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... Electrolyzed water is generated by electrolyzing a dilute sodium chloride (NaCl) solution with a current across an anode and cathode that are separated by a bipolar membrane. Electrolysis of the salt solution can produce reduced substances with strong biocidal activity such as hypochlorous acid (HOCl), hypochlorite ion (OCl-), hydroxyl (OH-), and superoxide radicals (O2-) (Abadias et al., 2008;Pinto et al., 2015;Posada-Izquierdo et al., 2014). ...
... High stability of neutral electrolyzed water due to low level of chlorine gas formed in near neutral pH (6-8) has been favored in the fresh-cut industry as it is less corrosive and hazardous to processing equipment and operators' health (Pangloli and Hung, 2011;Posada-Izquierdo et al., 2014). Navarro- Rico et al. (2014) reported that the microbial loads of mesophiles, psychrotrophes, Enterobaceriaceae, and yeasts and molds enumerated from fresh-cut kai-lan hybrid broccoli were approximately 1.7, 4.0, 0.9, and 4.0 lof CFU g ¡1 after washing with neutral electrolyzed water (FCC: 100 mg L ¡1 ; pH:7; ORP C900 mV) for 2 min. ...
Article
Minimally processed fresh produce is one of the fastest growing segments of the food industry due to consumer demand for fresh, healthy, and convenient foods. However, mechanical operations of cutting and peeling induce the liberation of cellular contents at the site of wounding that can promote the growth of pathogenic and spoilage microorganisms. In addition, rates of tissue senescence can be enhanced resulting in reduced storage life of fresh-cut fruits and vegetables. Chlorine has been widely adopted in the disinfection and washing procedures of fresh-cut produce due to its low cost and efficacy against a broad spectrum of microorganisms. Continuous replenishment of chlorine in high organic wash water can promote the formation of carcinogenic compounds such as trihalomethanes, which threaten human and environmental health. Alternative green and innovative chemical and physical postharvest treatments such as ozone, electrolyzed water, hydrogen peroxide, ultraviolet radiation, high pressure processing, and ultrasound can achieve similar reduction of microorganisms as chlorine without the production of harmful compounds or compromising the quality of fresh-cut produce.
... The evaluation of the posttreatment effect of EW treatment often demonstrated the dynamics of food microbiota associated with a decrease in the organoleptic characteristic of fresh produce during storage . To avoid posttreatment microbial survival, the combination of EW treatment with modified atmosphere packaging technology has been applied to limit the complex dynamics of spoilage and pathogenic bacteria and the associated decrease in quality of meat, shrimp muscle, and sweet cherries (Eda and Seckin 2015;Posada-Izquierdo et al. 2014;. Modified atmosphere packaging containing a concentration of 40-80% CO 2 is effective in the preservation of fresh produce safety and quality, primarily due to CO 2 retardation of growth by extension of the survival lag phase of microorganisms during storage in MAP containing high CO 2 levels (Qian et al. 2013;. ...
... The effect of storage under modified atmosphere packaged lettuce on the survival of E. coli O157:H7 subjected to NEW (50 mg/L free chlorine and a pH of 6.5) treatment was also investigated at different temperatures. Subsequently, a survival of E. coli O157:H7 model was developed to describe the combined treatment effect (Posada-Izquierdo et al. 2014). A wash processing for 30 s performed with NEW resulted in a reduction of 1.0 log CFU/g of E. coli O157:H7 on lettuce. ...
Chapter
Foods of animal origin, such as red meat and poultry products, are primary sources of superior protein for humans. With the production and consumption of these products increasing rapidly in recent decades, microbial safety and food quality are vital issues. Electrolyzed water (EW) as a sanitizer has awakened high interest in the food industry of many countries. The use of EW to decontaminate fresh red meat, ready-to-eat meat, poultry and shell eggs has been effective in reducing pathogenic microorganisms. Moreover, EW presents many advantages over traditional decontaminants; it provides effective antimicrobial activity and is environmentally friendly, simple to handle and relatively inexpensive. However, no complete elimination of pathogens on red meat and chicken meat was obtained after treatment of the meats with EW. This result probably occurs because organic matter and blood residue were present. This chapter provides a brief overview of how EW treatment affects foods of animal origin, especially the microbial safety and the physicochemical and sensory qualities of the food.
... The evaluation of the posttreatment effect of EW treatment often demonstrated the dynamics of food microbiota associated with a decrease in the organoleptic characteristic of fresh produce during storage (Botta et al. 2018). To avoid posttreatment microbial survival, the combination of EW treatment with modified atmosphere packaging technology has been applied to limit the complex dynamics of spoilage and pathogenic bacteria and the associated decrease in quality of meat, shrimp muscle, and sweet cherries (Eda and Seckin 2015;Posada-Izquierdo et al. 2014;Zhang et al. 2015). Modified atmosphere packaging containing a concentration of 40-80% CO 2 is effective in the preservation of fresh produce safety and quality, primarily due to CO 2 retardation of growth by extension of the survival lag phase of microorganisms during storage in MAP containing high CO 2 levels (Qian et al. 2013;Zhang et al. 2015). ...
... The effect of storage under modified atmosphere packaged lettuce on the survival of E. coli O157:H7 subjected to NEW (50 mg/L free chlorine and a pH of 6.5) treatment was also investigated at different temperatures. Subsequently, a survival of E. coli O157:H7 model was developed to describe the combined treatment effect (Posada-Izquierdo et al. 2014). A wash processing for 30 s performed with NEW resulted in a reduction of 1.0 log CFU/g of E. coli O157:H7 on lettuce. ...
Chapter
Full-text available
Improving the quality and safety aspects of fresh produce is one of the key issues in the food industry. EW is one of the most widely used sanitizers and is considered as an alternative technology to sodium chlorite treatment in the fresh produce industry. EW is well known to have a potential of microbial reduction of approximately 2 log CFU. The potential of this enhancement requires the application of combinations of EW with appropriate technologies susceptible to promoting standards in both microbial quality and safety and the sensory properties of fresh produce. In recent years, an increasing number of publications have shown that EW hurdle technology is considered as a potential food decontamination process, which can improve the microbial quality and safety and extend the shelf life of fresh produce. This chapter presents a complete picture of recent developments in EW hurdle technology applied to fresh produce, with a particular emphasis on microbial quality and safety. Several studies have been conducted to develop effective combined treatments of EW and thermal, chemical (especially organic), physical nonthermal, and various biological technologies. More specifically, the common use of chemical and biological treatments in simultaneous combination and the use of physical treatments in subsequent combination with different types of EW, including alkaline, acidic, and slightly acidic, are highlighted. The principles, mechanism of microbial and enzymatic inactivation, and microbial decontamination issues that can be overcome using a combination of EW with other treatments are also discussed. There are indications that the hurdle technology of EW can be used in the fresh produce industry; however, a better understanding of practical knowledge and the optimization of parameters of different treatments associated with EW would also contribute to reinforcing the future application of EW hurdle technologies in the fresh produce industry.
... The shelf-life effects of MAP on a range of factors including organoleptic qualities (Sivakumar and Korsten 2006;D ıaz-Mula et al. 2011;Fagundes et al. 2015), bacteria growth (Posada-Izquierdo et al. 2014), fungal (usually yeast) growth (Bastiaanse et al. 2010;Caponigro et al. 2010), coloringparticularly for anti-browning (Gomes, Beaudry, and Almeida 2012), fruit decay (Selcuk and Erkan 2015) and prevention of chilling injuries (Cheng et al. 2015), have been studied for a very wide range of minimally processed horticultural products. Finnegan et al. (2013) examined the effects of intrinsic factors (origin, physiological age and seasonality) and extrinsic factors (cut-size, blade-sharpness and dipping treatments) on respiration rate of fresh-cut pineapple chunks and concluded that, in general, physiological age and origin were found to be more important than season in determining the effects of MAP on quality attributes and shelf-life. ...
... Heat treatments (55 C for 45 s) combined with MAP reduced browning and increased the shelf-life of fresh-cut lotus root (Son et al. 2015). Prior treatment with neutral electrolyzed water (NEW) enhanced the shelf-life of MAP fresh-cut lettuce (Posada-Izquierdo et al. 2014). ...
Article
Modified atmosphere packaging (MAP) technology has been commercially viable since the 1970s. Currently, MAP is extensively used worldwide to preserve the quality and extend the shelf-life of whole fresh fruits and vegetables, but is also increasingly used to extend the shelf-life of minimally processed fresh fruit and vegetables. This review discusses new processes and technologies that can be used to improve quality preservation and consumer acceptability of minimally processed produce where high respiration rates and challenging degradation processes operate. New packaging innovations are enabling producers and retailers to further maintain quality for longer. Innovative approaches to extend shelf-life include active MAP with differentially permeable films, films that incorporate antimicrobial properties, edible coatings that confer barriers properties, and the use of non-traditional gases to modify respiration. Intelligent packaging using integrated sensor technologies that can indicate maturity, ripeness, respiration rate and spoilage are also appearing. This review demonstrates that preservation technologies and associated packaging developments that can be combined with modified atmosphere are constantly evolving technology platforms. Adoption of combinations of technology improvements will be critical in responding to commercial trends towards more minimally processed fresh-cut and ready-to-eat fruit and vegetable products, which require specialized packaging solutions.
... Most studies have defined EW with a pH of 5.0-6.5 as SAEW [1][2][3]15,28,33, . However, it has also been called electrolyzed neutral water [58] , near-neutral electrolyzed oxidizing water [25,59] and NEW [24,48,60,61] . It is important to distinguish SAEW and NEW using an agreed standard. ...
Article
Electrolyzed water (EW) can be produced by electrolysis of a dilute salt solution. Slightly acidic electrolyzed water (SAEW, pH 5.0-6.5) and neutral electrolyzed water (NEW, pH 6.5-8.5) are considered healthy and environmentally friendly because no hazardous chemicals are added in its production, there is reduced corrosion of surfaces and it minimizes the potential for damage to animal and human health. Over the last decade, EW has become increasingly popular as an alternative disinfectant for decontamination in animal houses. However, there have been some issues related to EW that are not well known, including different mechanisms for generation of SAEW and NEW, and the antimicrobial mechanism of EW. This review covers the definitions of SAEW and NEW, different generation systems for SAEW and NEW, the antimicrobial mechanism of EW, and recent developments related to the application of SAEW and NEW in animal houses.
