Listeria spp

Time to detection experiments (TTD) based on turbidometry using an automatic Bioscreen C is a useful and straightforward method for estimating microbial growth parameters (lag time (λ), growth rate (μ) and “work to be done” (h0)) at constant temperature. This study investigated the effects of slightly acidic electrolyzed water (SAEW) and heat treatment on Listeria monocytogenes growth at different recovery temperatures (10 °C, 15 °C, 25 °C, and 30 °C). Similar surviving and sublethally injured L. monocytogenes populations were obtained by heat treatment (55 °C for 10 min) and SAEW treatment (available chlorine concentration of 30 mg/l and ratio of bacteria against SAEW of 8:2 for 30 s). In these experimental conditions, stresses had greater impact on the λ and h0 parameter in comparison with recovery temperature while there was no great change in growth rate under isothermal conditions. Larger λ values and h0 parameters were observed in sublethal-heat injured L. monocytogenes (the maximum λ and h0 parameters are 30.199 h and 1.6492) as compared to SAEW groups (the maximum λ and h0 parameters are 22.634 h and 1.4396). The sensitivity analysis of SAEW and heat treatments on h0 parameter indicated that SAEW treatment showed a higher influence. The collinearity diagnostics of independent variables [recovery temperature (T), μ, λ] for dependent variable (h0 parameter) demonstrated that T, μ and λ had strong collinearity. In addition, the established secondary models in this study have good performances on predicting the effect of recovery temperature on bacterial growth parameters.

The effect of acidic electrolyzed water (AEW) on inactivating Escherichia coli O104:H4, Listeria monocytogenes, Aeromonas hydrophila, Vibrio parahaemolyticus and Campylobacter jejuni in laboratory contaminated live clam (Venerupis philippinarum) and mussel (Mytilus edulis) was investigated. The initial levels of bacterial contamination were: in clam 4.9 to 5.7 log10 CFU/g, and in mussel 5.1 to 5.5 log10 CFU/g. Two types of AEW were used for treatment time intervals of 1 and 2 h: strong (SAEW) with an available chlorine concentration (ACC) of 20 mg/L, pH = 3.1, and an oxidation-reduction potential (ORP) of 1150 mV, and weak (WAEW) at ACC of 10 mg/L, pH = 3.55 and ORP of 950 mV. SAEW and WAEW exhibited significant inhibitory activity against inoculated bacteria in both shellfish species with significant differences compared to saline solutions treatments (1–2% NaCl) and untreated controls (0 h). SAEW showed the largest inhibitory activity, the extent of reduction (log10 CFU/g) ranged from 1.4–1.7 for E. coli O104:H4; 1.0–1.6 for L. monocytogenes; 1.3–1.6 for A. hydrophila; 1.0–1.5 for V. parahaemolyticus; and 1.5–2.2 for C. jejuni in both types of shellfish. In comparison, significantly (P < 0.05) lower inhibitory effect of WAEW was achieved compared to SAEW, where the extent of reduction (log10 CFU/g) ranged from 0.7–1.1 for E. coli O104:H4; 0.6–0.9 for L. monocytogenes; 0.6–1.3 for A. hydrophila; 0.7–1.3 for V. parahaemolyticus; and 0.8–1.9 for C. jejuni in both types of shellfish. Among all bacterial strains examined in this study, AEW induced less bacterial injury (~ 0.1–1.0 log10 CFU/g) and more inactivation effect. This study revealed that AEW (10–20 mg/L ACC) could be used to reduce bacterial contamination in live clam and mussel, which may help control possible unhygienic practices during production and processing of shellfish without apparent changes in the quality of the shellfish.

The goal of this study was to enhance the antimicrobial effect of slightly acidic electrolyzed water (SAEW) through addition of synergistic treatment with ultrasound (US) and mild heat treatment in order to improve the microbial safety of fresh-cut bell pepper. To evaluate the synergistic effects, the Weibull model was used to mathematically measure the effectiveness of the individual and combined treatments against Listeria monocytogenes and Salmonella Typhimurium on the pepper. The combined treatment (SAEW+US+60 °C) resulted in the TR values of 0.04 and 0.09 min for L. monocytogenes and S. Typhimurium, respectively, as consequence of the minimum value. Subsequently, texture analysis was carried out to test the potential effect on quality of the samples due to the involved mild heat and ultrasound treatment. When compared to the control, there was no significant change (p ≥ 0.05) in the texture (color and hardness) of the samples that were treated by 1 min of the combined treatment (SAEW+US+60 °C) during storage at 4 °C for 7 days. This combined treatment achieved approximately 3.0 log CFU/g reduction in the two pathogens. The results demonstrate that the involved hurdle factors which are ultrasound and mild heat achieved the synergistic effect of SAEW against the two pathogens. According to the results of texture analysis, 1 min of SAEW+US+60 °C is the optimal condition due to without negative influence on the quality of the samples during the storage. The optimal condition shows the enhanced antimicrobial effect of SAEW and enables to improve microbial safety of fresh bell pepper in food industry as a consequence of hurdle approach.

