Microbe(s): Phytophthora parasitica var. nicotianae
The efficiency of slightly acidic electrolyzed water (SAEW with pH 5.06.5) and strong acidic electrolyzed water (StAEW with pH less than 3.0) on the inactivation of Phytophthora parasitica var. nicotianae growth in vitro was studied. The treatment conditions included inundating time (30, 60, 120 and 300 s), treatment interval (24, 48 and 72 h) and available chlorine concentration (ACC, 30, 60 and 90 mg/L) with either StAEW (pH 2.35) or SAEW (pH 6.06). The results showed that inundating time had no effect on the efficiency of SAEW for inactivation of pure P. parasitica var. nicotianae cultures (P > 0.05). The inhibition rate increased with increasing ACC and oxidation reduction potential (ORP) at the same pH and inundating time (P < 0.01) with electrolyzed water (EW). Although the pH of SAEW (pH 6.06) was much higher than that of StAEW (pH2.35), the inhibition rate of SAEW was similar to that of StAEW (P > 0.05) at ACCs of 60 and 90 mg/L. Moreover, the experiments confirmed that the optimal treatment interval was 48 h (P < 0.01). An inhibition rate of higher than 50% of P. parasitica var. nicotianae growth in vitro was achieved with SAEW (pH 6.06, ORP 922 mV and ACC of 90 mg/L) when inundating time was 30 s and treatment interval was 48 h. The findings of this study indicate that EW may be a promising disinfectant, which can achieve inactivation of P. parasitica var. nicotianae with added benefits of reduced health hazards and environmental pollution.
Microbe(s): Fusarium graminearum
Fusarium Head Blight (FHB), caused by a blend of Fusarium species, is a destructive fungal disease of wheat and other small grain cereals. FHB has become an important issue in food and feed industry. Moreover, the majority of FHB pathogens have the ability to synthesize a range of mycotoxins. Although several physical and chemical control measures can be taken to control these fungi in the field, research is needed to provide new techniques for control during storage and transport of cereals. Mounting evidence shows that electrolyzed oxidizing water (EOW) has antimicrobial activity and might be a useful alternative for conventional control measures. The objective of the present work, was to investigate the influence of EOW on outgrowth and germination of Fusarium spp. and deoxynivalenol (DON) production. Both an in vitro and in vivo approach were pursued. In a first approach, a screening of the main FHB causing species was conducted. Secondly, the effect of EOW on Fusarium graminearum and the effect on DON biosynthesis was investigated using a trichothecene knockout mutant. These experiments showed an increase in DON levels upon sub lethal amendments of EOW to F. graminearum spores. In addition, the reactive oxygen species H2O2 was shown to govern this induction. Finally, the work was validated on a laboratory scale via an in vivo assay using wheat grains in which the Fusarium outgrowth was measured. The present work demonstrates that EOW has potential to control Fusarium spp. in wheat grains during transport and storage although sub lethal concentrations can result in increased DON biosynthesis.
Microbe(s): Fusarium sp.
The effects of ultrasound (US) and electrolyzed oxidizing (EO) water on postharvest decay of pineapple cv. Phu Lae were investigated using Fusarium sp. isolated from pineapple fruits. The effect of EO water and US irradiation on in vitro growth inhibition of Fusarium sp. was studied. Spore suspensions were treated EO water with free chlorine at 100, 200 and 300 ppm and different frequencies of 108, 400, 700 KHz and 1 MHz US irradiation for 0, 10, 30 and 60 min and incubated at 27 C for 48 h The study showed that all treatments of EO water totally inhibited the spore germination of the fungus. Additionally, US irradiation of 1 MHz for 60 min was the most effective to suppress the spore germination when compared with the control. When the fruits inoculated with Fusarium sp. were washed in EO water at 100 ppm and US irradiation or combination of US and EO water significantly inhibited the decay incidence and prolonged the shelf life of the pineapple for 20 days. Treatments had no effect on fruit quality (weight loss percentage, total soluble solids, titratable acidity, pH, and ascorbic acid). The potential for EO water in combination with US in pineapple handling systems is high, due to marked synergistic effects against fungal decay of decrowned pineapple fruit during storage.
Acidic electrolyzed oxidizing water (AcEW) is prepared by electrolyzing electrolyte solution using an electrolysis apparatus with an ion-exchange membrane. AcEW has a pH < 3.0, a high oxidationreduction potential (ORP) >1000 mV and a high available chlorine concentration (ACC). In this research, the effectiveness of AcEW on decontamination of aflatoxin B1 (AFB1) from naturally contaminated peanuts was investigated. According to our results, after the contaminated peanuts were soaked with AcEW solution (the ratio of liquid to solid was 5:1 (v/m)) for 15 min at room temperature, the content of AFB1 in peanuts decreased from 34.80 g/kg to around 5 g/kg. That is, about 85% AFB1 was decontaminated from contaminated samples. Ambient temperature and soaking time could markedly influence the elimination rate of AFB1 in contaminated peanuts. The elimination of AFB1 was relatively high when the ambient temperature was 25 C or 45 C. And the contaminated peanuts soaked in AcEW for 15 min can effectively decontaminate AFB1. In addition, the nutrition of peanuts didnt significantly change after treatment including the appearance of color. We also found that high level of ACC is the primary factor in AFB1 elimination. Furthermore, ACC in the form of HClO is probably more efficient than ACC in the form of ClO on AFB1 elimination.