... Different growth models such as the Logistic model (Van Impe et al., 2005), the modified Gompertz model (Gibson et al., 1987), and the Baranyi and Roberts model (Baranyi and Roberts, 1994), have been developed. Among these models, the Baranyi and Roberts model is one of the most frequently used models and has been applied to numerous studies including Salmonella in ground sterile pork (Velugoti et al., 2011), Escherichia coli O157:H7 in fresh-cut lettuce (Posada-Izquierdo et al., 2014), Staphylococcus aureus in sterilized milk (Fujikawa and Morozumi, 2006), Listeria monocytogenes in pasteurized milk (Bovill et al., 2000), and Clostridium perfringens in cooked uncured meat and poultry , among others. ...
Article
The Baranyi and Roberts model is one of the most frequently used microbial growth models. It has been successfully applied to numerous studies of various microorganisms in different food products. Under dynamic conditions, the model is implicitly formulated as a set of two coupled differential equations which could be numerically solved using the Runge-Kutta method. In this study, an explicit form of the coupled differential equations was derived and used to simulate microbial growth under dynamic conditions in Microsoft Excel. As expected, the results obtained were the same as those from solving the coupled differential equations using a MATLAB Solver. In addition, model parameters were accurately identified by fitting the explicit equation to simulated growth curves under dynamic (time-varying) temperature conditions using the Microsoft Excel Solver. Copyright © 2015. Published by Elsevier B.V.
... AEO and NEO have bactericidal properties and have been reported to produce significant reductions of bacteria including Salmonella, Listeria monocytogenes, Escherichia coli O157:H7, and other pathogens (Kim & Hung, 2012;Posada-Izquierdo et al., 2014;Rodriguez-Garcia, Gonzalez-Romero, & Fernandez-Escartin, 2011;Zeng et al., 2010). AEO has been reported to be used to reduce hepatitis B virus, herpes simplex viruses, human norovirus surrogates and avian influenza viruses in suspension and on carriers (Park, Boston, Kase, Sampson, & Sobsey, 2007;Tagawa et al., 2000;Tamaki, Bui, Ngo, Ogawa, & Imai, 2014;Tanaka et al., 1999). ...
... However, for lower temperatures, anaerobic conditions were found after 6 and 15 days for 13 and 8 C, respectively. Posada Izquierdo et al., 2014 E. coli O157:H7 cocktail Iceberg lettuce, cucumber and carrots ...
Article
This review provides an overview of the effect of modified atmosphere packaging (MAP) on the survival and growth of foodborne pathogens on fresh-cut fruits and vegetables. Substantial technological advances have been made in this area, mainly in improving the quality and shelf-life of minimally processed products. Nevertheless, attention must be paid on the survival and growth of pathogenic microorganisms that may be present in fruits and vegetables. Modified atmosphere packaging (MAP) in combination with refrigeration temperatures could be used as a mild preservation technique for safety of minimally processed fruits and vegetables. However, the effect of MAP on microorganisms can vary, depending mainly on the storage conditions and the type of packaged product.
... Oxidizing agents loss is significantly reduced at pH values 6e9 which extends its stability during storage (Aider et al., 2012;Cui, Shang, Shi, Xin, & Cao, 2009). Due to its antimicrobial efficacy, NEW has been successfully used as a sanitizer on fresh foods (Hao, Li, Wan, & Liu, 2015;Posada-Izquierdo et al., 2014). A low redox potential (À750 mV) is characteristic of alkaline electrolyzed water (AEW) that, in addition, shows an excess of hydroxyl ions that can participate in the formation of more symmetric and weak hydrogen bonds (O/H/O) -. ...
Article
Full-text available
In the dairy industry, cleaning and disinfection of surfaces are important issues and development of innovative strategies may improve food safety. This study was aimed to optimize the combined effect of alkaline electrolyzed water (AEW) and neutral electrolyzed water (NEW) as alternative cleaning and disinfection procedure on stainless steel plates (SSP) with and without electropolishing. NEW at 10 ppm total available chlorine (TAC), achieved a [U+02C3]5 log CFU/mL reduction of milk spoilage bacterial suspension, grown in trypticase soy broth (8.7 log CFU/mL of each bacterial strain: Pseudomonas aeruginosa, Enterococcus faecalis and Micrococcus luteus) contacted for 30 s. An optimal design of experiments was used to assess the combined effect of cleaning with AEW, followed by disinfection with NEW (40 ppm TAC, contact time 3 min). Tested factors were contact time (10, 20 and 30 min), concentration of AEW (100, 200 and 300 mg NaOH/L), temperature (30, 40 and 50 °C), and surface type (304-2B SSP with or without electropolishing), using sixteen treatments with two replicates. The response variable was bacterial cells removal (log CFU/cm2). All main effects, two factors interactions and a quadratic term significantly influenced cells removal, and were modeled using a second order polynomial. Best cleaning procedures were significantly affected by surface roughness; electropolished SSP required 10 min, 100 mg/L AEW at 30 °C, whereas SSP without modification required 30 min, 300 mg/L AEW at 30 °C. From confirmatory tests cells removed were 3.90 ± 0.25 log CFU/cm2 for electropolished SSP, and 3.20 ± 0.20 log CFU/cm2 for SSP without modification. NEW is non-corrosive, and can be advantageously used for environmentally friendly cleaning and disinfection processes.
... Many studies have demonstrated that both AEW and SAEW have a strong ability to kill pathogens on fresh farm produce and seafood (Huang et al. 2008;Posada-Izquierdo et al. 2014;Wang et al. 2014b). Meanwhile, the disinfection efficacy of AEW and SAEW against pure microbial strains, including S. enteritidis, L. monocytogenes, B. Cereus, and E. coli O157:H7, has been demonstrated and reported widely (Chuang et al. 2013;Jadeja and Hung 2014;McCarthy and Burkhardt 2012). ...
Article
Full-text available
In the present study, the disinfection efficacy of slightly acidic electrolyzed water (SAEW) and strongly acidic electrolyzed water (AEW) was tested on three bacteria, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis and the disinfection mechanism was discussed. The results showed that SAEW had a stronger antibacterial efficacy against these tested bacteria in comparison with AEW. The results also showed that both SAEW and AEW treatments could damage the cell membrane, which was demonstrated microcosmically by scanning electron microscopy (SEM), thus causing leakages of protein, DNA, RNA, and ATP, resulting in the death of microbes. Moreover, AEW treatment could not cause the degradations of DNA and RNA, and nucleic acids including DNA and RNA are not the target point of its bactericidal efficacy. However, SAEW could maybe cause the degradation of RNA, and RNA may be the target in its antibacterial activity. We suggested that the differences in antibacterial efficacy between SAEW and AEW could be explained by the different impacts on RNA of tested strains.
... Most of the available literature regarding the use of sanitizers during RTE production, such as chlorine, has concluded that washing with water or with disinfectant solutions reduces the natural microbial populations on the surface of the product by only 2 to 3 log units (Allende et al., 2007;Beuchat et al., 2004;Gómez-López et al., 2007;Gonzalez et al., 2004;Inatsu et al., 2005;Selma et al., 2008;Ukuku et al., 2005) and it has been reported that current industrial sanitizing treatments do not guarantee the total elimination of pathogens when present (Abadias et al., 2008;Beuchat, 1996;Parish et al., 2003;Pérez-Rodríguez et al., 2011;Posada-Izquierdo et al., 2014). ...
Article
Fresh vegetables and their ready-to-eat (RTE) salads have become increasingly recognized as potential vehicles for foodborne diseases. The EU Reg. 1441/2007 establishes microbiological criteria for bacterial pathogens for products placed on the market during their shelf-life (i.e. Salmonella spp., Listeria monocytogenes) for pre-cut fruits and vegetables (RTE) whilst it does not address the problem of contamination by enteric viruses. In this study we investigated the contamination by hepatitis A virus (HAV), hepatitis E virus (HEV) and norovirus (NoV) in 911 ready-to-eat vegetable samples taken from products at retail in Apulia and in Lombardia. The vegetable samples were tested using validated real-time PCR (RT-qPCR) assays, ISO standardized virological methods and ISO culturing methods for bacteriological analysis. The total prevalence of HAV and HEV was 1.9% (18/911) and 0.6% (6/911), respectively. None of the samples analysed in this study was positive for NoV, Salmonella spp. or Listeria monocytogenes. The detection of HAV and HEV in RTE salads highlights a risk to consumers and the need to improve production hygiene. Appropriate implementation of hygiene procedures is required at all the steps of the RTE vegetable production chain and this should include monitoring of emerging viral pathogens.
... There are several methods to produce NEW. In general, NEW is produced by mixing catholyte with EW to increase the pH of EW ( Monnin, Lee, & Pascall, 2012;Posada-Izquierdo et al., 2014;Zhao, Zhang, & Yang, 2017). Another method involves using three tubs with two-membrane partitions and four sheets of electrodes in the electrolytic cells ( Umimoto et al., 2013). ...
Article
The aim of this study was to develop and evaluate the characteristics and performance of a portable electrolytic sanitising unit. Free available chlorine (FAC), oxidation-reduction potential, and pH of elec-trolysed water were measured. Response surface methodology coupled with a Box-Behnken design was used to describe the input-output relationship and optimise FAC production. A partial catholyte solution was reintroduced to electrolysis for generating neutral electrolysed water. The result found that RuO 2-IrO 2 /TiO 2 electrode was very effective. A FAC concentration of 4 mg/L achieved >2 log CFU/mL reduction, while a FAC concentration of 40 mg/L achieved >6 log CFU/mL reduction in Escherichia coli O157:H7 and Listeria monocytogenes BAA-839. The developed sanitiser had a pH of 7.08 ± 0.08, and the commercial sanitiser had a pH of 3.77 ± 0.18. The developed sanitiser had similar bactericidal effects as the commercial sanitiser. The results revealed that the developed sanitising unit is promising for the control of foodborne pathogens.