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

Three experiments were performed to enumerate the natural microflora on unwashed peaches, known as “field” peaches, and to determine the efficacy of using acidified electrolyzed water as a topical antimicrobial to remove or reduce the number of the natural microflora or inoculated Listeria innocua from to peach surfaces. During the first experiment, field peaches were divided into four treatment groups: no wash (NW), tap water wash (TW), acidified electrolyzed water wash (AEW), and chlorinated water wash (CL). Peaches were dipped into each of the treatment solutions at ambient temperature and immediately removed (approximately 5 seconds). Peaches were then rinsed in 100 mL of 0.1% peptone and rinsates were plated on aerobic plate count agar for enumeration. For the second experiment, exposure time to the treatment solutions and the temperature of the same treatment solutions were studied. Field peaches were again divided into NW, TW, AEW, and CL but treatments were applied using two exposure times of 5 seconds and 40 minutes at a temperature of 2°C (samples were given either a “0” or “40” in their labels to denote exposure time in minutes where 5 second exposures = 0 minutes e.g. TW-0, TW-40, AEW-0, etc.). Rinsing and plating was conducted as mentioned above. Experiment three investigated the efficacy of NW, TW, AEW, and Cl, in reducing numbers of Listeria innocua on peaches that were previously inoculated and held at 4°C for 24 hours. Inoculated peaches were dipped in treatment solutions for 5 second and 40 minute times at 2°C. Results showed that exposure time had a significant effect on bacterial reduction for both AEW and Cl treatments. Average aerobic counts from all NW peaches was 4.2 log10 CFU/g peach for natural microflora and 4.3 log10 CFU/g peach for samples inoculated with Listeria. The following results show the number of bacteria recovered (log10 CFU/g peach) from natural microflora samples and Listeria inoculated samples, respectively: NW = 4.2 and 4.9, TW-0 = 3.8 and 4.3, TW-40 = 3.2 and 4.7, AEW-0 = 3.6 and 3.7, AEW-40 = 2.6 and 1.6, CL=0 = 3.7 and 3.7, and CL-40 = 2.3 and 1.9. Greatest reductions were found with AEW-40 and CL-40 at refrigerated temperatures against both aerobic microorganisms and Listeria innocua. They reduced natural microflora counts by approximately 1.6 and 1.9 log10 CFU/g peach, respectively and they also reduced Listeria innocua counts by 3.3 and 3.0 log10 CFU/g peach, respectively. Listeria innocua, like monocytogenes, thrives in cold environments and the analysis of this study’s results suggest that Listeria in TW-40 may have reattached to peaches during exposure. Color studies were also performed on the peaches from the preliminary experiment and Experiment 2 to determine the effects of exposing the peaches to low pH environment such as that of the AEW used in this study. Peaches were analyzed for L*a*b* color data prior to their exposure to treatment solutions then they were analyzed again after their treatment concluded and they had air dried until no visible moisture remained. There was no significant color difference shown in any of the peaches when the pre- and post-treatment data was compared. Results from these studies demonstrate that total aerobic microorganisms and Listeriaspp. may be reduced, but not eliminated, during washing (by dipping) with AEW or CL with similar reductions for both antimicrobial treatment

Ultrasound (US) waves also have been shown to control L. monocytogenes populations in other commodities (Baumann, Martin, & Feng, 2005;Sagong et al., 2011). The hurdle approach of combined thermosonication (US with mild heat 40e60 C) and AEW showed higher reduction in L. monocytogenes counts on fresh-cut bell paper (Luo & Oh, 2015) and kale (Mansur & Oh, 2015) compared to their single treatments. However, little is known about the effects of AEW or/and UV combined with US in inactivating L. monocytogenes on raw salmon. ... ... The application of ultrasounds (US) as an additional hurdle to create the cavitation and enhance the cells' detachment from the food matrix, thereby making the microorganisms more susceptible to chlorine, could be a potential solution. Combined US or thermosonication (40e60 C) with AEW or near neutral pH electrolyzed (NEO) water have been reported as effective for microbial decontamination as well as the shelf life extension of fresh-cut kale (Mansur & Oh, 2015), bell pepper (Luo & Oh, 2015), kashk (Forghani, Eskandari, & Oh, 2015) and fresh produce such as lettuce and tomatoes (Afari, Hung, King, & Hu, 2016). Similarly, to the results of our study, Mansur and Oh (2015) revealed that the combination of US with AEW was more effective in reduction of L. monocytogenes counts (3.0 log CFU/g) on fresh-cut kale compared with dH 2 O, US þ dH 2 O and AEW treatments. ... ... Combined US or thermosonication (40e60 C) with AEW or near neutral pH electrolyzed (NEO) water have been reported as effective for microbial decontamination as well as the shelf life extension of fresh-cut kale (Mansur & Oh, 2015), bell pepper (Luo & Oh, 2015), kashk (Forghani, Eskandari, & Oh, 2015) and fresh produce such as lettuce and tomatoes (Afari, Hung, King, & Hu, 2016). Similarly, to the results of our study, Mansur and Oh (2015) revealed that the combination of US with AEW was more effective in reduction of L. monocytogenes counts (3.0 log CFU/g) on fresh-cut kale compared with dH 2 O, US þ dH 2 O and AEW treatments. It has been demonstrated that US significantly increases ORP of NEO from 847 to 950 mV, not affecting the pH and free chlorine content (pH 6.5, 155 mg/L), most probably due to the generation of free radicals in liquid phase (Afari et al., 2016).

