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Modeling Vibrio parahaemolyticus inactivation by acidic electrolyzed water on cooked shrimp using response surface methodology
... Vibrio parahaemolyticus is a common food-borne pathogen widely distributed in marine environments. In Asian countries, such as China, Japan, South Korea, and Taiwan, this pathogen has been frequently reported to cause gastrointestinal illness following the consumption of raw or improperly cooked fish and shellfish (Su & Liu, 2007;Wang, Zhang, et al., 2014;Wang, Sun, et al., 2014). In Taiwan, V. parahaemolyticus is the most prevalent food-borne pathogen, accounting for more than 50% of the annual bacterial food-poisoning outbreaks. ...
... Acidic electrolysed water (AEW) is collected from the anode side when salt-containing water is electrolysed through a diaphragm. AEW, which has a high positive oxidation-reduction potential (ORP) and high concentrations of dissolved chlorine and oxygen, functions as a bactericide and is used for sanitising medical equipment, food, and agricultural fields (Huang et al., 2006;Pangloli & Hung, 2013;Wang, Zhang, et al., 2014;Wang, Sun, et al., 2014). Slightly acidic electrolysed water (SlAEW) is generated by the electrolysis of dilute food-grade hydrochloric acid or NaCl solution by using an electrolytic cell without a membrane. ...
... Combining basic electrolysed water pretreatment and mild heat at 50°C considerably enhanced the bactericidal activity of AEW against V. parahaemolyticus and the total aerobic bacteria on shrimp (Xie, Sun, Pan, & Zhao, 2012b). A mathematical model of the inactivation of V. parahaemolyticus on cooked shrimp by using AEW showed that the effects of the treatment temperature on the response value were greater than those of the treatment time and using NaCl concentration in electrolysis (Wang, Zhang, et al., 2014). AEW could markedly decrease the growth rate and extend the lag time during post-treatment storage at room temperature, whereas the treatment did not reduce the maximum growth of V. parahaemolyticus on shrimp (Wang, Sun, et al., 2014). ...
Slightly acidic electrolysed water (SlAEW) and acidic electrolysed water (AEW) have been demonstrated to effectively inactivate food-borne pathogens. However, the underlying mechanism of inactivation remains unknown. Therefore, in this study, a differential proteomic platform was used to investigate the bactericidal mechanism of SlAEW, AEW, and sodium hypochlorite (NaOCl) solutions against Vibrio parahaemolyticus. The upregulated proteins after SlAEW, AEW, and NaOCl treatments were identified as outer membrane proteins K and U. The downregulated proteins after the SlAEW, AEW, and NaOCl treatments were identified as adenylate kinase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and enolase, all of which are responsible for energy metabolism. Protein synthesis-associated proteins were downregulated and identified as elongation factor Tu and GAPDH. The inhibitory effects of SlAEW and AEW solutions against V. parahaemolyticus may be attributed to the changes in cell membrane permeability, protein synthesis activity, and adenosine triphosphate (ATP) biosynthesis pathways such as glycolysis and ATP replenishment.
... Thus, V. parahaemolyticus has become the predominant harmful factor of raw shrimp (Pu et al., 2013;Su and Liu, 2007). Additionally, cooked shrimp are often picked by hand, and also can be easily contaminated with V. parahaemolyticus through bad manufacturing practices and poor personal hygiene McCarthy, 1997;Wang et al., 2014) during each course including storage, transportation and distribution (Dupard et al., 2006;Gudbjorndottir et al., 2005). Moreover, risk assessment of V. parahaemolyticus on cooked black tiger shrimp has been conducted in Malaysia in 2008 and 2012, and the results showed that consuming cooked shrimp could cause illness related with V. parahaemolyticus (Sani et al., 2012(Sani et al., , 2008. ...
... Moreover, risk assessment of V. parahaemolyticus on cooked black tiger shrimp has been conducted in Malaysia in 2008 and 2012, and the results showed that consuming cooked shrimp could cause illness related with V. parahaemolyticus (Sani et al., 2012(Sani et al., , 2008. Therefore, food scientists and food industry are searching for novel non-thermal methods that could destroy undesired microorganisms with less adverse effects on products (Ju et al., 2008;Wang et al., 2014). ...
... Several studies have been performed on non-thermal methods for decontaminating bacteria on fresh produce, such as organic acids, compounds of chlorine, pulsed electric field (PEF), etc. (Ding et al., 2010;Huang et al., 2014;Pipek et al., 2006). Acidic electrolyzed water (AEW) is regarded as one of the most promising, with a high efficacy for inactivating food-borne pathogens (Ding et al., 2010;Wang et al., 2014). It has been demonstrated that AEW has a strong disinfectant effect on V. parahaemolyticus. ...