... Similarly, neutral EOW treatment (306 ppm free Cl) of romaine lettuce reduced inoculated E. coli O157:H7, S. typhimurium, and L. monocytogenes loads by 2.0 log CFU g −1 [67]. E. coli O157:H7 grew slower in FC lettuce treated with NEW (50 ppm free Cl) during storage at 13-16℃, while no microbial growth was observed if the product was stored at ≤8℃ [68]. ...
Chapter
Full-text available
The current high demand of minimally processed or fresh-cut fruit and vegetables results from the consumer’s desire for healthy, convenient, fresh, and ready-to-eat plant food-derived commodities. Fresh-cut fruits and vegetables are usually packaged under active- or passive-modified atmosphere packaging, while its shelf life must be under refrigerated conditions. The most important goal to preserve quality and safety focuses on releasing the microbial spoilage flora, since every unit operation involved will influence the final load. Sanitation in the washing step is the only unit operation able to reduce microbial load throughout the production chain. Chlorine is widely used as an efficient sanitation agent, but some disadvantages force to find eco-friendly emerging alternatives. It is necessary to deal with aspects related to sustainability because it could positively contribute to the net carbon balance besides reducing its use. Several innovative techniques seem to reach that target. However, industrial changes for replacing conventional techniques request a fine knowledge of the benefits and restrictions as well as a practical outlook. This chapter reviews the principles of emerging eco-friendly techniques for preserving quality and safety of fresh-cut products in order to meet the expected market’s demand.
... Various growth studies employing primary modeling have been conducted for several foodborne pathogens in meat (33,34,42,43,51,(54)(55)(56)63), seafood (31,32,38,52,67), and dairy (10,23,44,58,61,62,75) products. However, not much is known about their growth in produce (17,21,29,30,50,57,60,74). In recent years, growth kinetics and predictive models have been derived for L. monocytogenes on whole and cut produce, including cantaloupe (17,21,30), leafy greens (16,36,37,60,76), celery (74), and olives (2). ...
Article
Full-text available
Cut produce continues to constitute a significant portion of the fresh fruit and vegetables sold directly to consumers. As such, the safety of these items during storage, handling, and display remains a concern. Cut tomatoes, cut leafy greens, and cut melons, which have been studied in relation to their ability to support pathogen growth, have been specifically identified as needing temperature control for safety. Data are needed on the growth behavior of foodborne pathogens in other types of cut produce items that are commonly offered for retail purchase and are potentially held without temperature control. This study assessed the survival and growth of Listeria monocytogenes in cut produce items that are commonly offered for retail purchase, specifically broccoli, green and red bell peppers, yellow onions, canned green and black olives, fresh green olives, cantaloupe flesh and rind, avocado pulp, cucumbers, and button mushrooms. The survival of L. monocytogenes strains representing serotypes 1/2a, 1/2b, and 4b was determined on the cut produce items for each strain individually at 5, 10, and 25°C for up to 720 h. The modified Baranyi model was used to determine the growth kinetics (the maximum growth rates and maximum population increases) in the L. monocytogenes populations. The products that supported the most rapid growth of L. monocytogenes, considering the fastest growth and resulting population levels, were cantaloupe flesh and avocado pulp. When stored at 25°C, the maximum growth rates for these products were 0.093 to 0.138 log CFU/g/h and 0.130 to 0.193 log CFU/g/h, respectively, depending on the strain. Green olives and broccoli did not support growth at any temperature. These results can be used to inform discussions surrounding whether specific time and temperature storage conditions should be recommended for additional cut produce items.
... MAP is a technology that alters the atmosphere within the package according to the interaction between the product respiration rate and the transfer of gases through the package [19]. These technologies have been successfully applied to whole and fresh-cut products such as artichokes [20], lettuce [21], strawberry [22,23], persimmon [17], cucumber [24], and water bamboo shoots [16]. To our knowledge, this is the first report on water bamboo shoots demonstrating that the combination of NO and MAP can delay softness and weight loss and enhance postharvest quality (Figures 1 and 2). ...
Article
Full-text available
Harvested water bamboo shoots can be stored for only a few days before they lose weight and become soft. Nitrogen oxide (NO) and modified atmosphere packaging (MAP) have previously been used to prolong horticultural crop storage. In the present study, we analyzed the joint effect of these two methods on extending the postharvest quality of water bamboo shoots. Water bamboo shoots were treated with (1) 30 μL L−1 NO, (2) MAP, and (3) a combination of NO and MAP. The NO treatment delayed the softness and weight loss through maintaining the integrity of the mitochondrial ultrastructure and enhancing the ATP level by activating the expressions and activities of succinic dehydrogenase, malic acid dehydrogenase, and cytochrome oxidase. MAP improved the effect of NO on the mitochondrial energy metabolism. These results indicate that NO and MAP treatments are effective at suppressing the quality deterioration of water bamboo shoots, MAP improves the effect of NO in extending postharvest life, and NO may be the main effective factor in the combination of NO and MAP.
... Contamination sources may come from the field by direct contact with animal waste, irrigated water, and inadequately treated manure (Johannessen et al., 2005). Further, fresh cut products are prone to contamination because the current industrial sanitizing treatments do not guarantee the total elimination of the pathogen when present (Beuchat, 1996;Parish et al., 2003;Abadias et al., 2008, Pérez-Rodríguez et al., 2011Posada-Izquierdo et al., 2014). ...
... 3 Electrolyzed water (EW) has a variety of applications; from disinfection to improving digestive functions and enhancing the quality of agricultural products in the food industry. [4][5][6] EW is prepared by electrolysis of tap water by ionizer machines. Depending on the electrolysis process conditions, five types of EW are produced, namely basic (pH: [10][11][12], mildly basic (pH: 8-10), neutral (pH: 6.5-7.5), ...
Article
Background: Microbial plaque-induced oral diseases are among the most common diseases worldwide. The present study aimed to compare the antimicrobial effect of electrolyzed water (EW), (acidic, mildly basic, and basic) on the growth of bacterial species producing dental plaque and to assess their cytotoxicity on fibroblasts and epithelial cells. Methods: The study was performed at Shahid Beheshti University of Medical Sciences in 2019. Several bacterial species (Streptococcus salivarius, Staphylococcus aureus, Lactobacillus casei, and Aggregatibacter actinomycetemcomitans) were treated with different EW types at three pH values (3, 9, and 11) for 30 seconds and subsequently, the colonies were counted. The cytotoxic effect of these EW types was evaluated on HeLa and L929 cell lines at 30 seconds, 1 minute, and 5 minutes. GraphPad Prism 6.0 was used for statistical analysis. The Kruskal-Wallis test followed by Mann-Whitney U and one-way analysis of variance followed by Tukey's test were used to analyze bacterial activity and cell cytotoxicity, respectively. P<0.05 was considered statistically significant. Results: EW types significantly inhibited bacterial growth at all pH values. The strongest antibacterial activity of EW was against A. actinomycetemcomitans (P<0.001) and the least significant antibacterial activity was against S. aureus (P<0.001). The EW types showed increased cytotoxic activity against L929 cells as the treatment time increased. The most cytotoxic effect was seen at 5 minutes of treatment in all EW types compared with the negative control group (P<0.0001). This negative cytotoxic effect on HeLa cells was shown just after 30 seconds and viable cell counts increased over time, reaching its highest value at 5 minutes of treatment with basic EW (P<0.0001). Conclusion: The contradictory effects of the EW types on both HeLa and fibroblasts, in addition to variable results at different exposure times, indicated that the effect of EW could vary depending on cell types and treatment periods.
... They also represent a bacterial growth substrate in their own right that could arise during the postharvest production process, e.g., from cut surfaces. A number of studies have shown the growth of foodborne bacteria on plant extracts during the production process (33)(34)(35), and the growth potential for E. coli O157:H7 has been evaluated in water (31). Here, maximum growth rates in plant extracts were strongly influenced by the plant tissue type and species, as well as the E. coli isolate tested, and were overlaid by temperature-dependent effects. ...
Article
Fresh produce is an important vehicle for STEC transmission, and experimental evidence shows that STEC can colonize plants as secondary hosts, but differences in the capacity to colonize occur between different plant species and tissues. Therefore, an understanding of the impact that these plant factors have on the ability of STEC to grow and establish is required for food safety considerations and risk assessment. Here, we determined whether growth and the ability of STEC to form biofilms in plant extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonize living plants. Growth rates for sprouted seeds (alfalfa and fenugreek) but not those for leafy vegetables (lettuce and spinach) exhibited a positive relationship between plant extracts and living plants. Therefore, the detailed variations at the level of the bacterial isolate, plant species, and tissue type all need to be considered in risk assessment.
... Then, secondary model is fitted to the primary model parameters to determine the dependence of those parameters to changes in environmental conditions (Longhi et al., 2013(Longhi et al., , 2018. Some papers have studied the modelling of microbial growth in refrigerated fresh fish, beef, and fresh-cut lettuce packed under MAP (Dalgaard, 1995;Dalgaard, Mejlholm, & Huss, 1997;Giannuzzi, Pinotti, & Zaritzky, 1998;Posada-Izquierdo et al., 2014). No study so far has explored the mathematical modeling of growth parameters of spoilage microorganism in MF cheese packed under MAP. ...
Article
The purpose of this study was to evaluate and model the growth of psychrotrophs and lactic acid bacteria in Minas Frescal (MF) cheese packed under modified atmosphere (vacuum, 20% CO2/40% N2, 40% CO2/60% N2, and 60% CO2/40% N2) and stored at 7°C for 21 days. Results indicate that psychrotrophs and lactic acid bacteria growth were declined as CO2 concentration increase in the packaging. Primary mathematical models were able to predict microbial growth in MF cheese under different modified atmosphere packaging (MAP). The maximum specific growth rate of psychrotrophs and lactic acid bacteria was reduced in approximately 55 and 60%, respectively, using 60% CO2/40% N2 MAP (compared with cheese packed under vacuum). Results from the secondary mathematical model suggest that the sensitivity to CO2 in psychrotrophs and lactic acid bacteria was similar. This research reports new information about the impact of MAP on the microbial growth in MF cheese. Practical applications This study could successfully be utilized to control the microbial growth of MF cheese. The modified atmosphere packaging used in this research can be scaled up for commercial manufacturing. High CO2 level (60% CO2/40% N2 MAP) have a similar effect on psychrotrophs and lactic acid bacteria in MF cheese. Exploring the effect on MAP on microbiological growth in MF cheese is important to manufacture the products with consistent quality on industrial scale.
