Research > Industry > Food > Application: Produce
Common Names for Hypochlorous Acid Solutions
- Electrolytically Generated Hypochlorous Acid
- Neutral Electrolyzed Water (NEW)
- Electrolyzed Oxidizing Water (EOW)
- Electro-chemically Activated Water (ECA)
- Super-oxidized water (SOW)
Results: 93 published articles
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
The effects of low-concentration electrolysed water (LcEW) (4 mg/L free available chlorine) combined with mild heat on the safety and quality of fresh organic broccoli (Brassica oleracea) were evaluated. Treatment with LcEW combined with mild heat (50 C) achieved the highest reduction in naturally occurring microorganisms and pathogens, including inoculated Escherichia coli O157:H7 and Listeria monocytogenes (P < 0.05). In terms of the antioxidant content of the treated broccoli, the total phenolic levels and ferric reducing antioxidant power remained unchanged however, the oxygen radical absorbance capacity of the treated broccoli was higher than that of the untreated control. In addition, mild heat treatment resulted in an increase in firmness. The increased firmness was attributed to changes in the pectin structure, including the assembly and dynamics of pectin. The results revealed that mild heat induced an antiparallel orientation and spontaneous aggregation of the pectin chains. This study demonstrated that LcEW combined with mild heat treatment was effective to reduce microbial counts on fresh organic broccoli without compromising the product quality.
Microbe(s): Total Microbial Count
Electrolyzed water (EW) is known by its bactericidal efficacy and capability to oxidize organic matter. The present research evaluated the efficacy of recently developed electrolytic cells able to generate higher concentration of reactive oxygen species using lower power and salt concentration than conventional cells. This study tested the inactivation of Escherichia coli O157:H7, the organic matter depletion and trihalomethane (THM) generation by EW in process wash water under dynamic conditions. To achieve this, clean tap water was continuously added up to 60 min with artificial process water with high chemical oxygen demand (COD) inoculated with E. coli O157:H7, in experiments performed in a pilot plant that recirculated water through one electrolytic cell. Plate counts of E. coli O157:H7, COD, THMs, free, combined and total chlorine, pH, temperature and oxidation-reduction potential were determined. Results indicate that the novel electrolysis system combined with minimal addition of NaCl (0.05) was able to suppress E. coli O157:H7 population build-up and decreased the COD accumulation in the process wash water. THM levels in the water were relatively high but its concentration in the washed product was marginal. Highly effective electrolysis has been proven to reduce the occurrence of foodborne diseases associated to cross-contamination in produce washers without having an accumulation of THMs in the washed product.
Microbe(s): Total Microbial Count
Product decontamination is one of the most important processes of the hygienic practice in food industries such as Minimally Processed Vegetables (MPV) plants and sodium hypochlorite (NaOCl) solutions are commonly used as a biocide for disinfection. Although it may be corrosive and irritating when compared to , reducing the free chlorine concentration needed to sanitize salads, also decreasing water consumption whilst taking into account environmental and food quality impacts.
Microbe(s): Total Microbial Count, Fungi, Yeast, Mold
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.
Microbe(s): Total Microbial Count
This paper focused on the effectiveness of electrolyzed water (EW) at different concentrations (5, 25, 50 and 100 mg/L) combined with passive atmosphere packaging on the quality of mushroom. In order to understand the effect of EW on mushrooms, gas composition inside packages, weight loss, pH, whiteness and browning index, texture profile analysis (TPA), cap development, electrolyte leakage and FT-NIR analysis were performed during the twelve days of storage at 4 C. Samples washed with 25 and 50 mg/L EW consumed O2 lower than the other treatments. Mushrooms treated with 25 mg/L EW had a significantly lower electrolyte leakage values than untreated and 5 mg/L treated mushrooms. Mushrooms treated with 25 mg/L EW had the highest whiteness index and lowest browning index. EW treatments at the concentrations of 25 and 50 mg/L maintained the textural parameters and slowed down the weight loss better than other treatments. FT-NIR analysis supported the results obtained by weight loss and electrolyte leakage. In conclusion, the results of this research support the idea that combined of EW treatment and passive modified atmosphere packaging can be used to extend the shelf life of mushrooms.
Microbe(s): Escherichia coli O157:H7, Salmonella Typhimurium
Automated produce washers can be a useful processing aid when treating fresh produce contaminated with pathogens. The of near neutral pH electrolyzed (NEO) water as a wash or sanitizing solution has been shown to lead to significant reductions of Escherichia coli O157:H7 and Salmonella on fresh produce. To further enhance reported pathogen reductions, the effects of a combined NEO water (155 mg/L free chlorine, pH 6.5) and ultrasound wash protocol on lettuce and tomatoes inoculated with E. coli O157:H7 and S. Typhimurium DT 104 were studied. The effects of the pH of NEO water and washer agitation on pathogen reductions were also assessed. Inoculated tomatoes and lettuce leaves were treated with either chilled deionized water or NEO water, with or without 20 kHz ultrasound (130 W and 210 W). Tomatoes were treated for 1, 3 and 5 min while lettuce was treated for 5, 10 and 15 min. Ultrasound significantly increased the oxidation-reduction potential (ORP) of NEO water (p < 0.05) but did not affect the pH and free chlorine concentration (p > 0.05). Increased washing time and higher ultrasonic power led to significantly greater reductions of both pathogens on produce items (p < 0.05). NEO water combined with 210 W ultrasonication for 15 min led to 4.4 and 4.3 log reductions of E. coli O157:H7 and S. Typhimurium on lettuce, respectively, while 210 W ultrasound for 5 min completely inactivated both pathogens on tomatoes. Both pathogens were completely inactivated in NEO water solutions, suggesting that its presents little chance of cross-contamination.
Microbe(s): Total Microbial Count, Fungi, Yeast, Mold
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.
Microbe(s): Total Microbial Count
In order to evaluate slightly acidic electrolyzed water (SAEW) and sodium hypochlorite solution, the washing agents on shelf-life and quality were investigated during 25 days cold storage. The resultsshowed that the specific maximum peak force of lettuce and carrot significantly increased after treated with SAEW, while carrot with sodium hypochlorite solution treatment was not significantly (P > 0.05) increased. Also the shelf-life of lettuce processed with SAEW was prolonged for another 4.5 days. The results indicated that SAEW technology had stronger decontamination ability than sodium hypochlorite with its conveniences.
Microbe(s): Listeria monocytogenes, Salmonella enterica
The goal of this study was to enhance the antimicrobial effect of slightly acidic electrolyzed water (SAEW) through addition of synergistic treatment with ultrasound (US) and mild heat treatment in order to improve the microbial safety of fresh-cut bell pepper. To evaluate the synergistic effects, the Weibull model was used to mathematically measure the effectiveness of the individual and combined treatments against Listeria monocytogenes and Salmonella Typhimurium on the pepper. The combined treatment (SAEWUS60 C) resulted in the TR values of 0.04 and 0.09 min for L. monocytogenes and S. Typhimurium, respectively, as consequence of the minimum value. Subsequently, texture analysis was carried out to test the potential effect on quality of the samples due to the involved mild heat and ultrasound treatment. When compared to the control, there was no significant change (p 0.05) in the texture (color and hardness) of the samples that were treated by 1 min of the combined treatment (SAEWUS60 C) during storage at 4 C for 7 days. This combined treatment achieved approximately 3.0 log CFU/g reduction in the two pathogens. The results demonstrate that the involved hurdle factors which are ultrasound and mild heat achieved the synergistic effect of SAEW against the two pathogens. According to the results of texture analysis, 1 min of SAEWUS60 C is the optimal condition due to without negative influence on the quality of the samples during the storage. The optimal condition shows the enhanced antimicrobial effect of SAEW and enables to improve microbial safety of fresh bell pepper in food industry as a consequence of hurdle approach.
Microbe(s): Staphylococcus aureus
Slightly acidic electrolyzed water (SAEW), considered as a broad-spectrum and high-performance bactericide are increasingly applied in the food industry. However, its disinfection mechanism has not been completely elucidated. This study aims to examine the disinfection efficacy and mechanism of SAEW on Staphylococcus aureus, compared with that of sodium hypochlorite (NaClO) and hydrochloric acid (HCl). SAEW treatment significantly reduced S. aureus by 5.8 log CFU/mL in 1 min, while 3.26 and 2.73 log reductions were obtained with NaClO and HCl treatments, respectively. A series of biological changes including intracellular potassium leakage, TTC-dehydrogenase relative activity and bacterial ultrastructure destruction were studied following disinfection treatment of S. aureus. The results showed that SAEW decreased the relative activity of TTC-dehydrogenase by 65.84%. Comparing intracellular potassium leakage, the SAEW treatment caused a greater percent of protein leakage (108.34%) than the NaClO (18.75%) or HCl (0.84%) treatments. These results demonstrated the potent impact SAEW had on the permeability of cell membranes. In addition, the ranking of partly agglutinated cellular inclusion formation was HCl > SAEW > NaClO. It appeared that HCl, along with its low pH value, are responsible for most of the cytoplasmic disruptions. Overall, this study demonstrated that the disinfection mechanism of SAEW was disrupting the permeability of cell membrane and the cytoplasmic ultrastructures in S. aureus cells.
Microbe(s): Bacillus cereus
Slightly acid electrolyzed water (SAcEW) and ultrasound (US) treatment have emerged as an environmental-friendly antimicrobial agent. However, SAcEW treatment alone shows low antimicrobial efficiency. Therefore, the aim of this study was to develop a hurdle approach that combined SAcEW and US to improve the antimicrobial effect against Bacillus cereus as well as inhibition of the growth on potato. US treatment under different conditions of dip times, acoustic energy densities (AED) and temperatures were conducted to obtain the optimal condition. Our findings demonstrate that 3 min of US with 400 W/L of AED at 40 C treatment (US 40 C) significantly (p 0.05) reduced B. cereus population by 2.3 0.1 log CFU/g with minimal change in the color of potato. In addition, 3 min of SAcEW (pH, 5.35.5 ORP, 958981 mV ACC, 2830 mg/L) simultaneous with US40 C treatment (SAcEW US40 C) an approximately 3.0 log CFU/g reduction in B. cereus. Furthermore, SAcEW US40 C treatment efficiently extended lag time of B. cereus by 0.210.5 hrs, reduced that of specific growth rate by 0.010.23 log CFU/h during storage at different temperatures from 5 to 35 C. Therefore, this combined hurdle technology is capable of improving microbial safety of potato during storage and distribution.
Microbe(s): Colletotrichum fructicola
Neutral electrolyzed water (NEW: pH 6.57.5) applied through an overhead irrigation system was evaluated for control of strawberry anthracnose caused by Colletotrichum fructicola. Conidia of the pathogen were completely killed by a 10-s exposure to 10.0 mg/L of available chlorine in the NEW. Disease suppression was significantly higher using the NEW treatment through overhead irrigation, either alone or combined with fungicides, than using conventional fungicides. Plants had no visible phytotoxicity after the NEW treatment, even when combined with fungicides. Thus, the NEW treatment was effective at controlling anthracnose caused by C. fructicola.
Microbe(s): Listeria monocytogenes
This study evaluated the efficacy of thermosonication combined with slightly acidic electrolyzed water (SAcEW) on the shelf life extension of fresh-cut kale during storage at 4 and 7 C. Each kale (10 0.2 g) was inoculated to contain approximately 6 log CFU/g of Listeria monocytogenes. Each inoculated or uninoculated samples was dip treated at 40 C for 3 min with deionized water, thermosonication (400 W/L), SAcEW (5 mg/L), sodium chlorite (SC; 100 mg/L), sodium hypochlorite (SH; 100 mg/L), and thermosonication combined with SAcEW, SC, and SH (TS + SAcEW, TS + SC, and TS + SH, respectively). Growths of L. monocytogenes and spoilage microorganisms and changes in sensory (overall visual quality, browning, and off-odour) were evaluated. The results show that lag time and specific growth rate of each microorganism were not significantly (P > 0.05) affected by treatment and storage temperature. Exceeding the unacceptable counts of spoilage microorganisms did not always result in adverse effects on sensory attributes. This study suggests that TS + SAcEW was the most effective method to prolong the shelf life of kale with an extension of around 4 and 6 days at 4 and 7 C, respectively, and seems to be a promising method for the shelf life extension of fresh produce.
Microbe(s): Dioscorea spp.