The objective of this study was to investigate the fate of Vibrio parahaemolyticus on shrimp after acidic electrolyzed water (AEW) treatment during storage. Shrimp, inoculated with a cocktail of four strains of V. parahaemolyticus, were stored at different temperatures (4-30°C) after AEW treatment. Experimental data were fitted to modified Gompertz and Log-linear models. The fate of V. parahaemolyticus was determined based on the growth and survival kinetics parameters (lag time, λ; the maximum growth rate, μmax; the maximum growth concentration, D; the inactivation value, K) depending on the respective storage conditions. Moreover, real-time PCR was employed to study the population dynamics of this pathogen during the refrigeration temperature storage (10, 7, 4°C). The results showed that AEW treatment could markedly (p<0.05) decrease the growth rate (μmax) and extend the lag time (λ) during the post-treatment storage at 30, 25, 20 and 15°C, while it did not present a capability to lower the maximum growth concentration (D). AEW treatment increased the sensitivity of V. parahaemolyticus to refrigeration temperatures, indicated by a higher (p<0.05) inactivation value (K) of V. parahaemolyticus, especially for 10°C storage. The results also revealed that AEW treatment could completely suppress the proliferation of V. parahaemolyticus in combination with refrigeration temperature. Based on above analysis, the present study demonstrates the potential of AEW in growth inhibition or death acceleration of V. parahaemolyticus on seafood, hence to greatly reduce the risk of illness caused by this pathogen during post-treatment storage.
... In recent years, acidic electrolyzed water (AEW) has been regarded as an effective sanitizer and widely used in the food industries of many countries (Smigic et al., 2009;Wang et al., 2014). By electrolysis in the specific device, a diluted sodium chloride solution dissociates into AEW, which has a low pH of 2-3, a high oxidation-reduction potential (ORP) of > 1100 mV, and an active chlorine content (ACC) of 10-90 ppm (Hricova et al., 2008). ...
... The bacterial enumeration method used in this study was the plating counting method according to previous studies (Belletti et al., 2013a;Wang et al., 2014). Briefly, shrimp samples were homogenized for 2 min in a stomacher (BagMixer400VW, Interscience, France). ...
... R 2 were 0.994 and 0.986, respectively. The value of the Adj.R 2 indicated a high degree of correlation between the observed and predicted values, which suggested that only 1.6% of the total variation cannot be explained by the current model (Wang et al., 2014). RMSE also provided a measure of the goodness-of-fit of the model to the data used to produce it (Wang et al., 2014) and its value was 0.29 indicating that the RS model fitted well with the observed data. ...
Acidic electrolyzed water (AEW), a novel non-thermal sterilization technology, is widely used in the food industry. In this study, we firstly investigated the effect of AEW as a new pressure transmitting medium for high hydrostatic pressure (AEW-HHP) processing on microorganisms inactivation on shelled fresh shrimp. The optimal conditions of AEW-HHP for Vibrio parahaemolyticus inactivation on sterile shelled fresh shrimp were obtained using response surface methodology: NaCl concentration to electrolysis 1.5 g/L, treatment pressure 400 MPa, treatment time 10 min. Under the optimal conditions mentioned above, AEW dramatically enhanced the efficiency of HHP for inactivating V. parahaemolyticus and Listeria monocytogenes on artificially contaminated shelled fresh shrimp, and the log reductions were up to 6.08 and 5.71 log10 CFU/g respectively, while the common HHP could only inactivate the two pathogens up to 4.74 and 4.31 log10 CFU/g respectively. Meanwhile, scanning electron microscopy (SEM) showed the same phenomenon. For the naturally contaminated shelled fresh shrimp, AEW-HHP could also significantly reduce the micro flora when examined using plate count and PCR-DGGE. There were also no significant changes, histologically, in the muscle tissues of shrimps undergoing the AEW-HHP treatment. In summary, using AEW as a new transmitting medium for HHP processing is an innovative non thermal technology for improving the food safety of shrimp and other aquatic products.
... For processes using multiple variables, RSM can be employed to determine the interactions among the tested variables at different ranges. The RSM models generated are used to describe the effects of different variables on the response [37,[44][45][46][47][48]. In this research, the process optimization of electrolyzing parameters for electrolyzed water (alkaline and acidic) was investigated using RSM. ...
