ClO2 Gas Research Articles

Evaluation of chlorine dioxide in liquid state and in gaseous state as virucidal agent against avian influenza virus and infectious bronchitis virus.

The antiviral activity of chlorine dioxide (ClO2) in liquid (ClO2 gas dissolved liquid) and gaseous state against avian influenza virus (AIV) and infectious bronchitis virus (IBV) was evaluated. To evaluate the effect of ClO2 in liquid state, suspension tests (10 ppm) and carrier tests in dropping / wiping techniques (100 ppm) were performed. In the suspension test, virus titers were reduced below the detection limit within 15 sec after treatment, in spite of the presence of an accompanying organic matter. In the carrier test by dropping technique, AIV and IBV were reduced to below the detection limit in 1 and 3 min, respectively. Following wiping technique, no virus was detected in the wiping sheets after 30 sec of reaction. Both viruses adhering to the carriers were also reduced by 3 logs, thereby indicating that they were effectively inactivated. In addition, the effect of ClO2 gas against IBV in aerosols was evaluated. After the exposure of sprayed IBV to ClO2 gas for a few seconds, 94.2% reduction of the virus titer was observed, as compared to the pre-treatment control. Altogether, hence, ClO2 has an evident potential to be an effective disinfectant for the prevention and control of AIV and IBV infections on poultry farms.

Chlorine Dioxide Treatment Modulates Ripening-Related Genes and Antioxidant System to Improve the Storability of Tomato

Chlorine dioxide (ClO2) is used to maintain quality and safety of fresh produce. However, ClO2 action mechanism in fresh produce is unknown. In this study, firstly, we evaluated the efficacy of ClO2 treatment on the quality, chilling injury, and calyx molding of tomatoes stored at two different temperatures. Then, ClO2 effect on the expression of cell wall- and ripening-related genes and on the activity of antioxidant enzymes was investigated. Tomatoes were treated with gaseous ClO2 for 15 min before transferring them to 13°C for 12 days and/or 4°C for 14 days, followed by 5 days at 20°C (shelf-life conditions). ClO2 treatment marginally reduced the rate of respiration but did not affect ethylene production at 13°C and 4°C storage or at shelf-life conditions. When stored at 13°C, treatment with ClO2 reduced the loss of firmness, with concomitant repression of pectin esterase 1, a cell wall-related gene. Additionally, at 13°C storage conditions, ClO2 treatment maintained tomato quality in terms of soluble solid content, titratable acidity, and color and was associated with the downregulation of the ripening-relatedethylene response factors B3/C1/E1 and the induction of antioxidant genes encoding catalase and ascorbate peroxidase. At 4°C storage conditions, ClO2 at a concentration of 15 ppm not only maintained the firmness and quality of tomatoes but also inhibited pitting during shelf-life with a concomitant increase of catalase activity. Moreover, treatment with 15 ppm ClO2 significantly reduced the calyx molding that is generally observed in fruits stored at 13°C and under shelf-life conditions. Hence, our results indicate that ClO2 treatment effectively maintained tomato quality and inhibited calyx molding by partially regulating ripening-related genes and antioxidant systems, thereby improving the storability of postharvest tomatoes.

Novel gaseous chlorine dioxide treatment system for improving the safety and quality of table grapes during cold storage

This study focused on the development of a gaseous ClO2 treatment system that contained dry ice that was used to form carbon dioxide (CO2) and an absorbent pad with sodium chlorite (NaClO2) solution for ClO2 gas generation. Furthermore, the effects of ClO2 gas on the populations of Listeria monocytogenes and the quality properties of table grapes during cold storage were evaluated. The system continuously released the sufficient concentrations of ClO2 gas to treat berries during 30 d of cold storage. After 20 h of ClO2 gas treatment, the populations of Listeria monocytogenes decreased from 5.88 log CFU/g to a non-detectable (ND) level. There were no significant (p > 0.05) changes in the color parameters (L*, a*, and b*) of table grapes treated with ClO2 gas. The firmness, weight, total soluble solids (TSS), and titratable acid (TA) losses of table grapes were significantly (p < 0.05) reduced by ClO2 gas, while Vitamin C was unaffected. Additionally, the residual ClO2 of table grapes were <0.5 mg/kg, which is considered a safe level. Overall, the novel gaseous ClO2 treatment system may be used as an effective intervention technology to improve the safety and quality of table grapes during cold storage.