In this study, the effects of electrolyzed oxidizing water (EOW) on the prevention of enzymatic browning of fresh-cut Jiu Jinhuang Chinese yam were investigated. The yams were immersed in the inhibitors for 25 min at 20 C. Compared with the tap water (TW) treatment, the chromatic attributes were significantly different after 72 h of storage (P < 0.05). The activities of polyphenol oxidase (PPO, EC 1.10.3.1), peroxidase (POD, EC 1.11.1.7), and L-phenylalanine ammonia lyase (PAL, EC 4.3.1.5) were inhibited when measured at 24 h. The contents of phenolic acids, including gallic and chlorogenic acid, in the group treated with the slightly acidic electrolyzed water (SAEW) were higher than those treated with TW and neutral electrolyzed water (NEW). The group treated with NEW had the highest total phenol content (P < 0.05, at 24 h), while the group treated with SAEW had the highest flavonoid content (P < 0.05) during storage. Without being treated with inhibitors, the Km and Vmax values of yam PPO were 0.0044 mol/L and 0.02627 U/min, respectively, and the Ki of samples treated with SAEW and citric acid (CA) were 15.6607 and 2.3969 mol/L, respectively. These results indicate that EOW is beneficial as a browning inhibitor.
Microbe(s): Total Microbial Count, RE: Nitrite
eafy vegetables are the major source of nitrite intake in the human diet, and technological processing to control nitrite levels in harvested vegetables is necessary. In the current work, the effect of electrolyzed oxidizing water (EOW) on the nitrite and nitrate levels in fresh spinach during storage was studied. EOW treatment, including slightly acidic electrolyzed water and acidic electrolyzed water, was found to effectively reduce nitrite levels in fresh spinach during storage levels in the late period were 30 to 40% lower than that of the control. However, the nitrate levels in fresh spinach during storage were not influenced by EOW treatment. The reduction of nitrite levels in EOW-treated fresh spinach during storage can be attributed to the inactivation of nitrate reductase directly and to the reduction of bacterial populations. Our results suggest that treatment with slightly acidic electrolyzed water may be a better choice to control nitrite levels in fresh vegetables during storage. This study provided a useful method to reduce nitrite levels in fresh spinach.
Microbe(s): Escherichia coli
In the present study, the disinfection efficacy on fresh-cut cilantro of the combination of strongly acidic electrolyzed water (AcEW) and alkaline electrolyzed water (AlEW) was evaluated, in comparison with single slightly acidic electrolyzed water (SAEW) and single AcEW treatments. The populations of E. Coli O78 on inoculated cilantro treated by AlEW 5 min + AcEW 5 min, was not detected while 3.43 and 3.73 log10 CFU/g in the AlEW 2.5 min + AcEW 2.5 min and AcEW 2 min + AlEW 2 min + AcEW 2 min treatments respectively. Our results implied that the bactericidal abilities of the combination of AlEW and AcEW treatments were higher than that of single AcEW and SAEW, which also was demonstrated microscopically by scanning electron microscopy (SEM). Moreover, the efficacy of combination of AcEW and AlEW in reducing natural micro flora on fresh-cut cilantro was also evaluated compared with single AcEW and SAEW. The results showed that the combination of AlEW and AcEW had stronger sterilization ability than single AcEW and SAEW. Considering the utilizations of AlEW and disinfection efficacy, we suggest that the combination of AlEW and AcEW may also be a better choice in fresh-cut produce.
Microbe(s): Salmonella
Tomato Best Management Practices require Florida packers to treat tomatoes in a flume system containing at least 150 ppm of free chlorine or other approved sanitizer. However, research is needed to determine the ability of these sanitizers to prevent the transfer of pathogens from contaminated to uncontaminated tomatoes, particularly under realistic packinghoconditions. The goal of this research was to assess the minimum levels of sanitizer needed to prevent Salmonella cross-contamination between tomatoes in a model flume system under clean conditions and conditions where organic matter was added. Inoculated tomatoes (ca. 8.3 log CFU per tomato) were treated along with uninoculated tomatoes in a model flume system containing 0, 10, or 25 ppm of hypochlorous acid (HOCl) under organic loading conditions of 0, 500, or 4,000 ppm of chemical oxygen demand (COD). In the absence of HOCl, uninoculated tomatoes were highly contaminated (ca. 5 log CFU per tomato) by 15 s. No contamination was detectable (<2 log CFU per tomato) on uninoculated tomatoes when HOCl was present, except with 10 ppm at 4,000 ppm of COD, suggesting failure of 10 ppm of HOCl as a sanitizer under very high organic loading conditions. In the presence of HOCl or peroxyacetic acid, Salmonella was undetectable (<1 log CFU/ml) in the model flume water samples after 2 and 30 s, respectively. Upon enrichment, none of the uninoculated tomatoes treated with 25 ppm of HOCl for 120 s were positive for Salmonella, even in the presence of organic loading at 500 ppm of COD. Based on these findings, 25 ppm of HOCl may be adequate to prevent cross-contamination when the concentration is properly maintained, COD does not exceed 500 ppm, and tomatoes are treated for at least 120 s. Further validation in a larger commercial setting and using higher organic loading levels is necessary becamanaging HOCl at this low concentration is difficult, especially in a recirculating system. The of less sanitizer by packers could reduce chemical and disposal costs.
Microbe(s): Total Microbial Count, Escherichia coli O157:H7, Listeria monocytogenes, Pseudomonas spp., Fungi, Yeast
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.
Microbe(s): MNV-1, Norovirus, HAV, Hepatitis A
The ability of acidic electrolyzed oxidizing water (AEO) and neutral electrolyzed oxidizing water (NEO) to inactivate the murine norovirus (MNV-1) surrogate for human norovirus and hepatitis A virus (HAV) in suspension and on stainless steel coupons in the presence of organic matter was investigated. Viruses containing tryptone (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) were mixed with AEO and NEO for 1 min. In addition, stainless steel coupons containing MNV-1 with or without organic matter were treated with AEO or NEO for 3, 5, and 10 min. AEO was proven effective and generally killed more MNV-1 and HAV in suspension than NEO. Depending on the EO water generator, free chlorine concentrations are required to inactivate MNV-1 and HAV by 3-log PFU/mL or greater ranged from 30 mg/L to 40 mg/L after a 1 min contact time. The virucidal effect increased with increasing free chlorine concentration and decreased with increasing tryptone concentration in suspension. Both AEO and NEO at 70100 mg/L of free chlorine concentration significantly reduced MNV-1 on coupons in the absence of organic matter. However, there was no significant difference between these two treatments in the presence of organic matter. In addition, the efficacy of these two EO waters on stainless steel coupons increased with the increasing treatment time. Results indicated that AEO and NEO can reduce MNV-1 and HAV in suspension. However, higher free chlorine concentrations and longer treatment times may be necessary to reduce viruses on contact surfaces or in the presence of organic matter.
Microbe(s): Pseudomonas spp.
In the present study, we evaluated the antimicrobial activity of neutral electrolyzed water (NEW) against 14 strains of spoilage Pseudomonas of fresh cut vegetables under cold storage. The NEW, produced from solutions of potassium and sodium chloride, and sodium bicarbonate developed up to 4000 mg/L of free chlorine, depending on the salt and relative concentration used. The antimicrobial effect of the NEW was evaluated against different bacterial strains at 105 cells/ml, with different combinations of free chlorine concentration/contact time; all concentrations above 100 mg/L, regardless of the salt used, were found to be bactericidal already after 2 min. When catalogna chicory and lettuce leaves were dipped for 5 min in diluted NEW, microbial loads of mesophilic bacteria and Enterobacteriaceae were reduced on average of 1.7 log cfu/g. In addition, when lettuce leaves were dipped in a cellular suspension of the spoiler Pseudomonas chicorii I3C strain, diluted NEW was able to reduce Pseudomonas population of about 1.0 log cfu/g. Thanks to its high antimicrobial activity against spoilage microorganisms, and low cost of operation, the application of cycles of electrolysis to the washing water looks as an effective tool in controlling fresh cut vegetable microbial spoilage contamination occurring during washing steps.
Microbe(s): Escherichia coli O157:H7
Water can be a vector for foodborne pathogen cross-contamination during washing of vegetables if an efficient method of water disinfection is not used. Chlorination is the disinfection method most widely used, but it generates disinfection by-products such as trihalomethanes (THMs). Therefore, alternative disinfection methods are sought. In this study, a dynamic system was used to simulate the commercial conditions of a washing tank. Organic matter and the inoculum of Escherichia coli O157:H7 were progressively added to the wash water in the washing tank. We evaluated the effectiveness of the electrolyzed water (EW) when combining with the addition of salt (1, 0.5 and 0.15 g/L NaCl) on the pathogenic inactivation, organic matter depletion and THM generation. Results indicated that electrolysis of vegetable wash water with addition of salt (0.5 g/L NaCl) was able to eliminate E. coli O157:H7 population build-up and decrease COD accumulation while low levels of THMs were produced.
Microbe(s): Escherichia coli O157:H7, Salmonella Typhimurium
The objective of this study was to determine the efficacy of neutral pH electrolyzed (NEO) water (155 mg/L free chlorine, pH 7.5) in reducing Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 on romaine lettuce, iceberg lettuce, and tomatoes washed in an automated produce washer for different times and washing speeds. Tomatoes and lettuce leaves were spot inoculated with 100 L of a 5 strain cocktail mixture of either pathogen and washed with 10 or 8 L of NEO water, respectively. Washing lettuce for 30 min at 65 rpm led to the greatest reductions, with 4.2 and 5.9 log CFU/g reductions achieved for E. coli O157:H7 and S. Typhimurium respectively on romaine, whereas iceberg lettuce reductions were 3.2 and 4.6 log CFU/g for E. coli O157:H7 and S. Typhimurium respectively. Washing tomatoes for 10 min at 65 rpm achieved reductions greater than 8 and 6 log CFU/tomato on S. Typhimurium and E. coli O157:H7 respectively. All pathogens were completely inactivated in NEO water wash solutions. No detrimental effects on the visual quality of the produce studied were observed under all treatment conditions. Results show the adoption of this washing procedure in food service operations could be useful in ensuring produce safety.
Microbe(s): Total Microbial Count, Listeria
Three experiments were performed to enumerate the natural microflora on unwashed peaches, known as field peaches, and to determine the efficacy of using acidified electrolyzed water as a topical antimicrobial to remove or reduce the number of the natural microflora or inoculated Listeria innocua from to peach surfaces. During the first experiment, field peaches were divided into four treatment groups: no wash (NW), tap water wash (TW), acidified electrolyzed water wash (AEW), and chlorinated water wash (CL). Peaches were dipped into each of the treatment solutions at ambient temperature and immediately removed (approximately 5 seconds). Peaches were then rinsed in 100 mL of 0.1% peptone and rinsates were plated on aerobic plate count agar for enumeration. For the second experiment, exposure time to the treatment solutions and the temperature of the same treatment solutions were studied. Field peaches were again divided into NW, TW, AEW, and CL but treatments were applied using two exposure times of 5 seconds and 40 minutes at a temperature of 2C (samples were given either a 0 or 40 in their labels to denote exposure time in minutes where 5 second exposures = 0 minutes e.g. TW-0, TW-40, AEW-0, etc.). Rinsing and plating was conducted as mentioned above. Experiment three investigated the efficacy of NW, TW, AEW, and Cl, in reducing numbers of Listeria innocua on peaches that were previously inoculated and held at 4C for 24 hours. Inoculated peaches were dipped in treatment solutions for 5 second and 40 minute times at 2C. Results showed that exposure time had a significant effect on bacterial reduction for both AEW and Cl treatments. Average aerobic counts from all NW peaches was 4.2 log10 CFU/g peach for natural microflora and 4.3 log10 CFU/g peach for samples inoculated with iii Listeria. The following results show the number of bacteria recovered (log10 CFU/g peach) from natural microflora samples and Listeria inoculated samples, respectively: NW = 4.2 and 4.9, TW0 = 3.8 and 4.3, TW-40 = 3.2 and 4.7, AEW-0 = 3.6 and 3.7, AEW-40 = 2.6 and 1.6, CL=0 = 3.7 and 3.7, and CL-40 = 2.3 and 1.9. Greatest reductions were found with AEW-40 and CL-40 at refrigerated temperatures against both aerobic microorganisms and Listeria innocua. They reduced natural microflora counts by approximately 1.6 and 1.9 log10 CFU/g peach, respectively and they also reduced Listeria innocua counts by 3.3 and 3.0 log10 CFU/g peach, respectively. Listeria innocua, like monocytogenes, thrives in cold environments and the analysis of this studys results suggest that Listeria in TW-40 may have reattached to peaches during exposure. Color studies were also performed on the peaches from the preliminary experiment and Experiment 2 to determine the effects of exposing the peaches to low pH environment such as that of the AEW used in this study. Peaches were analyzed for Lab color data prior to their exposure to treatment solutions then they were analyzed again after their treatment concluded and they had air dried until no visible moisture remained. There was no significant color difference shown in any of the peaches when the pre- and post-treatment data was compared. Results from these studies demonstrate that total aerobic microorganisms and Listeria spp. may be reduced, but not eliminated, during washing (by dipping) with AEW or CL with similar reductions for both antimicrobial treatments.