... This indicates that all other models are much more significant. Lack of fit for all the RS models were not significant, indicating the adequacy of all the models [45]. This is shown in Tables 8-12. ...
Electrolyzed water (EW) shows great potential as a green and economical sanitation solution for the food industry. However, only limited studies have investigated the optimum electrolysis parameters and the bactericidal effect of acidic electrolyzed water (AcEW) and alkaline electrolyzed water (AlEW). Here, the Box-Behnken experimental design was used to identify the optimum parameters. The tests were conducted with different types of electrodes, electrical voltages, electrolysis times, and NaCl concentrations. There were no obvious differences observed in the physico-chemical properties of EW when different electrodes were used. However, stainless steel was chosen as it meets most of the selection criteria. The best-optimized conditions for AcEW were at 11.39 V, 0.65 wt.% NaCl, and 7.23 min, while the best-optimized conditions for AlEW were at 10.32 V, 0.6 wt.% NaCl, and 7.49 min. The performance of the optimum EW (AcEW and AlEW) compared with commercial cleaning detergents for the food industry was then evaluated. The bactericidal activity of AcEW and AlEW was examined against Escherichia coli ATCC 10536 at different temperatures (30 • C and 50 • C) for 30 s. The results show that both AcEW and AlEW have the ability to reduce the Escherichia coli to non-detectable levels (less than 2 log CFU/mL).
... A predictive model is a useful tool for assessing and controlling food safety and quality, which can be used to describe the growth and inactivation of microorganisms under different conditions such as temperature, pH and water activity (Pujol et al., 2012;Swinnen, Bernaerts, Dens, Geeraerd, & Van Impe, 2004). In addition, studies on growth behavior of V. parahaemolyticus over a range of temperatures in broth, oyster slurry, live oyster and shrimp are also available (Fernandez-Piquer, Bowman, & Ross, 2011;Miles Ross & McMeekin, 1997;Wang, Sun et al., 2014;Wang, Zhang et al., 2014;Yang, Jiao, Li & Pan, 2009;Yoon, Min, Jung & Kwon, 2008). Miles et al. (1997) examined the growth rates of four strains of V. parahaemolyticus individually and picked out strain 38.349 for developing the model with it exhibiting the fastest growth rate. ...
... The experimental protocol was based on a previous study by Wang, Sun et al. (2014); Wang, Zhang et al. (2014). Briefly, the cocktail with adjusted concentration was added into 500 ml sterile 2.5% saline solution to obtain the inoculum solution. ...
Pathogenic Vibrio parahaemolyticus, an important foodborne bacterium, coexists with nonpathogenic strains of V. parahaemolyticus in the environment. However, current predictive models for V. parahaemolyticus usually focused on single strain without considering the pathogenic and nonpathogenic bacteria cocktail coexist situation. In this study, the behavior of four V. parahaemolyticus strains (F18: tlh+/trh+/tdh−, ATCC 17802: tlh+/trh+/tdh−, F36: tlh+/trh−/tdh−, ATCC 33847: tlh+/trh−/tdh+) and their cocktails on cooked shrimp were investigated at different temperatures (4, 7, 10, 15, 20, 25 and 30 °C). Total bacteria counts were enumerated by traditional plate count method, periodically. Results showed both V. parahaemolyticus cocktails and four single strains grew in a temperature range of 15–30 °C and died at 4–7 °C. At 10 °C, for the cocktails, it inactivated at initial 100 h and then grew rapidly; but for single strain, only one strain F18 displayed the similar growth tendency, while the others grew all the time. Compared with single strains, the primary and secondary model analysis showed that the cocktails displayed a better growth activity with higher maximum growth rate and shorter lag time. The above results indicated that modeling bacterial growth by using a cocktail of V. parahaemolyticus strains may be a better option for simulating growth in the real environment. This study will fill in the gap of predictive microbiology and improve significantly the accuracy of microbial risk assessment.
... Some AEW parameters was studied in Vibrio parahemolyticus and Listeria monocytogenes in shrimps storage at different temperatures (Xie et al., 2012). Others studies with Vibrio parahemolyticus were performed in shrimps (Wang, Sun, Jin et al., 2014;Wang, Zhang, Li et al., 2014), besides Vibrio parahemolyticus, Quan et al. (2010) studied SAEW action in Vibrio vulnificus, and compared effects of EW to sodium hypochlorite. The effect of EW in E. coli and Salmonella spp.present in freeze shrimp was studied, as well increasing quality (Loi-Braden et al., 2005). ...
