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Cross-contamination of Escherichia coli O157:H7 is inhibited by electrolyzed water combined with salt under dynamic conditions of increasing organic matter
... A number of investigators have evaluated the role of sanitizers in preventing cross-contamination of fresh produce from inoculated wash water (Allende et al., 2008;Gombas et al., 2017;Gómez-López et al., 2015;Pezzuto et al., 2016;Ravishankar et al., 2010). The chlorinebased sanitizer is a dominant sanitizer used in the fresh produce industry. ...
... It has been widely reported that maintaining 0.005 g/L (5 ppm) -0.010 g/L (10 ppm) of free chlorine is adequate to inactivate pathogens in wash water (Gombas et al., 2017;Luo et al., 2011). Due to the presence of organic content in wash water, total chlorine used for sanitation of wash water may exceed 0.2 g/L (200 ppm) to provide a free chlorine content of 0.005 g/L (5 ppm) to 0.010 g/L (10 ppm) in wash water (Gómez-López et al., 2015;Haute et al., 2015). Free chlorine content of 5 ppm-10 ppm can inactivate microbes in wash water, but inactivation of bacteria on organic particles in wash water has not been https://doi.org/10.1016/j.postharvbio.2020.111283 ...
Outbreaks of foodborne illnesses from fresh produce in recent years have prompted industrial community to consider new practices aimed at reducing the risks of pathogenic microbial contamination on the produce. The presence of organic matter in wash water not only decreases the efficacy of sanitizers to inactivate microorganisms, but also has the potential to transfer microbial contamination to fresh produce. This study aims to comprehensively evaluate the transfer of pathogens from inoculated organic matter to uninoculated fresh produce leaves during washing, as well as determination of the adequate active free chlorine concentration needed to prevent the potential risk of cross-contamination during produce washing process. In addition, the study also characterized the role of particles in increasing the mechanical shear at the leaf surface using numerical simulation. The results showed that cross-contamination of fresh produce occurred significantly in a short time (< 2 min) if the wash water was contaminated. The presence of contaminated organic matter (COD = 0.05 g/L) in wash water enhanced the transfer of bacteria to the fresh produce surface by approximately 1 log unit when compared to planktonic bacterial cells in the wash water. In addition, the presence of organic matter also significantly increased the shear stress at the leaf surface. The adequate active free chlorine (0.005 g/L) in wash water was able to prevent the cross-contamination of fresh produce and inactivate bacteria inoculated on organic contaminants in wash water during washing process. In summary, this study will contribute to guidelines for the design of fresh produce washing process.
... Prior to packaging, large-scale tomato producers in South Africa wash the tomatoes in dump tanks containing chlorinated water (NaOCl or Ca(OCl) 2 ) with a free chlorine level of approximately 150 mg/liter, which is a recommended means to control microbial proliferation during the storage and on-shelf period (6). The recommended pH during this disinfection wash step is close to neutral pH to avoid corrosive effects to the processing equipment (16,25), although this reduces the solution's bactericidal efficacy (1). The water temperature in the dump tank should also be closely monitored to avoid excessive warming. ...
... Warm temperatures facilitate the reactivity of chlorine towards microbial cellular targets; however, the heat also enhances the evaporation and loss of free chlorine (6). Similarly, the oxidation-reduction potential (ORP) of the solution in the dump tank impacts the efficacy of the disinfectant (16,21,25). Overhead sprays are also used in South Africa as an alternative to dump tanks for applying disinfectants to tomatoes in the packhouse. ...
Postharvest microbial spoilage due to suboptimal transportation and packaging conditions is a key concern for the South African tomato industry. This study investigated the influence of washing with tap water or aqueous disinfectant solutions (chlorinated and anolyte water) on the microbiological quality of tomatoes during storage after transportation in nonrefrigerated trucks along two supply routes when packaged in crates and boxes. Route 1 was 1,093 km from field to storage site, while route 2 was 1,057 km. During transport, the temperature in the trucks fluctuated between 16 and 28°C and the relative humidity between 25 and 94% for route 1, while for route 2, the temperature was between 16 and 30°C and the relative humidity between 28 and 71%. Tomatoes at the pink maturity stage were sampled, treated, and stored for 28 days (11°C). The tomato firmness before treatment was 24.8 N (box samples) and 17.4 N (crate samples) for route 1, whereas it was 22.1 N (box samples) and 20.2 N (crate samples) for route 2. Temperature fluctuation during transportation led to water condensation on tomato surfaces. Tomatoes treated with anolyte water showed the lowest microbial surface burden during storage, with mean aerobic plate counts (APC) of 2.9 log CFU/cm2, coliform counts (CC) of 1.1 log CFU/cm2, and fungal counts (FC) of 2.3 log CFU/cm2. Overall, of the total APC recorded during storage, anolyte-treated samples contributed 9% while chlorinated water–treated samples contributed 30%.
Of the total CC, anolyte samples presented 3% while chlorinated water samples made up 12%, and of the total recorded FC, anolyte samples contributed 7% while chlorinated water samples made up 22%. Scanning electron microscopy imaging showed surface cracks, which enable microbial colonization in crate-transported tomatoes. A combination of anolyte treatment and box packaging during transport resulted in the best microbiological quality during storage. The findings of this investigation provide motivation for the adoption of anolyte water as a postharvest disinfection treatment in the tomato industry.
... Also, as an alternative non-thermal method of knife disinfection, the use of ultraviolet radiation (UV) in relation to the inhibition of E. coli and S. aureus was proposed, the effectiveness of which depended on the presence of surface contaminants such as blood or fat [20]. The use of electrolysis-activated water (EW) has been proposed, which has shown effective antimicrobial activity against a wide range of microorganisms, including pathogens such as Salmonella typhimurium, E. coli and Yersinia [21,22]. It has been noted that EW contributes to the inhibition of the most common types of viruses, bacteria, fungi, and spores in a short period of time within 5-20 s [23]. ...
The development of approaches for the non-thermal sterilization of instruments is an urgent task to ensure the safety of meat industry products, where the use of hot water leads to the formation of condensates and a deterioration in the hygienic condition of the premises. In this study, an installation for sterilizing knives was created, which works by activating aqueous salt solutions with a glow discharge. The power consumption of the installation reactor is only 125–150 Wh. The temperature rise of the sterilizing agent used is about 1.1 ± 0.2 °C/min/L. The effectiveness of the installation for plasma-activation of aqueous solutions of chloride and sodium sulfate by glow discharge (PAW) in relation to the inactivation of microorganisms, including Staphylococcus aureus, Salmonella typhimurium, Pseudomonas gessardii and L. monocytogenes, on steel surfaces was evaluated. Samples of stainless steel (parts of knives) were used in two versions (new and artificially aged). Mono- and polyspecies bacterial biofilms were grown on the surface of the samples. The treatment was carried out by immersing samples of steel plates in plasma-activated aqueous solutions. It was found that the treatment of plates in a knife sterilizer for 1 min had an effective effect on the inhibition of all types of studied bacteria.
... The acidity of the water, the oxidation potential, and concentration of chlorine lead to reduced survival of bacteria such as E. coli, Listeria, and Salmonella. Electrolysis has been reported to have strong activity against most pathogenic bacteria and is recognized as a safe and relatively quick method, given a water flow of around 3.6 L/h (48,65). Moreover, combined strong acidic electrolyzed water and alkaline electrolyzed water have stronger sterilization ability than single acidic electrolyzed water or slightly acidic electrolyzed water (51). ...
Irrigation water can be a source of pathogenic contamination of fresh produce. Controlling the quality of the water used during primary production is important to ensure food safety and protect human health. Several measures to control the microbiological quality of irrigation water are available for growers, including preventative and mitigation strategies. However, clear guidance for growers on which strategies could be used to reduce microbiological contamination is needed. This study evaluates pathogenic microorganisms of concern in fresh produce and water, the microbiological criteria of water intended for agricultural purposes, and the preventative and mitigative microbial reduction strategies. This article provides suggestions for control measures that growers can take during primary production to reduce foodborne pathogenic contamination coming from irrigation water. Results show that controlling the water source, regime, and timing of irrigation may help to reduce the potential exposure of fresh produce to contamination. Moreover, mitigation strategies like electrolysis, ozone, UV, and photocatalysts hold promise either as a single treatment, with pretreatments that remove suspended material, or as combined treatments with another chemical or physical treatment(s). Based on the literature data, a decision tree was developed for growers, which describes preventative and mitigation strategies for irrigation-water disinfection based on the fecal coliform load of the irrigation water and the water turbidity. It helps guide growers when trying to evaluate possible control measures given the quality of the irrigation water available. Overall, the strategies available to control irrigation water used for fresh produce should be evaluated on a case-by-case basis because one strategy or technology does not apply to all scenarios.
