sterilized by immersion, respectively. The N95 mask performance test after 30 min of immersion in MA-T showed that MA-T disinfected the mask without degrading the performance of the mask. In conclusion, MA-T is useful for the reuse of masks because of its decontamination effect and safety while maintaining the function of the mask.

Aqueous chlorine dioxide generated with organic acids have higher antimicrobial efficacy than those generated with inorganic acids

Chlorine dioxide (ClO2) is commonly generated by mixing sodium chlorite and acid. This study aimed to evaluate how acid affects the release kinetics and antimicrobial property of ClO2. Solutions made with weak acids released ClO2 more slowly and had higher stability than those made with hydrochloric acid. Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were treated with 1, 2.5, and 5 ppm ClO2 for 3 or 5 min. Lettuce inoculated with the pathogenic bacteria were treated with 2.5 and 5 ppm ClO2 for 5 min. The effects of peptone load at 0.01% and 0.02% on the antimicrobial efficacy of ClO2 were investigated in S. Typhimurium cell suspensions. The contribution of acids alone at the pH of the ClO2 solutions to bacterial reduction was also evaluated. The 2.5 ppm ClO2 solutions made with citric acid, lactic acid, and malic acid showed higher reductions in all three bacteria than ClO2 made with hydrochloric acid and sodium bisulfate. The 5 ppm ClO2 solutions produced with organic acids reduced populations of all bacterial strains from 7 log CFU/mL to undetectable level in 3 min, except S. Typhimurium treated by ClO2 produced with lactic acid. On inoculated Romaine lettuce model, 5 ppm ClO2 produced with lactic acid and malic acid resulted in the highest reduction of E. coli O157:H7, S. Typhimurium, and L. monocytogenes of approximately 1.4, 1.7, and 2.4 log CFU/g, respectively. The antimicrobial efficacy of ClO2 made with HCl and NaHSO4 were affected by 0.01% and 0.02% peptone load, respectively. Food-grade organic acids produced aqueous ClO2 solutions with stronger antimicrobial properties than inorganic acids. The acids alone at the pH of ClO2 did not show significant bacterial reductions.

The bactericidal effect of oral care using matching transformation system: A prospective clinical study

AbstractAimMatching transformation system (MA‐T) is an on‐demand aqueous chlorine dioxide solution that realizes excellent safety with various antimicrobial activities even under abundant organic compound. By using MA‐T in human oral care, we examined its effectiveness against bacteria causing oral infections such as periodontal disease and dental caries.Materials and MethodsThe participants of the 75th Annual Meeting of the Japanese Stomatological Society held on May 13 and 14, 2021, were enrolled in this study. Saliva samples were collected on the first day after normal oral care and on the second day after oral care with MA‐T. The total number of bacteria and the numbers of Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Streptococcus mutans, and Candida albicans were compared for the two samples on Days 1 and 2.ResultsTwenty‐two subjects met the study criteria. The total bacterial count and the number of T. forsythia on Day 2 were significantly lower than those on Day 1 (p = 0.000177 and p = 0.0186, respectively). The numbers of T. denticola and S. mutans tended to decrease, although not significantly (p = 0.100 and p = 0.251, respectively). Statistical analysis was not performed for P. gingivalis and C. albicans because of sample size.ConclusionMA‐T is putatively effective for oral hygiene. MA‐T oral care reduces bacteria that cause periodontal disease and dental caries compared with regular oral care. The results of this study suggest that MA‐T, a new disinfectant, can be applied to oral care and may reduce periodontal disease, dental caries, and other oral infections.

Disinfection of Dental Chair Water Using Aqueous Chlorine Dioxide

Chlorine dioxide is a safe, environmentally friendly disinfecting agent. In this study, aqueous chlorine dioxide (ACD) was used to improve the water quality of dental chairs. However, chlorine dioxide is readily released from ACD solutions under open atmosphere conditions. Described herein is a water purification and disinfection system using ACD. The system was designed, fabricated, and integrated into an existing dental chair water system. This system is referred to as an ACD dental chair. Because ClO2 readily degasses from ACD, there needs to be a way to maintain and measure the ACD solution in real time. In our studies, we found that pH and oxidation-reduction potential (ORP) change as a function of chlorine dioxide concentration and are easily controlled and measured. The dosing of the ACD was designed to begin at 800 mV and stop dosing at 810 mV in the ACD dental chair. Through use of this continuous monitoring and automatic dosing system, the water ORP was controlled between 800 and 860 mV. This range is the effective concentration of chlorine dioxide that is without chlorine-like odor and microorganism growth. The ACD dental chair controlled the total bacterial count to &lt;5 CFU/mL and the chlorite concentration was less than 0.0004 mg/L, meeting legal standards of Taiwan, the USA, and China. In addition to the application of ACD in dental chairs, it may also be used in closed water systems for food, cosmetics, beverages, and other industries.