Article
Aims: The objective of this work was to study the growth potential of E. coli O157:H7 and Salmonella spp. in leafy vegetable extracts at different temperature conditions. Methods and results: Cocktails of five strains of E. coli O157: H7 and of S. enterica were used. Inoculated aqueous vegetable extracts were incubated at 8, 10, 16 and 20°C during 21 days. Microbial growth was monitored using Bioscreen C(®) . In spinach extract, results showed that for E. coli O157:H7 and Salmonella significant differences (p<0.05) for μabs (maximum absorbance rate) were obtained. For both pathogens, growth in chard was slightly lower. In contrast, iceberg lettuce and parsley showed the lowest values of μabs , below 0.008 h(-1) . The coefficients of variance (CoV) calculated for the different replicates evidenced that at low temperature (8 °C) a more variable behaviour of both pathogens is expected (CoV > 180%). Conclusions: This study provides evidence that aqueous extracts from vegetable tissues can result in distinct growth niche producing different response in various types of vegetables. Significance and impact of study: Finally, these results can be used as basis to establish risk rankings of pathogens and leafy vegetable matrices with relation to their potential growth. This article is protected by copyright. All rights reserved.
Article
The effects of peroxyacetic acid (PA), neutral electrolysed water (NEW), ultraviolet C light (UV-C) and superatmospheric O2 packaging (HO), single or combined, on the growth rate of Escherichia coli and S. Enteritidis inoculated onto fresh-cut kailan-hybrid broccoli were studied throughout 14 days of shelf life at 5 and 10 °C. As controls, unwashed, water-washed and NaClO-washed were used. PA and NEW showed a better sanitising effect than NaClO against both E. coli/S. Enteritidis with reductions of 2.2/2.7 and 2.6/2.6 log CFU g−1, respectively. UV-C attained E. coli/S. Enteritidis decreases of 1.3–1.4/2.1–2.2 log CFU g−1 compared to unwashed samples. The bacteriostatic effects of PA or NEW were improved when they were combined with UV-C, decreasing E. coli and S. Enteritidis counts by about 3 log CFU g−1. After 14 days, PA and NEW-treated samples attained E. coli/S. Enteritidis reductions at 5 °C of 2.3/1.4 and about 1 log CFU g−1, respectively. Storage of those samples at 10 °C masked that sanitising effect. At both storage temperatures, UV-C-treated samples registered lower E. coli and S. Enteritidis reductions (or higher increases for S. Enteritidis at 10 °C) regarding conventional NaClO-sanitized samples or other single treatments. However, PA, NEW or UV-C-treated samples under HO at both storage temperatures showed better bacterial control than individual treatments with the greatest effectiveness for UV-C + HO. Triple combination did not imply an enhanced benefit over double combinations. Conclusively, PA, NEW and UV-C seems to be effective emergent alternatives to NaClO to reduce initial E. coli and S. Enteritidis populations in fresh-cut kailan-hybrid broccoli. Storage at 5 or 10 °C under HO greatly controlled microbial growth.
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The combined effects of ultrasonication and slight acidic electrolyzed water were investigated to improve the microbial safety of brown rice against Bacillus cereus infection and to evaluate the growth kinetics of these bacteria during storage of untreated and treated rice at various temperatures (5, 10, 15, 20, 25, 30, and 35°C). The results indicate that this combination treatment was bactericidal against B. cereus, resulting in an approximately 3.29-log reduction. Although B. cereus can be efficiently reduced by treatment, temperature abuse during storage can allow B. cereus to recover and grow. A primary growth model (Baranyi and Roberts equation) was fitted to the raw growth data from untreated (control) and treated samples to estimate growth rate, lag time, and maximum population density, with a low standard error of the residuals (≤0.140) and high adjusted coefficient of determination (>0.990). The growth curves obtained from the Baranyi and Roberts model indicated that B. cereus grew more slowly on treated brown rice than on untreated brown rice. Secondary models predicting the square root of the maximum growth rate and the natural logarithm of the lag time as a function of temperature were satisfactory (bias factor = 0.993 to 1.013; accuracy factor = 1.290 to 1.352; standard error of prediction = 18.828 to 36.615%). Inactivation results and the model developed and validated in this study provided reliable and valuable growth kinetics information for quantitative microbiological risk assessment studies of B. cereus on brown rice.
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In the present paper, the chemical composition of Helichrysum italicum oil was analyzed by gas chromatography–mass spectrometry (GC-MS). Neryl acetate (32.65%) was the main component. The minimum inhibitory concentration and minimum bactericidal concentration of H. italicum oil against several bacteria were evaluated. The results showed that H. italicum oil exhibited high antibacterial activity against all of the bacteria tested. In addition, H. italicum oil also displayed a significant effect on inhibiting the growth rate of surviving Escherichia coli and Staphylococcus aureus in vitro and on vegetables. Meanwhile, addition of H. italicum oil to vegetable exerted a bacteriostatic effect. Besides, the mechanisms of the antimicrobial action of H. italicum oil to E. coli and S. aureus were concluded as that H. italicum oil could disrupt the cell membrane integrity, leading to the losses of intracellular constituents, such as the 260 nm absorbing materials, DNA and ATP.Practical ApplicationsAs a kind of natural, safe spice, Helichrysum italicum oil has been proven to be a good antibacterial agent against a wide range of bacteria at a low concentration and short incubation time. Especially, H. italicum oil exhibits a significant bacteriostatic effect in vegetables. Based on the results, we believe that H. italicum oil can be applied in vegetable processing and preservation.
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This study was aimed to evaluate the efficiency of the organic chlorine and acetic acid solutions on removing of adhered cells of Escherichia coli, Cronobacter sakazakii and Klebsiella pneumoniae to lettuce. Besides, the growth and inactivation of K. pneumoniae adhered to lettuce was modeled. According to the findings, with using of chlorine solution was used (170 mg/mL of total residual chlorine), a reduction of 1.8, 1.9, and 1.9 log for E. coli, C. sakazakii, and K pneumoniae, respectively, were recorded. In this regard, the organic chloramine was more effective in controlling the adhered microorganisms while compared with 1.5% acetic acid solution, while the addition of 0.5% sodium chloride to 1.5% acetic acid solution increased microbial inactivation. K. pneumoniae RC-34 inactivation was characterized by the presence of two sub-populations with different resistances against the proposed sanitizers. Moreover, the growth kinetic parameters of K. pneumoniae RC-34 adhered to lettuce leaves were very similar to that reported in the literature for non-adhered microorganisms. The predictive data generated can be valuable to assess the growth and inactivation of produce adhered microorganisms in leafy produce.
Article
This study was conducted to develop predictive models for the growth of Bacillus cereus on carrot treated with slightly acidic electrolyzed water (SAcEW) and ultrasonication (US) at different storage temperatures. In addition, the inactivation of B. cereus by US with SAcEW was investigated. US treatment with a frequency of 40 kHz and an acoustic energy density of 400 W/L at 40°C for 3 min showed the maximum reduction of 2.87 log CFU/g B. cereus on carrot, while combined treatment of US (400 W/L, 40°C, 3 min) with SAcEW reached to 3.1 log CFU/g reduction. Growth data of B. cereus on carrot treated with SAcEW and US at different temperatures (4, 10, 15, 20, 25, 30, and 35°C) were collected and used to develop predictive models. The modified Gompertz model was found to be more suitable to describe the growth data. The specific growth rate (SGR) and lag time (LT) obtained from the modified Gompertz model were employed to establish the secondary models. The newly developed secondary models were validated using the root mean square error, bias factor, and accuracy factor. All results of these factors were in the acceptable range of values. After compared SGR and LT of B. cereus on carrot, the results showed that the growth of B. cereus on carrot treated with SAcEW and US was slower than that of single treatment. This result indicates that shelf life of carrot treated with SAcEW and US could be extended. The developed predictive models might also be used to assess the microbiological risk of B. cereus infection in carrot treated with SAcEW and US.
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Bacteria treated with chlorine-based sanitizer could enter into viable but non-culturable (VBNC) state, which may be underestimated its health risk. In this study, E. coli O157: H7 was treated with slightly acidic electrolyzed water (SAEW), acidic electrolyzed water (AEW) and sodium hypochlorite with different available chlorine concentrations (ACC). The reduction of population was determined, as well as the status of treated cells (viable and culturable, VBNC, dead) was assayed using flow cytometry combined with plate counting. Finally, the cell which cannot be detected using routine media was cultured in p-TSB to resuscitate. The results showed that the reduction of E. coli O157: H7 increased with increasing ACC of SAEW, AEW and sodium hypochlorite and the antimicrobial effect of electrolyzed oxidizing (EO) waters was much higher than sodium hypochlorite. SAEW, AEW and sodium hypochlorite with ACC of 30, 20 and 60 mg/L achieved E. coli O157: H7 colonies to non-detectable level on solid media. The results obtained from flow cytometric assay indicated that culturable cells after EO water and sodium hypochlorite treatments with increasing ACC firstly enter VBNC state and then transferred to dead status. VBNC E.coli was able to be resuscitated in p-TSB and therefore regarded as a potential risk for human health. E. coli O157: H7 in VBNC state after EO water treatment should be taken into consideration and complete inactivation could be achieved by elevated chlorine concentration.
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Outbreaks of foodborne illnesses related to the consumption of fresh produce have been occurring all over the world. Quantitative microbial risk assessment (QMRA) for fresh produce will contribute to enhance microbiological safety of production, distribution, and consumption of fresh produce. This chapter describes the prevalence of contamination of fresh produce, possible route of pathogen contamination, and pathogen behavior on fresh produce during distribution. Predictive models and also web-based predictive tools described here will be useful for QMRA as an underpinning knowledge.