Microbe(s): Total Microbial Count
The disinfection efficacy of acidic electrolyzed water (AEW) on the fresh-cut vegetables has been recognized. However, the application of AEW in the fresh-keeping of fresh-cut vegetables was limited due to its low pH (<2.7) and higher available chlorine concentration (80200mg/L). In the present study, the microbial reduction and storage qualities of fresh-cut cilantro treated by slightly acidic electrolyzed water (SAEW) were evaluated. The results demonstrated that AEW, mild heat AEW, SAEW and mild heat SAEW treatments could reduce the populations on fresh-cut cilantro at 0 day. However, there were no significant differences among all the treatments during the late storage periods. SAEW and mild heat SAEW treatments could keep the firmness of fresh-cut cilantro and maintain the level of electrolyte leakage in comparison with other treatments. SAEW treatment showed the advantage in keeping the overall quality of fresh-cut cilantro compared with other treatments. SAEW may be a better choice in the storage of fresh-cut cilantro than AEW.
Microbe(s): Total Microbial Count, Fungi, Yeasts
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.
Microbe(s): Escherichia coli O157:H7
The purpose of this study was to evaluate and model the growth of Escherichia coli O157:H7 in fresh-cut lettuce submitted to a neutral electrolyzed water (NEW) treatment, packaged in passive modified atmosphere and subsequently stored at different temperatures (4, 8, 13, 16 C) for a maximum of 27 days. Results indicated that E. coli O157:H7 was able to grow at 8, 13, and 16 C, and declined at 4 C. However at 8 C, the lag time lasted 19 days, above the typical shelf-life time for this type of products. A secondary model predicting growth rate as a function of temperature was developed based on a square-root function. A comparison with literature data indicated that the growth predicted by the model for E. coli O157:H7 was again lower than those observed with other disinfection treatments or packaging conditions (chlorinated water, untreated product, NEW, etc.). The specific models here developed might be applied to predict growth in products treated with NEW and to improve existing quantitative risk assessments.
Microbe(s): Total Microbial Count
The decontamination efficacy of neutral electrolyzed water (NEW) was evaluated using shredded cabbages and carrots in both a scalable laboratory system (experiment I) and an actual processing line in a plant (experiment II). In experiment I, the antimicrobial effect of highly concentrated NEW (up to the maximum regulated level: 200 ppm) was tested to determine the appropriate conditions for use in an actual plant test: (1) hypochlorous acid (HClO) concentration (100, 150, and 200 ppm), (2) ratio of sample weight to NEW volume (1:5, 1:10, and 1:20), and (3) treatment time (5, 10, 20, and 30 min), using 2 kg of shredded cabbages and carrots. In experiment II, the feasibility of the NEW treatment was validated on an actual processing line (treatment unit: 20 kg), including cutting, three washing steps (two air bubble washes for 5 min each and 150 ppm NEW for 5 min at ratio of 1:10), rinsing (5 min), and dehydration (5 min). Overall, the microbial reductions tended to increase as the HClO concentration, ratio of sample to NEW, and treatment time increased. The results obtained from experiment I indicated that the maximum conditions (NEW 200 ppm, 1:20, 30 min) achieved 3.3 3.5 log CFU/g reductions in the coliform counts. After treatment with 200 ppm NEW for > 10 min, however, there were noticeable color changes (color differences, DE > 5.0) in both the shredded cabbages and carrots. In the experiment II, the microbial populations were not affected by cutting and two air bubble treatments, whereas washing with NEW greatly reduced both the aerobic plate counts (1.93 2.17 log CFU/g) and coliform counts (0.97 1.51 log CFU/g). More than 2 log CFU/g of indigenous flora were reduced from raw materials to final products with both shredded cabbages (2.05 2.48 log CFU/g) and carrots (2.34 2.76 log CFU/g). These results may provide useful recommendations for the practical application of highly concentrated NEW in the fresh-cut produce industry to improve the microbiological safety without quality deterioration.
Microbe(s): Total Microbial Count, Fungi, Yeasts
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.
Microbe(s): Escherichia coli O157:H7
This study was conducted to investigate the disinfection efficacy of hurdle treatments (thermosonication plus slightly acidic electrolyzed water [SAcEW]) and to develop a model for describing the effect of storage temperatures (4, 10, 15, 20, 25, 30, and 35 C) on the growth of Escherichia coli O157:H7 on fresh-cut kale treated with or without (control) thermosonication combined with SAcEW. The hurdle treatments of thermosonication plus SAcEW had strong bactericidal effects against E. coli O157:H7 on kale, with approximately 3.3-log reductions. A modified Gompertz model was used to describe growth parameters such as specific growth rate (SGR) and lag time (LT) as a function of storage temperature, with high coefficients of determination (R2 > 0.98). SGR increased and LT declined with rising temperatures in all samples. A significant difference was found between the SGR values obtained from treated and untreated samples. Secondary models were established for SGR and LT to evaluate the effects of storage temperature on the growth kinetics of E. coli O157:H7 in treated and untreated kale. Statistical evaluation was carried out to validate the performance of the developed models, based on the additional experimental data not used for the model development. The validation step indicated that the overall predictions were inside the acceptable prediction zone and had lower standard errors, indicating that this new growth model can be used to assess the risk of E. coli O157:H7 contamination on kale.
Microbe(s): Escherichia coli O157:H7
The effect of operating conditions (current density, recirculation flow rate and electrode doping level) on the efficacy of boron-doped diamond (BDD) electrodes to inactivate microorganisms and decrease chemical oxygen demand (COD) was studied in lettuce process wash water with a COD of 725 mg/L and inoculated with a 5-strain cocktail of Escherichia coli O157:H7. Changes in pathogen population, COD, pH, temperature, redox potential, and free and total chlorine were monitored in process wash water during treatments. Considering the specific characteristics of the washing step included in the fresh-cut processing, the disinfection of process wash water should be of fast action. A biphasic with a shoulder model was used to estimate shoulder length (Sl), log-linear inactivation rates (kmax1,kmax2), lowest population (Nf) and highest log reduction (HLR). Current density clearly influenced Sl, and kmax2; recirculation flow rate influenced Sl, kmax1,kmax2 and COD depletion; and doping level influenced Nf. No relationship was observed between inactivation parameters and chlorine concentration. Conditions including high current density (180 mA/cm2), high flow rate (750 l/h) and high doping level (8 000 mol/mol) seems to provide a disinfection efficiency suitable to decrease the chance of bacterial cross contamination in the fresh-cut industries while saving on water consumption and decreasing the amount of wastewater effluents.
Microbe(s): Escherichia coli O157:H7
Effect of ultrasonication (40 kHz) to enhance low concentration electrolyzed water (LcEW) efficacy for microbial decontamination on lettuce leaves was investigated. Lettuce was separately treated with LcEW, ultrasonication, LcEW combined with ultrasonication, LcEW followed by ultrasonication, and ultrasonication followed by LcEW for 1, 3, and 5 min for each step at room temperature. The highest reduction (2.3 log CFU/g) in total bacteria count (TBC) was resulted from ultrasonication followed by LcEW. Subsequently, the effect of temperature was studied resulting in 2.6 and 3.18 log CFU/g reduction of TBC and Escherichia coli O157:H7 respectively, in 3 min ultrasonication followed by 3 min LcEW treatment at 40 C. This optimum treatment also prevented lettuce from reaching 7.0 log CFU/g in TBC until the end of the 6 day storage at 10 C. Therefore, this newly developed approach may result in improved microbiological safety and enhanced shelf life of produce.
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.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
Slightly acidic electrolyzed water (SAEW) is well known as a good sanitizer against foodborne pathogens on fresh vegetables. However, microbial reductions from SAEW treatment are not enough to ensure produce safety. Therefore, it is necessary to improve its antimicrobial efficiency by combining it with other appropriate approaches. This study examined the microbicidal activity of SAEW (pH 5.2-5.5, oxidation reduction potential 500-600 mV, available chlorine concentration 21-22 mg/l) on Chinese cabbage, lettuce, sesame leaf and spinach, four common fresh vegetables in Korea under same laboratory conditions. Subsequently, effects of ultrasonication and water wash to enhance the sanitizing efficacy of SAEW were studied, separately. Finally, an optimized simple and easy approach consisting of simultaneous SAEW treatment with ultrasonication (3 min) followed by water wash (150 rpm, 1 min) was developed (SAEW + US-WW). This newly developed hurdle treatment significantly enhanced the microbial reductions compared to SAEW treatment alone, SAEW treatment with ultrasonication (SAEW + US) and SAEW treatment followed by water wash (SAEW-WW) at room temperature (23 2 C). Microbial reductions of yeasts and molds, total bacteria count and inoculated Escherichia coli O157:H7 and Listeria monocytogenes were in the range of 1.76-2.8 log cfu/g on different samples using the new hurdle approach.
Microbe(s): E. coli O157:H7
Increased interest in blueberries due to their nutritional and health benefits has led to an increase in consumption. However, blueberries are consumed mostly raw or minimally processed and are susceptible to microbial contamination like other type of fresh produce. This study was, therefore, undertaken to evaluate the efficacy of electrostatic spray of electrolyzed oxidizing (EO) water, UV light, ozone, and a combination of ozone and UV light in killing Escherichia coli O157:H7 on blueberries. A 5-strain mixture of E. coli O157:H7 were inoculated on the calyx and skin of blueberries and then subjected to the treatments. Electrostatic EO water spray reduced initial populations of E. coli O157:H7 by only 0.13 to 0.24 log CFU/g and 0.88 to 1.10 log CFU/g on calyx and skin of blueberries, respectively. Ozone treatment with 4000 mg/L reduced E. coli O157:H7 by only 0.66 and 0.72 log CFU/g on calyx and skin of blueberries, respectively. UV light at 20 mW/cm2 for 10 min was the most promising single technology and achieved 2.14 and greater than 4.05 log reductions of E. coli O157:H7 on the calyx and skin of blueberries, respectively. The combination treatment of 1 min ozone and followed by a 2 min UV achieved more than 1 and 2 log additional reductions on blueberry calyx than UV or ozone alone, respectively.
Microbe(s): Total Microbial Count
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 use of mildly heated SlAEW is suggested as an effective disinfection method for fresh cut carrots with low available chlorine.
Microbe(s): Escherichia coli, Listeria innocua, Salmonella choleraesuis
Chlorine (sodium hypochlorite solution) is the most common disinfectant used in the fresh-cut industry, however, environmental and health risks related to its use have resulted in a need to find new sanitizers. Electrolyzed water (EW) is a promising alternative, showing a broad spectrum of microbial decontamination. In this study the efficacy of acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW) as disinfectants of apple slices inoculated with Escherichia coli, Listeria innocua or Salmonella choleraesuis, individually or in a mixture, were compared to that of sodium hypochlorite solution and distilled water. Apple slices were inoculated with a 107 cfu/mL suspension of the pathogens and treated with diluted electrolyzed water. Bactericidal activity of washing treatments was assessed after 30 min and after storage for 5 days at 4 C. AEW and NEW disinfection efficacy was compared to that of washings with sodium hypochlorite at the same free chlorine concentration and with distilled water. AEW diluted to 100 mg/L of free chlorine was the treatment with the highest bactericidal activity in all tested conditions (reductions obtained ranged from 1.2 to 2.4 log units) followed by NEW and AEW at 100 and 50 mg/L of free chlorine respectively. In general these treatments were equal or more effective than sodium hypochlorite washings at 100 mg/L of free chlorine. The effect of the different sanitizer washings when pathogens where in a mixture was similar to that which occurred when pathogens were individually inoculated. The effectiveness of all washings slightly decreased when apple slices were stored for 5 days at 4 C.