Electrolyzed water (EW) is a new technology that emerged in the last years with potential
application in foods, mainly in microbiological aspects, with variation in application modes,
dipping the food in solution, where variation of time can be changed and be apply in the form
of spray. Because EW characteristics, its action in microorganisms are still been studied for
mechanism elucidation and possible damages, as well its influence in the intrinsic characteristics
of food, like color and oxidation. This unconventional or ‘green’ technology has the purpose
to prove microbiological quality of food and decrease the use of natural resources like water
with minimal generation of chemical/toxic residues. More studies are necessary in relation
to this technology and its possible applications in food industry, as well characteristics and
mechanisms.
... Chao et al. (2010) reported that V. parahaemolyticus can be spread by both seafood and freshwater products. While the locations that are primarily responsible for cross-contamination and foodborne disease outbreaks are markets, hotels, and restaurants, contamination can also occur through bad manufacturing and poor hygienic practices (Chao et al., 2009;Wang et al., 2014b). ...
... Priority factors were needed to be defined definitely to improve the yield of total flavonoids from S. baicalensis based on the established model. Pareto chart of the standardized coefficients corresponding to the independent variable and their interactions with statistical significance (p<0.05) was applied for investigating the relative contribution (Fig. 3) (dos Santos et al. 2012;Wang et al. 2014). The result showed the effects of the independent variable and their interactions were ranked as A 2 >> AD >> A > C > B 2 . ...
The response surface methodology (RSM) was used to optimize the conditions for total flavonoid extraction from Scutellaria baicalensis Georgi. The influences of the ethanol concentration, extraction time, temperature, and the liquid–solid ratio on flavonoid yield were investigated. Based on ANOVA results, a second-order quadratic polynomial model could be applied to characterize the extraction process. The following optimal extraction conditions were identified: ethanol concentration, 52.98 %; extraction time, 2.12 h; extraction temperature, 62.46 °C; and liquid–solid ratio, 35.23. The predicted extraction yield was 19.437 mg/g when these optimal conditions were used. The proposed method was successfully employed to extract flavonoids from S. baicalensis.
... The RSM has been recognized to be a powerful tool for determining the effects of different factors and the interactions among them (Bas and Boyaci, 2007). The central composite design (CCD) of RSM is the most common experimental design which has been successfully used to determine Salmonella inactivation on drycured ham (Bover-cid et al., 2012), and reduction of Bacillus subtilis (Aouadhi et al., 2013) and vibrio parahaemolyticus on cooked shrimp by acidic electrolyzed water (Wang et al., 2014). ...
In order to reduce the risk of enteric pathogens transmission in animal farms, the disinfection effectiveness of slightly acidic electrolyzed water ( SAEW: , pH 5.85 to 6.53) for inactivating Salmonella Enteritidis on the surface of plastic poultry transport cages was evaluated. The coupled effects of the tap water cleaning time (5 to 15 s), SAEW treatment time (20 to 40 s), and available chlorine concentrations ( ACC: s) of 30 to 70 mg/l on the reductions of S. Enteritidis on chick cages were investigated using a central composite design of the response surface methodology ( RSM: ). The established RS model had a goodness of fit quantified by the parameter R(2) (0.971), as well as a lack of fit test (P > 0.05). The maximum reduction of 3.12 log10 CFU/cm(2) for S. Enteritidis was obtained for the cage treated with tap water cleaning for 15 s followed by SAEW treatment for 40 s at an ACC of 50 mg/l. Results indicate that the established RS model has shown the potential of SAEW in disinfection of bacteria on cages.
© 2015 Poultry Science Association Inc.
... Table 2). The correlations between the predicted and observed values were used to evaluate by t-test the adequacy of the model for the treatment of Salmonella Typhimurium with nisin and EDTA (Wang et al., 2014). ...
Lantibiotics, such as nisin, generally act on Gram-positive bacteria, whereas Gram-negative bacteria exhibit natural resistance to the action of these bacteriocins. However, Gram-negative bacteria can become susceptible to the action of these antimicrobial peptides with the use of chelating agents, such as EDTA. The activity of bacteriocins can be influenced by several factors, such as environmental conditions and chemical composition of the medium. Moreover, the susceptibility of target microorganism can be altered, due to changes in cellular composition induced by environmental conditions. In this study, we examined the combined effect of variations in temperature and pH on the susceptibility of Salmonella Typhimurium to the action of nisin associated with EDTA. The reduction in the number of viable cells of Salmonella Typhimurium varied according to the temperature and pH, and major reduction in logarithmic cycles of viable cells occurred with a temperature increase. Under low temperature and low pH, a considerable reduction in the viability was also observed after prolonged exposure to bacteriocin, regardless of the presence of EDTA. According to results, temperature and pH conditions influence on the susceptibility of Salmonella Typhimurium to combination of nisin and EDTA and thus should be considered to establish optimal conditions for nisin use.