It doesn't involve production, handling and transportation of using conventional chlorine (Hricova, Stephan, & Zweifel, 2008), economical because the EW production only involves water, salt and electricity. It can be generated on site when needed, being much less costly than conventional chlorine aspect of sanitiser generation, transporting and handling (Hricova et al., 2008;Huang, Hung, Hsu, Huang, & Hwang, 2008), safety thus it has been approved as a food additive in Japan, and the application on food was also approved by both U.S. Food and Drug Administration (FDA) and U.S. Department of Agriculture (USDA) (Hricova et al., 2008), and having strong sanitising effect because of major component being hypochlorous acid and there are some other effective components including free radicals, active oxygen, hydrogen peroxide and ozone gas, which are not existed in clorox and with higher oxidation-reduction potential (ORP) (Yang, Feirtag, & Diez-Gonzalez, 2013). However, at low pH, EW is corrosive, has a short shelf-life, and may be toxic to the operator (Ayebah & Hung, 2005;Waters, Tatum, & Hung, 2014;Xuan et al., 2016). ... ... Even though several studies have reported the bactericidal effects of both EW and NEW (Luo, Kim, Wang, & Oh, 2016;Park, Guo, Rahman, Ahn, & Oh, 2009;Thorn, Lee, Robinson, Greenman, & Reynolds, 2012;Zhang, Li, Jadeja, Fang, & Hung, 2016), few researchers have investigated the effects of processing factors on the performance of EW/NEW generators. Current commercial EW-producing units are quite large and not convenient for applications in households and small food industries (Yang et al., 2013). A portable, user-friendly NEW generator is necessary to meet the market demands and improve food safety. ... ... Escherichia coli (strain ATCC 25922), E. coli O157:H7 (strain C7927), and Listeria monocytogenes (strain ATCC BAA-839) were used in this study. The bactericidal activity of the EW samples was determined as previously reported with slight modifications Yang et al., 2013). Briefly, 24-h bacterial suspensions (10 mL each) were centrifuged (3000Âg, 4 C) for 10 min, and the resulting pellets were rinsed with 10 mL of sterile 0.1% peptone water (PW), centrifuged, and re-suspended in 10 mL of PW.

Salmonella spp. may be found in the nest box of breeder chickens, cold egg-storage rooms at the farm, on the hatchery truck, or in the hatchery environment (5). These bacteria may then be spread to fertilized hatching eggs on the shell or, in some cases, may penetrate the shell and reside just be-neath the surface of the eggshell. Research has demonstrated that contamination of raw poultry products with Salmonella spp. may be attributable to cross-contamination in the hatchery from Salmonella infected eggs or surfaces to uninfect-ed baby chicks during the hatching process. Cox et al. (6 and 7) reported that broiler and breeder hatch-eries were highly contaminated with Salmonella spp. Within the broiler hatchery, 71 percent of eggshell fragments, 80 percent of chick conveyor belts swabs, and 74 percent of pad samples placed under newly hatched chicks contained Salmonella spp. (6). Cason et al. (4) reported that, although fertile hatch-ing eggs were contaminated with high levels of Salmonella typhimurium, they were still able to hatch. The authors stated that paratyphoid salmonellae do not cause adverse health affects to the develop-ing and hatching chick. During the hatching pro-cess, Salmonella spp. is readily spread throughout the hatching cabinet due to rapid air movement by circulation fans. When eggs were inoculated with a marker strain of Salmonella during hatching, greater than 80 percent of the chicks in the trays above and below the inoculated eggs were contaminated (4). In an earlier study, Cason et al. (3) demonstrated that salmonellae on the exterior of eggs or in eggshell membranes could be transmitted to baby chicks dur-ing pipping.