English

Chlorine dioxide has been condemned as a dangerous poison and has been touted as a cure for COVID-19. This narrative review examines the controversy surrounding the use of aqueous chlorine dioxide by investigating evidence-based research articles, government documents, press reports, and the results of the first clinical trial utilizing chlorine dioxide as a treatment for COVID-19. Chlorine dioxide was found to be employed by numerous industries for antimicrobial and other uses. Aqueous chlorine dioxide was found to be safe when ingested in low doses, but when ingested in high doses, it can cause adverse hematologic and renal effects. Additionally, chlorine dioxide was found to be a strong and rapidly acting virucide with activity against a wide range of viruses. Results of the first clinical trial utilizing chlorine dioxide to treat COVID-19 are reviewed and this molecule is found to be a safe and effective treatment. A dispassionate review of the evidence-based research literature finds preliminary evidence supporting the opinion that aqueous chlorine dioxide may be a safe and effective treatment of COVID-19, and likely for other viral illnesses as well. Further studies are needed to confirm these findings and to explore potential uses of chlorine dioxide. Key words: SARS-CoV-2, virucide, biocide, antimicrobial, oxidant, disinfectant, bleach, food additive, sterilant.

Fate of Salmonella Typhimurium and Listeria monocytogenes on Whole Papaya during Storage and Antimicrobial Efficiency of Aqueous Chlorine Dioxide Generated with HCl, Malic Acid or Lactic Acid on Whole Papaya.

Papaya-associated foodborne illness outbreaks have been frequently reported worldwide. The goal of this study was to evaluate the behavior of Salmonella Typhimurium and Listeria monocytogenes on whole papaya during storage and sanitizing process. Fresh green papayas were inoculated with approximately 7 log CFU of S. Typhimurium and L. monocytogenes and stored at 21 or 7 °C for 14 days. Bacteria counts were determined on day 0, 1, 7, 10 and 14. Fresh green papayas inoculated with approximately 8 log CFU of the bacteria were treated for 5 min with 2.5, 5 and 10 ppm aqueous chlorine dioxide (ClO2). The ClO2 solutions were generated by mixing sodium chlorite with an acid, which was HCl, lactic acid or malic acid. The detection limit of the enumeration method was 2.40 log CFU per papaya. At the end of storage period, S. Typhimurium and L. monocytogenes grew by 1.88 and 1.24 log CFU on papayas at 21 °C, respectively. Both bacteria maintained their initial population at inoculation on papayas stored at 7 °C. Higher concentrations of ClO2 reduced more bacteria on papaya. 10 ppm ClO2, regardless the acid used to generate the solutions, inactivated S. Typhimurium to undetectable level on papaya. 10 ppm ClO2 generated with HCl, lactic acid and malic acid reduced L. monocytogenes by 4.40, 6.54 and 8.04 log CFU on papaya, respectively. Overall, ClO2 generated with malic acid showed significantly higher bacterial reduction than ClO2 generated with HCl or lactic acid. These results indicate there is a risk of survival and growth for S. Typhimurium and L. monocytogenes on papaya at commercial storage conditions. Aqueous ClO2 generated with malic acid shows effectiveness in inactivating the pathogenic bacteria on papaya.

Evaluation of SDS and GRAS liquid disinfectants for mitigation of hepatitis A virus contamination of berries.

To evaluate generally recognized as safe (GRAS) liquid wash formulations against hepatitis A virus-contaminated strawberries and blackberries in order to identify a formulation suitable for reducing virus contamination. Formulations included the surfactant sodium dodecyl sulfate (SDS; 0·5% w/v) by itself, and in combination, with lactic acid (LA; 0·5% v/v), levulinic acid (LVA; 0·5% v/v) and 3ppm aqueous chlorine dioxide (ClO2 ). After contamination and drying overnight, the average total extracted contamination for both untreated strawberries and blackberries was 4·4log PFU. Three successive distilled H2 O only treatments reduced total contamination by up to 1·8log PFU for both strawberries and blackberries, while wash formulations showed significant (P≤0·05) total reductions ranging from 2·1 to 2·9log PFU. Considering results for both berry types, the combination of ClO2 and SDS was the most effective. Overall results indicate that adding surfactant and several types of sanitizers to berry wash can enhance HAV reduction on berries. This study indicates that industry could enhance the virologic safety of ready-to-eat berries by the combined use of surfactant and sanitizer.