Microbe(s): Escherichia coli O157:H7, Salmonella enteritidis
High microbial populations on mung beans and its sprouts are the primary reason of a short shelf life of these products, and potentially present pathogens may cause human illness outbreak. The efficiency for inactivating Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella enteritidis (S. enteritidis), which were artificially inoculated on mung bean seeds and sprouts, by means of slightly acidic electrolyzed water (SAEW, pH 5.0 to 6.5) generated through electrolysis of a mixture of NaCl and hydrochloric acid solution in a non-membrane electrolytic chamber, was evaluated at the different available chlorine concentrations (ACCs, 20-120 mg/l) and treatment time (3-15 min), respectively. The effect of SAEW treatment on the viability of seeds was also determined. Results indicate that the ACC had more significant effect on the bactericidal activity of SAEW for reducing both pathogens on the seeds and sprouts compared to treatment time (P < 0.05). The seeds and sprouts treated with SAEW at ACCs of 20 and 80 mg/l resulted in a reduction of 1.32-1.78 log10 CFU/g and 3.32-4.24 log10 CFU/g for E. coli, while 1.27-1.76 log10 CFU/g and 3.12-4.19 log10 CFU/g for S. enteritidis, respectively. The germination percentage of mung bean seeds was not significantly affected by the treatment of SAEW at an ACC of 20 mg/l for less than 10 min (P > 0.05). The finding of this study implies that SAEW with a near-neutral pH value and low available chlorine is an effective method to reduce foodborne pathogens on seeds and sprouts with less effects on the viability of seeds.
Microbe(s): Escherichia coli, Salmonella spp.
The sanitization efficacy of slightly acidic electrolyzed water (SAEW) against food pathogens on selected fresh ready-to-eat (RTE) vegetables and sprouts was evaluated and compared to sodium hypochlorite (NaOCl) solution. RTE vegetables and sprouts were dip-inoculated with Escherichia coli (E. coli) and Salmonella spp. and dip-treated with SAEW, NaOCl solution for 5 min. SAEW treatment significantly (p < 0.05) reduced the total aerobic mesophilic bacteria from Chinese celery, lettuce and daikon sprouts by 2.7, 2.5 and 2.45 log10CFU/g, respectively relative to un-treated. Pathogens were significantly (p < 0.05) reduced from Chinese celery, lettuce and daikon sprouts by 2.7, 2.8 and 2.8 log10CFU/g (E. coli) and 2.87, 2.91 and 2.91 log10CFU/g (Salmonella spp.), respectively following a SAEW treatment. SAEW and NaOCl solution showed no significant sanitization difference (p > 0.05). Results demonstrate that SAEW at low chlorine concentration and a near neutral pH is a potential non-thermal food sanitizer that could represent an alternative to NaOCl solution and would reduce the amount of free chlorine used in fresh-cut vegetables industry, since the same microbial reduction as NaOCl solution is obtained.
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.
Microbe(s): Total Microbial Count
Electrolyzed functional water possesses a wide variety of antimicrobial activities. Electrolyzed functional water, which used to take place of tap water in producing mung bean sprouts, was studied in this paper. The results showed that electrolyzed water can not only reduce the quantity of microorganism on the surface of mung bean sprouts, but also promote the growth of sprouts. Further research showed that electrolyte leakage rate of mung bean soaked in electrolyzed water was the lowest, while the catalase s activity of mung bean soaked in electrolyzed water was the highest. All of these contribute to the high activity of mung bean.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, Bacillus cereus
In this study we investigated the effects of low concentration electrolyzed water (LcEW) and several other sanitizers (strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl)) on the inactivation of natural microflora (total aerobic bacteria counts (TBC) and yeasts and moulds (YM)) and foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium and Bacillus cereus) on oyster mushroom. The effects of temperature and treatment time on the antimicrobial activity of LcEW to reduce the populations of foodborne pathogens were also determined. LcEW showed the strongest bactericidal efficacy among all the sanitizers on TBC, YM and pathogens by reductions of 1.35, 1.08 and 1.90 2.16 log CFU/g after 3 min treatment at room temperature (23 2 C), respectively. There was no significant difference between the antimicrobial effects of LcEW and SAEW (P > 0.05). Among those sanitizers, their relative influence of inactivation was LcEW > NaOCl > CA > AO.
Microbe(s): Total Microbial Count, Fungi, Yeast, Mold
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.
Microbe(s): Escherichia coli, Salmonella
The sanitization efficacy of slightly acidic electrolyzed water (SAEW) against food pathogens on 2.7, 2.8 and 2.8 log10CFU/g (E. coli) and 2.87, 2.91 and 2.91 log10CFU/g (Salmonella spp.), respectively following a SAEW treatment. SAEW and NaOCl solution showed no significant sanitization difference (p > 0.05). Results demonstrate that SAEW at low chlorine concentration and a near neutral pH is a potential non-thermal food sanitizer that could represent an s industry, since the same microbial reduction as NaOCl solution is obtained.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
The objective of this study was to determine the synergistic effect of alkaline electrolyzed water and citric acid with mild heat against background and pathogenic microorganisms on carrots. Shredded carrots were inoculated with approximately 6 7 log CFU/g of Escherichia coli O157:H7 (932, and 933) and Listeria monocytogenes (ATCC 19116, and 19111) and then dip treated with alkaline electrolyzed water (AlEW), acidic electrolyzed water (AcEW), 100 ppm sodium hypochlorite (NaOCl), deionized water (DaIW), or 1% citric acid (CA) alone or with combinations of AlEW and 1% CA (AlEW + CA). The populations of spoilage bacteria on the carrots were investigated after various exposure times (1, 3, and 5 min) and treatment at different dipping temperatures (1, 20, 40, and 50 C) and then optimal condition (3 min at 50 C) was applied against foodborne pathogens on the carrots. When compared to the untreated control, treatment AcEW most effectively reduced the numbers of total bacteria, yeast and fungi, followed by AlEW and 100 ppm NaOCl. Exposure to all treatments for 3 min significantly reduced the numbers of total bacteria, yeast and fungi on the carrots. As the dipping temperature increased from 1 C to 50 C, the reductions of total bacteria, yeast and fungi increased significantly from 0.22 to 2.67 log CFU/g during the wash treatment (p 0.05). The combined 1% citric acid and AlEW treatment at 50 C showed a reduction of the total bacterial count and the yeast and fungi of around 3.7 log CFU/g, as well as effective reduction of L. monocytogenes (3.97 log CFU/g), and E. Coli O157:H7 (4 log CFU/g). Combinations of alkaline electrolyzed water and citric acid better maintained the sensory and microbial quality of the fresh-cut carrots and enhanced the overall shelf-life of the produce.
Microbe(s): Escherichia coli O157:H7
The objective of this study was to evaluate the efficacy of slightly acidic electrolyzed (SAEO) water in killing or removing Escherichia coli O157:H7 on iceberg lettuce and tomatoes by washing and chilling treatment simulating protocols used in food service kitchens. Whole lettuce leaves and tomatoes were spot-inoculated with 100 L of a mixture of 5 strains of E. coli O157:H7. Washing lettuce with SAEO water for 15 s reduced the pathogen by 1.4 to 1.6 log CFU/leaf, but the treatments did not completely inactivate the pathogen in the wash solution. Increasing the washing time to 30 s increased the reductions to 1.7 to 2.3 log CFU/leaf. Sequential washing in SAEO water for 15 s and then chilling in SAEO water for 15 min also increased the reductions to 2.0 to 2.4 log CFU/leaf, and no cell survived in chilling solution after treatment. Washing tomatoes with SAEO water for 8 s reduced E. coli O157:H7 by 5.4 to 6.3 log CFU/tomato. The reductions were increased to 6.6 to 7.6 log CFU/tomato by increasing the washing time to 15 s. Results suggested that application of SAEO water to wash and chill lettuce and tomatoes in food service kitchens could minimize cross-contamination and reduce the risk of E. coli O157:H7 present on the produce.
Microbe(s): Total Microbial Count
The effects of 40, 70 or 100 mg L 1 free chlorine neutral and acidic electrolyzed water (NEW and AEW) during the washing and disinfection step, on quality attribute changes during shelf life of fresh-cut mizuna baby leaves, were studied. Physiological, nutritional, enzymatic, sensory, and microbial changes throughout 11 days at 5 C were monitored. Results were compared to those reached with a conventional industrial treatment of 100 mg L 1 NaClO at pH 6.5 and with a control washing with deionised water. Both NEW and AEW showed an inhibitory effect on natural microflora growth and retained the main quality attributes. Total chlorophyll content was preserved after shelf life. Initial total phenolic contents ranged between 1868 and 2518 mg CAE kg 1 fw for AEW 40 and AEW 100 treatments respectively and slightly increased throughout shelf life. In contrast, after shelf life the total antioxidant activity recorded on the processing day decreased around 35%. Throughout shelf life EW induced an increase in catalase activity while superoxide dismutase activity decreased. Scanning electron microscopy of the leaves showed that neither NEW nor AEW affected their surface structure. To the best of our knowledge, the effects of NEW and AEW on bioactive quality parameters, as well as on antioxidant enzyme activities for fresh-cut baby leaves are first reported here. EW provides an alternative sanitizing technique to NaClO for maintaining the quality of fresh-cut mizuna baby leaves up to 11 days at 5 C.
Microbe(s): Escherichia coli, Bacillus subtilis
The efficacy of slightly acidic electrolyzed water (SAEW) for reducing microbial contamination on fresh-cut cilantro was investigated in this study. The impacts of SAEW on the microbes of cilantro samples inoculated with two kinds of bacteria (Escherichia coli O78 and Bacillus subtilis 1.1849) were evaluated in comparison with NaClO solution and acidic electrolyzed water (AEW). Dipping with AEW, SAEW and NaClO solutions for 5 min resulted in a reduction in populations of E. coli O78 from 6.38 to 4.93, 3.89 and 4.88 log10 cfu/g and in populations of B. subtilis from 6.52 to 5.02, 4.98, 4.63 log10 cfu/g, respectively, The similar results were found that the populations on cilantro inoculated the mixture of two microbes of E. coli O78 treated with AEW, SAEW and NaClO solutions decreased to 4.15, 3.99, 5.10 log10 cfu/g, respectively, and the populations of B. subtili on cilantro decreased to 5.08,4.97,4.82 log10 cfu/g, respectively. The efficacies of SAEW wash in reducing natural micro flora on fresh-cut cilantro were studied. The results showed SAEW had strong disinfection ability to reduce the microbe population of fresh-cut cilantro and could be an alternative of AEW and NaClO solutions.
Microbe(s): Total Microbial Count
The efficacy of slightly acidic electrolyzed water (SAEW, 20 mg/l of available chlorine) and sodium hypochlorite solution (NaClO, 120 mg/l of available chlorine) used as potential sanitizers for fresh-cut cucumbers was evaluated. SAEW with a near-neutral pH value (5.0 to 6.5) and lower available chlorine concentration (ACC) had an equivalent or higher efficiency to reduce microbial counts on the cucumbers compared to NaClO solution. A 5-minute treatment of SAEW and NaClO solution significantly reduced the indigenous aerobic bacteria on cucumbers by 1.62 and 1.51 log10 CFU/g, and molds and yeasts by 1.35 and 1.12 log10 CFU/g, respectively (P < 0.05). The reduction of microbial counts on cucumbers by tap water was markedly less than that by SAEW and NaClO solution (P < 0.05). Results indicate that SAEW provides an alternative technique for sanitization of fresh-cut vegetables with environmentally friendly broad spectrum microbial decontamination.
Microbe(s): Listeria monocytogenes
Electrolyzed oxidizing water has been estimated that it has strong bactericidal activity and has been widely used as a disinfectant for inactivating microbial organisms. The combined effects of temperature (15 35C), chlorine concentration of electrolyzed oxidizing water (30 70 ppm) and treatment time (1 5 min) on the reduction of Listeria monocytogenes in lettuce were investigated. Reductions of 1.39 2.79 log10 cfu/g were observed in different combinations of the three factors. Also, a quadratic equation for L. monocytogenes inactivation kinetic was developed by multiple regression analysis using response surface methodology. The predicted values were shown to be significantly in good agreement with experimental values because the adjusted determination coefficient (inline image) was 0.9578 and the level of significance was P < 0.0001. Besides, average mean deviation (E%), bias factor (Bf) and accuracy factor (Af), which are validation indicators of the model were 0.0218, 1.0003 and 1.0220, respectively. Thus, predicted model showed a good correlation between the experimental and predicted values, indicating success at providing reliable predictions of L. monocytogenes growth in lettuce.
Microbe(s): Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes
This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm , respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.
Microbe(s): Fungi, Botrytis cinerea, Monilina fructicola
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.
