微生物による次亜塩素酸の研究 - 結果 Type: All Microbe: Fungi

This study was designed to evaluate the efficacy of slightly acidic electrolyzed water (SAEW) to reduce natural microbiota on celery and cilantro at different available chlorine concentrations (ACC), different treatment time and temperatures. Additionally, SAEW treated celery and cilantro were stored at 4 and 20 C for 6 days and population of total aerobic bacteria and yeast and mold were also determined at day 0, 2, 4 and 6, separately. Results showed that log reduction of total aerobic bacteria and yeast and mold significantly increased with increasing ACC and treatment time, respectively (p < 0.05). Celery and cilantro treated with SAEW at 30 mg/L ACC for 5 min and 25 mg/L for 7 min reduced yeast and mold to non-detectable level. No significant difference was observed for disinfection efficacy of SAEW on celery and cilantro at different temperatures (4, 20 and 37 C) (p > 0.05). The microbial population on celery and cilantro maintained at a low level during storage at 4 and 20 C after SAEW treatment (total aerobic bacteria: 3.34.1 log CFU/g, yeast and mold: 2.23.5 log CFU/g). The microbial inactivation effect as well as the absence of any sensory alterations on treated celery and cilantro rendered SAEW a promising disinfectant, which can be applied in fresh produce wash to control natural microbiota.

The objective of this study was to determine the efficacy of electrolyzed oxidizing (EO) water in reducing natural microbiota on radish seed and sprout during seed soaking and sprouting. EO water with different available chlorine concentrations (ACC, 15, 20, 28, 33 and 40 mg/L) and different pH (2.5, 3.5, 4.5, 5.5 and 6.5) were used to soak radish seeds for 12 h and the surviving population of total aerobic bacteria, yeast and mold, and germination rate were determined. On the other hand, EO water with ACC of 30 and 50 mg/L was applied to spray sprouts during seed sprouting and the antimicrobial efficacy of EO water, as well as length, gross weight and dry weight of sprout were evaluated. The results showed that the population of natural microbiota decreased with increasing ACC of EO water, while no significant difference was observed among EO waters with different pH levels that were applied while soaking the seeds. EO water with higher ACC and lower pH slightly reduced the germination percentage of radish seed during seed soaking. EO waters with ACC of 30 and 50 mg/L sprayed during seed sprouting resulted in 1.39 and 1.58 log reductions of total aerobic bacteria, yeast and mold, respectively, and improved the length, gross weight and dry weight of the sprouts. Therefore, EO water with low ACC and near neutral pH could be used to soak seeds and water sprouts throughout seed germination and sprouting to control the population of natural microbiota on seeds and sprouts.

This study investigated the effect of ultrasonic treatment on the physicochemical properties (pH, available chlorine concentration (ACC), oxidation reduction potential (ORP), spectrophotometric characteristics) of slightly acidic electrolyzed water (SAEW). The effects of individual treatments (ultrasound and SAEW) and their combination on microbial loads and quality of cherry tomatoes and strawberries were also studied. The results indicated that a 10 min ultrasonic treatment had no effect on pH, ACC, or ORP of SAEW. Ultrasound enhanced the bactericidal activity of SAEW which resulted in 1.77 and 1.29 log reductions on total aerobic bacteria, and 1.50 and 1.29 log reductions on yeasts and molds, respectively for cherry tomatoes and strawberries. The firmness of cherry tomatoes decreased while all other qualities considered were unaffected. This research indicates that SAEW in combination with ultrasound treatment has potential as a sanitization treatment to improve the efficacy of microbial inactivation on fresh produce without compromising product quality.