... The model was adequate since the Lack of Fit test (p > 0.05) was not significant ( Wang et al., 2014). The items including B, C, BC, and A 2 had a significant effect on EOs yield of C. japonicum; the items including A, C, AB, BC, B 2 and C 2 had a highly significant effect on EOs yield of C. setosum (see Supplementary Table S1). ...
... Moreover, SAEW and sodium hypochlorite treatment have an equivalent disinfection efficacy in fresh-cut cilantro, spinach, and cut cabbage samples (Koide et al., 2009;Rahman et al., 2010;Hao et al., 2011). Furthermore, Rahman et al. (2013) and Wang et al. (2014) demonstrated that SAEW treatment can be utilized to disinfect fresh shrimp and pork. Based on these experimental results, the United States Environmental Protection Agency (EPA) has approved the use of EW generators for disinfection in the food processing field. ...
To consistently disinfect fresh vegetables efficiently, the decay of disinfectants such as chlorine, electrolyzed oxidizing water (EOW), ozonated water, and plasma-activated water during the disinfection maintenance stage needs to be understood. The aim of our study was to evaluate the changes in the inactivation kinetics of slightly acidic electrolyzed water (SAEW) against human norovirus (HuNoV), based on the cabbage-to-SAEW ratio. After disinfection of fresh cabbage with disinfected SAEW solution, SAEW samples were collected and analyzed for physicochemical properties such as pH, available chlorine concentrations (ACCs), and oxidation-reduction potential (ORP). SAEW virucidal effects were evaluated. We confirmed the decay of post-disinfection SAEW solution and demonstrated the different patterns of the decay kinetic model for HuNoV GI.6 and GII.4. In addition, the goodness of fit of the tested models based on a lower Akaike information criterion, root-mean-square error (RMSE), and residual sum of squares (RSS) was close to zero. In particular, the change in both the HuNoV GI.6 and GII.4 inactivation exhibited a strong correlation with the changes in the ACC of post-disinfection SAEW. These findings demonstrate that physicochemical parameters of SAEW play a key role in influencing the kinetic behavior of changes in the disinfection efficiency of SAEW during the disinfection process. Therefore, to optimize the efficiency of SAEW, it is necessary to optimize the produce-to-SAEW ratio in future studies.
... The strong bactericidal efficacy of SAEW has been recognized by many studies on lots of microorganisms including the pure stains and the attachment to food materials and food-contact surfaces (Koide, et al., 2009;Quan, Choi, Chung, & Shin, 2010;Rahman, et al., 2013;Wang, et al., 2014). Our present study also demonstrated the strong bactericidal efficacy of SAEW on the pure strains of L. monocytogenes on food-contact surfaces, which is consistent to the previous reports. ...
In the present study, the bactericidal efficacy of slightly acidic electrolyzed water (SAEW) against L. monocytogenes planktonic cells and biofilm on food-contact surfaces including stainless steel and glass was systematically evaluated. The results showed that SAEW (pH of 5.09 and available chlorine concentration (ACC) of 60.33 mg/L) could kill L. monocytogenes on food-contact surfaces completely in 30 s, whose disinfection efficacy is equal to that of NaClO solutions (pH of 9.23 and ACC of 253.53 mg/L). The results showed that long exposure time and high ACC contributed to the enhancement of the disinfection efficacy of SAEW on L. monocytogenes on food-contact surfaces. Moreover, the log reduction of SAEW treatment presented an increasing tendency within the prolonging of treatment time when SAEW was used to remove the L. monocytogenes biofilm formed on stainless steel and glass surfaces, which suggested that SAEW could remove L. monocytogenes biofilm effectively and its disinfection efficacy is equal to (in case of stainless steel) or higher than (in case of glass) that of high ACC of NaClO solutions. In addition, the results of the crystal violet staining and scanning electron microscopy (SEM) also demonstrated that SAEW treatment could remove the L. monocytogenes biofilm on food-contact surfaces.