Chapter
In an effort to eat healthfully, consumers have increased their consumption of fruits and vegetables over the past three decades only to find that produce, in spite of its minimal processing and perishability is now almost as frequently implicated as a vehicle of foodborne illness as food of animal origin. It is apparent that produce can be easily contaminated by bacteria, viruses or parasites at any of the many steps from farm to table including: the growing environment (soil, water, fertilizer, agri-chemicals); by workers using poor hygiene; by contact with equipment used in production, harvesting, processing and transportation, as well as at wholesale and retail sale. Salmonella spp. (lettuce, melons, spinach, tomatoes, seed sprouts and spices) and Escherichia coli O157:H7 (lettuce and spinach) are the leading pathogens associated with foodborne illnesses linked to fresh produce, but Listeria (L.) monocytogenes (cantaloupe) and non-O157 Shiga-toxigenic (STEC) E. coli (sprouts) have been implicated in recent deadly outbreaks. Post-harvest washing of fresh produce with chlorine is widely used for sanitizing, but its efficacy is inadequate and its disadvantages are such that alternative disinfection methods including chemical or natural antimicrobial solutions and physical methods are being examined.
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Contamination of fresh produce with pathogenic Escherichia coli, including Shigatoxigenic E. coli (STEC), represents a serious risk to human health. Colonisation is governed by multiple bacterial and plant factors that can impact on the probability and suitability of bacterial growth. Thus, we aimed to determine whether the growth potential of STEC for plants associated with foodborne outbreaks (two leafy vegetables and two sprouted seed species), is predictive for colonisation of living plants as assessed from growth kinetics and biofilm formation in plant extracts. Fitness of STEC was compared to environmental E. coli , at temperatures relevant to plant growth. Growth kinetics in plant extracts varied in a plant-dependent and isolate-dependent manner for all isolates, with spinach leaf lysates supporting the fastest rates of growth. Spinach extracts also supported the highest levels of biofilm formation. Saccharides were identified as the major driver of bacterial growth, although no single metabolite could be correlated with growth kinetics. The highest level of in planta colonisation occurred on alfalfa sprouts, though internalisation was 10-times more prevalent in the leafy vegetables than in sprouted seeds. Marked differences in in planta growth meant that growth potential could only be inferred for STEC for sprouted seeds. In contrast, biofilm formation in extracts related to spinach colonisation. Overall, the capacity of E. coli to colonise, grow and internalise within plants or plant-derived matrices were influenced by the isolate type, plant species, plant tissue type and temperature, complicating any straight-forward relationship between in vitro and in planta behaviours. Importance Fresh produce is an important vehicle for STEC transmission and experimental evidence shows that STEC can colonise plants as secondary hosts, but differences in the capacity to colonise occur between different plant species and tissues. Therefore, an understanding of the impact of these plant factors have on the ability of STEC to grow and establish is required for food safety considerations and risk assessment. Here, we determined whether growth and the ability of STEC to form biofilms in plants extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonise living plants. Growth rates for sprouted seeds (alfalfa and fenugreek) exhibited a positive relationship between plant extracts and living plants, but not for leafy vegetables (lettuce and spinach). Therefore, the detailed variations at the level of the bacterial isolate, plant species and tissue type all need to be considered in risk assessment.
Article
In the recent years food safety has become a target for the fresh-cut industry. Several outbreaks of foodborne illness caused by pathogens as Escherichia coli and Salmonella spp., among other enteric pathogens, have been widely reported in fruits and vegetables. Chlorine is the most widely used sanitizing agent for reducing pathogens on whole and fresh-cut produce, although it has some disadvantages that have led to research on new alternatives. The present work studied the single and combined effects of neutral electrolyzed water (NEW) in the washing step (ORP = 900 mV, 5°C, pH = 7, contact time = 2 min), UV-C irradiation (6 kJ m⁻²) before packaging and high oxygen active modified atmosphere packaging (HO) (>50 kPa O2 + 10⁻¹5 kPa CO2) on Bimi® broccoli (Brassica oleracea Italica Group × Alboglabra Group) inoculated with 6.1 and 5.2 cfu g⁻¹ of E. Coli and Salmonella respectively. These treatments were compare with conventional NaOCl washing (100 mg L⁻¹, 5°C, pH = 6.5, contact time = 2 min). Inoculated samples were packed, after treatment, into polypropylene baskets under MAP conditions and were stored in darkness throughout 14 days at 5 and 10°C. Among single treatments, NEW was more effective than UV-C irradiation and HO, with a reduction of 49 and 45% for E. Coli and S. enteritidis respectively. However the triple combination (NEW+UV-C+HO) was even more effective with a reduction of 56 and 49% for E. Coli and S. enteritidis respectively. Generally, when stored at 5°C both pathogens counts decreased greater than at 10°C, where S. enteritidis growth was detected. As main conclusion, washing with selected NEW and a subsequent 6 kJ m⁻² UV-C treatment before packaging under high O2 conditions seems to be a promising sanitising treatment to reduce E. Coli and S. enteritidis counts in fresh-cut Bimi® broccoli. © 2018 International Society for Horticultural Science. All rights reserved.
Chapter
This chapter reviews various aspects of fresh-cut vegetables, including sensory, physiological, microbial, and manufacturing details. To obtain fresh-cut vegetables, the basic premise is minimal processing to retain fresh like texture, color, and flavor, and safe-to-use quality. This chapter illustrates the normal processing steps for fresh-cut vegetables. Wounding or injury associated with processing and handling fresh-cut vegetables can cause physiological changes, which influence ethylene production, respiration rate, discoloration, deterioration of texture, and water loss. Good manufacturing practice (GMP) and Hazard Analysis and Critical Control Points (HACCP) based production and handling, and proper documentations related to sourcing, processing, quality checking, packaging, and storage are important to ensure the safety and traceability of fresh-cut vegetables. There are many physical methods that have been researched to reduce the microbial load in fresh-cut vegetables, including modified atmosphere packaging (MAP), ultraviolet (UV) light, irradiation, high-pressure processing, and ultrasonics. Among these techniques, MAP has been widely used commercially.
Chapter
In minimally processed fruits and vegetables (MPFV) the exposure of internal tissues, the lack of skin or cuticle and the accelerated metabolism after processing lead to deterioration of sensory attributes mainly due to biochemical processes, physiological ageing and microbial spoilage. Therefore, processing operations such as peeling, slicing or shredding make MPFV more perishable than intact fresh produce. Shelf life of these products is not homogenous and can greatly vary mainly due to differences in manufacturing processes to which they are subjected. Reliable techniques that allow determining shelf life in an effective and precise way are necessary, as small changes in shelf life determinations could represent big economic losses. The shelf life of MPFV is usually determined by means of methods that evaluate changes in organoleptic characteristics during the distribution chain. Hence, it is essential to understand the processes influencing changes in MPFV quality as well as treatments and management techniques that are applied to evaluate and monitor their quality. Innovative techniques that allow modelling the influence of different environmental conditions and processing operations on MPFV quality are being proposed as more objective techniques to determine shelf life. Within these innovative procedures, shelf life estimation by means of the use of predictive microbiology models is one of the most useful ones. The purpose of this chapter is to provide an overview on processes influencing quality changes of minimally processed fruits and vegetables as well as the available procedures and quantitative tools that are applied in shelf life determination.
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Introdução: Os norovírus (NoV) são importantes agentes causadores de gastroenterite de origem alimentar, com surtos associados ao consumo de frutas, vegetais folhosos, moluscos bivalves e alimentos de delicatessen. O aumento da importância epidemiológica destes vírus tem sido demonstrado pelo estabelecimento de redes laboratoriais de vigilância em diversos continentes. As infecções por NoV se tornaram mais conhecidas especialmente com a consolidação do mercado de navios de cruzeiros no país a partir de 2004. Objetivo: Este estudo tem como objetivo apresentar avanços relacionados à pesquisa de NoV em alimentos, destacando características deste patógeno e estratégias para sua detecção nestas matrizes. Método: Foi realizada uma revisão integrativa, pelo levantamento de artigos científicos com o objetivo de tratar dos principais aspectos de NoV. Resultados: Foi realizada uma ampla revisão da literatura, com a descrição dos principais resultados presentes na literatura consultada e a discussão de aspectos como doenças transmitidas por alimentos (DTA), vírus como contaminantes de alimentos, estabilidade e desinfecção, surtos de origem alimentar associados aos NoV, alimentos associados à contaminação por NoV, métodos de concentração e detecção de NoV em alimentos, estudos de avaliação de risco e prevenção e controle. Conclusões: Os registros de envolvimento de NoV em surtos de origem alimentar e a crescente diversidade genética destes vírus reforçam a necessidade de vigilância laboratorial e epidemiológica sobretudo nos países em desenvolvimento, como o Brasil. ============================================ Introduction: Noroviruses (NoV) are important causative agents of foodborne gastroenteritis outbreaks associated with the consumption of fruits, leafy vegetables, bivalve molluscs and delicatessen foods. The establishment of laboratory surveillance networks in different continents has demonstrated increased epidemiological importance of those viruses. In Brazil, the NoV infection is considered an important public health issue with socioeconomic burden, but the investigation of these viruses in foodborne outbreaks is still restricted to research laboratories. NoV infections have become more known especially with the consolidation of the cruise ship market in the country since 2004. Objective: This study aims to present advances related to NoV research in foods, highlighting features of this pathogen and strategies for its detection in these matrices. Method: An integrative review, collecting scientific articles with the objective of dealing with the main aspects of NoV, was carried out. Results: A broad literature review was performed, describing the main results in the literature and discussing aspects such as foodborne diseases, viruses as food contaminants, stability and disinfection, foodborne outbreaks associated with NoV, food associated with NoV contamination, NoV concentration and detection methods in food, risk assessment studies and prevention and control. Conclusions: records of foodborne outbreaks associated with NoV and the increasing genetic diversity of these viruses reinforce the need for laboratory and epidemiological surveillance, especially in developing countries, such as Brazil.
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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.