This study evaluated the efficacy of individual treatments (thermosonication [TS+DW] and slightly acidic electrolyzed water [SAcEW]) and their combination on reducing Escherichia coli O157:H7, Listeria monocytogenes, and spoilage microorganisms (total bacterial counts [TBC], Enterobacteriaceae, Pseudomonas spp., and yeast and mold counts [YMC]) on fresh-cut kale. For comparison, the antimicrobial efficacies of sodium chlorite (SC; 100 mg/L) and sodium hypochlorite (SH; 100 mg/L) were also evaluated. Each 10 g sample of kale leaves was inoculated to contain approximately 6 log CFU/g of E. coli O157:H7 or L. monocytogenes. Each inoculated or uninoculated samples was then dip treated with deionized water (DW; control), TS+DW, and SAcEW at various treatment conditions (temperature, physicochemical properties, and time) to assess the efficacy of each individual treatment. The efficacy of TS+DW or SAcEW was enhanced at 40 C for 3 min, with an acoustic energy density of 400 W/L for TS+DW and available chlorine concentration of 5 mg/L for SAcEW. At 40 C for 3 min, combined treatment of thermosonication 400 W/L and SAcEW 5 mg/L (TS+SAcEW) was more effective in reducing microorganisms compared to the individual treatments (SAcEW, SC, SH, and TS+DW) and combined treatments (TS+SC and TS+SH), which significantly (P < 0.05) reduced E. coli O157:H7, L. monocytogenes, TBC, Enterobacteriaceae, Pseudomonas spp., and YMC by 3.32, 3.11, 3.97, 3.66, 3.62, and >3.24 log CFU/g, respectively. The results suggest that the combined treatment of TS+SAcEW has the potential as a decontamination process in fresh-cut industry.

The work presented here aims to contribute with a sustainable alternative to chemicals for avoiding deterioration of harvested date palm fruits by evaluating the single or combined use of UV-C radiation and ozonated or electrolyzed water (EW). In this way, the effects of UV-C light (0; 2.37; 6.22; 8.29 and 12.14 kJ m 2) alone, and the combined effect of 6.22 kJ m 2 UV-C with neutral EW (NEW, pH 6.99, 870 mV ORP, 100 mg L 1 free chlorine), alkaline EW (AEW, pH 11.28, 880 mV ORP, 1.83 mg L 1 free chlorine) and ozonated (O3, 0.55 mg/L ozone) water on overall quality of Deglet Nour dates stored for 30 days at 20 C were studied. Microbial growth, weight loss, firmness, pH, titratable acidity, moisture, water activity, sugars and phenolics content, antioxidant activity color and sensory quality were monitored. UV-C light, mainly at 6.22 kJ m 2, alone or combined with NEW, AEW and O3, kept the overall quality of dates during storage, Moreover, those treatments reduced the most mesophilic, coliforms, yeasts and molds counts. In summary, these combined emergent sanitizers could be useful for disinfection of fresh dates while keeping quality and prolonging shelf-life.

The fungicidal influencing factors of electrolyzed oxidizing water (EOW) on Candida albicans were investigated by suspension quantitative germicidal tests. Results showed that EOW possessed predominant fungicidal rate on C. albican, as high as consummately 100% after 0.5 min duration of 65.5 mg/L active available chlorine concentration (ACC). The fungicidal effect was promoted proportionally along with ACC but was inhibited by organic interferential bovine serum albumin (BSA). The fungicidal mechanism was also investigated at a biological molecular level by detecting series of biochemical indices. Fluorescent microscopy showed that almost all C. albicans cells were stained red in 1 min, suggesting that cell membrane was one of EOW s action targets. Transmission electron microscopy (TEM) showed that EOW destroyed the cellular protective barriers and imposed some damage upon the nucleus area, which verified EOW s effects on microbial ultra-structures. EOW improved membrane permeabilities with the result that the leakages of cellular inclusions (K+, proteins and DNA) and the conductivity increased rapidly. The dehydrogenase relative activities of C. albicans decreased by 44.0% after 10 min, indicating that EOW also had a destructive effect on cellular dehydrogenase.

A study was carried out on the disinfection efficiency of electrolyzed oxidizing water (EOW) on spores of Bacillus subtilis var. niger. The results showed a remarkable fungicidal rate of 100% after 20 min duration of 191 mg/L active available chlorine (ACC). The disinfection effect was improved with increased ACC or prolonged disinfection time, while organic interferents exerted a strong concentration-dependent inhibition against the disinfection. The disinfection mechanism was also investigated at bio-molecular level. EOW decreased dehydrogenase activity, intensified membrane permeability, elevated suspension conductivity, and caused leakage of intracellular K+, proteins, and DNA, indicating a damage of cell walls and membranes. Effects of EOW on microbiological ultra-structures were also verified by transmission electronic microscopy (TEM) images, showing that EOW destroyed protective barriers of the microbe and imposed some damages upon the nucleus area.