The objective of this study was to develop amodel of the growth of Listeria monocytogenes in porkuntreated or treated with low concentration electrolyzedwater (LcEW) and strong acid electrolyzed water (SAEW),as a function of temperature. The experimental dataobtained under different temperatures (4, 10, 15, 20, 25,and 30oC) were fitted into the modified Gompertz model togenerate the growth parameters including specific growthrate (SGR) and lag time (LT) with high coefficients ofdetermination (R2 >0.97). The obtained SGR and LT wereemployed to develop square root models to evaluate theeffects of storage temperature on the growth kinetics of L.monocytogenes in pork. The values of bias factor (0.924-1.009) and accuracy factor (1.105-1.186), which wereregarded as acceptable, demonstrated that the obtainedmodels could provide good and reliable predictions and besuitable for the purpose of microbiological risk assessmentof L.monocytogenes in pork.Keywords: Listeria monocytogenes, predictive microbiology, temperature, pork, electrolyzed water in food. L. monocytogenes is a dangerous foodbornepathogen that can cause clinical infections with a mortalityrate of 20 to 30% (1). Listeriosis, which usually occurs inindividuals who have weak immune systems such as pregnantwomen, newborns, and elders, has recently become a serioushealth problem. Indeed, data provided by the Mead et al.(2) shows that there are approximately 2,500 cases oflisteriosis and 500 deaths in the United States every year. Amajority of these infections are caused by consuming foodcontaminated with L. monocytogenes.

Low concentration electrolyzed water (LcEW) has been proved to be an effective sanitizer against pathogens in cell suspensions as well as pathogens and spoilage organisms attached to vegetables, poultry and meat. In this study, effect of current, electrolysis time and salt concentration on physical properties (pH, ORP and ACC) and inactivation efficacy of LcEW was monitored. Pure cultures of Escherichia coli O157:H7 and Listeria monocytogenes were prepared and exposure treatment was performed for bacteria inactivation study in cell suspensions at room temperature (23 ± 2 °C). Our results showed increased reduction of both pathogens with the increase in current. Changes of current also affected the ACC, pH and ORP values of the tested solution. Values of ACC, pH and ORP were increased with the increase in current. Log reduction of 4.9–5.6 log CFU/mL for both pathogens was achieved when the current was increased from 1.15 to 1.45 A. Electrolysis time and percent of salt concentration also influenced the physical properties of LcEW. Stability of LcEW was also investigated under different conditions and it was observed that LcEW produced with increased electrical current was more stable during storage. Therefore, current might influence the properties and sanitizing effect of LcEW. Highlights ► Low concentration electrolyzed water as an effective sanitizer. ► Effect of current on stability and inactivation efficacy of LcEW. ► Electrolysis time and salt concentration influence the properties of LcEW. ► Properties of LcEW under storage condition.

Listeria monocytogenes and Morganella morganii have been implicated in listeriosis outbreaks and histamine fish poisoning, respectively. Possible sources of contamination of food products include processing equipment, food handlers, and fish smokehouses. Treatment of food preparation surfaces and of whole fish during handling with agents such as, electrolyzed oxidizing (EO) water, could reduce biofilm formation on seafood products and in seafood processing plants. We examined the efficacy of EO water against L. monocytogenes and M. morganii biofilms using the MBEC™ Assay System (Innovotech Inc.), conveyor belt coupons, and raw fish surfaces. The MBEC™ Assay System was used to assess the activity of EO water against 24-h biofilms of 90 L. monocytogenes strains and five M. morganii strains. Biofilms were exposed to PBS or EO water for 0 (control), 5, 15, and 30 min. All bacterial isolates were susceptible (reduction of 7 log10CFU) to treatment with EO water for 5 min based on results obtained using this assay system. EO water was used to treat four L. monocytogenes strains and one M. morganii strain attached to conveyor belt coupons and fish surfaces. Three L. monocytogenes strains and one M. morganii strain on belt coupons were reduced by 1–2.5 log10CFU/cm2 by exposure (5 min) to EO water compared to exposure to sterile distilled water. Strain to strain variability in susceptibility to EO water was evidenced by the fact that numbers of one L. monocytogenes strain were not reduced by EO water treatment of belt surfaces. EO water was not effective against L. monocytogenes and M. morganii on fish surfaces as growth occurred during cold storage. These results suggest that exposure of conveyor belts to EO water for a minimum of 5 min could assist in the removal of some biofilms. Removal of food residue with continuous or intermittent spraying of food processing equipment (e.g., conveyor belts, slicers) could reduce or prevent further biofilm formation. Additional sanitizers must be investigated for activity against bacteria associated with raw fish.