Chapter
Microbiological safety of the fresh-cut produce may not be guaranteed if the quality of wash water is not maintained. Thus, the vegetable processing industry needs to develop alternative sustainable cleaning and disinfection methods in order to reduce cross-contamination and consumption of water throughout the washing process. To assure water quality, chemical and microbial parameters need to be measured based on standard analytical methods. New generation of analytical methods has also emerged to detect priority pollutants, as pharmaceutical compounds, or “emerging pathogens” with antibiotic-resistant genes. Conventional disinfection treatment of wastewaters as chlorination leads to the formation of undesired disinfection by-products and presents limited efficacy against some pathogens. Thus, a more effective and lower-energy demand technology as advanced oxidation processes (AOPs), capable of generating a high amount of hydroxyl radicals upon irradiation, may be considered as alternative. Successful application of solar AOPs has been reported at pilot plants. Predictive design of large-scale AOPs requires the conservation equations of momentum, energy, and mass. These photoactivated processes additionally require the calculation of the local volumetric rate of photon absorption in any position of the system. Quantitative risk assessment studies are required to assess the impact of AOPs as alternative sanitation process and way of enhancing water recycling, on the microbial risk of RTE vegetables. This method is based on four steps: hazard identification and characterization, exposure assessment, and risk characterization. Predictive microbiology models are necessary as not always experimental data are available.
Chapter
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.
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Microbial control of postharvest diseases has been extensively studied and appears to be a viable technology. Food safety must be ensured at each postharvest processing step, including handling, washing of raw materials, cleaning of utensils and pipelines, and packaging. Several commercial products are available for this purpose. The time is ripe for developing new techniques and technologies. The use of electrolyzed water (EW) is the product of a new concept developed in Japan, which is now gaining popularity in other countries. Little is known about the principle behind its sterilizing e#ect, but it has been shown to have significant bactericidal and virucidal and moderate fungicidal properties. Some studies have been carried out in Japan, China, and the USA on the pre-and postharvest application of EW in the field of food processing. EW may be produced using common salt and an apparatus connected to a power source. As the size of the machine is quite small, the water can be manufactured on-site. Studies have been carried out on the use of EW as a sanitizer for fruits, utensils, and cutting boards. It can also be used as a fungicide during postharvest processing of fruits and vegetables, and as a sanitizer for washing the carcasses of meat and poultry. It is cost-e#ective and environment-friendly. The use of EW is an emerging technology with considerable potential.
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The aim of this work was to investigate the disinfectant effect of electrolysis on chlorine-free water, artificially contaminated with Escherichia coli (CCT-1457) and to evaluate the bactericidal activity of electrolysis and kinetic behavior of a single-cell reactor, with a DSA (Dimensionally Stable Anode) electrode to develop a scaled-up system. A high-density E. coli suspension (10(6) CFU mL(-1)) was electrolyzed in this reactor at 25, 50 and 75 mA cm(-2) for up to 60 min, at flow rates of 200 and 500 L h(-1). Bacterial survival fell by 98.9% without addition of chlorinated compounds and a power consumption rate not more than 5.60 kWh m(-3) at flow rate of 200 L h(-1) and 75 mA cm(-2). The process produced a germicidal effect that reached this inactivation rate within a relatively short contact time. Also, a solution of electrolyzed 0.08 M Na2SO4 added to the inoculum showed residual bactericidal effect. The efficiency of disinfection was regulated by both the contact time and current density applied, and a kinetic function for the survival rate was developed for the purpose of scaling up.
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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.
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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.
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The effectiveness of calcium hypochlorite on inactivation of Escherichia coli inoculated on fresh produce was investigated. Different exposure times and concentrations of chlorine were studied. Dipping was not effective at eliminating E. coli populations although it significantly reduced the E. coli counts compared with inoculated, undipped lettuce. Dipping inoculated cos lettuce leaves into hypochlorite solutions containing 50 mg/l or greater free chlorine for times of 30 s or greater reduced E. coli cells by approximately 1.9–2.8 log10 CFU/g from an initial population of approximately 6.8 log10 CFU/g. Dipping inoculated broccoli florets into hypochlorite solution reduced E. coli cells by approximately 1.7–2.5 log10 CFU/g, depending on the time and concentration of the free chlorine. Dipping lettuce or broccoli in water alone reduced cell numbers by 1.5–1.8 log10 CFU/g. Dipping broccoli florets for 2 min in a 100 mg/l free chlorine solution at temperatures between 4 and 25°C reduced E. coli cells by approximately 2.4 log10 CFU/g. No significant effect of temperature on the rate of cell reduction was observed.
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Due to the limitations associated with the use of existing biocidal agents, there is a need to explore new methods of disinfection to help maintain effective bioburden control, especially within the healthcare environment. The transformation of low mineral salt solutions into an activated metastable state, by electrochemical unipolar action, produces a solution containing a variety of oxidants, including hypochlorous acid, free chlorine and free radicals, known to possess antimicrobial properties. Electrochemically activated solutions (ECAS) have been shown to have broad-spectrum antimicrobial activity, and have the potential to be widely adopted within the healthcare environment due to low-cost raw material requirements and ease of production (either remotely or in situ). Numerous studies have found ECAS to be highly efficacious, as both a novel environmental decontaminant and a topical treatment agent (with low accompanying toxicity), but they are still not in widespread use, particularly within the healthcare environment. This review provides an overview of the scientific evidence for the mode of action, antimicrobial spectrum and potential healthcare-related applications of ECAS, providing an insight into these novel yet seldom utilised biocides.
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The Institute of Food Technologists has issued this Scientific Status Summary to provide readers with a tutorial on biofilms, their purposeful mechanism of interaction (quorum sensing), and recent findings on how to inhibit their formation.
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The Arrhenius Law, which was originally proposed to describe the temperature dependence of the specific reaction rate constant in chemical reactions, does not adequately describe the effect of temperature on bacterial growth. Microbiologists have attempted to apply a modified version of this law to bacterial growth by replacing the reaction rate constant by the growth rate constant, but the modified law relationship fits data poorly, as graphs of the logarithm of the growth rate constant against reciprocal absolute temperature result in curves rather than straight lines. Instead, a linear relationship between in square root of growth rate constant (r) and temperature (T), namely, square root = b (T - T0), where b is the regression coefficient and T0 is a hypothetical temperature which is an intrinsic property of the organism, is proposed and found to apply to the growth of a wide range of bacteria. The relationship is also applicable to nucleotide breakdown and to the growth of yeast and molds.
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A new member of the family of growth models described by Baranyi et al. (1993a) is introduced in which the physiological state of the cells is represented by a single variable. The duration of lag is determined by the value of that variable at inoculation and by the post-inoculation environment. When the subculturing procedure is standardized, as occurs in laboratory experiments leading to models, the physiological state of the inoculum is relatively constant and independent of subsequent growth conditions. It is shown that, with cells with the same pre-inoculation history, the product of the lag parameter and the maximum specific growth rate is a simple transformation of the initial physiological state. An important consequence is that it is sufficient to estimate this constant product and to determine how the environmental factors define the specific growth rate without modelling the environment dependence of the lag separately. Assuming that the specific growth rate follows the environmental changes instantaneously, the new model can also describe the bacterial growth in an environment where the factors, such as temperature, pH and aw, change with time.
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This study investigates the resistance of Listeria monocytogenes biofilms on stainless steel surfaces to electrolyzed oxidizing (EO) water. A direct agar overlay method was used to estimate the attached bacteria on stainless steel coupons after an EO water treatment. A scraping method was also used to quantify the adherent cell populations after the EO water treatment. The stainless steel surface allowed 10 to 15% of the surface area to be covered by Listeria biofilm when the inoculated stainless steel coupon was incubated in 10% tryptic soy broth (TSB) at 23C for 48 h. When the stainless steel coupons containing adherent cells were treated with EO water (56 mg/L of residual chlorine) for 10, 30, 60, 180, and 300 s, adherent cell populations (10.3 log10 CFU/coupon) were reduced with increasing treatment time. Although the direct agar overlay methods do not quantify survival of single bacteria, only one to five cell clumps per coupon survived after 300 s of the EO water treatment. Using the scraping method, the adherent cell population on the stainless steel coupons was reduced by about 9 log cycles after 300 s of EO water treatment.
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Summary Demand for fresh, convenient, minimally processed vegetables has led to an increase in the quantity and variety of products available to the consumer. Modified atmosphere packaging, in combination with refrigeration, is increasingly being employed as a mild preservation technique to ensure quality and storage-life. The fresh nature of these products, together with the mild processing techniques and subsequent storage conditions, have presented indigenous and pathogenic microorganisms with new ecosystems and potential infection vehicles; a number of outbreaks of foodborne disease being attributed to their consumption. Psychrotrophic pathogens and pathogens which are capable of maintaining an infectious potential under mild preservation regimes are of particular concern; Listeria monocytogenes, Aeromonas hydrophila and Clostridium botulinum being amongst the most notable. This review describes the processing, packaging and storage procedures involved in the production of minimally processed vegetables, and details their impact upon the survival and growth of associated pathogens. Gaps in our current understanding of the consequences of this novel technology for microbiological safety are highlighted.
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Unlabelled: The effects of various sanitizers on the viability and cellular injury to structures of Escherichia coli and Listeria innocua were investigated. A food grade organic acidic formulation (pH 2.5) and acidic, neutral, and basic electrolyzed water [AEW (pH 2.7, oxidation reduction potential; ORP: 1100 mV, free available chlorine; FAC: 150 ppm), NEW (pH 6.9, ORP: 840 mV, FAC: 150 ppm), BEW (pH 11.6, ORP: -810 mV)] were used to treat E. coli and L. innocua cells. After 10 min of exposure to the sanitizers, changes to the bacterial numbers and cell structures were evaluated by plate counting and transmission electron microscopy (TEM), respectively. It was concluded from the results that the sanitizers reduced the E. coli cells between 2 and 3 log CFU/mL. Except for the BEW treatment, reductions in L. innocua population were greater (>1 log CFU/mL) than that of E. coli for all treatments. Data from the TEM showed that all sanitizers caused changes to the cell envelope and cytoplasm of both organisms. However, smaller changes were observed for L. innocua cells. Decrease in the integrity of the cell envelope and aggregation of the cytoplasmic components appeared to be mainly because of exposure to the sanitizers. The organic acid formulation and AEW were the most effective sanitizers against bacterial cells, indicating that penetration of acidic substances effectively caused the cell inactivation. Practical application: An understanding of the method in which E-water and an acidic sanitizer cause injury to E. coli and L. innocua would be helpful in selecting an effective chemical agent as a food safety tool. This will allow a scientist to target similar microorganisms such as food borne bacteria with structures that are vulnerable to the sanitizer.