Microbe(s): Listeria monocytogenes, Escherichia coli O157 : H7
Effects of alkaline electrolyzed water (AlEW), acidic electrolyzed water (AcEW), 100 ppm sodium hypochlorite (NaClO), deionized water (DIW), 1% citric acid (CA) alone, and combinations of AlEW with 1% CA (AlEW + CA), in reducing the populations of spoilage bacteria and foodborne pathogens on cabbage were investigated at various dipping times (3, 5, and 10 min) with different dipping temperatures (1, 20, 40, and 50 C). Inhibitory effect of the selected optimal treatment against Listeria monocytogenes and Escherichia coli O157 : H7 on cabbage were also evaluated. Compared to the untreated control, AlEW treatment most effectively reduced the numbers of total bacteria, yeast, and mold, followed by AcEW and 100-ppm NaClO treatments. All treatments dip washed for 5 min significantly reduced the numbers of total bacteria, yeast, and mold on cabbage. With increasing dipping temperature from 1 to 50 C, the reductions of total bacteria, yeast, and mold were significantly increased from 0.19 to 1.12 log CFU/g in the DIW wash treatment (P < 0.05). Combined 1% CA with AlEW treatment at 50 C showed the reduction of around 3.98 and 3.45 log CFU/g on the total count, and yeast and mold, effective reduction of L. monocytogenes (3.99 log CFU/g), and E. coli O157 : H7 (4.19 log CFU/g) on cabbage. The results suggest that combining AlEW with CA could be a possible method to control foodborne pathogens and spoilage bacteria effectively on produce.
Microbe(s): Escherichia coli O157:H7
Inoculated strawberries were treated with deionized water (control), electrolyzed oxidizing (EO) water (23 and 55 mg/L of residual chlorine), and chlorinated water (55 mg/L of residual chlorine), either with or without ultrasonication. Inoculated broccoli was treated with EO water containing 55 and 100 mg/L of residual chlorine and chlorinated water with 100 mg/L of residual chlorine. Treatments were conducted for 1 and 5 min at temperatures of 4 and 24C, respectively. Dipping strawberries and broccoli into EO water or chlorinated water significantly (P < 0.05) reduced the Escherichia coli O157:H7 counts compared with inoculated controls. Dipping inoculated strawberries with chlorinated water or EO water with ultrasonication reduced E. coli O157:H7 cells by 0.7 to 1.9 log cfu/g depending on the treatment time and treatment solution temperature. Dipping inoculated broccoli into chlorinated water or EO water with ultrasonication for 1 or 5 min reduced the bacterial population by 1.2 to 2.2 log cfu/g. Significant (P < 0.05) reductions in pathogen populations were observed when produce was treated with EO water in conjunction with ultrasonication. Results revealed that EO water was either more than or as effective as chlorinated water in killing E. coli O157:H7 cells on strawberries and broccoli.
Microbe(s): Total Microbial Count
For the special efficacy of electrolyzed water and the status that electrolyzed water is less studied on leafy vegetables,in order to provide basis for electrolyzed water used in the cultivation of Chinese cabbage and other leafy vegetables,the effect of soaking Chinese cabbage seeds with electrolyzed water was studied under laboratory conditions.The results showed that pH value of the electrolyzed water was an important factor that affected the Chinese cabbage seeds germination.The acidic electrolyzed water of pH 3.30 could accelerate seeds germinating and raise fresh weight of shoots significantly;strong acidic electrolyzed water and alkaline electrolyzed water would slow down the speed of seeds germination and inhibit both germination rate and fresh weight of shoots;besides,neutral electrolyzed water have no clear effect on germination potential,germination rate and fresh weight of shoots.Preliminary view was that,In addition,the results also showed that 2h of soaking time was appropriate;when soaking time was too short,the electrolyzed water could not have any effect,and soaking too long would have a negative effect on the seeds germination.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
The efficacy of newly developed low concentration electrolyzed water (LcEW) was investigated to inactivate the pathogens on spinach leaves as a convenient and safe alternative sanitizer and it was compared to other sanitizers. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and dip treated with deionized water (DIW), LcEW, strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl) for 3 min at room temperature (23 +/- 2 C). For all pathogens, the similar pattern of microbial reduction on spinach was apparent with LcEW and SAEW washing. In the present study, it was found that LcEW inactivated, at maximum, 1.64-2.80 log cfu/g and DIW resulted in lowest reduction, 0.31-0.95 log cfu/g of background or pathogenic microflora present on spinach leaves compared to the unwashed control. The findings of this study indicate that LcEW and SAEW did not differ significantly (P > 0.05) in reducing background or pathogenic microflora on spinach and LcEW may be a promising sanitizer for washing vegetables without environmental pollution instead of using electrolyzed oxidizing (EO) water or SAEW.
Microbe(s): Salmonella Enteritidis, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus
The bactericidal effect of slightly acidic hypochlorous water (SAHW) on Salmonella Enteritidis, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus, as well as some bacterial strains isolated from fresh lettuce was evaluated. Viable counts of all tested bacterial samples decreased immediately after treatment by SAHW. Most bacterial cells with the exception of B. cereus, and S. aureus were not culturable on TSA after treatment by 1 to 30 mg/L SAHW. Likewise, Pseudomonas sp., and Flavobacterium or Xanthomonas sp., Kurthia sp., Micrococcus sp., and Corynebacterium or Microbacterium sp. were not culturable on TSA after treatment by 30 mg/L SAHW. Viable counts of S. aureus, E. coli, Flavobacterium or Xanthomonas sp., and Pseudomonas sp. showed a 5 to 6 log cfu/mL reduction at day 0 and maintained a count of less than 1 log cfu/mL from day 1 to day 7 following treatment by 30 mg/L SAHW. Sodium hypochlorite (NaOCl, 0.5-1.0 mg/L) decreased the viable counts of S. Enteritidis to less than the lower limit of detection, 1 log cfu/mL, from day 1 to day 7 following treatment by 1 mg/L. NaOCl was not sufficient at 0.5-0.75 mg/L in reducing viable counts of S. Enteritidis because of a 2 to 5 log cfu/mL increase from day 2 to day 5 due to recovery from injury. Initial counts of S. Enteritidis after hydrogen
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Salmonella Typhimurium
Strong acid electrolyzed water (SAEW) has a very limited application due to its low pH value (< 2.7) and corrosive characteristics. Thus, we developed new low concentration electrolyzed water (LcEW). The efficacy of LcEW under various treatment conditions for the inactivation of different foodborne pathogens in pure culture was evaluated and compared with SAEW. The efficiency of LcEW and SAEW for the inactivation of predominant foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus and Salmonella Typhimurium) with different dipping times (1, 3, 5, 7 and 10 min), pH values (2.5, 4.0, 5.0, 6.0 and 9.0) and temperatures (4, 15, 23, 35 and 50 C) were determined. Reductions of bacterial populations of 1.7 to 6.6 log10 CFU/mL in various treated conditions in cell suspensions were observed after treatment with LcEW and SAEW, compared to the untreated control. Dip washing (1 min at 35 C) of lettuce leaves in both electrolyzed water resulted in 2.5 to 4.0 log10 CFU/g compared to the unwashed control. Strong inactivation effects were observed in LcEW, and no significant difference (p > 0.05) was observed between LcEW and SAEW. The effective form of chlorine compounds in LcEW was almost exclusively hypochlorous acid (HOCl), which has strong antimicrobial activity and leaves no residuals due to the low concentration of residual chlorine. Thus, LcEW could be widely applied as a new sanitizer in the food industry.
Microbe(s): Salmonella spp., Escherichia coli
Antimicrobial effect of slightly acidic electrolyzed water (SAEW: pH 5.6 0.1, 20.5 1.3 mg/L available chlorine concentration; ACC) against indigenous aerobic mesophiles and inoculated Escherichia coli and Salmonella spp. on fresh strawberry was assessed. The antimicrobial effect of SAEW was compared with that of strong acidic electrolyzed water (StAEW) and sodium hypochlorite (NaOCl) solution. SAEW effectively reduced total aerobic mesophilic bacteria from strawberries by 1.68 log10CFU/g and was not significantly different from that ofNaOCl solution (p > 0.05). Antimicrobial effect of SAEW against Salmonella spp. andE. coli was indicated by a more than 2 log10CFU/g reduction of their population andthe effect was not significantly different from that of NaOCl solution and StAEW at similar treatment conditions (p > 0.05). From these findings, SAEW with a near-neutral pH and low available chlorine concentration exhibits an equivalent bactericidal effectiveness to NaOCl solution and thus SAEW is a potential sanitizer that would be used as an alternative for StAEW and NaOCl solution in the fresh fruit and vegetables industry.
Microbe(s): Total Microbial Count
Pre-treatment steps of fresh produce as Saengshik raw materials are followed by initial clean-up, dipping, primary washing, and cutting. Hypochlorous acid solution was applied in the dipping step to reduce natural microflora. Also, procedures were changed by cutting, dipping and then primary washing, and the efficacy of hypochlorus acid was evaluated. Potatoes, carrots, kales, and angelicas were submerged in water or 100 ppm of hypochlorous acid for 5 min. After initial clean-up, the aerobic plate counts of potatoes, carrots, kales and angelicas were 4.7, 5.3, 5.6, and 5.7 log CFU/g, respectively. When samples were submerged into water, it only reduced the population of natural microflora by 0.2 to 1.1 log CFU/g, whereas when treated with hypochlorous acid, it reduced the population by 0.5 to 2.8 log CFU/g. Reductions of natural microflora in green leafy vegetables were more highly achieved than bulbs such as potatoes and carrots. However, the numbers of natural microflora were increased after cutting step. To control the cross contamination at the cutting process, the process was changed as follows: initial clean-up, cutting, dipping in hypochlorous acid, and then primary washing. It showed effective reduction of the population by 2.3 to 3.2 log CFU/g. Hypochlorous acid solution could be useful as a sanitizer for surface washing of fresh vegetables.
Microbe(s): Total Microbial Count
A chlorine sanitizer that gives high disinfection efficacy with minimal available chlorine has a potential to be an environmentally-friendly method for disinfection of vegetables. In the present study, disinfection efficacy of slightly acidic electrolyzed water (SlAEW: pH 6.1, 20 mg/L available chlorine) produced by electrolysis for fresh cut cabbage was compared to that of sodium hypochlorite solution (NaOCl solution: pH 9.6, about 150 mg/L available chlorine). SlAEW reduced about by 1.5 log CFU/g for total aerobic bacteria and 1.3 log CFU/g for moulds and yeasts, compared to fresh cut cabbage before dipping. Statistical analysis of the results showed that the disinfectant efficacy of SlAEW was equivalent to or higher than that of NaOCl solution. Results also indicated that SlAEW under shaded and sealed conditions could keep its available chlorine during storage.
Microbe(s): Escherichia coli O157:H7, Salmonella typhimurium, Listeria monocytogenes
Acidic electrolyzed water (AC-EW) has strong bactericidal activity against foodborne pathogens on fresh vegetables. However, the efficacy of AC-EW is influenced by soil or other organic materials present. This study examined the bactericidal activity of AC-EW in the presence of organic matter, in the form of bovine serum against foodborne pathogens on the surfaces of green onions and tomatoes. Green onions and tomatoes were inoculated with a culture cocktail of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes. Treatment of these organisms with AC-EW containing bovine serum concentrations of 5, 10, 15, and 20 ml/l was performed for 15 s, 30 s, 1 min, 3 min and 5 min. The total residual chlorine concentrations of AC-EW decreased proportional to the addition of serum. The bactericidal activity of AC-EW also decreased with increasing bovine serum concentration, whereas unamended AC-EW treatment reduced levels of cells to below the detection limit (0.7 logCFU/g) within 3 min.
Microbe(s): Escherichia coli O157:H7
This study compared the efficacy of chlorine (20 200 ppm), acidic electrolyzed water (50 ppm chlorine, pH 2.6), acidified sodium chlorite (20 200 ppm chlorite ion concentration, Sanova ), and aqueous chlorine dioxide (20 200 ppm chlorite ion concentration, TriNova ) washes in reducing populations of Escherichia coli O157:H7 on artificially inoculated lettuce. Fresh-cut leaves of Romaine or Iceberg lettuce were inoculated by immersion in water containing E. coli O157:H7 (8 log CFU/ml) for 5 min and dried in a salad spinner. Leaves (25 g) were then washed for 2 min, immediately or following 24 h of storage at 4 C. The washing treatments containing chlorite ion concentrations of 100 and 200 ppm were the most effective against E. coli O157:H7 populations on Iceberg lettuce, with log reductions as high as 1.25 log CFU/g and 1.05 log CFU/g for TriNova and Sanova wash treatments, respectively. All other wash treatments resulted in population reductions of less than 1 log CFU/g. Chlorine (200 ppm), TriNova , Sanova , and acidic electrolyzed water were all equally effective against E. coli O157:H7 on Romaine, with log reductions of ~ 1 log CFU/g. The 20 ppm chlorine wash was as effective as the deionized water wash in reducing populations of E. coli O157:H7 on Romaine and Iceberg lettuce. Scanning electron microscopy indicated that E. coli O157:H7 that was incorporated into biofilms or located in damage lettuce tissue remained on the lettuce leaf, while individual cells on undamaged leaf surfaces were more likely to be washed away.