Microbe(s): Escherichia coli O157: H7
Electrolyzed oxidizing water is a relatively new concept that has been utilized in agriculture, livestock management, medical sterilization, and food sanitation. Electrolyzed oxidizing (EO) water generated by passing sodium chloride solution through an EO water generator was used to treat alfalfa seeds and sprouts inoculated with a five-strain cocktail of nalidixic acid resistant Escherichia coli O157:H7. EO water had a pH of 2.6, an oxidation reduction potential of 1150 mV and about 50 ppm free chlorine. The percentage reduction in bacterial load was determined for reaction times of 2, 4, 8, 16, 32, and 64 min. Mechanical agitation was done while treating the seeds at different time intervals to increase the effectiveness of the treatment. Since E. coli O157:H7 was released due to soaking during treatment, the initial counts on seeds and sprouts were determined by soaking the contaminated seeds/sprouts in 0.1% peptone water for a period equivalent to treatment time. The samples were then pummeled in 0.1% peptone water and spread plated on tryptic soy agar with 50 g/ml of nalidixic acid (TSAN). Results showed that there were reductions between 38.2% and 97.1% (0.22 1.56 log10 CFU/g) in the bacterial load of treated seeds. The reductions for sprouts were between 91.1% and 99.8% (1.05 2.72 log10 CFU/g). An increase in treatment time increased the percentage reduction of E. coli O157:H7. However, germination of the treated seeds reduced from 92% to 49% as amperage to make EO water and soaking time increased. EO water did not cause any visible damage to the sprouts.
Degradation of the 3 pesticides (acephate, omethoate, and dimethyl dichloroviny phosphate [DDVP]) by electrolyzed water was investigated. These pesticides were commonly used as broad-spectrum insecticides in pest control and high-residual levels had been detected in vegetables. Our research showed that the electrolyzed oxidizing (EO) water (pH 2.3, available chlorine concentration:70 ppm, oxidation-reduction potential [ORP]: 1170 mV) and the electrolyzed reducing (ER) water (pH 11.6, ORP: -860 mV) can reduce the pesticide residues effectively. Pesticide residues on fresh spinach after 30 min of immersion in electrolyzed water reduced acephate by 74% (EO) and 86% (ER), omethoate by 62% (EO) and 75% (ER), DDVP by 59% (EO) and 46% (ER), respectively. The efficacy of using EO water or ER water was found to be better than that of using tap water or detergent (both were reduced by more than 25%). Besides spinach, the cabbage and leek polluted by DDVP were also investigated and the degradation efficacies were similar to the spinach. Moreover, we found that the residual level of pesticide residue decreased with prolonged immersion time. Using EO or ER water to wash the vegetables did not affect the contents of Vitamin C, which inferred that the applications of EO or ER water to wash the vegetables would not result in loss of nutrition.
Microbial control of postharvest diseases has been extensively studied and appears to be a viable technology. Food safety must be ensured at each postharvest processing step, including handling, washing of raw materials, cleaning of utensils and pipelines, and packaging. Several commercial products are available for this purpose. The time is ripe for developing new techniques and technologies. The use of electrolyzed water (EW) is the product of a new concept developed in Japan, which is now gaining popularity in other countries. Little is known about the principle behind its sterilizing effect, but it has been shown to have significant bactericidal and virucidal and moderate fungicidal properties. Some studies have been carried out in Japan, China, and the USA on the pre- and postharvest application of EW in the field of food processing. EW may be produced using common salt and an apparatus connected to a power source. As the size of the machine is quite small, the water can be manufactured on-site. Studies have been carried out on the use of EW as a sanitizer for fruits, utensils, and cutting boards. It can also be used as a fungicide during postharvest processing of fruits and vegetables, and as a sanitizer for washing the carcasses of meat and poultry. It is cost-effective and environment-friendly. The use of EW is an emerging technology with considerable potential.
Microbe(s): Botrytis cinerea, Monilinia fructicola
Near neutral (pH 6.36.5) electrolyzed oxidizing water (EO water) has been demonstrated to inactivate fungi in pure culture and to mitigate infection on fruit surfaces. One possible and as effective as a once per week captan/once per week EO treatment. The once per week captan/once per week EO treatment was significantly more effective (P 0.05) than the captan once per week treatment. Dip treatments of strawberries in near neutral EO solutions (50 and 100 ppm TRC pH 6.36.5) did not leave a chlorine residue on the fruit relative to a water dip. The results from this study suggest that near neutral EO solutions could be used to manage infection of B. cinerea on strawberry plants in the field and also as a disinfection solution for harvesting equipment, greenhouses, packing houses and in commercial facilities to prevent or manage infections of B. cinerea and M. fructicola.
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.
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.
Microbe(s): Tilletia indica
Definitive identification of free teliospores of Tilletia indica, causal agent of Karnal bunt of wheat, requires polymerase chain reaction (PCR)-based diagnostic tests. Since direct PCR amplification from teliospores has not been reliable, teliospores first must be germinated in order to obtain adequate DNA. We have routinely surface-sterilized teliospores for 2 min with 0.4% (vol/vol) sodium hypochlorite (NaOCl) to stimulate germination and produce axenic cultures. However, we observed that some spores were killed even with a 2-min NaOCl treatment, the shortest feasible duration. Decreasing the NaOCl concentration in our study from 0.4% to 0.3 and 0.2%, respectively, increased teliospore germination, but treatment times longer than 2 min still progressively reduced the germination percentages. In testing alternative methods, we found acidic electrolyzed water (AEW), generated by electrolysis of a weak solution of sodium chloride, also surface-sterilized and increased the rate of T. indica teliospore germination. In a representative experiment comparing the two methods, NaOCl (0.4%) for 2 min and AEW for 30 min increased germination from 19% (control) to 41 and 54%, respectively, by 7 days after treatment. Because teliospores can be treated with AEW for up to 2 h with little, if any, loss of viability, compared with 1 to 2 min for NaOCl, treatment with AEW has certain advantages over NaOCl for surface sterilizing and increasing germination of teliospores of suspect T. indica.
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(.)