Activated release of chlorine dioxide gas from polyvinyl alcohol microcapsule (ethylcellulose/sodium-chlorite) hybrid films for active packaging of litchi during postharvest storage

Current methods of preserving fruit and vegetables are costly with accompanying health risks from preserver residue. ClO2 gas preservatives can regulate the respiration and transpiration of fruit and vegetables, kill bacteria and fungi on their surface, and prolong their postharvest shelf life. Low concentration ClO2 gas preservative will not cause safety problems and is a novel gas preservative. In this study, ethylcellulose (EC) was used as a shell material to encapsulate aqueous NaClO2 to obtain EC-NaClO2 microcapsules with core-shell structures. The microcapsules were inlaid in polyvinyl alcohol (PVA) film, and citric acid in the PVA film enters the microcapsules with water vapor, reacts with NaClO2 and releases ClO2 gas. Film-forming properties of the PVA/EC-NaClO2 film-forming fluids were evaluated considering their viscosity and viscoelastic properties. The mechanical and gas barrier properties of the films were most suitable for the preparation of litchi storage bags when the microcapsule content was 6.0 wt%. Furthermore, the highest ClO2 concentration in the storage bags was 263.22 ± 12.34 mg m−3, which could kill etiological bacteria (E. coli and L. monocytogenes) and inhibit the growth of B. cinerea. The storage bags can extend the post-harvest shelf life of litchis and maintain their sensorial properties, such as color, moisture, hardness, weight, anthocyanins and pH. Therefore, our analysis indicates that the proposed PVA/EC-NaClO2 active package films exhibit significant potential for applications in the field of fruit and vegetable postharvest storage.

Reduction of Aspergillus flavus and aflatoxin on almond kernels using gaseous chlorine dioxide fumigation

The almond industry suffers product losses caused by mold growth and toxin contamination. Gaseous chlorine dioxide (ClO2) has the potential for postharvest reduction of mycotoxic Aspergillus flavus. In this study, almonds inoculated with A. flavus were fumigated with gaseous ClO2 for 1, 2, 3, 8, 12, and 24 h using a dry precursor sachet batch method. The headspace concentration ranged from 0.5 to 2.4 mg/L, depending on initial dosing and time. At its highest concentration, gaseous ClO2 demonstrated an 84.4 % degradation efficiency of aflatoxin B1 (AFB1) with a reduction of 2.4 log CFU/g of A. flavus on almond kernels. Additionally, suppression of AFB1 continued after one-month storage at 4 °C. No significant oxidative effect and color difference (ΔE) was observed on the treated kernels. The almond industry can apply gaseous ClO2 technology to reduce mold contamination and product losses.

The effects of continuous exposure to low-dose chlorine dioxide gas on the characteristics of induced pluripotent stem cells.

BackgroundRecently, various regenerative therapies have been developed based on induced pluripotent stem (iPS) cells. However, hygienic control strategies have not been established at the manufacturing facilities. We aimed to evaluate the safety and effects of continuous exposure to low-dose chlorine dioxide (ClO2) gas on cell fates, and to determine the optimum dose for safe usage of this disinfectant.MethodsWe cultured an iPS cell line in the absence or presence of various doses of ClO2 gas. We evaluated cell proliferation, cell death, the maintenance of undifferentiated state, and cell senescence.ResultsWe found that iPS cell proliferation was not affected by 0.05 or 0.1 ppmv ClO2 gas in the atmosphere. Although 0.1 ppmv ClO2 slightly affected apoptosis, it was not a significant effect. Moreover, neither at 0.05 nor 0.1 ppmv ClO2 gas significantly affected the characteristics of iPS cells.Discussion and conclusionContinuous exposure to 0.05 or 0.1 ppmv ClO2 gas did not affect the fate of iPS cells. These results may contribute to the development of new strategies for hygiene control in cell processing facilities.