Microbe(s): Escherichia coli O157:H7
Treatment of fresh fruits and vegetables with electrolyzed water (EW) has been shown to kill or reduce foodborne pathogens. We evaluated the efficacy of EW in killing Escherichia coli O157:H7 on iceberg lettuce, cabbage, lemons, and tomatoes by using washing and/or chilling treatments simulating those followed in some food service kitchens. Greatest reduction levels on lettuce were achieved by sequentially washing with 14-A (amperage) acidic EW (AcEW) for 15 or 30 s followed by chilling in 16-A AcEW for 15 min. This procedure reduced the pathogen by 2.8 and 3.0 log CFU per leaf, respectively, whereas washing and chilling with tap water reduced the pathogen by 1.9 and 2.4 log CFU per leaf. Washing cabbage leaves for 15 or 30 s with tap water or 14-A AcEW reduced the pathogen by 2.0 and 3.0 log CFU per leaf and 2.5 to 3.0 log CFU per leaf, respectively. The pathogen was reduced by 4.7 log CFU per lemon by washing with 14-A AcEW and 4.1 and 4.5 log CFU per lemon by washing with tap water for 15 or 30 s. A reduction of 5.3 log CFU per lemon was achieved by washing with 14-A alkaline EW for 15 s prior to washing with 14-A AcEW for 15 s. Washing tomatoes with tap water or 14-A AcEW for 15 s reduced the pathogen by 6.4 and 7.9 log CFU per tomato, respectively. Application of AcEW using procedures mimicking food service operations should help minimize cross-contamination and reduce the risk of E. coli O157:H7 being present on produce at the time of consumption.
Microbe(s): Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes
Recent foodborne outbreaks implicating spinach and lettuce have increased consumer concerns regarding the safety of fresh produce. While the most common commercial antimicrobial intervention for fresh produce is wash water containing 50 to 200 ppm chlorine, this study compares the effectiveness of acidified sodium chlorite, chlorine, and acidic electrolyzed water for inactivating Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes inoculated onto leafy greens. Fresh mixed greens were left uninoculated or inoculated with approximately 6 log CFU/g of E. coli O157:H7, Salmonella, and L. monocytogenes and treated by immersion for 60 or 90 s in different wash solutions (1:150, wt/vol), including 50 ppm of chlorine solution acidified to pH 6.5, acidic electrolyzed water (pH 2.1 0.2, oxygen reduction potential of 1,100 mV, 30 to 35 ppm of free chlorine), and acidified sodium chlorite (1,200 ppm, pH 2.5). Samples were neutralized and homogenized. Bacterial survival was determined by standard spread plating on selective media. Each test case (organism treatment time) was replicated twice with five samples per replicate. There was no difference (P 0.05) in the time of immersion on the antimicrobial effectiveness of the treatments. Furthermore, there was no difference (P 0.05) in survival of the three organisms regardless of treatment or time. Acidified sodium chlorite, resulted in reductions in populations of 3 to 3.8 log CFU/g and was more effective than chlorinated water (2.1 to 2.8 log CFU/g reduction). These results provide the produce industry with important information to assist in selection of effective antimicrobial strategies.
Microbe(s): Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis
Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution (1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl2, HOCl/ClO-). At a near-neutral pH (pH 6.3-6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900 mV. The biocidal activity of near-neutral EO water was evaluated at 25 C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120 ppm total residual chlorine (TRC) and 10 min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1-6.7 log10 CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278-310 ppm TRC (pH 6.38) resulted in a 79-100% reduction of microbial growth. Dip (10 min) treatment of spinach at 100 and 120 ppm TRC resulted in a 4.0-5.0 log10 CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10 min) of lettuce at 100 and 120 ppm TRC reduced bacterial counts of E. coli by 0.24-0.25 log10 CFU/mL and reduced all other organisms by 2.43-3.81 log10 CFU/mL.
Microbe(s): Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes
The ability of electrolyzed water (EW) to inactivate foodborne pathogens on the surfaces of lettuce and spinach was investigated. Lettuce and spinach leaves were inoculated with a cocktail of 3 strains each of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and treated with acidic electrolyzed water (AC-EW), alkaline electrolyzed water (AK-EW), alkaline electrolyzed water followed by acidic electrolyzed water (sequential treatment, AK-EW + AC-EW), deionized water followed by acidic electrolyzed water (sequential treatment, DW + AC-EW), and deionized water (control, DW) for 15, 30 s, and 1, 3, and 5 min at room temperature (22 2 C). For all 3 pathogens, the same pattern of microbial reduction on lettuce and spinach were apparent. The relative efficacy of reduction was AC-EW > DW + AC-EW = AK-EW + AC-EW > AK-EW > control. After a 3-min treatment of AC-EW, the 3 tested pathogens were reduced below the detection limit (0.7 log). DW + AC-EW and AK-EW + AC-EW produced the same levels of reduction after 5 min when compared to the control. AK-EW did not reduce levels of pathogens even after a 5-min treatment on lettuce and spinach. Results suggest that AC-EW treatment was able to significantly reduce populations of the 3 tested pathogens from the surfaces of lettuce and spinach with increasing time of exposure.
Microbe(s): Salmonella, Listeria monocytogenes, Escherichia coli O157:H7, Erwinia carotovora
Consumption of minimally-processed, or fresh-cut, fruit and vegetables has rapidly increased in recent years, but there have also been several reported outbreaks associated with the consumption of these products. Sodium hypochlorite is currently the most widespread disinfectant used by fresh-cut industries. Neutral electrolyzed water (NEW) is a novel disinfection system that could represent an alternative to sodium hypochlorite. The aim of the study was to determine whether NEW could replace sodium hypochlorite in the fresh-cut produce industry. The effects of NEW, applied in different concentrations, at different treatment temperatures and for different times, in the reduction of the foodborne pathogens Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 and against the spoilage bacterium Erwinia carotovora were tested in lettuce. Lettuce was artificially inoculated by dipping it in a suspension of the studied pathogens at 108, 107 or 105 cfu ml 1, depending on the assay. The NEW treatment was always compared with washing with deionized water and with a standard hypochlorite treatment. The effect of inoculum size was also studied. Finally, the effect of NEW on the indigenous microbiota of different packaged fresh-cut products was also determined. The bactericidal activity of diluted NEW (containing approximately 50 ppm of free chlorine, pH 8.60) against E. coli O157:H7, Salmonella, L. innocua and E. carotovora on lettuce was similar to that of chlorinated water (120 ppm of free chlorine) with reductions of 1 2 log units. There were generally no significant differences when treating lettuce with NEW for 1 and 3 min. Neither inoculation dose (107 or 105 cfu ml 1) influenced the bacterial reduction achieved. Treating fresh-cut lettuce, carrot, endive, corn salad and Four seasons salad with NEW 1:5 (containing about 50 ppm of free chlorine) was equally effective as applying chlorinated water at 120 ppm. Microbial reduction depended on the vegetable tested: NEW and sodium hypochlorite treatments were more effective on carrot and endive than on iceberg lettuce, Four seasons salad and corn salad. The reductions of indigenous microbiota were smaller than those obtained with the artificially inoculated bacteria tested (0.5 1.2 log reduction). NEW seems to be a promising disinfection method as it would allow to reduce the amount of free chlorine used for the disinfection of fresh-cut produce by the food industry, as the same microbial reduction as sodium hypochlorite is obtained. This would constitute a safer, in situ , and easier to handle way of ensuring food safety.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
Antibacterial activity of electrolyzed oxidizing (EO) water prepared from 0.05% or 0.10% (w/v) sodium chloride (NaCl) solutions against indigenous bacteria associated with fresh strawberries (Fragaria ananassa) was evaluated. The efficacy of EO water and sodium hypochlorite (NaOCl) solution in eliminating and controlling the growth of Listeria monocytogenes and Escherichia coli O157:H7 inoculated onto strawberries stored at 4 +/- 1 C up to 15 d was investigated at exposure time of 1, 5, or 10 min. Posttreatment neutralization of fruit surfaces was also determined. More than 2 log10 CFU/g reductions of aerobic mesophiles were obtained in fruits washed for 10 or 15 min in EO water prepared from 0.10% (w/v) NaCl solution. Bactericidal activity of the disinfectants against L. monocytogenes and E. coli O157:H7 was not affected by posttreatment neutralization, and increasing exposure time did not significantly increase the antibacterial efficacy against both pathogens. While washing fruit surfaces with distilled water resulted in 1.90 and 1.27 log10 CFU/mL of rinse fluid reduction of L. monocytogenes and E. coli O157:H7, respectively, > 2.60 log10 CFU/mL of rinse fluid reduction of L. monocytogenes and up to 2.35 and 3.12 log10 CFU/mL of rinse fluid reduction of E. coli O157:H7 were observed on fruit surfaces washed with EO water and NaOCl solution, respectively. Listeria monocytogenes and E. coli O157:H7 populations decreased over storage regardless of prior treatment. However, EO water and aqueous NaOCl did not show higher antimicrobial potential than water treatment during refrigeration storage.
Microbe(s): Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes
Shredded carrots were inoculated with Escherichia coli O157:H7, Salmonella or Listeria monocytogenes and washed for 1 or 2 min with chlorine (Cl; 200 ppm), peroxyacetic acid (PA; 40 ppm) or acidified sodium chlorite (ASC; 100, 200, 500 ppm) under simulated commercial processing conditions. After washed, the carrots were spin dried, packaged and stored at 5 C for up to 10 days. Bacterial enumeration was significantly (P 0.05) reduced by 1, 1.5 and 2.5 log CFU/g after washing with ASC 100, 250 and 500 ppm, respectively. All sanitizers reduced pathogen load below that of tap water wash and unwashed controls. During storage at 5 C the bacterial load of all treatments increased gradually, but to different extent in different treatments. ASC inhibited bacterial growth more effectively than the other sanitizers and also maintained the lowest pathogen counts (<1 log CFU/g) during storage. Organic matter in the process water significantly (P 0.05) reduced the antibacterial efficacy of Cl, but not that of PA or ASC. Therefore, ASC shows the potential to be used as a commercial sanitizer for washing shredded carrots.
Microbe(s): Escherichia coli
Electrolyzed - oxidizing (EO) water is a relatively new method that has been utilized for killing pathogens in agriculture, medical sterilization and food sanitation. This water is generated by passing sodium chloride solution through EO water generator. In this study, the EO water was used to treat holy basil inoculated with Escherichia coli. The initial pH and oxidation - reduction potential (ORP) of EO water were 2.09 and 1200 mV, respectively. The treatments changed ORP to 800,950 and 1100 mV. The contact times were 10,30 and 60 min. In pure culture, E. coli viable counts in the sample treated with EO water were reduced to undetectable levels at all ORP and times. However no reduction in E. coli counts was achieved in the control sample (treated with deionized water). The initial population of E. coli was about 8.5 log10 CFU / ml which was inoculated on 5 g of holy basil. Results showed that the treatment treated with EO water was reduced about 2 log10 CFU / ml in ORP 800 and 950 mV, 4 log10 CFU / ml in ORP 1100 mV for 10 min. When the contact time increased to 30 min, the reduction of E. coli count was about 3 log 10 CFU / ml in ORP 950 mV and 5 log10 CFU / ml in ORP 1100 mV. But the reduction was not different from 10 min when treated with ORP 800 mV. When the contact time increased to 60 min, the reduction of E. coli count was about 3 log10 CFU / ml in ORP 800 mV, 4 log10 CFU / ml in ORP 950 mV. and 6 log10 CFU / ml in ORP 1100 mV. These results could be concluded that the ORP of EO water and contact time significantly inactivated E. coli.
Microbe(s): Fungi, Penicillium expansum
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.