... The model was adequate since the Lack of Fit test (p > 0.05) was not significant ( Wang et al., 2014). The items including B, C, BC, and A 2 had a significant effect on EOs yield of C. japonicum; the items including A, C, AB, BC, B 2 and C 2 had a highly significant effect on EOs yield of C. setosum (see Supplementary Table S1). ...
In this study, the whole protein of Arthrospira (Spirulina) platensis was extracted and hydrolyzed with trypsin. Screening process for new peptides was driven by 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity assay, and a hexapeptide with sequence of GMCCSR was identified. Its anti-oxidant activity was measured based on ABTS, 1,1’-diphenyl-2-picrylhydrazyl (DPPH), and ferric reducing ability of plasma (FRAP) assays. Hemolysis inhibition on human erythrocytes and collagen-stimulating activities on human skin fibroblasts (HSFs) were investigated. Results showed that its radical scavenging effect could compete with ascorbic acid. Intracellular assays revealed the reduction of reactive oxygen species (ROS) and malondialdehyde (MDA) contents and the increase in activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in erythrocytes pretreated with hexapeptide, demonstrating that the peptide could protect erythrocytes from lipid peroxidation and protein oxidation. Moreover, results from HSFs showed that it could promote proliferation and collagen production of HSFs pro-damaged by UVB. These results suggest the potential of the hexapeptide in food and pharmaceutical industries.
... typhimurium, and Listeria monocytogenes pathogens from the surfaces of lettuce and spinach leaves with increasing time of exposure, while alkaline electrolyzed water did not decrease pathogen levels even after a 5 min treatment on lettuce and spinach (Park et al. 2008). Acidic electrolyzed water has been recognized to be an effective disinfectant for inactivating food-borne pathogens including Escherichia coli, Vibrio parahaemolyticus, and Listeria monocytogenes (Wang et al. 2014b). ...
... Studies on operating parameters indicated that an increase in the electrical potential enhanced the electrical current flow and ultimately the production of chlorine, and a similar effect was reported by increasing electrolysis time. However, the electrolysis time showed no significant effect on the total chlorine production after achieving the highest chlorine level [19][20][21]. Studies on the EW generator optimization using the RSM technique are rare; only one study was found where electrical voltages, different types of electrodes, NaCl concentrations, and electrolysis times were studied along with the bactericidal activity of the produced EW. ...
Hypochlorous acid (HOCl), also known as electrolyzed water (EW), is a sustainable and environment-friendly disinfectant, which can comply with food safety regulations. In this study, HOCl was produced through HCl electrolysis using an acrylic electrolyzing reactor without a diaphragm between iridium oxide electrodes coated with titanium. The Box–Behnken design (BBD) was adopted to study the effects of feed water flow rate (FR), pH, temperature, electric voltage, acid concentration (AC), and acid dosing pump stroke (APS) on HOCl production measured as available chlorine concentration (ACC). Then, optimum parameters were explored using response surface methodology (RSM). The proposed quadratic models defined the relationship between HOCl production and the process variables. The models were statistically significant as shown by analysis of variance. The optimum operating parameters for HOCl production were 6.5 L/min, pH 7.5 at 20 °C, 3.8 volts, 6% AC, and APS at 3%. The FR, AC, and APS were significant parameters, and no substantial effect was observed for pH and temperature of feed water or the variation in current–voltage. High FR caused a conspicuous drop, and the high voltage showed a slight increase in ACC. However, an increase in AC and APS significantly enhanced the ACC, although the pH dropped below 5.0–6.5, indicating the presence of other chlorine-based compounds apart from HOCl. RSM model validation through experimental results indicated that the proposed model could effectively provide a relationship between ACC and process variables. Additionally, an artificial neural network model was tested to predict the ACC that showed good fitness to the experimental results.
... Basic electrolytic water (BEW) was prepared by our previous method [20]. BEW were produced by electrolyzing sodium chloride (0.5%, 1%, 1.5% NaCl, w/v) solution using electrolyzed water generator (FW-200, AMANO, Japan). ...
A novel protein extraction method of ultrasound-assisted basic electrolyzed water (BEW) was proposed, and its effects on the structural and functional properties of Antarctic krill proteins were investigated. Results showed that BEW reduced 30.9% (w/w) NaOH consumption for the extraction of krill proteins, and its negative redox
potential (−800 ~ −900 mV) protected the active groups (carbonyl, free sulfhydryl, etc.) of the proteins from oxidation compared to deionized water (DW). Moreover, the ultrasound-assisted BEW increased the extraction yield (9.4%), improved the solubility (8.5%), reduced the particle size (57 nm), favored the transition of α-helix
and β-turn to β-sheet, promoted the surface hydrophobicity and disulfide bonds formation of krill proteins when compared to BEW without ultrasound. These changes contributed to the enhanced foam capacity, foam stabilityand emulsifying capacity of the krill proteins. Notably, all the physicochemical, structural and functional properties
of the krill proteins were comparable to those extracted by the traditional ultrasound-assisted DW. This study suggests that the ultrasound-assisted BEW can be a potential candidate to extract proteins, especially offering an alternative way to produce marine proteins with high nutritional quality.