The efficacy of mildly heated, slightly acidic electrolyzed water (mildly heated SlAEW) at 45 C for disinfection and maintenance of sliced carrot quality was studied. Mildly heated SlAEW (23 mg/L available chlorine, pH at 5.5) was used to treat the carrots, followed by rinsing with tap water (TW) for 2 min at 4 C, and its effectiveness as a disinfectant was evaluated. The physicochemical properties of the carrots were determined and a comparison was made between treatments with SlAEW at room temperature (18 C), TW at 18 C and mildly heated TW at 45 C. Results show that total aerobic bacteria, mold and yeast populations were significantly lower after mildly heated SlAEW treatment. Mildly heated SlAEW treatment reduced the total aerobic bacteria by 2.2 log10 CFU/g and molds and yeasts by >1.9 log10 CFU/g compared with TW treatment. Color indices of hue and chroma of sample surfaces were not affected by mildly heated SlAEW treatment and there were insignificant differences in hardness or the ascorbic acid and -carotene contents of sliced carrots. The of mildly heated SlAEW is suggested as an effective disinfection method for fresh cut carrots with low available chlorine.

Bioaerosols in the animal feeding facility might be the potential health risk factors to agricultural workers. A novel on-site membrane-less electrolyzed water(MLEW) generating and fogging-spread system was designed and installed in : https://www.researchgate.net/publication/265268194_A_Study_of_Membrane-less_Electrolyzed_Water_fogging-_spread_for_Airborne_Bacteria_and_Fungus_Decontamination_in_Hen_Hoaccessed Feb 27 2018.

The effect of electrolyzed oxidizing (EO) water in combination with ozone to control postharvest decay of tangerine was investigated. The spore suspension containing 105 conidia ml 1 of Penicillium digitatum was prepared. EO water was generated by electrolysis of various concentrations of NaCl solution (5, 25, 50% and saturated NaCl). The spore suspension was inoculated into EO water and incubated at 27 C for 1, 2, 4, 8 and 32 min. It was found that the EO water with saturated NaCl completely inhibited the spore germination of the fungus within 1 min. When the fruits inoculated with P. digitatum were washed in EO water at the same concentrations as previous experiment for 4, 8 and 16 min and stored at 5 C for 18 days, it was found that immersion of the fruit in EO water for 8 min was the most effective to reduce disease incidences. Moreover, washing fruit in EO water and kept in a refrigerated chamber at 5 C with continuous ozone exposure at a concentration of 200 mg l 1 for 2 h day 1 to extend storage life suppressed the disease incidence until 28 days. However, none of the treatments had any effect on the quality of fruit such as total soluble solids, titratable acidity, percent weight loss and peel color. Therefore EO water may be useful for surface sanitation and ozone has potential to control the recontamination of postharvest diseases in tangerine fruit in storage room.

This study evaluated the potential of near-neutral (pH 6.36.5) electrolyzed oxidizing water (EO water) to inactivate pure cultures of Botrytis cinerea and Monilinia fructicola and to mitigate fungal infection of these organisms on fruit surfaces. Treatment of these organisms, in pure culture, with EO water at concentrations of 25, 50, 75, and 100 ppm total residual chlorine (TRC) and 10 min of contact time resulted in a 6 log10 spores/mL reduction of both organisms. A dip treatment or a dip and daily spray treatment of EO water were used to evaluate its ability to prevent or delay the onof surface infection on fruit during postharvest packaging and in retail shelf environments. A 10 minute dip treatment of surface inoculated peaches (M. fructicola) in EO water prevented infection for 3 days and resulted in a 12.5 incidence of infection and a disease severity rating of 6 after 5 days of storage at 25 C. Dipping of green table grapes inoculated with B. cinerea into EO water prevented infection for 7 days and resulted in a 1 incidence of infection and a disease severity rating of 2 after 10 days of storage at 25 C. A dip and daily spray of peaches with EO water prevented infection for 12 days and resulted in a 10 incidence of infection and a 6 disease severity after 14 days of storage at 25 C. A dip and daily spray of grapes with EO water prevented infection for 24 days and resulted in a 2 incidence of infection and a disease severity rating of 2 after 26 days of storage at 25 C. The results from this study suggest that these solutions may prove to be effective for postharvest sanitation of fruit surfaces prior to packaging and may increase the shelf life of the fruit in commercial settings.