Highlights:
... Other advantages of electrochemical disinfection include on-site production, raw material availability, an environment-friendly process, a less-hazardous reaction, low cytotoxicity, and no reported microbial resistance [10]. Furthermore, it has been utilized in several sectors, such as agricultural and food industries, since the disinfectant can be produced over wide pH ranges [11][12][13][14][15]. Xie et al. [12] investigated the effect of acidic electrolyzed water stored at different temperatures on contaminated raw shrimp, while Kasai et al. [16] investigated the effect of electrolyzed seawater (ESW) in naturally contaminated oysters. ...
The study investigated the effect of storage conditions on the stability of electrolyzed seawater (ESW)’s physicochemical properties (pH, oxidation-reduction potential (ORP), and free chlorine (FC) concentration), and bactericidal efficiency on the fecal coliform Escherichia coli for 30 days. Preliminary experiments were conducted to determine the optimal current and electrolysis time. Two batches of 2750 mL filtered seawater were electrolyzed using 50 mm × 192 mm platinum–titanium mesh electrodes at a current of 1.5 A for 20 min. One hundred milliliters of electrolyzed solution was transferred into each amber glass and high-density polyethylene (HDPE) bottles. The bottles were stored in a dark area at ambient temperature. The results showed an increase in pH and a decrease in ORP and FC concentration through time. Hypochlorous acid remained as the dominant component since the pH levels of the solutions remained below 7.5. FC decay was investigated using Chick’s Law. It was determined that the decay in HDPE bottles (k = −0.066 day−1) was faster compared to amber glass bottles (k = −0.046 day−1). Nonetheless, HDPE bottles could still be used as an alternative container for 30 days only due to observed instability beyond 30 days. ESW remained effective since no surviving population of E. coli was observed throughout the experimentation.
... ED is relatively an environmentally friendly and strong technique with a two-stage mechanism of action (Table 2) [27,[58][59][60]. ...
To protect environmental and human health, enhanced treatment methods are more than required to kill microorganisms from wastewater. The electrocoagulation (EC) process is more and more employed to remedy wastewater. This review aims to focus on the EC process as an electrodisinfection (ED) technique, i.e., a microorganism killing method, in terms of the mechanisms involved. An excellent performance of EC is shown through a large review of the literature. The electric field (EF) contribution remains fundamental in killing microorganisms. Also, the adsorption or cohesion of bacteria onto Fe/Al hydroxides is considered a key stage in ED upon EC. Much more effort needs to be performed to qualitatively and quantitatively decide between EF and cohesion contributions. More research should be addressed to assessing more and more probable generation of the hydroxyl radical (OH) through the EC process.
... Recently, electrochemical demolition of pathogenic microorganisms has been largely proven [31][32][33]. This is because the common electrochemical methods are eco-friendly, cost-effective, amenable to automation and simple to manipulate as killing microorganisms' techniques [34][35][36]. Moreover, many killing microorganisms' procedures have been suggested to interpret the poisonous bacteria removal upon techniques based on EF application, which may be listed as [3, 37- . ...
Electrocoagulation (EC) process has been largely found efficient in terms of pathogens removal. This literature review focuses on describing the key killing microorganisms' pathway followed throughout the EC technique. The pathogens removal route using EC is deeply assessed following the practical experimentation realized during these last years. Physical elimination and chemical deactivation pathways are suggested for bacteria reduction procedure throughout the EC method employing Fe/Al anodes: (1) entrapping pathogens in flocs, (2) destabilizing negatively charged microbes through sweep flocculation, and (3) demobilizing bacteria cell envelopes upon electrochemically formed reactive oxygen species or direct impact of the electric field. Finally, deepest investigation works on microbes' removal through EC are more called to promote the industrial applications of this performant technology.
... Further treatment of all types of organic pollutants in waste fluid is necessary prior to its reuse or discharge. Electrochemical method is an effective way for processing fracturing flow-back fluid in oilfield [3] and involves electrocoagulation [4][5][6], electrolytic flotation, [7][8][9] and electrochemical oxidation methods [10][11][12][13]. These electrochemical methods produce a considerable amount of gases, such as H 2 , O 2 or Cl 2 , in the electrode during the fracturing fluid treatment [14][15]. ...
... Electrolyzed water has been widely recommended as a substitute disinfectant for SH, due to its strong bactericidal effects on various dominant spoilage and pathogen microorganisms, such as Salmonella, Escherichia coli, and Shewanella (Gómez-López, Gil, Pupunat, & Allende, 2015;Han, Hung, & Wang, 2018). In fact, electrolyzed water is typically used in two forms: acid electrolyzed water (AEW) and slightly acid electrolyzed water (sAEW). ...
The application of electrolyzed water effectively reduces microbial contamination and has greatly contributed to delayed meat spoilage. However, concerns about applying electrolyzed water in the meat industry, which include the stability of available chlorine in various storage conditions, corrosion resistance and residual chlorate, have attracted much attention. In this study, primary concerns regarding acid electrolyzed water (AEW) and slightly acid electrolyzed water (sAEW) were evaluated in comparison to those of sodium hypochlorite (SH) widely used in meat processing plants. The results showed that closed and 4 °C storage conditions, which just declined about 30% ACC of available chlorine concentration (ACC), were more beneficial than open and 20 °C storage conditions for maintaining the stability of electrolyzed water, whereas no differences in stability were observed between dark and light storage. The decline of ACC positively depended on the concentrations of organic materials ranged from 0.1% to 0.3%, and the ACC was close to 10 mg/mL after 30 min trearment. The corrosion of AEW was equal to that of SH, but it was higher than that of sAEW. In addition, the concentration of residual chlorate in meat sprayed by electrolyzed water was less than meat sprayed by SH. The findings suggested that electrolyzed water is a great potential substitute for SH in the meat industry.
... In the last decade, many studies combining E.O. water with other treatments have been carried out to optimise the efficacy of E.O. water and to evaluate the effects of treatments on subsequent product quality (Gomez-Lopez et al. 2015;Mahmoud et al. 2007;Xie et al. 2012;Zhou et al. 2011). For example, there has been study on a combination of E.O. water with 1% of essential oil (0.5% carvacrol ? ...
Electrolysed oxidising water (E.O. water) is produced by electrolysis of sodium chloride to yield primarily chlorine based oxidising products. At neutral pH this results in hypochlorous acid in the un-protonated form which has the greatest oxidising potential and ability to penetrate microbial cell walls to disrupt the cell membranes. E.O. water has been shown to be an effective method to reduce microbial contamination on food processing surfaces. The efficacy of E.O. water against pathogenic bacteria such as Listeria monocytogenes, Escherichia coli and Vibrio parahaemolyticus has also been extensively confirmed in growth studies of bacteria in culture where the sanitising agent can have direct contact with the bacteria. However it can only lower, but not eliminate, bacteria on processed seafoods. More research is required to understand and optimise the impacts of E.O. pre-treatment sanitation processes on subsequent microbial growth, shelf life, sensory and safety outcomes for packaged seafood products.
... Electrolysed water (EW), also known as electrolysed oxidising water, has a strong bactericidal effect on many pathogenic bacteria (G omez-L opez, Gil, Pupunat, & Allende, 2015;Huang, Hung, Hsu, Huang, & Hwang, 2008;Inatsu et al., 2010;Liu, Tan, Yang, & Wang, 2016). The sanitising action of acidic EW has been attributed to the high oxidation-reduction potential and the oxidative action of hypochlorous acid ( Ding et al., 2015;Zhao, Zhang, & Yang, 2017). ...