... In these supply chains, hygienic processing is an essential tool for reducing or eliminating the contamination of pathogenic bacteria and EW has been widely adopted (Xie et al. 2012a, b;Al-Qadiri et al. 2016) (Table 6.1). Wang et al. (2014a) modelled the inactivation of V. parahaemolyticus on cooked shrimp by AEW. This study measured the log reductions of V. parahaemolyticus versus NaCl concentration (0.7-2.4 g/L), treatment time (3.6-10.4 ...
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.
In this study, the efficacy of electro activated water (EAW) and its mechanism on Escherichia coli and Enterococcus faecalis were investigated. The effects of different operating parameters of EAW on inactivation of bacteria were evaluated by response surface methodology (RSM). The interaction of free chlorine concentration and treatment time at 25 °C had a synergetic effect on E. coli and E. faecalis inactivation. The increase in crystal violet uptake showed the deterioration of cell membrane permeability. The release of 260 nm absorbing materials from both bacteria increased after EAW treatment. Protein degeneration increased with deformation of E. coli and E. faecalis cell membranes, which in turn was followed by the release of proteins together with other intracellular components such as DNA, RNA, potassium, and phosphate.
Practical applications
An electrode module was setup to produce EAW from a mixture of salt and tap water. Freshly prepared EAW was added to the bacterial pellets, mixing thoroughly and immediately initiating a timer. The mixtures were set at different treatment times. The effects of three operating parameters (treatment time, free chlorine concentration (FCC) and temperature) on bacteria inactivation were investigated using Response surface methodology. Crystal violet uptake assay, 260 nm release study and FT-IR spectroscopy analysis were conducted to determine the mechanism of action of EAW.
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.
Electrolyzed water (EW) considered as a novel broad-spectrum and high-performance bactericide has gained immense popularity over the last few decades. It offers several advantages over other sanitizers for sanitation of both food contact and noncontact surfaces, such as safety, effective disinfection, easy operation, relatively inexpensive, and environmentally friendly. EW can be produced by electrolyzing soft tap water with sodium chloride as the chemical additive. Different producing equipment and parameters greatly influence the types and properties of EW. During production period, preparation settings are vital factors on the basic properties of EW (available chlorine concentration (ACC), pH, and oxidization reduction potential (ORP)) and then influence its inactivation efficiency, including current, water flow rate, salt/acid concentration, electrolyte and electrode, water temperature and hardness, storage environments, and so on. This chapter provides an overview of the production, properties, types of EW, as well as a section on its advantages and disadvantages.
Pseudomonas spp. have emerged as the main spoilage bacteria, with many strains easily forming biofilms on food-contact surfaces and causing cross-contamination. The efficacy of disinfectants against bacteria is usually tested with planktonic cells; however, the disinfection tolerance of biofilms, especially detached biofilms, remains unknown. Here, we investigated the tolerance responses of detached and adhered biofilms of Pseudomonas fluorescens to acidic electrolyzed water (AEW) by determining tolerance responses by plate counting, comparing them using a Weibull model, and verifying changes in bacterial morphology by scanning electron microscopy. The experimental data and the responses calculated using Weibull a (scale) and b (shape) parameters agreed well (R ² values: 0.974–0.999), and we found that AEW exhibited effective antimicrobial activity against P. fluorescens, with adhered biofilms were more resistant than detached biofilms and planktonic cells. Additionally, AEW increased the bacterial membrane permeability and decreased the membrane potential, intracellular ATP concentrations, and intracellular pH while also triggering the disruption of extracellular polymeric substances. These results demonstrated that the morphophysiological responses of detached and adhered biofilms differed significantly and provided information on disinfectant-resistance strategies potentially beneficial to the development of novel disinfection approaches.