Efficacy of gaseous chlorine dioxide generated by sodium chlorite - carbon dioxide reaction on safety and quality of blueberries, cherry tomatoes, and grapes

This research evaluated the inactivation of Salmonella spp. and Listeria monocytogenes inoculated onto the calyces of blueberries, stem scars of cherry tomatoes, and surfaces of grapes using gaseous chlorine dioxide (ClO2) produced by the reaction between sodium chlorite (NaClO2) and carbon dioxide (CO2). The inoculated samples were treated with ClO2 gas in a treatment chamber for 3 h. The results suggested that the exposures of 366–477 ppm-h achieved 2.8 to 3.8, 2.4 to 4.3, and 3.8 to 6.4 log CFU/g in inactivation of both pathogens on blueberries, cherry tomatoes, and grapes, respectively. The inactivation of pathogens on grapes were significantly greater (p < 0.05) than those on blueberries and cherry tomatoes, likely due to the difference in the inoculation sites. During an 8-day post-treatment storage at 25 °C, the color attributes (L*, a*, and b*) of the fruit samples were not or little affected by either storage time or ClO2 treatment. The weight loss of treated and untreated samples during the storage was more affected by and increased with storage time, but it was higher in the untreated samples. The hardness was significantly affected by and decreased with storage time. It was higher in ClO2-treated blueberry and grape samples, but not in cherry tomato samples. The residual ClO2 on treated fruits, ranging from 0.08 to 0.35 mg/kg, was not affected by the storage time, but it was the highest in blueberry and the lowest in cherry tomato samples. These results clearly demonstrated that this method of gaseous ClO2 generation can be used to reduce pathogens on the fruit samples during postharvest intervention and storage, while improving product safety and quality.

Antimicrobial activities of a combination of chlorine dioxide gas and heat against Xanthomonas campestris and Salmonella enterica on cabbage, chili pepper, and radish seeds

We developed a short-time treatment to inactivate Xanthomonas campestris and Salmonella enterica on cabbage, chili pepper, and radish seeds by a combination of chlorine dioxide (ClO2) gas and heat. ClO2 gas was evaporated from a mixed solution which contained hydrochloric acid (1 N) and sodium chlorite (100,000 ppm) (ClO2 solution). To produce ClO2 gas (3,000 ppm) in an 1.8 L airtight container, a standard curve indicating the amount of ClO2 solution and time needed to produce desired concentrations was constructed (y = 5758.3x; R2 = 0.9981). The influence of simultaneous treatment with ClO2 gas (3,000 ppm) and heat (70 °C at 85% relative humidity [RH]) on seed germination rates was determined. It was found that the germination rates of cabbage, chili pepper, and radish seeds were not significantly (P > 0.05) changed after 30, 20, and 60 min of treatment, respectively. The antimicrobial effects of the combined treatment against X. campestris and S. enterica on cabbage, chili pepper, and radish seeds were determined. When 3,000 ppm of ClO2 gas were applied at 70 °C and 85% RH for 10 min, the populations of X. campestris (initial populations: 6.2–6.4 log CFU/g) on seeds were reduced by > 4.4 log CFU/g regardless of seed type. The initial populations of S. enterica (6.3–6.5 log CFU/g) on cabbage and chili pepper seeds treated for 10 min was reduced by > 5.3 log CFU/g. However, populations on radish seeds decreased only by 2.5 log CFU/g. The lower lethality against S. enterica on radish seeds, revealed by field-emission scanning microscopy to have a rougher surface than do cabbage and chili pepper seeds, is attributed in part to inhibited access of ClO2 gas to cells in protected areas. Our findings provide useful information when developing more efficacious methods to decontaminate vegetable seeds using a combination of ClO2 gas and heat.

Surface pasteurization of fresh pomelo juice vesicles by gaseous chlorine dioxide

AbstractThis study developed an in‐package pasteurization method that released gaseous chlorine dioxide (ClO2) triggered when moisture vapor from the fresh produce interacted with a ClO2 precursor. The samples were placed in sealed containers (750 ml) containing mixtures (0.1–1.0 g) of sodium chlorite and citric acid powders (1:1) and treated for up to 15 min at 25°C. Our results showed that, production of gaseous ClO2 was linearly correlated with the reaction time (R2&gt;0.95) with mean concentrations in the range of 1.70 – 8.66 mg/L. The gaseous ClO2 treatments for 15 min significantly reduced Escherichia coli and fungi populations on pomelo juice vesicles with reductions of 6 and 2 log CFU/g, respectively. Perchlorate and chlorite in samples were not detected, and chlorate was only detected when the mean ClO2 concentration was over 4.09 mg/L. The treatments did not significantly affect total soluble solids, total acids, pectin and malondialdehyde contents, and color of pomelo juice vesicles. The contents of ascorbic acid, naringin, and limonin, and bitterness score decreased with the increase of mean ClO2 concentrations. Overall, our results demonstrate an effective nonthermal approach for microbial inactivation while maintaining the quality of fresh pomelo juice vesicles.