... In the case of chlorine, great concerns have arisen due to the potential hazards associated with DBPs, particularly when high or excessive chlorine doses are used, as in the case of hyperchlorination (Banach, Sampers, van Haute, & van der Fels-klerx, 2015;Gil et al., 2015b;L opez-G alvez et al., 2010b). Additionally, some studies indicate that the commonly used chlorine concentrations (10e50 ppm) are not effective in reducing pathogen load on fresh-cut produce (Gil et al., 2015b) affecting their usefulness for avoiding cross-contamination both in the process water and on contact surfaces (G omez-L opez, Gil, Pupunat, & Allende, 2015;P erez-Rodríguez et al., 2011). Mostly because of the potential generation of DBPs, the European Commission left each Member State to decide regarding the approval of the use of chlorine-based disinfectants in fresh-cut produce washing. ...
The popularity of the consumption of fresh ready-to-eat (RTE) products has increased globally. Simultaneously, the number of outbreaks and cases of foodborne illness associated with the consumption of contaminated fresh produce continues to escalate. Thus, it becomes clear that fresh and fresh-cut vegetables are not processed in ways that effectively eliminate human pathogens. Processing of fresh vegetables involves the application of several unit operations that can provide opportunities for cross-contamination whereby a small proportion of contaminated product may cause the contamination of a large proportion of processed product. Some of these unit operations where contamination and cross-contamination may occur are selection, cleaning, washing, trimming, peeling, cutting and shredding, sanitizing and packing. It is recommended that processors ensure that their suppliers (growers, harvesters, packers and distributors) adopt the principles outlined in the Code of Hygienic Practice for Fresh Fruits and Vegetables. A variety of intervention methods may be used such as mild preservation and/or disinfection techniques to enhance safety of minimally processed produce. Traditional methods of reducing microbial populations on produce involve chemical and physical treatments.
This review brings an overview of the main microbial risks faced by the producers and the available alternative strategies to reduce these risks. The information shown gives insights on microbial contamination throughout the processing operations involved in RTE vegetable production.
... Iceberg lettuce (Lactuca sativa L.) was purchased from a local wholesale market in Murcia (Spain). Process wash water was produced by homogenizing lettuce pieces in water using a stomacher as described by G omez-L opez, Gil, Pupunat, and Allende (2015). The batch of process wash water was divided in portions and frozen at e 18 C until use. ...
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.
... The experiments performed at a pilot plant were carried out using a 'dynamic system' previously described (G omez-L opez, Gil, Pupunat, & Allende, 2014b). A washing tank was filled with a volume of 10 L of tap water before starting the tests. ...
... The low concentration of sodium bicarbonate used in this work (0.1% w/v) could be responsible for the absence of antimicrobial activity of electrolyzed NaHCO 3 solution against Pseudomonas bacteria. Since this work demonstrated that NEW produced by sodium bicarbonate resulted ineffective against Pseudomonas bacteria, the use of NEW from carbonate/bicarbonate for disinfecting fresh cut vegetables washing water, should carefully evaluated against various pathogenic bacteria, whose inactivation with electrolyzed water produced by NaCl solutions is instead widely described (Deza et al., 2003;G omez-L opez et al., 2015;L opez-G alvez et al., 2012;Yang et al., 2003;Park et al., 2004). Our results underline the difficulty in vegetable decontamination by NEW confirming its main application in avoiding the accumulation of spoilage bacteria in washing water immediately after its contamination. ...
... The combined effect of AC-EW and chitosan was also used successfully to reduce microbial load and to extend the shelf life of American shad fillets stored under refrigeration (Xu et al., 2014). Additionally, when AC-EW was added to wash water used for vegetable produce, it was effective in eliminating E. coli O157:H7 and in reducing the possibility of cross-contamination (Vicente, Gomez, Gil, Pupunat, & Allende, 2015). ...
The bactericidal efficacy of acidic electrolyzed oxidizing water (AC-EW) (pH = 2.30, free chlorine = 38 ppm) and sterile distilled water (DW) on three pathogens (Escherichia coli O157:H7 Salmonella Typhimurium, and Listeria monocytogenes) inoculated on raw trout skin, chicken legs and beef meat surfaces was evaluated. The decontaminating effect of AC-EW and DW was tested for 0 (control), 1, 3, 5 and 10 min at 22 °C. AC-EW significantly (P < 0.05) reduced the three pathogens in the inoculated samples compared to the control and DW. The level of reduction ranged between ca.1.5–1.6 logs for E. coli O157:H7 and S. Typhimurium in the inoculated foods. However, AC-EW exhibited less bactericidal effect against L. monocytogenes (1.1–1.3 logs reduction). AC-EW elicited about 1.6–2.0 log reduction in the total mesophilic count. Similar treatment with DW reduced pathogens load by ca. 0.2–1.0 log reduction and total mesophiles by ca. 0.5–0.7 logs. No complete elimination of the three pathogens was obtained using AC-EW possibly because of the level of organic matter and blood moving from food samples to the AC-EW solution. This study demonstrates that AC-EW could considerably reduce common foodborne pathogens in fish, chicken and beef products.
Chemical sanitisers are needed for controlling microbial contamination and growth in various settings, including healthcare, domestic settings and the food industry. One promising sanitiser with proposed applications in the food industry is the oxidising sanitiser electrolysed water (EW). For EW applications to be effective, a more in-depth understanding of EW mode-of-action is needed, together with the identification of limiting factors associated with the chemical matrices in relevant EW applications. This study investigated the reactivity of EW with different organic substances. For this purpose, the common food spoilage fungus Aspergillus niger was treated with EW in the presence or absence of the organic materials. The sanitiser retained partial fungicidal activity at high levels of added soil, commonly associated with freshly harvested produce. By narrowing down the reactivity of EW from complex matrices to specific organic molecules, proteins and amino acids were found to strongly suppress EW fungicidal activity. The potential implications of EW reactivity with proteins and amino acids within cells were investigated in the fungal model organism Saccharomyces cerevisiae. This capitalised on the advanced understanding of the uptake and metabolism of diverse compounds and the availability of convenient genetic tools in this model organism. Pre-culture with methionine but not with other tested amino acids increased yeast resistance to subsequent treatments (in the absence of methionine) with sanitisers (EW, sodium hypochlorite, ozonated water). Further tests suggested a direct role of the methionine molecule itself, as opposed to downstream products of methionine metabolism or methionine misincorporation in proteins, in increasing yeast EW resistance. Intracellular methionine oxidation can disturb FeS cluster proteins and this study found that EW treatment impairs FeS cluster protein activity. Because active species in EW can be inactivated by organic compounds, microorganisms may be exposed to low effective EW doses during EW treatments where organic matter is present. When low, sub-lethal EW doses were applied to A. niger, early germination events and colony growth post-treatment were delayed and there was increased variation in size among resultant colonies. The delay and increased variation were non-heritable and were observed with chlorine-containing sanitisers (EW, sodium hypochlorite) but not the chlorine-free oxidant ozonated water. The collective findings led to a hypothesis that chloramine formation within spores during EW treatment may contribute to the observed phenotypes. This study increases the understanding of limiting chemical factors for EW applications and sheds light onto the cellular mode-of-action of EW and the fungal response mechanisms to sanitiser treatments. Such insights can improve the rational development of EW application processes and contribute to understanding and prediction of antimicrobial efficacy in diverse settings.
Currently no standard benchtop preparation method exists for simulated produce wash water, which makes it challenging to compare sanitizer efficacy reports and provide guidance for growers regarding water quality monitoring and free chlorine quantification. This work compares benchtop preparation methods for spinach-based model wash water (blender vs stomacher), metrics for organic load standardization (chemical oxygen demand (COD) vs nephelometric turbidity units (NTU)), and free chlorine quantitation methods (N,N-diethyl-p-phenylenediamine (DPD) vs iodometric titration (IOD)). It was found that COD is a more reliable metric for organic load standardization than NTU. Blender- and stomacher-generated wash water had similar physicochemical properties at organic loads up to 1000 mg/L COD, so both methods are acceptable, and DPD titration reflected expected patterns of free chlorine consumption in wash water more accurately than IOD. These results support the use of select wash water preparation and free chlorine detection methods, informing the development of a standardized protocol.