The objective of this study was to evaluate physicochemical properties and bactericidal activities of acidic electrolyzed water (AEW) used or stored at different temperatures on shrimp. Three independent experiments were carried out. The first experiment was to evaluate the physicochemical properties and bactericidal activities of AEW used at three different temperatures (4, 20, 50 °C) against food-borne pathogens (Listeria monocytogenes and Vibrio parahaemolyticus) contamination on cooked shrimp at 1 or 5 min; the second one was to monitor the bactericidal activity of AEW used at two temperatures (20, 50 °C) against total aerobic bacteria on raw shrimp at 5 min by conventional plate count method and PCR–DGGE method; the last one was to examine the physicochemical properties and bactericidal activities of AEW (AEW1, AEW2) stored at two temperatures (− 18, 25 °C) for 30 d against total aerobic bacteria on raw shrimp at 2 min. Results showed that AEW used at 50 °C showed the best bactericidal activity, leading to a log reduction of 3.11 for V. parahaemolyticus, 1.96 for L. monocytogenes and 1.44 for total aerobic bacteria at 5 min, respectively. Conventional plate count and PCR–DGGE (denaturing gradient gel electrophoresis) study further suggested that the bactericidal activity of AEW used at 50 °C was higher than at 20 °C. The loss of bactericidal activity of AEW stored at − 18 °C was less than that of stored at 25 °C, and the ORP and ACC decreased more slowly than those of stored at 25 °C. However, the ORP and ACC of AEW used at 50 °C showed a remarkably faster decrease than that of used at 20 °C. We suggest using AEW at 50 °C to enhance bactericidal activity and storing at − 18 °C to keep the content of ACC and the bactericidal activity.

All food processing surfaces are potential sites for biofilm formation of foodborne pathogens, which may result in increased virulence and better adaptation to survival in foods. This study was aimed to evaluate the effect of two antimicrobials, neutral electrolyzed water (NEW) and nisin, and their combination, on Listeria monocytogenes Scott A biofilms formed on glass and stainless steel surfaces. We also examined the effects of sub-lethal doses of NEW on listeriolysin O (LLO) activity from free and biofilm listerial cells. Coupons inoculated with L. monocytogenes cells were used to produce biofilms by incubation for four days at 37 °C. An orthogonal experimental design with two replicates was used to test the effect of four factors on biofilm population. The factors were antimicrobial agents: NEW (65 ppm), nisin (6976 IU/per coupon), and their combination; temperature: 20 °C and 37 °C; contact time: 5, 10, 20 and 45 min; and type of material: glass or stainless steel. Antimicrobial compounds and exposure time significantly affected L. monocytogenes populations in biofilms from both surfaces. A bactericidal effect was shown by NEW on free listerial cells at 30 ppm for 0.5 min of exposure, regardless treatment temperature. Same effect was observed on listerial biofilms at 65 ppm or higher concentrations, after 10 min contact time. A sub-lethal concentration of NEW acting on listerial biofilms resulted in an increased LLO activity, while non-treated biofilms exhibited a reduced activity, but higher than that found for free cells. The use of NEW as a sanitizer may be effective in reducing bacterial contamination. In addition because of its safety, which would benefit the food industry and its environmental friendliness, NEW may be of significant use in the food industry.

This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm², respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.

The objective of this study was to determine the synergistic effect of alkaline electrolyzed water and citric acid with mild heat against background and pathogenic microorganisms on carrots. Shredded carrots were inoculated with approximately 6-7 log CFU/g of Escherichia coli O157:H7 (932, and 933) and Listeria monocytogenes (ATCC 19116, and 19111) and then dip treated with alkaline electrolyzed water (AlEW), acidic electrolyzed water (AcEW), 100 ppm sodium hypochlorite (NaOCl), deionized water (DaIW), or 1% citric acid (CA) alone or with combinations of AlEW and 1% CA (AlEW + CA). The populations of spoilage bacteria on the carrots were investigated after various exposure times (1, 3, and 5 min) and treatment at different dipping temperatures (1, 20, 40, and 50 °C) and then optimal condition (3 min at 50 °C) was applied against foodborne pathogens on the carrots. When compared to the untreated control, treatment AcEW most effectively reduced the numbers of total bacteria, yeast and fungi, followed by AlEW and 100 ppm NaOCl. Exposure to all treatments for 3 min significantly reduced the numbers of total bacteria, yeast and fungi on the carrots. As the dipping temperature increased from 1 °C to 50 °C, the reductions of total bacteria, yeast and fungi increased significantly from 0.22 to 2.67 log CFU/g during the wash treatment (p ≤ 0.05). The combined 1% citric acid and AlEW treatment at 50 °C showed a reduction of the total bacterial count and the yeast and fungi of around 3.7 log CFU/g, as well as effective reduction of L. monocytogenes (3.97 log CFU/g), and E. Coli O157:H7 (4 log CFU/g). Combinations of alkaline electrolyzed water and citric acid better maintained the sensory and microbial quality of the fresh-cut carrots and enhanced the overall shelf-life of the produce.