Efficacy of gaseous chlorine dioxide for decontamination of Salmonella, Shiga toxin-producing Escherichia coli, and Listeria monocytogenes on almonds and peppercorns

Almonds and peppercorns have been implicated in outbreaks of foodborne illnesses. The objective of this study was to evaluate the efficacy of gaseous chlorine dioxide (ClO2) for pilot-scale decontamination of Salmonella, Shiga toxin-producing Escherichia coli (STEC), and Listeria monocytogenes on almonds and black peppercorns. Pathogens-inoculated almonds and peppercorns were exposed to ClO2 gas generated by mixing of sodium chlorite (NaClO2) and ferric chloride (FeCl3) in dry form or by dosing hydrogen chloride (HCl) into NaClO2. The concentrations of ClO2 (ppm) during the treatment duration (h) were recorded to obtain the cumulative ClO2 exposure (ppm-h), and the reductions in the pathogen populations resulting from exposure to the cumulative exposures were determined. For almonds, increasing the exposures from 983 to 10,408 ppm-h increased the reductions of Salmonella, STEC, and L. monocytogenes from 1.1 to 4.1, 1.6 to 4.1, and 1.4 to 4.1 log CFU/g, respectively. For peppercorns, increasing the exposures from 983 to 8039 ppm-h increased the reductions of Salmonella, STEC, and L. monocytogenes from 3.0 to 6.0, 3.7 to 7.2, and 3.2 to 7.3 log CFU/g, respectively. A 4.0-log reduction of the pathogens was achieved by using 10,408 ppm-h for almonds and 3112 ppm-h for peppercorns. Treatment parameters obtained from this study could be used in pilot-scale or larger decontamination applications for almonds and peppercorns.

Respiratory Safety Evaluation in Mice and Inhibition of Adenoviral Amplification in Human Bronchial Endothelial Cells Using a Novel Type of Chlorine Dioxide Gas Reactor.

Since the onset of the COVID-19 pandemic, there has been a growing demand for effective and safe disinfectants. A novel use of chlorine dioxide (ClO2) gas, which can satisfy such demand, has been reported. However, its efficacy and safety remain unclear. For the safe use of this gas, the stable release of specific concentrations is a must. A new type of ClO2 generator called Dr.CLOTM has recently been introduced. This study aimed to investigate: (1) the effects of Dr.CLOTM on inhibiting adenoviral amplification on human bronchial epithelial (HBE) cells; and (2) the acute inhalation safety of using Dr.CLOTM in animal models. After infecting HBE cells with a recombinant adenovirus, the inhibitory power of Dr.CLOTM on the virus was expressed as IFU/mL in comparison with the control group. The safety of ClO2 gas was indirectly predicted using mice by measuring single-dose inhalation toxicity in specially designed chambers. Dr.CLOTM was found to evaporate in a very constant concentration range at 0–0.011 ppm/m3 for 42 days. In addition, 36–100% of adenoviral amplification was suppressed by Dr.CLOTM, depending on the conditions. The LC50 of ClO2 gas to mice was approximately 68 ppm for males and 141 ppm for females. Histopathological evaluation showed that the lungs of female mice were more resistant to the toxicity from higher ClO2 gas concentrations than those of male mice. Taken together, these results indicate that Dr.CLOTM can be used to provide a safe indoor environment due to its technology that maintains the stable concentration and release of ClO2 gas, which could suppress viral amplification and may prevent viral infections.

Fresh Produce Safety and Quality: Chlorine Dioxide's Role.

Maintaining microbial safety and quality of fresh fruits and vegetables are a global concern. Harmful microbes can contaminate fresh produce at any stage from farm to fork. Microbial contamination can affect the quality and shelf-life of fresh produce, and the consumption of contaminated food can cause foodborne illnesses. Additionally, there has been an increased emphasis on the freshness and appearance of fresh produce by modern consumers. Hence, disinfection methods that not only reduce microbial load but also preserve the quality of fresh produce are required. Chlorine dioxide (ClO2) has emerged as a better alternative to chlorine-based disinfectants. In this review, we discuss the efficacy of gaseous and aqueous ClO2 in inhibiting microbial growth immediately after treatment (short-term effect) versus regulating microbial growth during storage of fresh produce (long-term effect). We further elaborate upon the effects of ClO2 application on retaining or enhancing the quality of fresh produce and discuss the current understanding of the mode of action of ClO2 against microbes affecting fresh produce.