Inadequate access to clean water and sanitation are the most relevant problems afflicting developing and industrialized nations. Global water scarcity is expected to grow worse in the coming decades and this has motivated the scientific community to identify new, safe, and robust water disinfection technologies at lower cost and with less energy, diminishing the use of chemicals and impact on the environment. Usually, conventional methods of water treatment can solve this problem satisfactorily, such as chlorination, but, sometimes, they can be chemically, energetically, and operationally intensive. Therefore, the science and technology has encouraged the development of other alternative disinfection technologies. In this frame, electrochemical disinfection or electrodisinfection is currently experiencing a renaissance due to the tremendous contributions of novel electrocatalytic materials as well as the use of electric current as an inexpensive and suitable reagent to drive the inactivation of waterborne pathogens, avoiding conventional chemical oxidizers or reducing agents. Electrodisinfection has a significant technical impact, because it can be easily scaled up or design small–portable devices, benefiting from advantages such as versatility, environmental compatibility, automation, inherent safety, and potential cost effectiveness among others. Diamond films emerge as a novel and sustainable solution to electrogenerate powerful oxidants for effectively controlling waterborne pathogens in drinking water. The overarching goal of this critical review is to evidence the importance of diamond electrochemical methods as alternative for the eradication of waterborne infectious agents from public and drinking waters. The mechanisms of bacteria inactivation, and the fundamentals and applications of electrochemical oxidation with diamond to disinfect synthetic and real waters and wastewaters are exhaustively discussed. The use of hybrid and sequential processes involving electrochemical oxidation with other techniques, as well as endodontic and food control applications, are also analyzed. A section remarking the future challenges of electrodisinfection with diamond is finally presented.
As food industry flourished, the use of EW as a novel sanitizing agent has gained interest worldwide. The chapter reviews recent progress in the application of EW in fruits and vegetables industry, summarizing its efficacy on disinfection and pesticide removal during their processing, and disease control along with inhibiting moth infestation throughout storage as well as the effect on physiochemical properties, chemical components, and postharvest physiology. Furthermore, it specially generalized the application of EW in the field of sprouts vegetables (our researching focus) to open up a new way for the development of functional food. It indicated that EW has sufficient obliterating efficacy on spoilage or pathogenic microorganisms, pesticide residues, and some insect pests existing on fruits and vegetables without compromising sensory and nutritional quality of them in most occasions. Besides, the employment of EW to sprouts vegetables makes those healthful components such as CABA and flavonoids accumulated. However, optimal processing parameters such as washing time along with physiochemical properties of EW need further selection. And, hurdle technology should not be tolerated to maximize treatment efficacy and prolong the shelf life of fresh produce. In brief, EW has a promising prospect in future utilization of fruits and vegetables.
This chapter reviews the implications of water quality in the fresh produce industry and the associated problems from the food safety and environmental perspectives including the wastewater generated. Guidelines and national regulations focused on Good Agricultural Practices (GAP), Good Handling Practices (GHP), and Good Manufacturing Practices (GMP) recommend that water must be of potable quality when contacting the fresh commodity throughout all postharvest operations including washing, cooling, and rinsing. Water may become contaminated during processing and promote cross-contamination among different product lots. Water disinfection is needed to minimize the potential of cross-contamination of process wash water although it does not completely eliminate microbial contamination on a contaminated product. Disinfectant efficacy must be monitored and controlled throughout establishment of critical operational limits for water quality variables ensuring that optimal doses are maintained. A critical water quality variable is the organic matter content as it will directly affect the maintenance of minimum effective doses which should be enough to avoid cross-contamination in process wash water while avoiding accumulation and formation of disinfection by-products (DBPs). Selection of the most adequate disinfectant for each washing system will also have an impact on the DBP. Formation and accumulation of DBPs in process wash water must be avoided to reduce chemical risks but without compromising the maximum degree of protection against microbial risks. Large volumes of water are used in the fresh produce industry directly, impacting the generation of wastewater. The water quality variables of the generated wastewater, mainly influenced by the organic matter content and presence of DBP, and the efficacy of disinfection treatments for water reconditioning will determine the potential reuse of wastewater generated in the fresh produce industry.
Microbubbles (MB) technology was applied in a washing process a few studies have been done with food materials, particularly to reduce the microbial contamination on leafy vegetables. This study determined the effectiveness of MB (Ø ∼ 50–70 μm) combined with three sanitizers acidic electrolyte water (AEO, 20 and 40 mg/L, ORP 910–1010 mV, pH 2.7–3.1), chlorine dioxide (ClO2, 3 and 5 mg/L, ORP 550–680 mV, pH 7.1–7.5), and sodium hypochlorite (NaOCl, 40 and 80 mg/L, ORP 900–990 mV, pH 6.5–6.7) in order to inactivate Escherichia coli and Salmonella Typhimurium on artificially contaminated sweet basil (Ocimum basilicum Linh) and Thai mint (Mentha cordifolia Opiz.). Although air MB alone did not possess antimicrobial activity, washing with MB combined with the two oxidizing sanitizers (NaOCl and AEO) for 5 min resulted in an effective reduction in S. Typhimurium and E. coli on sweet basil and Thai mint with 2–3 log reductions (99.2–99.8%). Washing vegetables with MB and NaOCl at a concentration of free chlorine of 40 mg/L NaOCl or 20 mg/L AEO yielded the best results in killing S. Typhimurium with 1.21–1.90 and 0.67–2.25 log reductions, respectively. In addition, the reduction of E. coli and S. Typhimurium on sweet basil appeared to be higher than on Thai mint. Differences in surface roughness may assist the bubbles and sanitizers to detach bacterial cells and therefore increase the washing efficacy. Furthermore, applying sanitizers in washing solution was a powerful means of killing planktonic E. coli and S. Typhimurium in the wash water and preventing cross-contamination in the washing process.
Fine bubble is defined as the small bubbles with a diameter ranging in micro and nanoscale. The sizes of micro bubble are smaller than millimeter and have distinctive properties. The applications of micro bubbles technology has been successfully proved in waste water treatment. More application was investigated in washing process to reduce microorganisms and pesticides. The effectiveness of micro bubble water to reduce E. coli and Salmonella contamination on six Thai fresh vegetables during washing step was conducted. A preliminary study was performed on artificially contaminated coriander, Marsh mint, asparagus, okra, lemongrass and ginger. Washing samples for 15 minutes by micro bubble water at flow rate of 4.5 L/ min successfully reduced both pathogens in these tested vegetables. Second experiment was done to investigate the combination of micro bubbles with sanitizers, sodium hypochlorite, acetic acid and citric acid in washing Chinese kale. The results showed the promising methods to reduce microbial load compared to normal washing, although no significant among the different at concentration levels. These techniques have potential to apply in washing steps to enhance the safety of food, particular in fresh produce process.
Water disinfection is one of the most critical processing steps in fresh-cut vegetable production. Technologies capable for the efficient disinfection of process water and recycled water would allow reducing wastewater and have less impact on the environment. Among the chemical disinfectants, hypochlorite solutions are still the most widely used. Electrochemical disinfection of the wash water has been demonstrated to be effective in eliminating a wide spectrum of pathogens in process water. Both hypochlorite solutions and electrochemically produced chlorine compounds, in particular hypochlorous acid, are effective disinfectants when adequate doses are used. A new electrochemical process using boron-doped diamond electrodes can generate additional reactive oxidant species than chlorine and further enhance the disinfecting capacity. However, there are pros and cons on the use of one or other disinfectant agents. In this review, the technological advantages and the limitations of electrolyzed water, particularly regarding the organic matter content, are discussed and compared to the use of hypochlorite.