The effect of acidic, electrolyzed oxidizing (EO) water and chlorinated water on the spoilage microflora of processed broiler carcasses was examined. Carcasses were sprayed for 5 s at 80 psi with tap, chlorinated, or EO water in an inside-outside bird washer. Treated carcasses were then stored at 4 C for 0, 3, 7, or 14 d, and the microbial flora of the carcasses was sampled using the whole-carcass rinse procedure. Populations of psychrotrophic bacteria and yeasts in the carcass rinsates were enumerated. Results indicated that immediately after spraying the carcasses, significantly fewer psychrotrophic bacteria were recovered from carcasses sprayed with chlorinated or EO water than from carcasses sprayed with tap water. Furthermore, significantly fewer yeasts were recovered from carcasses sprayed with EO water than from carcasses sprayed with tap or chlorinated water. The population of psychrotrophic bacteria and yeasts increased on all carcasses during refrigerated storage. However, after 14 d of storage, significantly fewer psychrotrophic bacteria and yeasts were recovered from carcasses sprayed with EO water than from carcasses sprayed with tap or chlorinated water, and significantly fewer microorganisms were recovered from carcasses sprayed with chlorinated water than from carcasses sprayed with tap water. Pseudomonas spp. and Candida spp. were the primary microbial isolates recovered from the broiler carcasses. Findings from the present study indicate that EO water can effectively be used in inside-outside bird washers to decrease the population of spoilage bacteria and yeasts on processed broiler carcasses.

The use of water flotation tanks during apple packing increases the risk of contamination of apples by spores of Penicillium expansum, which may accumulate in the recirculating water. Routine addition of sanitizers to the water may prevent such contamination. Sodium hypochlorite (NaOCl), chlorine dioxide (ClO2), and electrolyzed oxidizing (EO) water have varied activity against spores of P. expansum, and their effectiveness could be enhanced using surfactants. The objective of this study was to determine the ability of three nonionic surfactants, polyoxyethylene sorbitan monooleate (Tween 80), polyoxyethylene sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20), to enhance the efficacy of NaOCl, ClO2, and EO water against spores of P. expansum in aqueous suspension at various temperatures and pH conditions. The efficacy of NaOCl solutions was enhanced by the addition of surfactants at both pH 6.3 and pH 8 (up to 5 log CFU reduction). EO water and ClO2 were effective against P. expansum spores (up to 5 log CFU and 4 log CFU reduction, respectively), but addition of surfactants was not beneficial. All solutions were less effective at 4 C compared to 24 C irrespective of the presence of surfactants. Nonionic surfactants could potentially be used with NaOCl to improve control of P. expansum in flotation tanks, but the efficacy of such formulations should be validated under apple packing conditions.

Spores of Penicillium expansum, the primary organism responsible for the occurrence of patulin in apple juice, were exposed to electrolyzed oxidizing (EO) water in an aqueous suspension and on wounded apples. Full-strength and 50% EO water decreased viable spore populations by greater than 4 and 2 log units, respectively. Although EO water did not prevent lesion formation on fruit previously inoculated with P. expansum, cross-contamination of wounded apples from decayed fruit or by direct addition of spores to a simulated dump tank was substantially reduced. EO water, therefore, has potential as an alternative to chlorine disinfectants for controlling infection of apples by P. expansum during handling and processing operations.

Acidic electrolyzed oxidizing (EO) water, generated by electrolysis of a dilute salt solution, recently gained attention in the food industry as a nonthermal method for microbial inactivation. Our objective was to determine if EO water has potential to control foliar diseases in greenhouses. Test fungi suspended in distilled water were combined with EO water (1:9 water:EO water) for various time periods, the EO water was neutralized, and germination was assessed after 24 h. Germination of all 22 fungal species tested was significantly reduced or prevented by EO water. All relatively thin-walled species (e.g., Botrytis, Monilinia) were killed by incubation times of 30 s or less. Thicker-walled, pigmented fungi (e.g., Curvularia, Helminthosporium) required 2 min or longer for germination to be reduced significantly. Dilution of EO water with tap water at ratios of 1:4 and 1:9 (EO:tap water) decreased efficacy against Botrytis cinerea. The presence of Triton X-100 (all concentrations) and Tween 20 (1 and 10%) eliminated the activity of EO water against B. cinerea. EO water did not damage geranium leaf tissue and inhibited lesion development by B. cinerea when applied up to 24 h postinoculation. EO water has a wide fungicidal activity which could facilitate its use as a contact fungicide on aerial plant surfaces and for general sanitation in the greenhouse.