Microbe(s): Pseudomonas fluorescens, Pantoea agglomerans or Rahnella aquatilis
The efficacy of Electrolysed Oxidising Water (EOW) for inactivating spoilage microorganisms in process water and on minimally processed vegetables was investigated. The direct effect of EOW on three important spoilage bacteria namely; Pseudomonas fluorescens, Pantoea agglomerans or Rahnella aquatilis was determined by inoculating tap water or artificial process water with approximately 8 log CFU/ml pure culture and electrolysing the resultant solutions. The three bacteria were each reduced to undetectable levels at low (0.5 A) and relatively higher levels (1.0 A) of current in tap water and artificial process water , respectively. The residual effect of EOW on P. fluorescens, P. agglomerans or R. aquatilis was determined by incubating at room temperature 1 ml (approximately 9 log CFU/ml) pure culture suspensions in 9 ml of EOW-T (EOW produced from tap water), EOW-A (EOW produced from artificial process water supplemented with approximately 60.7 mg Cl /l and 39.3 mg Na+/l) or deionised water (control) for 0, 15, 45 or 90 min. The bactericidal activity of both EOW-T and EOW-A increased with the concentration of free oxidants and incubation period and the three bacteria were completely reduced at free oxidants-incubation period combinations of 3.88 mg/l 45 min and 5.1 mg/l 90 min in EOW-T and EOW-A, respectively. Two types of industrial vegetable process water; salad-mix and soup process water, which had each a total psychrotrophic count of approximately 8 log CFU/ml were then electrolysed. Without any NaCl addition, only 1.2 and 2.1 log reductions of the psychrotrophs in soup and salad-mix process water was attained respectively. Supplementation of the process water with approximately 60.7 mg Cl /l and 39.3 mg Na+/l afterwards resulted in complete reduction of the psychrotrophic count in both process waters, but soup process water required relatively higher levels of current compared to salad-mix water. Finally, fresh-cut lettuce was washed in EOW-T containing 3.62 mg free oxidants/l, EOW-IP (EOW produced from industrial process water) containing 2.8 mg free oxidants/l or tap water (control) for 1 or 5 min. Washing the vegetables for 1 min in EOW-T resulted in 1.9, 1.2, and 1.3 log reductions of psychrotrophs, lactic acid bacteria and Enterobacteriacae, respectively, which increased to 3.3, 2.6, and 1.9 log reductions after washing for 5 min instead. EOW-IP tested in this work had no bactericidal effect on the microflora of fresh-cut lettuce. Electrolysis could therefore be used to decontaminate process water for vegetable pre-washing and to sanitise tap water for final rinsing of vegetables, respectively.
Microbe(s): Listeria monocytogenes
The effectiveness of electrolyzed oxidizing (EO) water for the inactivation of L. monocytogenes insuspension and when inoculated on lettuce leaves was evaluated. An electrolytic cell for the production of EO water was built and a solution of 5% NaCl was used. The EO water produced had a residual chlorine concentration of 29 parts per million (ppm) and pH 2.83. Ten strains of L. monocytogenes isolated from processed chicken (109 CFU/ml) were inoculated into 9 ml of EO water or 9 ml of deionized water (control) and incubated at 15 C for 5, 10, 15 and 20 min. The surviving population of each strain was determined on Columbia agar. An exposure time of 5 min reduced the populations by approximately 6.6log CFU/ml. The most resistant strains to sodium hypochlorite (NaOCl) were selected and used in a strain mixture (9.56 log CFU/ml, 109UFC/ml approximately) for the inoculation of 35 lettuce samples, by the dip inoculation method using distilled water as control. The population mean of L. monocytogenes after treatment with EO water and distilled water was reduced by 3.92 and 2.46 log CFU/ml respectively (p=0.00001). EO water and 6% acetic acid (vinegar) were combined to improve the EO water effect on L. monocytogenes inoculated in lettuce; the effectiveness of this combination was examined. The results showed that there was a synergistic effect of both antimicrobial agents (population reduction by 5.49 logCFU/ml approximately) on the viability of L. monocytogenes cells.
Microbe(s): Total Microbial Count
An examination was made of the efficacy of acidic electrolyzed water (AcEW, 30 ppm free available chlorine), ozonated water (5 ppm ozone), and a sodium hypochlorite solution (NaOCl, 150 ppm free available chlorine) for use as potential sanitizers of cucumbers and strawberries. AcEW and NaOCl reduced the aerobic mesophiles naturally present on cucumbers within 10 min by 1.4 and 1.2 log CFU per cucumber, respectively. The reduction by ozonated water (0.7 log CFU per cucumber) was significantly less than that of AcEW or NaOCl (P 0.05). Cucumbers washed in alkaline electrolyzed water for 5 min and then treated with AcEW for 5 min showed a reduction in aerobic mesophiles that was at least 2 log CFU per cucumber greater than that of other treatments (P 0.05). This treatment was also effective in reducing levels of coliform bacteria and fungi associated with cucumbers. All treatments offered greater microbial reduction on the cucumber surface than in the cucumber homogenate. Aerobic mesophiles associated with strawberries were reduced by less than 1 log CFU per strawberry after each treatment. Coliform bacteria and fungi associated with strawberries were reduced by 1.0 to 1.5 log CFU per strawberry after each treatment. Microbial reduction was approximately 0.5 log CFU per strawberry greater on the strawberry surface than in the strawberry homogenate. However, neither treatment was able to completely inactivate or remove the microorganisms from the surface of the cucumber or strawberry.
Microbe(s): Listeria monocytogenes, Escherichia coli O157:H7
Acidic electrolyzed water (AcEW) was used as frozen AcEW (AcEW-ice) for inactivation of Listeria monocytogenes and Escherichia coli O157:H7 on lettuce. AcEW-ice was prepared from AcEW with 20, 50, 100, and 200 ppm of available chlorine by freezing at 40 C and generated 30, 70, 150, and 240 ppm of chlorine gas (Cl2), respectively. The AcEW-ice was placed into styrene-foam containers with lettuce samples at 20 C for 24 h. Although AcEW-ice generating 30 ppm Cl2 had no effect on L. monocytogenes cell counts, AcEW-ice generating 70 to 240 ppm of Cl2 significantly (P < 0.05) reduced L. monocytogenes by ca. 1.5 log CFU/g. E. coli O157:H7 cell counts were reduced by 1.0 log CFU/g with AcEW-ice generating 30 ppm of Cl2. AcEW-ice generating 70 and 150 ppm of Cl2 reduced E. coli O157:H7 by 2.0 log CFU/g. Further significant reduction of E. coli O157:H7 (2.5 log CFU/g) was demonstrated by treatment with AcEW-ice generating 240 ppm of Cl2. However, treatment with AcEW-ice generating 240 ppm of Cl2 resulted in a physiological disorder resembling leaf burn. AcEW-ice that generated less than 150 ppm of Cl2 had no effect on the surface color of the lettuce. AcEW-ice, regardless of the concentration of the emission of Cl2, had no effect on the ascorbic acid content in the lettuce. The weight ratio of lettuce to AcEW-ice required was determined to be over 1:10. The bactericidal effect of AcEW-ice appeared within the first 2 h. The use of AcEW-ice provides simultaneously for low temperature storage and inactivation of bacteria.
Microbe(s): Escherichia coli O157:H7, Salmonella
Cut lettuce dip-inoculated with Escherichia coli O157:H7 and Salmonella was treated with alkaline electrolyzed water (AlEW) at 20 C for 5 min, and subsequently washed with acidic electrolyzed water (AcEW) at 20 C for 5 min. Pre-treatment with AlEW resulted in an approximate 1.8 log10 cfu/g reduction of microbial populations, which was significantly (p 0.05) greater than microbial reductions resulting from other pre-treatment solutions, including distilled water and AcEW. Repeated AcEW treatment did not show a significant bacterial reduction. Mildly heated (50 C) sanitizers were compared with normal (20 C) or chilled (4 C) sanitizers for their bactericidal effect. Mildly heated AcEW and chlorinated water (200 ppm free available chlorine) with a treatment period of 1 or 5 min produced equal reductions of pathogenic bacteria of 3 log10 and 4 log10 cfu/g, respectively. The procedure of treating with mildly heated AlEW for 5 min, and subsequent washing with chilled (4 C) AcEW for period of 1 or 5 min resulted in 3 4 log10 cfu/g reductions of both the pathogenic bacterial counts on lettuce. Extending the mild heat pre-treatment time increased the bactericidal effect more than that observed from the subsequent washing time with chilled AcEW. The appearance of the mildly heated lettuce was not deteriorated after the treatment. In this study, we have illustrated the efficacious application of AlEW as a pre-wash agent, and the effective combined use of AlEW and AcEW.
Microbe(s): Fungi, Penicillium expansum
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.
Microbe(s): Salmonella enterica
Alfalfa sprouts have been implicated in several salmonellosis outbreaks in recent years. The disinfectant effects of acidic electrolyzed oxidizing (EO) water against Salmonella enterica both in an aqueous system and on artificially contaminated alfalfa seeds were determined. The optimum ratio of seeds to EO water was determined in order to maximize the antimicrobial effect of EO water. Seeds were combined with EO water at ratios (wt/vol) of 1:4, 1:10, 1:20, 1:40, and 1:100, and the characteristics of EO water (pH, oxidation reduction potential [ORP], and free chlorine concentration)were determined. When the ratio of seeds to EO water was increased from 1:4 to 1:100, the pH decreased from 3.82 to 2.63, while the ORP increased from +455 to +1,073 mV. EO water (with a pH of 2.54 to 2.38 and an ORP of +1,083 to +1,092 mV) exhibited strong potential for the inactivation of S. enterica in an aqueous system (producing a reduction of at least 6.6 log CFU/ml). Treatment of artificially contaminated alfalfa seeds with EO water at a seed to EO water ratio of 1:100 for 15 and 60 min significantly reduced Salmonella populations by 2.04 and 1.96 log CFU/g, respectively (P < 0.05), while a Butterfield s buffer wash decreased Salmonella populations by 0.18 and 0.23 log CFU/g, respectively. After treatment, EO water was Salmonella negative by enrichment with or without neutralization. Germination of seeds was not significantly affected (P > 0.05) by treatment for up to 60 min in electrolyzed water. The uptake of liquid into the seeds was influenced by the internal gas composition (air, N2, or O2) of seeds before the liquid was added.
Microbe(s): Escherichia coli O157:H7, Salmonella enterica, Listeria monocytogenes
Fresh-cut lettuce samples inoculated with S. Typhimurium, E. coli O157:H7 or L. monocytogenes were dipped into 300 ppm electrolyzed water (EW) at pH 4 to 9 and 30 C for 5 min. The effects of treatment pH on bacterial reduction and visual quality of the lettuce were determined. The treatments at pH 4 and 8 resulted in the most effective inactivation of E. coli O157:H7, but the effect of pH was not significant (P > 0.05) for S. Typhimurium and L. monocytogenes. The treatment at pH 7 retained the best visual quality of lettuce, and achieved a reduction of approximately 2 log CFU/g for above 3 bacteria.
Microbe(s): Escherichia coli O157: H7, Salmonella Enteritidis, Listeria monocytogenes
A study was conducted to evaluate the efficacy of electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water in killing Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on the surfaces of spot-inoculated tomatoes. Inoculated tomatoes were sprayed with electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water (control) and rubbed by hand for 40 s. Populations of E. coli O157:H7, Salmonella, and L. monocytogenes in the rinse water and in the peptone wash solution were determined. Treatment with 200-ppm chlorine water and electrolyzed acidic water resulted in 4.87- and 7.85-log10 reductions, respectively, in Escherichia coli O157:H7 counts and 4.69- and 7.46-log10 reductions, respectively, in Salmonella counts. Treatment with 200-ppm chlorine water and electrolyzed acidic water reduced the number of L. monocytogenes by 4.76 and 7.54 log10 CFU per tomato, respectively. This study s findings suggest that electrolyzed acidic water could be useful in controlling pathogenic microorganisms on fresh produce.