Chlorine (sodium hypochlorite solution) is the most common disinfectant used in the fresh-cut industry, however, environmental and health risks related to its use have resulted in a need to find new sanitizers. Electrolyzed water (EW) is a promising alternative, showing a broad spectrum of microbial decontamination. In this study the efficacy of acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW) as disinfectants of apple slices inoculated with Escherichia coli, Listeria innocua or Salmonella choleraesuis, individually or in a mixture, were compared to that of sodium hypochlorite solution and distilled water. Apple slices were inoculated with a 107 cfu/mL suspension of the pathogens and treated with diluted electrolyzed water. Bactericidal activity of washing treatments was assessed after 30 min and after storage for 5 days at 4 °C. AEW and NEW disinfection efficacy was compared to that of washings with sodium hypochlorite at the same free chlorine concentration and with distilled water. AEW diluted to 100 mg/L of free chlorine was the treatment with the highest bactericidal activity in all tested conditions (reductions obtained ranged from 1.2 to 2.4 log units) followed by NEW and AEW at 100 and 50 mg/L of free chlorine respectively. In general these treatments were equal or more effective than sodium hypochlorite washings at 100 mg/L of free chlorine. The effect of the different sanitizer washings when pathogens where in a mixture was similar to that which occurred when pathogens were individually inoculated. The effectiveness of all washings slightly decreased when apple slices were stored for 5 days at 4 °C.

This study investigated the efficacy of sanitized ice for the reduction of bacteria in the water collected from the ice that melted during storage of whole and filleted Tilapia fish. Also, bacterial reductions on the fish fillets were investigated. The sanitized ice was prepared by freezing solutions of PRO-SAN® (an organic acid formulation) and neutral electrolyzed water (NEW). For the whole fish study, the survival of the natural microflora was determined from the water of the melted ice prepared with PRO-SAN® and tap water. These water samples were collected during an 8 h storage period. For the fish fillet study, samples were inoculated with Escherichia coli K12, Listeria innocua, and Pseudomonas putida then stored on crushed sanitized ice. The efficacies of these were tested by enumerating each bacterial species on the fish fillet and in the water samples at 12 and 24 h intervals for 72 h, respectively. Results showed that each bacterial population was reduced during the test. However, a bacterial reduction of < 1 log CFU was obtained for the fillet samples. A maximum of approximately 2 log CFU and > 3 log CFU reductions were obtained in the waters sampled after the storage of whole fish and the fillets, respectively. These reductions were significantly (P < 0.05) higher in the water from sanitized ice when compared with the water from the unsanitized melted ice. These results showed that the organic acid formulation and NEW considerably reduced the bacterial numbers in the melted ice and thus reduced the potential for cross-contamination.

Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution (∼1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl2, HOCl/ClO−). At a near-neutral pH (pH 6.3–6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900 mV. The biocidal activity of near-neutral EO water was evaluated at 25 °C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120 ppm total residual chlorine (TRC) and 10 min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1–6.7 log10 CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278–310 ppm TRC (pH 6.38) resulted in a 79–100% reduction of microbial growth. Dip (10 min) treatment of spinach at 100 and 120 ppm TRC resulted in a 4.0–5.0 log10 CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10 min) of lettuce at 100 and 120 ppm TRC reduced bacterial counts of E. coli by 0.24–0.25 log10 CFU/mL and reduced all other organisms by 2.43–3.81 log10 CFU/mL.