Verification of MA-T Safety and Efficacy Against Pathogens Including SARS-CoV-2

Matching transformation system (MA-T) is an on-demand aqueous chlorine dioxide solution. It is a disinfectant developed to maximize the safety of chlorine dioxide radical in water and its effectiveness against various microorganisms. In this study, we examined the safety and effectiveness of MA-T for its use in various infectious disease countermeasures, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and consider if MA-T can be implemented in society. To validate the safety of MA-T, we conducted safety tests and efficacy tests in accordance with GLP-based reliability criteria. To evaluate the efficacy, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) confirmation tests against various bacteria, and virus inactivation test against various viruses including SARS-CoV-2 by TCID50 method were performed. The results of safety tests showed that MA-T was at least as safe as Japanese tap water. As a result of efficacy tests for microorganisms, MA-T was effective against many bacteria. Efficacy tests for virus showed that MA-T inactivates SARS-CoV-1, Middle East respiratory syndrome coronavirus (MERS-CoV), rotavirus A (RV-A), hepatitis C virus (HCV), dengue virus (DENV), and hepatitis B virus (HBV). MA-T also inactivated 99.98% of SARS-CoV-2, which is equivalent to ethanol for disinfection. MA-T has proven to be a safe and effective disinfectant. MA-T is a next-generation disinfectant that has the potential to be safer and more effective than conventional chlorine disinfectants and other disinfectants. It also proved to be an effective disinfectant against SARS-CoV-2, which is currently causing pandemic all over the world.

Effectiveness of Aqueous Chlorine Dioxide in Minimizing Food Safety Risk Associated with Salmonella, E. coli O157:H7, and Listeria monocytogenes on Sweet Potatoes.

Sodium hypochlorite (NaOCl) is a commonly used sanitizer in the produce industry despite its limited effectiveness against contaminated human pathogens in fresh produce. Aqueous chlorine dioxide (ClO2) is an alternative sanitizer offering a greater oxidizing potency with greater efficacy in reducing a large number of microorganisms. We investigated the effect of aqueous chlorine dioxide treatment against human pathogens, Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes seeded on sweet potatoes. Sweet potatoes were spot inoculated (4.2 to 5.7 log CFU/cm2) with multi-strain cocktails of Salmonella spp., E. coli O157:H7, and L. monocytogenes and treated for 10–30 min with 5 ppm aqueous ClO2 or water. Aqueous ClO2 treatment was significantly (p < 0.05) effective in reducing Salmonella with a reduction of 2.14 log CFU/cm2 within 20 min compared to 1.44 log CFU/cm2 for water treatment. Similar results were observed for L. monocytogenes with a 1.98 log CFU/cm2 reduction compared to 0.49 log CFU/cm2 reduction observed after 30 min treatment with aqueous ClO2 the water respectively. The maximum reduction in E. coli O157: H7 reached 2.1 Log CFU/cm2 after 20 min of treatment with aqueous ClO2. The level of the pathogens in ClO2 wash solutions, after the treatment, was below the detectable limit. While in the water wash solutions, the pathogens’ populations ranged from 3.47 to 4.63 log CFU/mL. Our study indicates that aqueous ClO2 is highly effective in controlling cross-contamination during postharvest washing of sweet potatoes.

Combined effects of ultrasound and aqueous chlorine dioxide treatments on nitrate content during storage and postharvest storage quality of spinach (Spinacia oleracea L.)

The objectives of this study were to optimize the condition of ultrasonic treatment combined with aqueous chlorine dioxide (ClO2) on nitrate content of spinach by response surface methodology (RSM), and determine the effectiveness of ultrasound (US) and ClO2 alone and in combination, on spinach postharvest quality during 7 days′ storage period. The optimal treatment parameters obtained were ultrasonic power (300 W), ClO2 concentration (50 ppm), treatment time (4 min). The combined treatments significantly reduced the nitrate content and maintained better storage quality in terms of total soluble solids (TSS) and ascorbic acid content compared with the individual treatment or untreated. For Chlorophyll content, the combined treatment was significantly higher than the control and ClO2 treatment, but lower than ultrasonic treatment. The results demonstrated that US combined with ClO2 are promising alternatives for the reduction of nitrate content, as well as preserving the quality of stored leafy vegetables.

Effectiveness of daily rinsing of alfalfa sprouts with aqueous chlorine dioxide and ozonated water on the growth of Listeria monocytogenes during sprouting.