Purpose of review: This review discusses the application of physical treatments including ionizing and non-ionizing (UV-C) radiation, ultrasound, electrolyzed water and cold plasma as decontamination methods to reduce surface and internal contamination of the product and to avoid cross-contamination in process wash water. Potential combinations of physical and chemical treatments are also discussed. This manuscript shows the suitability of specific physical treatments to reduce microbial contamination of fresh produce as well as their implementation during processing of fruits and vegetables.Main findings: Data presented in this review highlight which physical methods are suitable processing technologies to be applied without detrimental effects on the organoleptic properties and nutritional quality of fresh fruits and vegetables. The microbiological tests carried out after pathogen inoculation offer insights into the antibacterial capacity of these treatments on different produce surfaces as well as in the process wash water. Although the physical methods described in this manuscript have potential use in inactivating foodborne pathogens, high operational costs, consumer acceptance and difficulties to eliminate internalized microorganisms make it difficult to introduce them as suitable intervention strategies to assure the safety of fresh produce.Directions for future research : This review shows the current application of selected physical methods to reduce microbial risk of fresh produce and also highlights the limitations of these technologies. Although most of the physical methods are able to reduce the superficial microbiota of fruits and vegetables they largely fail in eliminating internalized microorganisms. However, we believe that more research and technological advances might demonstrate the suitability of these technologies for producers and consumers in the near future. Therefore, further studies might lead to the development of appropriate largescale equipment for sanitation techniques for fresh fruits and vegetables and disinfection agents able to be implemented on processing lines.
The use of alternative control means to reduce water contamination and postharvest decay of fruit and vegetables is becoming increasingly important to enhance food safety and minimize chemical contamination of fresh produce. In the present investigation, the effects of electrolyzed salt solutions using thin-film diamond-coated electrodes on Penicillium spp. population of citrus fruit wash water and fruit decay were evaluated. Different organic and inorganic salts were tested. Electrolyzed water (EW) in combination with sodium bicarbonate (SBC) resulted the most effective treatment in inhibiting spore germination of Penicillium spp. and among the best in reducing Penicillium rot, with no deleterious effects on the fruits. Commercial trials conducted in packinghouses in Sicily (insular Italy) confirmed that the electrolyzed SBC solution was more effective than the electrolyzed tap water in reducing the population of Penicillium spp. Indeed, in the presence of SBC a 93% reduction of the pathogen population was observed 1 h after the beginning of the electrolysis process, whereas in the absence of the salt similar results were observed only after 7 h. In addition, rot incidence in fruit exposed to electrolyzed SBC solution was reduced by up to 100%, as compared to 70% in the absence of the salt. These results demonstrate that among the range of salts tested, the combination of electrolysis and SBC has a synergic effect and is a promising strategy for controlling postharvest Penicillium decay of citrus fruits.
Chlorine was assessed as a reconditioning agent and wash water disinfectant in the fresh-cut produce industry. Artificial
fresh-cut lettuce wash water, made from butterhead lettuce, was used for the experiments. In the reconditioning experiments,
chlorine was added to artificial wash water inoculated with Escherichia coli O157 (6 log CFU/ml). Regression models were constructed based on the inactivation data and validated in actual wash water
from leafy vegetable processing companies. The model that incorporated chlorine dose and chemical oxygen demand (COD) of the
wash water accurately predicted inactivation. Listeria monocytogenes was more resistant to chlorine reconditioning in artificial wash water than Salmonella spp. and Escherichia coli O157. During the washing process with inoculated lettuce (4 log CFU/g), in the absence of chlorine, there was a rapid microbial
buildup in the water that accumulated to 5.4 ± 0.4 log CFU/100 ml after 1 h. When maintaining a residual concentration of
1 mg/liter free chlorine, wash water contamination was maintained below 2.7, 2.5, and 2.5 log CFU/100 ml for tap water and
artificial process water with COD values of 500 and 1,000 mg O2/liter, respectively. A model was developed to predict water contamination during the dynamic washing process. Only minor
amounts of total trihalomethanes were formed in the water during reconditioning. Total trihalomethanes accumulated to larger
amounts in the water during the wash water disinfection experiments and reached 124.5 ± 13.4 μg/liter after 1 h of execution
of the washing process in water with a COD of 1,000 mg O2/liter. However, no total trihalomethanes were found on the fresh-cut lettuce after rinsing.
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 () 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.PRACTICAL APPLICATIONSElectrolyzed oxidizing water is an important sanitizer, and nowadays it has been widely used in food industry. Lettuce is regarded as a “healthier” food, which is one of the most popular vegetables consumed, whereas many outbreaks caused by L. monocytogenes have been reported until now. According to the model developed in this study, inactivation of L. monocytogenes in lettuce treated with EO water could be predicted by inputting a certain group of environmental factors.
Outbreaks associated with fresh produce have been traced to farms in several cases. Potential sources of contamination in preharvest environments have been identified, and minimizing their input is needed. In addition, understanding the fate of enteric pathogens introduced to soil and plant systems is essential to providing safe guidelines on when crops may be planted and harvested. Moisture availability and temperature are key abiotic factors affecting pathogen survival. Indigenous soil and epiphytic bacteria, however, also appear to play an important role in a pathogen's fate and thus future survival studies should routinely monitor the types and levels present. Internalization of enteric pathogens through lateral root junctions or through leaf stomata has been documented but generally requires high exposure concentrations. Plant defenses, whether basal or activated by the invading enteric pathogen, appear to inactivate internalized populations as persistence has not been observed, but this subject deserves further investigation.
This chapter focuses on the use of electrolyzed oxidizing (EO) water for washing fresh and fresh-cut produce. It revises the different types of EO water, its advantages and disadvantages, types of generation devices, the microbial inactivation mechanism, and factors affecting its efficacy. It also summarizes the effect of EO water on pathogenic and spoilage microorganisms and produce shelf life, vegetable physiology, sensory quality, and nutritional and phytochemical composition, as well as the potential persistence of residues and formation of toxic by-products and EO regulatory status.
The efficacy of gaseous and liquid ClO2 or neutral electrolysed water (NEW) to decontaminate minimally processed vegetables, without affecting sensory quality, was evaluated using aerobic plate counts and triangle tests. Gaseous ClO2 yielded >1 log cfu/g reduction in lettuce and cabbage. but caused browning. Aqueous ClO2 did not reduce aerobic plate count of lettuce and cabbage, but yielded >1 log reduction in carrots. Lettuce was sensorially affected by ClO2 washings, but cabbage and carrots were not. NEW yielded >1 log reduction in lettuce, cabbage and carrots; a 5 min treatment did not damage their sensory quality. Aqueous ClO2 was most appropriate to decontaminate carrots and NEW for lettuce, cabbage, and carrots. Gaseous ClO2 was effective in decreasing lettuce and cabbage microbial load but significantly affected their sensory quality.
The potential generation of trihalomethanes (THMs) during washing of vegetable products as a consequence of the use of chlorine has become one of the main concerns for researchers, industry and regulatory agencies. However, only scarce information is known about the actual THM formation in process wash water and in the final product to establish the real risks associated with it. The aim of this work was to evaluate the THM formation in process wash water after washing baby spinach with chlorine-based sanitizers such as sodium hypochlorite and electrolyzed oxidizing water with and without the addition of salt (EOW + NaCl and EOW, respectively). Additionally, the impact of these chlorine-based sanitizers on the microbial, nutritional and sensory quality of baby spinach was compared with a non-chlorine based sanitizer such as peroxyacetic acid. The total THM levels of the process wash water treated with sodium hypochlorite and EOW + NaCl were over the authorized limit fixed by the European legislation and USEPA (100 and 80 μg L−1, respectively) for drinking water. However, the THM levels after treatment with EOW did not exceed these established limits. In baby spinach, THMs were detected in low levels in sodium hypochlorite and EOW washed samples because the rinsing step reduced them to levels below the detection limit. Chlorine and non-chlorine based sanitizers such as peroxyacetic acid, did not affect the quality and shelf-life of the product. After washing and during storage in modified atmosphere packaging, similar headspace gas concentrations, microbial and sensory quality, instrumental texture and colour measures and electrolyte leakage were observed for all sanitizers. The results provide evidence that, under these specific experimental conditions, chlorine-based sanitizers do not represent a risk for THM formation during baby spinach leaf processing. In our opinion, current experimental data does not support banning the use of chlorine-based sanitizers in the fresh-cut vegetable industry because of THM generation in commodities such as spinach.