Consumption of minimally-processed, or fresh-cut, fruit and vegetables has rapidly increased in recent years, but there have also been several reported outbreaks associated with the consumption of these products. Sodium hypochlorite is currently the most widespread disinfectant used by fresh-cut industries. Neutral electrolyzed water (NEW) is a novel disinfection system that could represent an alternative to sodium hypochlorite. The aim of the study was to determine whether NEW could replace sodium hypochlorite in the fresh-cut produce industry. The effects of NEW, applied in different concentrations, at different treatment temperatures and for different times, in the reduction of the foodborne pathogens Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 and against the spoilage bacterium Erwinia carotovora were tested in lettuce. Lettuce was artificially inoculated by dipping it in a suspension of the studied pathogens at 10(8), 10(7) or 10(5) cfu ml(-1), depending on the assay. The NEW treatment was always compared with washing with deionized water and with a standard hypochlorite treatment. The effect of inoculum size was also studied. Finally, the effect of NEW on the indigenous microbiota of different packaged fresh-cut products was also determined. The bactericidal activity of diluted NEW (containing approximately 50 ppm of free chlorine, pH 8.60) against E. coli O157:H7, Salmonella, L. innocua and E. carotovora on lettuce was similar to that of chlorinated water (120 ppm of free chlorine) with reductions of 1-2 log units. There were generally no significant differences when treating lettuce with NEW for 1 and 3 min. Neither inoculation dose (10(7) or 10(5) cfu ml(-1)) influenced the bacterial reduction achieved. Treating fresh-cut lettuce, carrot, endive, corn salad and 'Four seasons' salad with NEW 1:5 (containing about 50 ppm of free chlorine) was equally effective as applying chlorinated water at 120 ppm. Microbial reduction depended on the vegetable tested: NEW and sodium hypochlorite treatments were more effective on carrot and endive than on iceberg lettuce, 'Four seasons' salad and corn salad. The reductions of indigenous microbiota were smaller than those obtained with the artificially inoculated bacteria tested (0.5-1.2 log reduction). NEW seems to be a promising disinfection method as it would allow to reduce the amount of free chlorine used for the disinfection of fresh-cut produce by the food industry, as the same microbial reduction as sodium hypochlorite is obtained. This would constitute a safer, 'in situ', and easier to handle way of ensuring food safety.

Antibacterial activity of electrolyzed oxidizing (EO) water prepared from 0.05% or 0.10% (w/v) sodium chloride (NaCl) solutions against indigenous bacteria associated with fresh strawberries (Fragaria×ananassa) was evaluated. The efficacy of EO water and sodium hypochlorite (NaOCl) solution in eliminating and controlling the growth of Listeria monocytogenes and Escherichia coli O157:H7 inoculated onto strawberries stored at 4 ± 1 °C up to 15 d was investigated at exposure time of 1, 5, or 10 min. Posttreatment neutralization of fruit surfaces was also determined. More than 2 log10 CFU/g reductions of aerobic mesophiles were obtained in fruits washed for 10 or 15 min in EO water prepared from 0.10% (w/v) NaCl solution. Bactericidal activity of the disinfectants against L. monocytogenes and E. coli O157:H7 was not affected by posttreatment neutralization, and increasing exposure time did not significantly increase the antibacterial efficacy against both pathogens. While washing fruit surfaces with distilled water resulted in 1.90 and 1.27 log10 CFU/mL of rinse fluid reduction of L. monocytogenes and E. coli O157:H7, respectively, ≥ 2.60 log10 CFU/mL of rinse fluid reduction of L. monocytogenes and up to 2.35 and 3.12 log10 CFU/mL of rinse fluid reduction of E. coli O157:H7 were observed on fruit surfaces washed with EO water and NaOCl solution, respectively. Listeria monocytogenes and E. coli O157:H7 populations decreased over storage regardless of prior treatment. However, EO water and aqueous NaOCl did not show higher antimicrobial potential than water treatment during refrigeration storage.

The effects of electrolyzed oxidizing (EO) water on reducing Listeria monocytogenes contamination on seafood processing surfaces were studied. Chips (5 × 5 cm2) of stainless steel sheet (SS), ceramic tile (CT), and floor tile (FT) with and without crabmeat residue on the surface were inoculated with L. monocytogenes and soaked in tap or EO water for 5 min. Viable cells of L. monocytogenes were detected on all chip surfaces with or without crabmeat residue after being held at room temperature for 1 h. Soaking contaminated chips in tap water resulted in small-degree reductions of the organism (0.40–0.66 log cfu/chip on clean surfaces and 0.78–1.33 log cfu/chip on dirty surfaces). Treatments of EO water significantly (p < 0.05) reduced L. monocytogenes on clean surfaces (3.73 log on SS, 4.24 log on CT, and 5.12 log on FT). Presence of crabmeat residue on chip surfaces reduced the effectiveness of EO water on inactivating Listeria cells. However, treatments of EO water also resulted in significant reductions of L. monocytogenes on dirty surfaces (2.33 log on SS and CT and 1.52 log on FT) when compared with tap water treatments. The antimicrobial activity of EO water was positively correlated with its chlorine content. High oxidation–reduction potential (ORP) of EO water also contributed significantly to its antimicrobial activity against L. monocytogenes. EO water was more effective than chlorine water on inactivating L. monocytogenes on surfaces and could be used as a chlorine alternative for sanitation purpose. Application of EO water following a thorough cleaning process could greatly reduce L. monocytogenes contamination in seafood processing environments.