Alfalfa sprouts have been implicated in multiple foodborne disease outbreaks. This study evaluated the growth of Listeria monocytogenes during sprouting of alfalfa seeds and the effectiveness of daily chlorine dioxide & ozone rinsing in controlling the growth. Alfalfa seeds inoculated with L. monocytogenes were sprouted for 5days (25°C) with a daily aqueous ClO2 (3ppm, 10min) or ozone water (2ppm, 5min) rinse. Neither treatment significantly reduced the growth of L. monocytogenes on sprouting alfalfa seeds. The initial level of L. monocytogenes was 3·44±0·27, which increased to c. 7·0 log CFU per g following 3days of sprouting. There was no significant difference in the bacterial population between the treatment schemes. Bacterial distribution in roots (7·63±0·511 log CFU per g), stems (7·51±0·511 log CFU per g) and leaves (7·41±0·511 log CFU per g) were similar after 5days. Spent sanitizers had significantly lower levels of bacterial populations compared to the spent distilled water control. The results indicated that sprouting process provides a favourable condition for the growth of L. monocytogenes and the sanitizer treatment alone may not be able to reduce food safety risks. SIGNIFICANCE AND IMPACT OF THE STUDY: Sprouts are high-risk foods. Consumption of raw sprouts is frequently associated with foodborne disease outbreaks. Optimum sprouting procedure involves soaking seeds in water followed by daily water rinsing to maintain a moist environment that is also favourable for the growth of pathogenic micro-organisms. The present study emphasized the potential food safety risks during sprouting and the effect of applying daily sanitizer rinsing in the place of water rinsing to reduce those risks. The finding of this study may be useful in the development of pre-harvest and post-harvest risk management strategies.

Use of chlorine dioxide to sterilize medium for tissue culture of potato

In vitro cultured seedlings or microtubers are the major starting materials for the production of potato. Currently, seedlings are cultured in media sterilized by autoclaving, which, however, consumes more electricity and takes longer for sterilization, and also requires high temperature-tolerant vessel materials. In order to identify alternative methods of sterilizing culture conditions, the disinfection effects of chlorine dioxide (CD) at 88.0, 29.3, 17.6, 12.6 and 8.8 μM were evaluated in potato medium and vessels. The ≥12.6 μM gaseous CD effectively disinfected vessel through a 30-min fumigation process, and its aqueous solution disinfected potato medium efficiently as well. In presence of 12.6 μM CD in the medium, the potato seedlings had similar morphological features as those grown on autoclaved medium, with some exceptions. The use of 12.6–29.3 μM aqueous CD to sterilize the medium increased antioxidant enzyme activities in potato seedlings, while the use of higher concentration decreased antioxidant enzyme activity levels. SSR analysis did not reveal significant molecular differences in potato seedlings cultured between autoclaved and CD-sterilized medium. In addition to this, CD-sterilized medium induced potato microtuber formation at a similar rate as autoclaved medium. In summary, using CD to sterilize potato medium and vessels did not compromise the growth of seedlings and microtuber induction. This study provides an economical and simplified sterilization method for media used to culture potato plantlets, and this can improve energy use of the large-scale tissue culture industry.

Combined effects of aqueous chlorine dioxide and ultrasonic treatments on shelf-life and nutritional quality of bok choy (Brassica chinensis)

The combined effects of aqueous chlorine dioxide (ClO2) and ultrasonic treatment on the shelf-life, some nutrients and bioactive compounds of bok choy were investigated. Minimally processed bok choy was treated in 50 ppm aqueous ClO2 solution subjected to 80 kHz frequency ultrasound at 0, 120, 150, 180, and 210 W for 10 min. Aqueous ClO2 plus ultrasound treatments significantly (p < 0.05) reduced total bacterial counts by up to 2.8 log CFU/g and Pseudomonas spp. by up to 2.5 log CFU/g, respectively, on day 0, and inhibited their growth on bok choy throughout the 12 d storage period at 4 °C. Among the treatments studied, aqueous ClO2 plus 180 W-ultrasound treatment demonstrated maximum reduction of microbial loads and minimum impact on visual quality (L*, a*, and b* values), chlorophyll degradation, membrane permeability, ascorbic acid and total phenolic contents. In addition, the combined treatment significantly (p < 0.05) inhibited the activities of polyphenol oxidase and polyphenol peroxidase and increased the activity of phenylalanine ammonia lyase as compared with controls. These results indicated that aqueous ClO2 plus ultrasonic treatments is an effective approach for maintaining some nutrients and bioactive compounds, as well as extending the shelf-life of fresh bok choy.