Bactericidal and Fungicidal Efficacy of Chlorine Dioxide in Various Workspaces

Previously, we demonstrated the virucidal efficacy of low concentration chlorine dioxide (ClO2) gas in room settings. The purpose of these studies was to evaluate novel ClO2 formats as potential biocidal interventions for real world congregate settings and air systems. Three types of studies were conducted to determine the efficacy of ClO2 in reducing bacteria and mold in various workspaces: hard and soft surfaces (gymnasium & equipment), aerosol (in-room), and within a laboratory environment. The study demonstrated that ClO2 was highly effective against both bacteria and mold with reduction ranging from 85.0% - > 99.4% for bacteria and >99.4% for yeast and mold. Treatments on hard and soft surfaces (gymnasiums and sports equipment), reduced bacteria by an average of 90% - 95%. The following treatments were applied overnight: 1) hard surface spraying with dilute ClO2 solutions, 2) carpet and tumbling treatments with powdered ClO2 releasing impregnates, and 3) HVAC treatment and overall room deodorization with low dose ClO2 gas from controlled releasing sachets. The in-room study treating air with a ClO2 filtration media also indicated significant air and surface room efficacy, with an average of 94% reduction in bacteria after 24-hour, and 99.4% reduction in mold after 24-hours. In a related air study, a biological combination of Raoultella terrigena and Staphylococcus aureus was injected as a bio-aerosol into a 4-inch diameter pipe with air flowing at approximately 1200 ft/min. Dry ClO2 gas was introduced into the air flow to achieve an effective concentration of 5 or 10 ppmv. Air samples were collected at sampling ports downstream from the fan at 10, 22, 55 and 100 ft along the pipe and used to evaluate changes in airborne bacteria and mold. Testing was conducted in a laboratory setting at ambient conditions. The data showed ClO2 gas reduced viable organisms at both gas concentrations, and indicated that reductions were higher for 10 ppmv concentration, and longer pipe runs. In a final study, laboratory application of gaseous chlorine dioxide was tested. Low gas release filter testing demonstrated significant surface reductions of airborne bacteria with an overall average 99.4% reduction in the 24-hour testing period. Higher gas treatments of a class II biological cabinet reduced bacillus spores on steel coupons throughout cabinet by 6 log. ClO2 was effective as a bactericidal and fungicidal treatment providing significant reduction in both surface and air. Novel product delivery forms may be useful for rapidly disinfecting air and solid surfaces in complex congregate settings.

Virucidal Efficacy of Chlorine Dioxide Interventions on MS2 Phage Bioaerosol in a Laboratory Chamber

The ongoing SARS-CoV-2 outbreak has rapidly increased the desire to manage bioaerosol exposures in indoor settings. Studies using chlorine dioxide gas (ClO2) at low concentrations have shown this intervention to be an effective mitigation strategy against viral, bacterial, and fungal elements in ambient air. There is an array of available products for generating ClO2 gas however most involve the use of expensive or sophisticated technology that makes their applicability limited to specialized consumers. The purpose of this study was to determine the virucidal efficacy of three pragmatic and affordable, ClO2 generating products using an aerosolized MS2 surrogate in a sealed chamber room under five different scenarios. The products tested included: Ultrashock—a ClO2 releasing pod (30 ppmv), Filter Media—a ClO2 impregnated zeolite media made to fit into an air blower housing (2 impregnated media filled air reactor tube (2 air samples were collected from sampling ports on the outer chamber wall at 0, 90 and 180 minutes. The Ultrashock and Filter Media with air flow in the rapid sweep scenario showed the greatest reduction in air MS2 (T180 = 99.992% and T180 = 99.996% respectively) compared to the control (T180 = 99.6%). When compared to the control results, the filter media with air flow engaged prior to the introduction of MS2 yielded reductions of 99.87% and 99.93% in air and on surfaces respectively at T0, demonstrating the protective effect residual ClO2 has against air and surface contamination. These product formats have potential uses as remedial and preventative interventions against viral constituents in air and should undergo further evaluation to determine efficacy and human health risk.