The effects of hardness and pH of water used to prepare electrolyzed oxidizing (EO) water and bleach solutions on the bactericidal activity of sanitizer prepared from the water were examined. EO water and bleach solutions were prepared with hard water of 0, 50, 100, and 200 mg/l as CaCO3 at pH 5, 6, 7, and 8. Increased water hardness tended to increase free chlorine and oxidation–reduction potential (ORP) and decrease pH of EO water. Chlorine levels also increased with water pH. Water hardness and pH only had minor effect on the pH of bleach solutions. Increasing hardness to 50 mg/l increased antimicrobial effect of EO water against Escherichia coli O157:H7, but reduced when water hardness further increased to 100 mg/l or higher. Water pH had no effect on EO water produced against E. coli O157:H7. Water hardness had no significant effect on bactericidal activity of EO water against Listeria monocytogenes but elevated water pH decreased bactericidal activity of EO water produced against L. monocytogenes. Bleach solution prepared using hard water at 200 mg/l or at pH 7 or higher had significant lower efficacy in inactivating E. coli O157:H7, but had no effect on the inactivation of L. monocytogenes. Results indicate that increasing the hardness or pH of water used to prepare EO water or bleach solutions will decrease the bactericidal activity of sanitizers prepared from the water.
The effect of different processing parameters on the efficacy of commercial post-harvest biocidal washes to decrease the bacterial loading on spinach and lettuce has been evaluated. Sampling was performed at two spinach processors (Facility A & B) and a shredded lettuce producer (Facility C). Aerobic colony counts (ACC) and coliform counts were determined on samples taken at pre- and post-wash. In parallel, the heterotrophic plate count (HPC) and coliform levels in wash water was also determined. Processing parameters measured were the temperature of leafy greens (pre- and post-washing) and wash water. The sanitizer levels (peroxyacetic acid, oxidation–reduction potential), pH, conductivity and turbidity were also measured. The wash process in Facility B had a residence time of 50 s for the spinach, maintained a constant hypochlorite concentration and continuously re-charged the tanks with fresh water. In contrast, Facility A had a short residence time (15 s) did not maintain a constant sanitizer (peroxyacetic acid) concentration or re-charge tanks with fresh water. Despite the differences in processing operations there was no statistical difference between the log count reductions (LCR) obtained in ACC and coliform counts although counts were only reduced by <0.6 log cfu/g. The carriage of Escherichia coli on pre-wash spinach was 19% and 25% in Facility A and B respectively. There was a high prevalence (57% positive) of E. coli in the wash water of Facility A with none being recovered in water samples taken from Facility B. Yet, the carriage of E. coli on post-wash spinach was the same in the two facilities (7%). Lettuce harboured a lower level of both ACC and coliforms with LCR being significantly greater than spinach. In general, the LCR in ACC and coliforms could be positively correlated to bacterial counts of pre-washed leafy greens and conductivity (solids content) of the wash water. A negative correlation was found between LCR and water temperature. Interestingly, within the ranges measured the LCR was independent of the bacterial loading of the water. The results of the study confirmed the limited efficacy of biocidal washes to remove field acquired contamination. Although it is thought maintaining a low microbial loading in the wash water and maintaining sanitizer concentration is key the current study suggests high conductivity and low temperature of the wash water enhances the LCR achieved.
Acidic electrolyzed water (acidic EW), which is prepared by the electrolysis of an aqueous NaCl solution, has recently become of great importance for disinfection in a variety of fields, including medicine, the food industry and agriculture. In a previous paper we showed that: 1) acidic EW is a mixture of hypocholorite ion, hypochlorous acid and chlorine, depending upon the pH; 2) hypochlorous acid is primarily responsible for disinfection in the case of Escherichia coli K12 and Bacillus subtilis PCI219, both in clean culture media. In practice, however, the use of acidic EW is in many cases severely hampered due to the presence of a variety of non-selective reducing agents. In view of the salient nature of acidic EW, it is therefore strongly urged to establish an optimum way to use acidic EW in a variety of systems. The present paper is the first report on our attempt along this line in order to characterize the nature of the chemical changes that the bactericidal activity of the acidic EW deteriorates in the presence of organic materials, which include amino acids and proteins.
Chemical water treatment problems such as disinfection by-products formation have urged on the search of better water treatment technologies such as electrochemical water technologies which have been applied successfully in different water/wastewater pollutant removal. However, their wide extension is hindered by some technical problems such as chlorine by-products (CBPs) generated species. Indeed, during electrochemical process, these carcinogenic substances may be formed depending on the electrode material and applied voltage. This review concerns the dependence of CBPs generated species formation of the electrode material and applied charge during electrochemical water treatment. It is concluded that the use of electrodes producing highly reactive species must be more carefully controlled in hygienically and environmentally oriented applications. From this point of view, Pt and boron-doped diamond (BDD) anodes are proved more convenient than other electrodes. Indeed, the great capability of a BDD anode to produce reactive oxygen species and other oxidising species during the electrolysis allows establishing a chlorine-free disinfection process.Research Highlights► At [Cl−] < 100 mg L–1, free Cl2(g) can be produced with the risk of DBPs formation. ► Electric field conditions must be optimised to avoid DBPs formation. ► The DBPs formed can be removed by passing through activated carbon.
OVERVIEW: This paper provides an overview of some fundamental aspects of electrochemical oxidation and gives updated information on the application of this technology to waste-water treatment. In recent years, electrochemical oxidation has gained increasing interest due to its outstanding technical characteristics for eliminating a wide variety of pollutants normally present in waste-waters such as refractory organic matter, nitrogen species and microorganisms.
IMPACT: The strict disposal limits and health quality standards set by legislation may be met by applying electrochemical oxidation. However, treatment costs have to be cut down before full-scale application of this technology. Deployment of electrochemical oxidation in combination with other technologies and the use of renewable sources to power this process are two steps in this direction.
APPLICATIONS: Effluents from landfill and a wide diversity of industrial effluents including the agro-industry, chemical, textile, tannery and food industry, have been effectively treated by this technology. Its high efficiency together with its disinfection capabilities makes electro-oxidation a suitable technology for water reuse programs. Copyright
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.
In this work the products of the oxidation at BDD anode of chloride ions in aqueous solutions were identified during galvanostatic
electrolyses performed in a filter-press reactor operating both in batch and continuous mode. A set of experiments were preformed
in order to study the effect of operating conditions (current density, residence time, hydrodynamics and chloride concentration)
on distribution and concentration of electrolysis by-products. As a comparison experiments were also performed using a commercial
DSA anode. A simple mathematical model was formulated, and the model predictions agree with the experimental data in a wide
range of experimental conditions. The results of this work showed that at low chloride concentrations electrolysis with BDD
anode produce a mixture of powerful oxidant: low current density, high mass transfer conditions and low residence time were
found as optimal conditions to maximize the concentration of oxidants and minimize the concentration of chlorates. The proposed
reaction mechanism may also justify the controversial effect of chloride ions in wastewater treatments: the electrolysis carried
out with BDD anodes and electrolyte containing chloride concentration higher 1g/L could meet the target of the process only
if the active chlorine is effective in oxidation of the pollutant that must be removed.
Aqueous chlorine dioxide (ClO2) has been postulated as an alternative to sodium hypochlorite (NaClO) for fresh-cut produce sanitization with the advantage of avoiding the risks associated with chlorination by-products. However, little is known about its influence on preserving quality and the potential formation of trihalomethanes (THMs) under typical processing conditions. The suitability of aqueous chlorine dioxide (3 mg L−1) as an effective sanitizer of fresh-cut iceberg lettuce stored under active modified atmosphere packaging (MAP) at refrigerated conditions was determined and compared with sodium hypochlorite (100 mg L−1). Fresh-cut lettuce washed with tap water was used as a control. The epiphytic microbiota were characterized by the evaluation of the major relevant microbial groups such as mesophiles, psychrophiles, Pseudomonas spp., Enterobacteriaceae, lactic acid bacteria, yeasts and moulds. Additionally, gas composition, sensory quality, vitamin C and individual and total phenolics were monitored after washing and during storage for 3 d at 4 °C followed by 7 d at 8 °C. In general, the natural microbiota of fresh-cut lettuce after washing and storage was equally affected by the different washing solutions, with the exception of yeasts which showed the highest growth after 10 d storage in samples washed with chlorine dioxide. None of the tested washings negatively affected sensory quality, which was acceptable after 10 d storage. Additionally, the content of bioactive compounds was not significantly affected either by washing solution or by storage time. The potential formation of THMs was evaluated by the analysis of lettuce washed in water with a chemical oxygen demand (COD) of 700 mg L−1 treated for 30 min with sodium hypochlorite (100 mg L−1) or chlorine dioxide (3.7 mg L−1). Trihalomethane formation was only detected in the process water in which sodium hypochlorite was applied (217 ± 38 μg L−1). However, THMs formation in fresh-cut lettuce was negligible despite the sanitation procedure. The formation of THMs was only detected in fresh-cut lettuce when sodium hypochlorite was used under very extreme conditions where lettuce was washed in water with a high level of organic matter (COD = 1800 mg L−1), high sodium hypochlorite concentration (700 mg L−1) and long contact time (60 min). Our data suggest that aqueous chlorine dioxide is as suitable as sodium hypochlorite for fresh-cut lettuce sanitation with the advantage of preventing the formation of THMs.