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The effects of alternative decontamination processes to chlorine: ozonated-water (1 ppm/5 min), hot water (100 °C/45 s) and ultrasonication (45 kHz/1 min), applied pre- or post-cut in the technological diagram of minimal processing of carrots were tested. Ultrasonication in chlorinated-water and thermo-ultrasonication as combined processes applied just in pre-cut carrot were also tested. The initial microbial load reduction, soluble solids content, pH and sensorial attributes of shredded carrot just after processing were evaluated. Decontamination processes applied on pre-cut carrot provided maintenance of fresh-like sensorial quality, regardless the type of treatment, due to diminished leaching phenomena which is critical for shredded carrot. Chlorination, ozonization and ultrasonication achieved ca. 1 Log10 reduction of initial microbial load. No additional decontamination effect in combined processes was observed. The use of heat in pre-cut carrot proved to be the most efficient process regarding microbial reduction (3 Log10 units) providing, as well, an acceptable fresh-like quality product.Industrial relevanceThe major constraint for marketability of minimally processed shredded carrot is its limited shelf-life due to rapid microbial growth and colour loss (decrease of orange intensity and/or whitening of the shreds). These questions arise from the practical experience of a fresh-cut industry directly involved in the R&D research project which supported this study. Chlorine solutions have been widely used to sanitize fruit and vegetables in the fresh-cut industry. However, reduced microbiological efficiency allied to the eventual formation of carcinogenic chlorinated compounds pointed out the need for alternative methodologies. The present work aimed the evaluation of clean alternative decontamination processes applied both to pre- and post-cut carrot for the production of shredded carrot, operating under conditions of industrial practice at pilot-plant scale.
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In this study, chlorine dioxide (ClO2) was used as an alternative disinfection agent with humic acid as the organic precursor in a natural aquatic environment. The major topics in this investigation consisted of the disinfection efficiency of ClO2, the formation of disinfection by-products (DBPs), and the operating conditions. The results indicated that the pH value (pH 5–9) did not affect the efficiency of disinfection while the concentration of organic precursors did. The primary DBPs formed were trihalomethanes (THMs) and haloacetic acids (HAAs). The distribution of the individual species was a function of the bromide content. The higher the ClO2 dosage, the lower the amount of DBPs produced. The amount of DBPs increased with reaction time, with chlorite ions as the primary inorganic by-product.
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The minimal processing industry for fruit and vegetables needs appropriate selection of raw materials and operation of improved sustainable strategies for reducing losses and providing high quality and safe commodities. The most important target for keeping overall quality of these commodities is a decrease in microbial spoilage flora as these cause both decay and safety problems. Every step in the production chain will influence microbial load and the implementation of an accurate disinfection program should be the main concern of commercial processing. The only step that reduces microbial load throughout the production chain is washing disinfection, and the keys are proper handling and optimizing existing techniques or a combination of them. Chlorine is a common efficient sanitation agent but there is the risk of undesirable by-products upon reaction with organic matter and this may lead to new regulatory restrictions in the future. Moreover, its efficacy is poor for some products. Consequently the minimal processing industry wants safer alternatives. Several antimicrobial washing solutions, O3, UV–C radiation, intense light pulses, super high O2, N2O and noble gases, alone or in combination, are presently considered promising treatments. However, change from use of conventional to innovative sanitizers requires knowledge of the benefits and restrictions as well as a practical outlook. This review addresses some recent results obtained with these eco-innovative sanitizers on fresh-cut plant commodities.
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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.
Article
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.
Article
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.
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Escherichia coli O157:H7, an occasional contaminant of fresh produce, can present a serious health risk in minimally processed leafy green vegetables. A good predictive model is needed for Quantitative Risk Assessment (QRA) purposes, which adequately describes the growth or die-off of this pathogen under variable temperature conditions experienced during processing, storage and shipping. Literature data on behaviour of this pathogen on fresh-cut lettuce and spinach was taken from published graphs by digitization, published tables or from personal communications. A three-phase growth function was fitted to the data from 13 studies, and a square root model for growth rate (μ) as a function of temperature was derived: μ=(0.023*(Temperature-1.20))(2). Variability in the published data was incorporated into the growth model by the use of weighted regression and the 95% prediction limits. A log-linear die-off function was fitted to the data from 13 studies, and the resulting rate constants were fitted to a shifted lognormal distribution (Mean: 0.013; Standard Deviation, 0.010; Shift, 0.001). The combined growth-death model successfully predicted pathogen behaviour under both isothermal and non-isothermal conditions when compared to new published data. By incorporating variability, the resulting model is an improvement over existing ones, and is suitable for QRA applications.
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Since early May 2011, a large outbreak of enterohemorrhagic gastroenteritis and hemolytic uremic syndrome (HUS) related to infections with Shiga toxin-producing Escherichia coli O104:H4 (STEC O104:H4) had been reported in Germany, which marks one of the largest outbreaks ever described of the HUS worldwide. The HUS outbreak was unusual, and there were important differences between this outbreak and previous large outbreaks, primarily those of STEC O157:H7 both clinically and microbiologically. This outbreak highlights the importance of collaboration of all aspects of public health to detect the outbreak, to identify and characterize the causative agent, to find the vehicles of transmission, and to control the infection.
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Several outbreaks of Escherichia coli O157:H7 infections have been associated with minimally processed leafy vegetables in the United States. Harvesting and processing cause plant tissue damage. In order to assess the role of plant tissue damage in the contamination of leafy greens with E. coli O157:H7, the effect of mechanical, physiological, and plant disease-induced lesions on the growth of this pathogen on postharvest romaine lettuce was investigated. Within only 4 h after inoculation, the population sizes of E. coli O157:H7 increased 4.0-, 4.5-, and 11.0-fold on lettuce leaves that were mechanically bruised, cut into large pieces, and shredded into multiple pieces, respectively. During the same time, E. coli O157:H7 population sizes increased only twofold on leaves that were left intact after harvest. Also, the population size of E. coli O157:H7 was 27 times greater on young leaves affected by soft rot due to infection by Erwinia chrysanthemi than on healthy middle-aged leaves. Confocal microscopy revealed that leaf tip burn lesions, which are caused by a common physiological disorder of lettuce, harbored dense populations of E. coli O157:H7 cells both internally and externally. Investigation of the colonization of cut lettuce stems by E. coli O157:H7 showed that the pathogen grew 11-fold over 4 h of incubation after its inoculation onto the stems, from which large amounts of latex were released. The results of this study indicate that plant tissue damage of various types can promote significant multiplication of E. coli O157:H7 over a short time and suggest that harvesting and processing are critical control points in the prevention or reduction of E. coli O157:H7 contamination of lettuce.
Article
This project was undertaken to relate what is known about the behavior of Escherichia coli O157:H7 under laboratory conditions and integrate this information to what is known regarding the 2006 E. coli O157:H7 spinach outbreak in the context of a quantitative microbial risk assessment. The risk model explicitly assumes that all contamination arises from exposure in the field. Extracted data, models, and user inputs were entered into an Excel spreadsheet, and the modeling software @RISK was used to perform Monte Carlo simulations. The model predicts that cut leafy greens that are temperature abused will support the growth of E. coli O157:H7, and populations of the organism may increase by as much a 1 log CFU/day under optimal temperature conditions. When the risk model used a starting level of -1 log CFU/g, with 0.1% of incoming servings contaminated, the predicted numbers of cells per serving were within the range of best available estimates of pathogen levels during the outbreak. The model predicts that levels in the field of -1 log CFU/g and 0.1% prevalence could have resulted in an outbreak approximately the size of the 2006 E. coli O157:H7 outbreak. This quantitative microbial risk assessment model represents a preliminary framework that identifies available data and provides initial risk estimates for pathogenic E. coli in leafy greens. Data gaps include retail storage times, correlations between storage time and temperature, determining the importance of E. coli O157:H7 in leafy greens lag time models, and validation of the importance of cross-contamination during the washing process.
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The objective of this review has been to disclose collected information on benefits and risks of selected "less-than - sterilizing" processes applied to control microbial hazards in food that was meticulously collected and critically reviewed during five years of EU Sixth framework project "Pathogen Combat". The target organisms of the project, and thus of this review, too, were Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter jejuni. Due to their specific response and high relevancy to the food safety, foodborne viruses and spores, were also discussed within the scope of this review. Selected treatments comprised High Pressure Processing, Intense Light Pulses, treatments with organic acids, treatments with chlorine dioxide and for their relevancy also mild heat treatments and Pulsed Electric Field processing were included. The main aspects included in this review were principles of the processes used and their application, sub-lethal injury and its consequences on microbial food safety, and legal platform and its impact on wide use of the treatments. Finally a reflection has been made to combined application of different hurdles and accompanying risks.
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Neutralized electrolyzed oxidizing water (NEW) and acidic electrolyzed oxidizing water (AcEW) are electrolyzed oxidizing waters (EOW) that have significantly different fungicidal efficiencies against Aspergillus flavus (A. flavus) (The actuation durations of no survival population to NEW and AcEW were 90s and 120s, respectively.), even when used at the same available chlorine concentration (30ppm). It has been verified by our previous research. This study hypothesized that this difference did not originate from the structure of water but based on the OH radical (OH). It was proved by the UV spectroscopy, (17)O-NMR spectroscopy and electron spin resonance analysis. NEW contains more OH compared with AcEW in the same available chlorine concentration level. The OH that exists in NEW and AcEW was found to have an important fungicidal factor that destroys the cellular structures of the A. flavus conidia. It also damages the cellular normal function of A. flavus conidia that brought about K+ and Mg2+ leakages. The levels of OH that exist in NEW and AcEW could be the important reason that leads to significant fungicidal efficiencies against A. flavus.