Microbe(s): Salmonella
Studies have demonstrated that electrolyzed oxidizing (EO) water is effective in reducing foodborne pathogens on fresh produce. This study was undertaken to determine the efficacy of EO water and two different forms of chlorinated water (chlorine water from Cl2 and Ca(OCl)2 as sources of chlorine) in inactivating Salmonella on alfalfa seeds and sprouts. Tengram sets of alfalfa seeds inoculated with a five-strain cocktail of Salmonella (6.3 104 CFU/g) were subjected to 90 ml of deionized water (control), EO water (84 mg/liter of active chlorine), chlorine water (84 mg/liter of active chlorine), and Ca(OCl)2 solutions at 90 and 20,000 mg/liter of active chlorine for 10 min at 24 2 C. The application of EO water, chlorinated water, and 90 mg/liter of Ca(OCl)2 to alfalfa seeds for 10 min reduced initial populations of Salmonella by at least 1.5 log10 CFU/g. For seed sprouting, alfalfa seeds were soaked in the different treatment solutions described above for 3 h. Ca(OCl)2 (20,000 mg/liter of active chlorine) was the most effective treatment in reducing the populations of Salmonella and non-Salmonella microflora (4.6 and 7.0 log10 CFU/g, respectively). However, the use of high concentrations of chlorine generates worker safety concerns. Also, the Ca(OCl)2 treatment significantly reduced seed germination rates (70% versus 90 to 96%). For alfalfa sprouts, higher bacterial populations were recovered from treated sprouts containing seed coats than from sprouts with seed coats removed. The effectiveness of EO water improved when soaking treatments were applied to sprouts in conjunction with sonication and seed coat removal. The combined treatment achieved 2.3- and 1.5-log10 CFU/g greater reductions than EO water alone in populations of Salmonella and non-Salmonella microflora, respectively. This combination treatment resulted in a 3.3-log10 CFU/g greater reduction in Salmonella populations than the control (deionized water) treatment.
Microbe(s): Salmonella enteritidis, Listeria monocytogenes
Aims: To determine the efficacy of neutral electrolyzed water (NEW) in killing Escherichia coli O157:H7, Salmonella enteritidis and Listeria monocytogenes, as well as nonpathogenic E. coli, on the surface of tomatoes, and to evaluate the effect of rinsing with NEW on the organoleptic characteristics of the tomatoes. Methods and Results: The bactericidal activity of NEW, containing 444 or 89 mg l-1 of active chlorine, was evaluated over pure cultures (8-5 log CFU ml-1) of the above-mentioned strains. All of them were reduced by more than 6 log CFU ml-1 within 5 min of exposure to NEW. Fresh tomatoes were surface-inoculated with the same strains, and rinsed in NEW (89 mg l-1 of active chlorine) or in deionized sterile water (control), for 30 or 60 s. In the NEW treatments, independent of the strain and of the treatment time, an initial surface population of about 5 log CFU sq.cm-1 was reduced to <1 log CFU sq.cm-1, and no cells were detected in the washing solution by plating procedure. A sensory evaluation was conducted to ascertain possible alterations in organoleptic qualities, yielding no significant differences with regard to untreated tomatoes. Significance and Impact of the Study: Rinsing in NEW reveals as an effective method to control the presence of E. coli O157:H7, S. enteritidis and L. monocytogenes on the surface of fresh tomatoes, without affecting their organoleptic characteristics. This indicates its potential application for the decontamination of fresh produce surfaces.
Microbe(s): Escherichia coli O157: H7, Salmonella Enteritidis, and Listeria monocytogenes
A study was conducted to evaluate the efficacy of electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water in killing Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on the surfaces of spot-inoculated tomatoes. Inoculated tomatoes were sprayed with electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water (control) and rubbed by hand for 40 s. Populations of E. coli O157:H7, Salmonella, and L. monocytogenes in the rinse water and in the peptone wash solution were determined. Treatment with 200-ppm chlorine water and electrolyzed acidic water resulted in 4.87- and 7.85-log10 reductions, respectively, in Escherichia coli O157:H7 counts and 4.69- and 7.46-log10 reductions, respectively, in Salmonella counts. Treatment with 200-ppm chlorine water and electrolyzed acidic water reduced the number of L. monocytogenes by 4.76 and 7.54 log10 CFU per tomato, respectively. This study s findings suggest that electrolyzed acidic water could be useful in controlling pathogenic microorganisms on fresh produce.
Microbe(s): Total Microbial Count
The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AlEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCl solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.
Microbe(s): Total Microbial Count
We investigated the effects of frozen acidic electrolyzed water (AcEW) on lettuce during storage in a styrene-foam container. The lettuce was kept at 2 to 3 degrees C for 24 h. Populations of aerobic bacteria associated with lettuce packed in frozen AcEW were reduced by 1.5 log CFU/g after storage for 24 h. With frozen tap water, no microorganism populations tested in this study were reduced. A frozen mixture of AcEW and alkaline electrolyzed water (AlEW) also failed to reduce populations of microorganisms associated with lettuce. Although chlorine gas was produced by frozen AcEW, it was not produced by the AcEW-AlEW mixture. This result indicates that the main factor in the decontaminative effect of frozen AcEW was the production of chlorine gas. Accordingly, low-temperature storage and decontamination could be achieved simultaneously with frozen AcEW during distribution.
Microbe(s): Botryosphaeria berengeriana
Chlorination presents one of the few chemical options available to help manage postharvest decay. Electrolyzed oxidizing (EO) water, containing free chlorine, is the product of a new concept developed by scientists in Japan. The effectiveness of pear (Pyrus communis L.) immersion in EO water on the control of Bot. rot on European pear, cv. La-France, was investigated. Four independent experiments were carried out. A wound was found necessary for infection. Wounded fruit were inoculated with 20 l spore suspension of 5 105 conidia/ml of Botryosphaeria berengeriana, incubated for 4 h, immersed in EO water, and held at 20 C, 90% relative humidity (simulated retail conditions) for ripening and disease development. No chlorine-induced phytotoxicity was observed on the treated fruit. EO water suppressed the incidence and disease severity. The minimum incidence and severity were recorded for a 10-min immersion period. This study revealed that EO water is an effective surface sanitizer.
Microbe(s): Total Microbial Count, Coliforms, Bacillus cereus
Effects of storage temperature (1, 5, and 10 C) on growth of microbial populations (total aerobic bacteria, coliform bacteria, Bacillus cereus, and psychrotrophic bacteria) on acidic electrolyzed water (AcEW)-treated fresh-cut lettuce and cabbage were determined. A modified Gompertz function was used to describe the kinetics of microbial growth. Growth data were analyzed using regression analysis to generate best-fit modified Gompertz equations, which were subsequently used to calculate lag time, exponential growth rate, and generation time. The data indicated that the growth kinetics of each bacterium were dependent on storage temperature, except at 1 C storage. At 1 C storage, no increases were observed in bacterial populations. Treatment of vegetables with AcEW produced a decrease in initial microbial populations. However, subsequent growth rates were higher than on nontreated vegetables. The recovery time required by the reduced microbial population to reach the initial (treated with tap water [TW]) population was also determined in this study, with the recovery time of the microbial population at 10 C being <3 days. The benefits of reducing the initial microbial populations on fresh-cut vegetables were greatly affected by storage temperature. Results from this study could be used to predict microbial quality of fresh-cut lettuce and cabbage throughout their distribution.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
The efficacy of electrolyzed oxidizing (EO) and acidified chlorinated water (45 ppm residual chlorine) was evaluated in killing Escherichia coli O157:H7 and Listeria monocytogenes on lettuce. After surface inoculation, each leaf was immersed in 1.5 L of EO or acidified chlorinated water for 1 or 3 min at 22 C. Compared to a water wash only, the EO water washes significantly decreased mean populations of E. coli O157:H7 and L. monocytogenes by 2.41 and 2.65 log10 CFU per lettuce leaf for 3 min treatments, respectively (p < 0.05). However, the difference between the bactericidal activity of EO and acidified chlorinated waters was not significant (p > 0.05). Change in the quality of lettuce subjected to the different wash treatments was not significant at the end of 2 wk of storage.
Microbe(s): Escherichia coli O157: H7
Survival of Escherichia coli O157:H7 was studied on strawberry, a fruit that is not usually washed during production, harvest, or postharvest handling. Two strains of the bacteria were tested separately on the fruit surface or injected into the fruit. Both strains of E. coli O157:H7 survived externally and internally at 23 C for 24 h and at 10, 5, and 20 C for 3 days. The largest reduction in bacterial population occurred at 20 C and on the fruit surface during refrigeration. In all experiments, the bacteria inside the fruit either survived as well as or better than bacteria on the surface, and ATCC 43895 frequently exhibited greater survival than did ATCC 35150. Two strains of E. coli also survived at 23 C on the surface and particularly inside strawberry fruit. Chemical agents in aqueous solution comprising NaOCl (100 and 200 ppm), Tween 80 (100 and 200 ppm), acetic acid (2 and 5%), Na3PO4 (2 and 5%), and H2O2 (1 and 3%) were studied for their effects on reduction of surface-inoculated (108 CFU/ml) E. coli O157:H7 populations on strawberry fruit. Dipping the inoculated fruit in water alone reduced the pathogen population about 0.8 log unit. None of the compounds with the exception of H2O2 exhibited more than a 2-log CFU/g reduction of the bacteria on the fruit surface. Three percent H2O2, the most effective chemical treatment, reduced the bacterial population on strawberries by about 2.2 log CFU/g.
Microbe(s): Total Microbial Count
The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AlEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCl solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.
Microbe(s): Escherichia coli O157:H7, Listeria monocytogenes
The efficacy of electrolyzed oxidizing (EO) and acidified chlorinated water (45 ppm residual chlorine) was evaluated in killing Escherichia coli O157:H7 and Listeria monocytogenes on lettuce. After surface inoculation, each leaf was immersed in 1.5 L of EO or acidified chlorinated water for 1 or 3 min at 22 C. Compared to a water wash only, the EO water washes significantly decreased mean populations of E. coli O157:H7 and L. monocytogenes by 2.41 and 2.65 log10 CFU per lettuce leaf for 3 min treatments, respectively (p < 0.05). However, the difference between the bactericidal activity of EO and acidified chlorinated waters was not significant (p > 0.05). Change in the quality of lettuce subjected to the different wash treatments was not significant at the end of 2 wk of storage.
Microbe(s): Total Microbial Count
The main factor contributing to the disinfecting potential of acidic electrolyzed water (AcEW) is deduced to be the oxidizing power of available chlorine. In this study, we compared the reliability of two different methods for measuring the available chlorine concentration (ACC). Several AcEW solutions with different levels of ACC to which various reducing agents (ascorbic acid, ammonium iron (II) sulfate, and iron (II) chloride) had been added were prepared. These ACC levels were quantified by iodometry and the DPD (N, N-diethyl-p-phenylenediamine) method. In the case of AcEW with iron (II) ions, iodometry did not show the correct ACC. On the other hand, the DPD method correctly quantified ACC even in the case of AcEW with iron (II) ions. Thus, the DPD method is an appropriate method for measuring ACC in AcEW. Moreover, we investigated the effect of the available chlorine concentration (ACC) in AcEW on its disinfecting potential. First, we examined the disinfectant effects of AcEW on shredded vegetables. We found that there was no difference in the disinfectant effects between AcEW with high ACC (40ppm) and low ACC (0.4ppm). The similar effect was detected in AcEW with 0ppm of ACC, a solution that seemed to be the same as hydrochloric acid. Moreover, tap water with pH adjusted to 2.4 showed the same disinfectant effect as that of AcEW. These results indicated that AcEW is a solution in which available chlorine is activated in a low pH condition. Next, we examined the disinfectant effects of AcEW on a suspension obtained from shredded vegetables in vitro. The disinfecting potential became weaker, but did not completely disappear, when ACC was reduced to 0ppm. Thus, AcEW with low ACC could be used to disinfect shredded vegetables, although the disinfecting potential of AcEW would become weak. When the effective concentration of Acc was examined, it was found that the AcEW with ACC of less than 20ppm did not have sufficient disinfectant potential. Moreover, it was found that high ORP (above 1000mV) does not contribute to disinfecting potential. Thus, the lower limit of ACC in AcEW for AcEW to exert a sufficient disinfectant effect will be 20ppm.
Microbe(s): Total Microbial Count
The effect of electrolyzed water on total microbial count was evaluated on several fresh-cut vegetables. When fresh-cut carrots, bell peppers, spinach, Japanese radish, and potatoes were treated with electrolyzed water (pH 6.8, 20 ppm available chlorine) by dipping, rinsing, or dipping/blowing, microbes on all cuts were reduced by 0.6 to 2.6 logs CFU/g. Rinsing or dipping/blowing were more effective than dipping. Electrolyzed water containing 50 ppm available chlorine had a stronger bactericidal effect than that containing 15 or 30 ppm chlorine for fresh-cut carrots, spinach, or cucumber. Electrolyzed water did not affect tissue pH, surface color, or general appearance of fresh-cut vegetables.