Effect of chlorine dioxide on avian influenza A (H7N9) virus

Avian influenza remains a threat to human wellbeing. Hypochlorite derivatives are commonly used as disinfectants to prevent the spread of the disease. The World Health Organization (WHO) has listed chlorine dioxide (ClO2) as an A1-level, safe, and efficient disinfectant. In this study, we tested the efficacy of ClO2, in aqueous solution and gas forms, against avian influenza A (H7N9) virus. The virus suspension was mixed with ClO2 aqueous solutions of various concentrations and for various time intervals. Aliquots of the mixture were then serially diluted, and the 50% tissue culture infective dose (TCID50) was measured with a hemagglutination test on MDCK cells. ClO2 gas produced from generators was introduced in a chamber containing the virus suspension in a Petri dish. The infective activity of the surviving virus was measured by the hemagglutination test. An aqueous solution of ClO2 at 126 µg/mL for 15 s was effective given that no surviving virus was detected with the hemagglutination test. ClO2 gas at >5 µL/L sustained for 1 h inactivated the virus effectively, while at 2.5 µL/L for 1 h, it only partially inactivated the virus. ClO2 as gas or aqueous solution at a certain concentration is effective in inactivating the H7N9 virus, and can be applied for the decontamination and disinfection of environments.

Gaseous chlorine dioxide inactivation of microbial contamination on whole black peppercorns

AbstractBlack peppercorn is a common ingredient imported and used in uncooked or ready‐to‐eat foods in the United States. They might be exposed to fecal coliforms and other microbial contamination due to a lack of good agricultural and manufacturing practices in some developing countries under which they were grown and harvested, thus causing economic losses to the peppercorn industry in the United States. We investigated the effect of gaseous chlorine dioxide (ClO2) on reducing the microbial population levels of coliforms, aerobic bacteria, yeasts, and molds on unprocessed black peppercorns. Treatments on peppercorns were conducted in a 30‐L airtight chamber, and equal amounts of dry media precursors were used to generate gaseous ClO2. Whole peppercorns (200 g) were exposed to 20, 30, and 40 g of precursor dose for up to 60 min at 21 ± 0.4°C and in combination with mild heat at 40 ± 2°C. Aerobic bacteria, coliforms, yeasts, and molds on peppercorns were enumerated before (7.4, 7.2, and 7.1 log CFU/g, respectively) and after treatments. Results after treatment demonstrated 0.8–1 log10 (90%) reduction for all the microbes post‐treatment at 21 ± 0.4°C. The treatments conducted with a 30 g precursor dose for 60 min at 21 ± 0.4°C reduced statistically higher (p &lt; .05) microorganisms than those at 40 ± 2°C. Our work demonstrated that gaseous ClO2 could be used as a part of an overall hurdle technology to reduce the coliforms, aerobes, yeasts, and molds on black peppercorns without affecting the visual quality.

The Potential of Gaseous Chlorine Dioxide for the Control of Citrus Postharvest Stem-End Rot Caused by Lasiodiplodia theobromae.

The focus of this study was to develop technologies using chlorine dioxide (ClO2) gas to control postharvest stem-end rot of citrus caused by Lasiodiplodia theobromae. Mycelial growth of L. theobromae on potato dextrose agar (PDA) plugs was completely inhibited by a 24-h ClO2 exposure provided by 0.5 g of solid ClO2 generating granular mixture in a 7.7-liter sealed container. In vivo experiments were conducted on artificially inoculated Tango and naturally infected U.S. Early Pride mandarins. When ClO2 treatments were initiated 0 to 6 h after inoculation, decay development was significantly reduced as compared with the control, and higher ClO2 doses were more effective. A ClO2 treatment (using 3 g of generating mixture per 7.7-liter sealed container) administered 0 h after inoculation resulted in 17.6% Diplodia stem-end rot incidence compared with 95.6% in the control, whereas the same treatment administered 24 h after inoculation was much less effective, resulting in 63.0% incidence compared with 85.4% in the control. Diplodia stem-end rot incidence of naturally infected fruit after using 6 or 9 g of generating mixture per 24-liter sealed box was 23.8 or 25.7%, respectively, compared with 47.9% for control fruit. The ClO2 treatments had no negative effects on fruit quality characteristics including weight loss, firmness, puncture resistance, titratable acids (TAs), total soluble solids (TSSs), and rind color. Albedo pH at wounds was significantly reduced from 6.0 to 4.8 by the ClO2 treatments, whereas undamaged albedo remained at 5.8. In addition, no visible physiologic defects, such as peel browning and bleaching, were observed on ClO2-treated fruit. These results indicate that ClO2 gas has the potential to be developed as a component of an integrated citrus postharvest decay control system to minimize fruit losses.