Electrolyzed oxidizing (EO) water has been regarded as a new sanitizer in recent years. Production of EO water needs only water and salt (sodium chloride). EO water have the following advantages over other traditional cleaning agents: effective disinfection, easy operation, relatively inexpensive, and environmentally friendly. The main advantage of EO water is its safety. EO water which is also a strong acid, is different to hydrochloric acid or sulfuric acid in that it is not corrosive to skin, mucous membrane, or organic material. Electrolyzed water has been tested and used as a disinfectant in the food industry and other applications. Combination of EO water and other measures are also possible. This review includes a brief overview of issues related to the electrolyzed water and its effective cleaning of food surfaces in food processing plants and the cleaning of animal products and fresh produce.
The food industry has recognized electrolyzed oxidizing water (EOW) as a promising alternative decontamination technique. However, there is not a consensus about the sanitizing mechanism of EOW. In this study, we evaluated the disinfection efficacy of different types of EOW on Escherichia coli. Based on the hypothesis of hydroxyl radicals existing in EOW, in the present study, the hydroxyl radicals existed in slightly acidic electrolyzed water (SAEW) and acidic electrolyzed water (AEW) diluted to different levels were detected quantitatively. An ultraviolet (UV) spectrophotometer was used to scan EOW with different pH values. Accounting for the results of UV scanning to EOW with different pH value and the disinfection efficacy of different types of EOW, it can be concluded that considering the lower chlorine concentration of EOW compared with traditional chlorine disinfectants, the existing form of chlorine compounds rather than the hydroxyl radicals played important role in the disinfection efficacy of EOW.
The efficacy of an electrochemical treatment in water disinfection, using boron-doped diamond electrodes, was studied and its suitability for the fresh-cut produce industry analyzed. Tap water (TW), and tap water supplemented with NaCl (NaClW) containing different levels of organic matter (Chemical Oxygen Demand (COD) around 60, 300, 550 ± 50 and 750 ± 50 mg/L) obtained from lettuce, were inoculated with a cocktail of Escherichia coli O157:H7 at 10⁵ cfu/mL. Changes in levels of E. coli O157:H7, free, combined and total chlorine, pH, oxidation-reduction potential, COD and temperature were monitored during the treatments. In NaClW, free chlorine was produced more rapidly than in TW and, as a consequence, reductions of 5 log units of E. coli O157:H7 were achieved faster (0.17, 4, 15 and 24 min for water with 60, 300, 500 and 750 mg/L of COD, respectively) than in TW alone (0.9, 25, 60 min and 90 min for water with 60, 300, 600 and 800 mg/L of COD, respectively). Nonetheless, the equipment showed potential for water disinfection and organic matter reduction even without adding NaCl. Additionally, different mathematical models were assessed to account for microbial inactivation curves obtained from the electrochemical treatments.
The viability of the electro-oxidation technology provided with boron doped diamond (BDD) electrodes for the treatment and reuse of the seawater used in a Recirculating Aquaculture System (RAS) was evaluated in this work. The influence of the applied current density (5-50 A m(-2)) in the removal of Total Ammonia Nitrogen (TAN), nitrite and chemical oxygen demand (COD) was analyzed observing that complete TAN removal together with important reductions of the other considered contaminants could be achieved, thus meeting the requirements for reuse of seawater in RAS systems. TAN removal, mainly due to an indirect oxidation mechanism was described by a second order kinetics while COD and nitrite removal followed zero-th order kinetics. The values of the kinetic constants for the anodic oxidation of each compound were obtained as a function of the applied current density (k(TAN) = 7.86 × 10(-5) · exp(6.30 × 10(-2) J); kNO2 = 3.43 × 10(-2) J; k(COD) = 1.35 × 10(-2) J). The formation of free chlorine and oxidation by-products, i.e., trihalomethanes (THMs) was followed along the electro-oxidation process. Although a maximum concentration of 1.7 mg l(-1) of total trihalomethanes was detected an integrated process combining electrochemical oxidation in order to eliminate TAN, nitrite and COD and adsorption onto activated carbon to remove the residual chlorine and THMs is proposed, as an efficient alternative to treat and reuse the seawater in fish culture systems. Finally, the energy consumption of the treatment has been evaluated.
Suspension quantitative germicidal test showed that electrolyzed oxidizing water (EO water) was an efficient and rapid disinfectant. Disinfection rates towards E. coli (available chlorine concentration ACC: 12.40 mg/L) and Staphylococcus aureus (ACC: 37.30 mg/L) could reach 100% at 1 and 3 min, respectively. Disinfection mechanism of EO water was investigated at a molecular biological level by detecting a series of biochemical indices. The results showed that the dehydrogenase activities of E. coli and S. aureus decreased rapidly, respectively, at the rates of 45.9% and 32% in the 1st minute treatment with EO water. EO water also improved the bacterial membrane permeability, causing the rise of conductivities and the rapid leakages of intracellular DNA, K(+), and proteins in 1 min. The leakages of DNA and K(+) tended to slow down after about 1 min while those of proteins began to decrease a little after reaching the peak values. The sodium dodecyl sulfonate polyacrylamide gel electrophoresis (SDS-PAGE) showed that EO water destroyed intracellular proteins. The protein bands got fainter and even disappeared as the treatment proceeded. EO water's effects on the bacterial ultrastructures were also verified by the transmission electronic microscopy (TEM) photos. The disinfection mechanism of EO water was composed of several comprehensive factors including the destruction of bacterial protective barriers, the increase of membrane permeability, the leakage of cellular inclusions, and the activity decrease of some key enzymes.
Trihalomethanes (THMs, namely, CHCl3, CHCl2Br, CHClBr2 and CHBr3) are disinfection by-products that are present in drinking water. These toxic chemicals are also present in meat, dairy products, vegetables, baked goods, beverages and other foods, although information regarding their concentrations and origin is very limited. This study investigates sorption of THMs occurring during rinsing and cooking of foods and the significance of food as an exposure source.
Initial estimates of THM uptake were measured in experiments representing rinsing with tap water at 25 C using nine types of food, and for cooking in tap water at 90 C for fourteen other foods. A subset of foods was then selected for further study over a range of THM concentrations (23.7–118.7 μg/l), temperatures (25 C and 90 C), food concentrations (0.2–1.4, food weight: water weight), and contact times (5–240 min). Data were analyzed using regression and exponential models, and diffusion models were used to help explain the trends of THM uptake.
Among vegetables, sorbed THM concentrations at 25 C were 213 to 774 ng/g for CHCl3, 53 to 609 ng/g for CHCl2Br, and 150–845 ng/g for CHClBr2. Meats at 90 C tended to have higher concentrations, e.g., 870–2634 ng/g for CHCl3. Sorbed concentrations increased with contact time and THM concentration, and decreased with food concentration in rinsing tests (using spinach, iceberg-head lettuce and cauliflower) and cooking tests (using tomato, potato, beef and miso–tofu soup). For most foods, THM uptake was diffusion limited and several hours were needed to approach steady-state levels. Swelling, hydrolysis and other physical and chemical changes in the food can significantly affect sorption. Screening level estimates for CHCl3 exposures, based on experimental results and typical food consumption patterns, show that uptake via foods can dominate that due to direct tap water consumption, suggesting the importance of sorption and the need for further evaluation of THM intake due to foods.