Article
This study investigated the effect of storage temperature and time on the survival and growth of Escherichia coli O157:H7, the growth of indigenous microorganisms, and the changes in product quality of packaged baby spinach. Commercial packages of spinach within 2 days of processing were cut open at one end, sprayed with fine mists of E. coli O157:H7 inoculum, resealed, and then stored at 1, 5, 8, and 12 degrees C for 12 days until their labeled best-if-used-by dates. Microbial enumeration and product quality evaluation were conducted on day(s) 0, 3, 6, 9, and 12 postinoculation. Spinach held at 12 degrees C supported significant (P < 0.001) E. coli O157:H7 growth, with a 1.0-log CFU/g increase within 3 days postinoculation, which was followed by additional growth during continued storage. E. coli O157:H7 grew slowly when held at 8 degrees C, with a significant (P < 0.01) level of growth reached after 6 days of storage. However, on products held at 1 and 5 degrees C, E. coli O157:H7 populations declined significantly (P < 0.01 and P < 0.001, respectively) within 3 days of storage. Aerobic mesophilic bacteria, psychrotrophic bacteria, and yeast and mold populations increased significantly at all storage temperatures, with more growth on products held at elevated temperatures. Product quality scores remained high within the first 6 days of storage, with a sharp decline noted on samples held at 12 degrees C on day 9. Results suggest that E. coli O157:H7 can grow significantly on commercially packaged spinach held at 8 degrees C or above before significant product quality deterioration occurs.
Article
The utilization of sub-lethal decontamination treatments gains more and more interest due to the increased consumers' demand for fresh, minimally processed and convenient food products. These products rely on cold chain and hurdle (combination) technology to provide microbiological safety and quality during their shelf life. To investigate the ability of surviving cells to resuscitate and grow in a food simulating environment, sub-lethal decontamination treatments were coupled with subsequent storage under sub-optimal growth conditions. For this purpose chlorine dioxide (ClO2) and neutralized electrolyzed oxidizing water (NEW)-treated cultures of Escherichia coli O157:H7 were inoculated in TSB-YE of pH 5.8 and aw 0.99, and stored at 10 degrees C, 12.5 degrees C and 15 degrees C, under four different atmospheres (0%, 30% and 60% CO2 balanced with N2, and air). Due to the severity of injury, lactic acid-treated cells were inoculated in TSB-YE pH 7.0. Data obtained reveal that the fraction of sub-lethally injured E. coli O157:H7 undergoes an additional inhibitory effect during the storage period under of sub-optimal conditions. Observed extension in the lag growth phase was a direct consequence prior sub-lethal injury. The effects of liquid ClO2 and NEW were less pronounced in comparison to lactic acid. The current study signifies the potential utilization of appropriate combination of different extrinsic and intrinsic factors in the elimination or growth inhibition of food-borne pathogens.
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The efficacy of fresh-cut produce sanitizers has mainly been evaluated by measuring microbial reductions on produce. However, its suitability to ensure that pathogens are rapidly killed avoiding cross-contamination of subsequent product also needs to be considered. The efficacy of chlorine, Tsunami, Citrox and Purac on non pathogenic Escherichia coli reductions in processing water and on fresh-cut lettuce were studied. Selection of minimum effective doses was carried out in processing water, which contained a chemical oxygen demand (COD) within the range of 700-1000 mg/l and a total mesophilic load of about 7 log CFU/ml. The processing water was inoculated with two inoculum levels (3 and 5 log CFU/ml). It was observed that 40 mg/l of chlorine and 500 mg/l of Tsunami were effective in reducing the inoculum levels in the processing water to the detection limit (5 and 4 log units). However, Citrox and Purac were not effective in reducing E. coli population even at the highest manufacturer's recommended doses. Evaluation of cross-contamination in fresh-cut lettuce was carried out by measuring E. coli transfer from inoculated (~5 log CFU/g) to uninoculated lettuce after washing the contaminated product in the water containing different sanitizing agents. Chlorine and Tsunami were able to inactivate E. coli in wash water, avoiding cross-contamination between contaminated and non-contaminated product. However, Citrox and Purac at the recommended doses did not prevent transfer of E. coli cells between inoculated and uninoculated fresh-cut lettuce and therefore indicating cross-contamination. The results obtained show that chlorine and Tsunami are recommended as water disinfection agents preventing E. coli cross-contamination of produce during processing.
Article
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 degrees 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 approximately 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.
Article
Electrochemical disinfection has gained increasing attention as an alternative for conventional drinking water treatment due to its high effectiveness and environmental compatibility. The most common method of electrochemical disinfection is the use of electro-generated oxidants, such as active chlorine and reactive oxygen species, as disinfectants. This study examined the role of electrode material on the generation of oxidants, and elucidated the different reaction pathways for generating individual oxidants by employing boron-doped diamond (BDD), Ti/RuO(2), Ti/IrO(2), Ti/Pt-IrO(2), and Pt as anode materials. The efficiency of ()OH production, as determined by para-chlorobenzoic acid (pCBA) degradation, was in the order of BDD>Ti/RuO(2) approximately Pt. No significant production of ()OH was observed at Ti/IrO(2) and Ti/Pt-IrO(2). The ()OH was found to play a key role in O(3) generation at BDD, but not at the other electrodes. The production of active chlorine was in the order of Ti/IrO(2)>Ti/RuO(2)>Ti/Pt-IrO(2)>BDD>Pt. The large difference in this order from that of ROS was attributed to the difference in the electrocatalytic activity of each electrode material toward the production of active chlorine, as evidenced by linear sweep voltammetry (LSV) measurements. In addition, the characteristics of microbial inactivation as a function of electrode material were examined under the presence of an inert electrolyte, using Escherichia coli as an indicator microorganism.
Article
Rapid methods still rely on a prior (shortened) enrichment step before application. Quantitative information is a prerequisite for understanding the resuscitation kinetics of the growth during the enrichment step. In this study various basal and newly introduced selective enrichment broths were evaluated. First, growth parameters (lambda, mu(max)) of both healthy and sub-lethally injured cells were determined. Next, a selection of enrichment broths was compared for their capacity to support detection within 24h of low numbers of Listeria monocytogenes in artificially and naturally contaminated food samples. Detection was performed either by phage protein-based capture (Listeria Capture kit, Profos, Regensburg, Germany) combined with plating on chromogenic medium or by fluorescence in situ hybridization (FISH) using the VIT-Listeria kit (Vermicon, Munich, Germany). Kinetics of resuscitation and growth of L. monocytogenes in various enrichment broths showed that for detection of low numbers of sub-lethally injured L. monocytogenes cells at least an overnight enrichment was needed. A selective enrichment broth was needed to enable proliferation of L. monocytogenes within the indigenous bacterial flora present in foods. However, combination of an appropriate enrichment condition with advanced detection techniques may enable a 24h detection of L. monocytogenes.
Article
Electrolyzed water (EW) is gaining popularity as a sanitizer in the food industries of many countries. By electrolysis, a dilute sodium chloride solution dissociates into acidic electrolyzed water (AEW), which has a pH of 2 to 3, an oxidation-reduction potential of >1,100 mV, and an active chlorine content of 10 to 90 ppm, and basic electrolyzed water (BEW), which has a pH of 10 to 13 and an oxidation-reduction potential of -800 to -900 mV. Vegetative cells of various bacteria in suspension were generally reduced by > 6.0 log CFU/ml when AEW was used. However, AEW is a less effective bactericide on utensils, surfaces, and food products because of factors such as surface type and the presence of organic matter. Reductions of bacteria on surfaces and utensils or vegetables and fruits mainly ranged from about 2.0 to 6.0 or 1.0 to 3.5 orders of magnitude, respectively. Higher reductions were obtained for tomatoes. For chicken carcasses, pork, and fish, reductions ranged from about 0.8 to 3.0, 1.0 to 1.8, and 0.4 to 2.8 orders of magnitude, respectively. Considerable reductions were achieved with AEW on eggs. On some food commodities, treatment with BEW followed by AEW produced higher reductions than did treatment with AEW only. EW technology deserves consideration when discussing industrial sanitization of equipment and decontamination of food products. Nevertheless, decontamination treatments for food products always should be considered part of an integral food safety system. Such treatments cannot replace strict adherence to good manufacturing and hygiene practices.
Article
The duration of the lag phase of Salmonella typhimurium surviving heat, freezing, drying and gamma-radiation was used to indicate the time needed to repair sublethal injury. Following equivalent lethal treatments, heat and freeze-injured cells needed longer to repair than those injured by drying or gamma-radiation. Measurement of repair on membrane filters showed that in a heat-injured population having a lag time of 9 h, some individual cells needed up to 14 h to recover maximum tolerance to 3% NaCl.
Article
Two complementary measures are proposed as simple indices of the performance of models in predictive food microbiology. The indices assess the level of confidence one can have in the predictions of the model and whether the model displays any bias which could lead to 'fail-dangerous' predictions. The use of the indices is demonstrated using data collated from independent and published literature. This analysis supports previous reports that evaluation of predictive models by comparison to published microbial growth rate data may be inappropriate because of limitations in that data. The indices may fail to reveal some forms of systematic deviation between observed and predicted behaviour. It is concluded, however, that the indices provide an objective and readily interpreted summary of model performance and may serve as a first step towards the development of an objective and useful definition of the term 'validated model' in predictive food microbiology.
Article
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.
Article
This study determined the effects of mild heat and chlorine treatment followed by storage for up to 18 days at 5 degrees C or 7 days at 15 degrees C on the survival and growth of Escherichia coli O157:H7 inoculated onto fresh-cut iceberg lettuce. The efficacy of treatment with 20 ppm chlorine in killing the pathogen on lettuce at 50 degrees C was determined. Treatment of lettuce with 20 ppm chlorine at either 20 or 50 degrees C did not result in significantly greater reductions in populations of E. coli O157:H7 compared to respective treatments in water without chlorine. The pathogen steadily decreased in viability on treated lettuce throughout subsequent storage at 5 degrees C for 18 days. The population increased by 2.3 to 3.2 log10 CFU/g within 2 days, then continued to increase at a slower rate through 7 days of storage at 15 degrees C. At 4 and 7 days, significantly (alpha = 0.05) higher populations were reached on lettuce that had been treated at 50 degrees C, compared to respective samples that had been treated at 20 degrees C, regardless of the presence of 20 ppm chlorine in the treatment water. Treatment of lettuce with 20 ppm chlorine at 50 or 20 degrees C before or after inoculation with E. coli O157:H7 did not have a marked influence on behavior of the pathogen during subsequent storage at 5 or 15 degrees C.