Chlorine dioxide gas generation using rotating packed bed for air disinfection in a hospital

Chlorine dioxide (ClO2) has proven its efficiency as a fumigant toward bacteria and viruses. However, it still has challenges on its portability and simplicity of ClO2 generation to meet the demand for disinfection in public and medical sectors. In this study, ClO2 stripping process via a rotating packed bed (RPB) from the commercial ClO2 solution was developed to a non-chemical-reaction ClO2 generation for air sterilization in a hospital. The ClO2 stripping efficiency (η) and the volumetric liquid mass-transfer coefficient (KLa) were examined under various operating variables, such as initial liquid concentration (CLi), rotational speed (ω), gas-to-liquid flow rate ratio (QG/QL), and liquid flow rate (QL). The results indicated that the gaseous ClO2 can be rapidly and continuously generated via stripping using RPB with η varied above 97% in the certain range of CLi (100–2000 mg/L) and QL (0.04–0.250 L/min). The overall KLa depends on the change of QL and ω, varied from 0.009 s−1 to 0.027 s−1. The output concentration of gaseous ClO2 (CG) can be adjusted from around 10 ppm to over 1000 ppm based on the established prediction model and controlling CLi, QL, QG, and ω. The results of the on-site disinfection test in the Mycobacterium Tuberculosis Laboratory in a hospital have shown effective elimination of all sites of E. coli and 2 of 5 sites of G. stearothermophilus with a CT value at the gas monitoring point of 642 ppm-h and humidity of 81%.

Controlled self-release of ClO2 as an encapsulated antimicrobial agent for smart packaging

Facilitating the use of ClO2 gas in retail applications can improve the shelf life of produce and overcome the application limits of this gas. Moreover, the controlled release of ClO2 gas is desirable for preventing unwanted reactions. A novel controlled self-release material for ClO2 was developed, focusing on its applicability, convenience, and sustainability. Porous halloysite nanotubes (HNTs) were employed to encapsulate NaClO2 via an evacuation method. The HNT–NaClO2 was covered with hydrophilic polyethylene glycol to control the release behavior. Material characterizations confirm the success of the encapsulation and covering processes. Additionally, morphologies were observed to determine the inner and outer structures of the samples. Furthermore, the ClO2 release rates and applicability of the samples in packaging were investigated, indicating that sufficient gas in the packaging headspace can prolong the shelf life of cherry tomatoes. Therefore, this material can serve as an effective antimicrobial agent for packaging and agriculture products. Industrial relevanceThe retail application of ClO2 is limited, owing to its equipment requirements for on-set production (ClO2 generator), its safety (ClO2 is explosive at concentrations exceeding 10%), and its burst-release challenges. Therefore, the developed material with controlled release feature can be applied to various packaging purposes, in which minimal equipment and consumer safety are required.

Gaseous chlorine dioxide technology for improving microbial safety of spices

In this study, black peppercorns and cumin seeds were inoculated with a five-serotype cocktail of Salmonella or its surrogate Enterococcus faecium NRRL B-2354. The inoculated samples (ca. 107 CFU/g) were treated by ClO2 gas at different gas concentrations (5, 10, and 15 mg/L) and relative humidities (60, 70, and 80%) at room temperature (25 °C) at five gas exposure times (60, 120, 180, 240, 300 min). More than 5-log reduction of Salmonella was achieved in both spices with 300 min of ClO2 gas treatment at 15 mg/L and 80% RH. The corresponding values for E. faecium were 4.36 and 4.17 log CFU/g in black peppercorns and cumin seeds, respectively, which were significant lower than Salmonella (p < 0.05). Gas concentration, RH, and exposure time showed significantly positive linear associations with Salmonella inactivation. E. faecium appears a suitable surrogate for Salmonella and can be used for future process validations using comparable conditions.