The effects of electrolyzed oxidizing (EO) water on reducing Listeria monocytogenes contamination on seafood processing surfaces were studied. Chips (5 × 5 cm2) of stainless steel sheet (SS), ceramic tile (CT), and floor tile (FT) with and without crabmeat residue on the surface were inoculated with L. monocytogenes and soaked in tap or EO water for 5 min. Viable cells of L. monocytogenes were detected on all chip surfaces with or without crabmeat residue after being held at room temperature for 1 h. Soaking contaminated chips in tap water resulted in small-degree reductions of the organism (0.40–0.66 log cfu/chip on clean surfaces and 0.78–1.33 log cfu/chip on dirty surfaces). Treatments of EO water significantly (p < 0.05) reduced L. monocytogenes on clean surfaces (3.73 log on SS, 4.24 log on CT, and 5.12 log on FT). Presence of crabmeat residue on chip surfaces reduced the effectiveness of EO water on inactivating Listeria cells. However, treatments of EO water also resulted in significant reductions of L. monocytogenes on dirty surfaces (2.33 log on SS and CT and 1.52 log on FT) when compared with tap water treatments. The antimicrobial activity of EO water was positively correlated with its chlorine content. High oxidation–reduction potential (ORP) of EO water also contributed significantly to its antimicrobial activity against L. monocytogenes. EO water was more effective than chlorine water on inactivating L. monocytogenes on surfaces and could be used as a chlorine alternative for sanitation purpose. Application of EO water following a thorough cleaning process could greatly reduce L. monocytogenes contamination in seafood processing environments.

Biofilms are potential sources of contamination to food in processing plants, because they frequently survive sanitizertreatments during cleaning. The objective of this research was to investigate the combined use of alkaline and acidic electro-lyzed (EO) water in the inactivation ofListeria monocytogenesbiofilms on stainless steel surfaces. Biofilms were grown onrectangular stainless steel (type 304, no. 4 finish) coupons (2 by 5 cm) in a 1:10 dilution of tryptic soy broth that containeda five-strain mixture ofL. monocytogenesfor48hat258C. The coupons with biofilms were then treated with acidic EO wateror alkaline EO water or with alkaline EO water followed by acidic EO water produced at 14 and 20 A for 30, 60, and 120s. Alkaline EO water alone did not produce significant reductions inL. monocytogenesbiofilms when compared with thecontrol. Treatment with acidic EO water only for 30 to 120 s, on the other hand, reduced the viable bacterial populations inthe biofilms by 4.3 to 5.2 log CFU per coupon, whereas the combined treatment of alkaline EO water followed by acidic EOwater produced an additional 0.3- to 1.2-log CFU per coupon reduction. The population ofL. monocytogenesreduced bytreatments with acidic EO water increased significantly with increasing time of exposure. However, no significant differencesoccurred between treatments with EO water produced at 14 and 20 A. Results suggest that alkaline and acidic EO water canbe used together to achieve a better inactivation of biofilms than when applied individually.

Raw fish is prone to risk of microbial outbreaks due to contamination of pathogenic microorganisms. Escherichia coli O157:H7 and Listeria monocytogenes are among the pathogens associated with raw fish. Therefore, it is important to treat raw fish to inactivate pathogenic microorganisms. Electrolyzed oxidizing water is novel antimicrobial agent containing acidic solution with a pH of 2.6- 2.9, ORP of 1120 1180 mV, and 76-90 ppm free chlorine, and alkaline solution with a pH of 11.5 and ORP of 795 mV. This study was undertaken to evaluate the efficacy of electrolyzed oxidizing (EO) water for inactivation of E. coli O157:H7 and L. monocytogenes Scott A on the surfaces (muscle and skin surfaces) of inoculated salmon fillets. Inoculated salmon fillets were treated only with acidic EO water at 22C and 35C and sodium hypochlorite solution (90 ppm free chlorine) as control at 22C for 2, 4, 8, 16, 32, and 64 min, respectively. For the treatment with alkaline EO water followed by acidic EO water, a response surface model was developed to predict effective times in the range of 5-30 min and temperatures in the range of 22-35C for both alkaline and acidic water treatments. The acidic EO water treatments resulted in reductions of population of L. monocytogenes Scott A ranging from 0.40 log10 CFU/g (60 %) at 22oC to 1.12 log10 CFU/g (92.3 %) at 35oC. Treatment of inoculated salmon fillets in acidic EO water reduced E. coli O157:H7 populations by 0.49 log10 CFU/g (67 %) 22C and 1.07 log10 CFU/g (91.1 %) at 35C, respectively. Response surface analysis for alkaline EO water treatment followed by acidic treatment demonstrated that, maximum log reduction of 1.33 log10 CFU/g (95.3 %) for E. coli O157:H7 and 1.09 log10 CFU/g (91.9 %) for L. monocytogenes Scott A.

Scroll to Top