A study was conducted to demonstrate direct and mediated anodic processes for the oxidation of organic pollutants. The study proposed different expressions of current efficiency, such as instantaneous current efficiency (ICE), electrochemical oxidation index (EOI), general current efficiency (GCE), and mineralization current efficiency (MCE). ICE of electro-oxidation was determined by the oxygen flow rate (OFR) method or chemical oxygen demand (COD). GCE represented an average value of current efficiency between the initial time t = 0 and t. Efforts were made to perform electrolysis at a high anodic potential in the region of water discharge, using intermediates of electrogenerated hydroxyl radicals. Another strategy involved oxidizing pollutants by indirect electrolysis, generating a redox reagent in situ as a chemical reactant.
It is well known that fresh-cut processors usually rely on wash water sanitizers to reduce microbial counts in order to maintain quality and extend shelf-life of the end product. Water is a useful tool for reducing potential contamination but it can also transfer pathogenic microorganisms. Washing with sanitizers is important in fresh-cut produce hygiene, particularly removing soil and debris, but especially in water disinfection to avoid cross-contamination between clean and contaminated product. Most of the sanitizing solutions induce higher microbial reduction after washing when compared to water washing, but after storage, epiphytic microorganisms grow rapidly, reaching similar levels. In fact, despite the general idea that sanitizers are used to reduce the microbial population on the produce, their main effect is maintaining the microbial quality of the water. The use of potable water instead of water containing chemical disinfection agents for washing fresh-cut vegetables is being advocated in some European countries. However, the problems of using an inadequate sanitizer or even none are considered in this manuscript. The need for a standardized approach to evaluate and compare the efficiency of sanitizing agents is also presented. Most new alternative techniques accentuate the problems with chlorine suggesting that the industry should move away from this traditional disinfection agent. However, the use of chlorine based sanitizers are presented as belonging to the most effective and efficient sanitizers when adequate doses are used. In this review improvements in water disinfection and sanitation strategies, including a shower pre-washing step and a final rinse of the produce, are suggested.
To evaluate the efficacy of acidic electrolysed water (EW) in the presence of organic matter (bovine serum) on the inoculated surfaces of lettuce and spinach.
Lettuce and spinach leaves were inoculated with a cocktail of three strains each of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes and treated with deionized water, acidic EW and acidic EW containing bovine serum (5, 10, 15 and 20 ml l(-1)) for 15 s, 30 s, 1 min, 3 min and 5 min at room temperature (22 +/- 2 degrees C). In the absence of bovine serum, acidic EW treatment reduced levels of cells below the detection limit (0.7 log) in 5 min. In the presence of bovine serum, bactericidal activity of acidic EW decreased with increasing serum concentration.
Organic matter reduces the effectiveness of acidic EW for reducing pathogens on the surfaces of lettuce and spinach.
From a practical standpoint, organic matter reduces the efficacy of acidic EW. This study was conducted to confirm the effect of organic matter on the properties of acidic EW in the inactivation of foodborne pathogens on the surface of vegetables.
This study was undertaken to evaluate the efficacy of electrolyzed oxidizing (EO) and chemically modified water with properties similar to the EO water for inactivation of different types of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes and Bacillus cereus). A five-strain cocktail of each microorganism was exposed to deionized water (control), EO water and chemically modified water. To evaluate the effect of individual properties (pH, oxidation-reduction potential (ORP) and residual chlorine) of treatment solutions on microbial inactivation, iron was added to reduce ORP readings and neutralizing buffer was added to neutralize chlorine. Inactivation of E. coli O157:H7 occurred within 30 s after application of JAW EO water with 10 mg/l residual chlorine and chemically modified solutions containing 13 mg/l residual chlorine. Inactivation of Gram-positive and -negative microorganisms occurred within 10 s after application of ROX EO water with 56 mg/l residual chlorine and chemically modified solutions containing 60 mg/l residual chlorine. B. cereus was more resistant to the treatments than E. coli O157:H7 and L. monocytogenes and only 3 log10 reductions were achieved after 10 s of ROX EO water treatment. B. cereus spores were the most resistant pathogen. However, more than 3 log10 reductions were achieved with 120-s EO water treatment.
Electrolyzed strong acid water (ESW) containing free chlorine at various concentrations is becoming to be available in clinical settings as a disinfectant. ESW is prepared by electrolysis of a NaCl solution, and has a corrosive activity against medical instruments. Although lower concentrations of NaCl and free chlorine are desired to eliminate corrosion, the germicidal effect of ESW with low NaCl and free-chlorine concentrations (ESW-L) has not been fully clarified. In this study, we demonstrated that ESW-L possesses bactericidal activity against Mycobacteria and spores of Bacillus subtilis. The effect was slightly weaker than that of ESW containing higher NaCl and free-chlorine concentrations (ESW-H), but acceptable as a disinfectant. To clarify the mechanism of the bactericidal activity, we investigated ESW-L-treated Pseudomonas aeruginosa by transmission electron microscopy, a bacterial enzyme assay and restriction fragment length polymorphism pattern (RFLP) assay. Since the bacterium, whose growth was completely inhibited by ESW-L, revealed the inactivation of cytoplasmic enzyme, blebs and breaks in its outer membrane and remained complete RFLP of DNA, damage of the outer membrane and inactivation of cytoplasmic enzyme are the important determinants of the bactericidal activity.
The effects of chlorine and pH on the bactericidal activity of electrolyzed (EO) water were examined against Escherichia coli O157:H7 and Listeria monocytogenes. The residual chlorine concentration of EO water ranged from 0.1 to 5.0 mg/l, and the pH effect was examined at pH 3.0, 5.0, and 7.0. The bactericidal activity of EO water increased with residual chlorine concentration for both pathogens, and complete inactivation was achieved at residual chlorine levels equal to or higher than 1.0 mg/l. The results showed that both pathogens are very sensitive to chlorine, and residual chlorine level of EO water should be maintained at 1.0 mg/l or higher for practical applications. For each residual chlorine level, bactericidal activity of EO water increased with decreasing pH for both pathogens. However, with sufficient residual chlorine (greater than 2 mg/l), EO water can be applied in a pH range between 2.6 (original pH of EO water) and 7.0 while still achieving complete inactivation of E. coli O157:H7 and L. monocytogenes.
Electrochemical disinfection has emerged as one of the most promising alternatives to the conventional disinfection of water in many applications. Although the mechanism of electrochemical disinfection has been largely attributed to the action of electro-generated active chlorine, the role of other oxidants, such as the reactive oxygen species (ROS) *OH, O3, H2O2, and *O2- remains unclear. In this study, we examined the role of ROS in the electrochemical disinfection using a boron-doped diamond (BDD) electrode in a chloride-free phosphate buffer medium, in order to avoid any confusion caused by the generation of chlorine. To determine which species of ROS plays the major role in the inactivation, the effects of several operating factors, such as the presence of *OH scavenger, pH, temperature, and the initial population of microorganisms, were systematically investigated. This study clearly showed that the *OH is the major lethal species responsible for the E. coli inactivation in the chloride-free electrochemical disinfection process, and that the E. coli inactivation was highly promoted at a lower temperature, which was ascribed to the enhanced generation of O3.
Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-mug/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for approximately 60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.
Microbial ecology Decontamina-tion of Fresh and Minimally Processed Produce
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Salt addition improves the control of citrus postharvest diseases using electrolysis with conductive dia-mond electrodes On the dependence of chlorine by-products generated species formation of the electrode material and applied charge during electrochemical water treatment
- F Fallanaj
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Sorption of trihalomethanes in foods Application of electrolysed w ater in the food industry
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The role of reactive oxygen species in the elec-trochemical inactivation of microorganisms Efficacy of electrolyzed oxidizing (EO) and chemically modified water on different types of foodborne pathogens
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Electrochemical disinfection: an efficacy treatment to inactivate Escherichia coli O157:H7 in process water containing organic matter
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inactivate Escherichia coli O157:H7 in process water containing organic matter.
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