Electrolysis of a 0.1% (17.1 mM) solution of NaCl using separate anode and cathode compartments gives rise to solutions containing active chemical species. The strongly acidic anode solution (EW(+)) has high levels of dissolved oxygen and available chlorine in a form of hypochlorous acid (HOCl) with a strong potential for sterilization, which we have investigated here. Exposing Aspergillus parasiticus at an initial density of 103spores in 10 L to a 50-fold volume (500 L) of EW(+) containing ca. 390 mol HOCl for 15 min at room temperature resulted in a complete inhibition of fungal growth, whereas the cathode solution (EW( )) had negligible inhibitory effects. Moreover, the mutagenicity of aflatoxin B1 (AFB1) for Salmonella typhimurium TA-98 and TA-100 strains was strongly reduced after AFB1 exposure to the EW(+) but not with the EW( ). In high-performance liquid chromatography analysis, the peak corresponding to AFB1 disappeared after treatment with the EW(+), indicating decomposition of the aflatoxin. In contrast, the routinely used disinfectant sodium hypochlorite, NaOCl, of the same available chlorine content as that of EW(+) but in a different chemical form, hypochlorite (OCl-) ion, did not decompose AFB1 at pH 11. However, NaOCl did decompose AFB1 at pH 3, which indicated that the principle chemical formula to participate in the decomposition of AFB1 is not the OCl- ion but HOCl. Furthermore, because the decomposition of AFB1 was suppressed by pretreating the EW(+) with the OH radical scavenger thiourea, the chemical species responsible for the AFB1-decomposing property of the EW(+) should be at least due to the OH radical originated from HOCl. The OH in EW(+) was proved by electron spin resonance analysis.

The fungicidal effectiveness of electrolyzed oxidizing (EO) water on peach [Prunus persica (L.) Batsch.] fruit was studied. Fruit were inoculated with a spore suspension of 5 105 conidia/mL of Monilinia fructicola [(G. Wint.) Honey] applied as a drop on wounded and nonwounded fruits, or by a uniform spray-mist on nonwounded fruits. Fruit were immersed in tap water at 26 C for 5 or 10 minutes (control), or treated with EO water varying in oxidation-reduction potential (ORP), pH, and free available chlorine (FAC). Following treatment, fruit were held at 20 C and 95% relative humidity for 10 days to simulate retail conditions. Disease incidence was determined as the percentage of fruits showing symptoms of the disease, while severity was expressed as lesion diameter. EO water did not control brown rot in wound-inoculated fruits, but reduced disease incidence and severity in nonwound-inoculated peach. Symptoms of brown rot were further delayed in fruit inoculated by a uniform-spray mist compared with the nonwounded-drop-inoculated peaches. Fruit treated with EO water held for 8 days at 2 C, 50% RH, did not develop brown rot, until they were transferred to 20 C, 95% RH. The lowest disease incidence and severity occurred in fruit immersed in EO water for up to 5 minutes. EO water having pH 4.0, ORP 1,100 mV, FAC 290 mg L-1 delayed the onset of brown rot to 7 days, i.e., about the period peach stays in the market from a packing house to consumer. No chlorine-induced phytotoxicity was observed on the treated fruit. This study revealed that EO water is an effective surface sanitizer, but only delayed disease development.

Electrolytically generated chlorine was injected into citrus microirrigation systems. Propagules of Phytophthora nicotianae var. parasitica, P. citrophthora, Fusarium spp., algae, and slime-forming bacteria were killed. Nematodes were found to resist free-chlorine levels in water of up to 50 g ml-1. Microemitters delivering chlorinated water were less frequently blocked by bacterial and/or bacterial slime than those delivering unchlorinated water. Soil and root populations of Phytophthora and nematodes under citrus trees in the field were unaffected by chlorinated water. No chlorine-induced phytotoxicity was observed on field-grown plants(.)