The Response Surface Methodology (RSM) was used to establish a predictive model of inactivation of S. flexneri using ultrasound time of 5–20 min, pH of 4.0–7.0 and nisin concentration of 29.1–291.1 μM as independent variables. In addition, a survival of S. flexneri at 7 °C for 120 h after treatment with ultrasound and nisin was evaluated as well as the ATP leakage. The response surface model (RS model) had a goodness fit with R ² and Adj.R ² of 0.942 and 0.916, respectively. The parameters of the RS model had a good performance and can be considered validated. The results demonstrated that at pH below 5.0, microbial death increases when ultrasound combined with nisin was used. The results showed that the pathogen inactivation is most pronounced immediately after treatment with ultrasound and nisin, but the viable cell number continues to reduce under storage conditions at 7 °C for 120 h. The microbial inactivation had a correlation with the leakage of ATP to the extracellular medium after the treatment.
Ultrasound (US) has a high capacity to increase food safety. Although high and/or moderate temperature in combination with US has been studied, the knowledge about cooling/low temperatures as well as its combined effect with chemical preservation methods is scarce. Therefore, the aim of this study was to describe the inactivation of Staphylococcus spp. (SA) present in the natural microbiota of sliced Brazilian dry-cured loin (Socol, BDL) using US (40 kHz and 5.40 W/g) at 1.6-17.9 kJ/g, temperature (T) between 6.4 and 73.6 °C and peracetic acid (PA) between 5.5 and 274.5 mg/L employing the Central Composite Rotatable Design. The model fully describes how the combination of US, T, and PA affects SA inactivation. In BDL, an increase in US acoustic energy density (kJ/g) allows the reduction of T necessary to inactivate SA because of the occurrence of synergistic effect. However, US applied at low T was inefficient. On the other hand, PA was more efficient at low T, since high T degraded this compound at different rates according to the holding T. Therefore, the data indicates a relation between the technologies used in the combined decontamination of sliced BDL improving dry-cured meat safety.
Extracellular DNA (eDNA) is considered as important determinant in bacterial biofilm formation. This study investigated the effects of DNase I and acidic electrolytic water (AEW) in beaking down mature Vibrio parahaemolyticus biofilms. Changes of key chemical components i.e. eDNA, extracellular proteins, extracellular polysaccharides, extracellular polymeric substances (EPS), and biofilm architecture were primarily used to quantify this effect. A secondary measure was the regulation of genes involved in biofilm formation. DNase I significantly inactivated bacterial cells, degraded eDNA and down-regulated expression of genes involved in biofilm formation (P < 0.05). However, biofilm architecture was only partially affected. AEW also induced deleterious changes in key chemical components of EPS, and effectively down-regulated genes involved in biofilm formation. In contrast, AEW collapsed the three-dimensional structures of biofilms and prevented the resestablishment of mature biofilms by 12 h when compared to the DNase I. AEW is therefore a more effective agent for controlling Vibrio parahaemolyticus biofilms.
Biofilms, which are complex microbial communities embedded in the protective extracellular polymeric substances (EPS), are difficult to remove in food production facilities. In this study, the use of acidic electrolyzed water (AEW) to remove foodborne pathogen biofilms was evaluated. We used a green fluorescent protein-tagged Escherichia coli for monitoring the efficiency of AEW for removing biofilms, where under the optimal treatment conditions, the fluorescent signal of cells in the biofilm disappeared rapidly and the population of biofilm cells was reduced by more than 67%. Additionally, AEW triggered EPS disruption, as indicated by the deformation of the carbohydrate C-O-C bond and deformation of the aromatic rings in the amino acids tyrosine and phenylalanine. These deformations were identified by EPS chemical analysis and Raman spectroscopic analysis. Scanning electron microscopy (SEM) images confirmed that the breakup and detachment of biofilm were enhanced after AEW treatment. Further, AEW also eradicated biofilms formed by both Gram-negative bacteria (Vibrio parahaemolyticus) and Gram-positive bacteria (Listeria monocytogenes) and was observed to inactivate the detached cells which are a potential source of secondary pollution. This study demonstrates that AEW could be a reliable foodborne pathogen biofilm disrupter and an eco-friendly alternative to sanitizers traditionally used in the food industry.
The aim of this study was to determine the combined effects of slightly acidic electrolyzed water [SAEW (pH range 5.0–6.5, oxidation–reduction potential 650–1000 mV, available chlorine concentration 10–80 mg/L)] containing 0, 15, and 30 ppm chlorine and 0, 50, and 100 min of ultrasound [US (37 kHz, 380 W)] using the central composite design (CCD) on the reductions of Escherichia coli and Vibrio parahaemolyticus (initial value, approximately 6–7 log10 colony forming unit (CFU) of E. coli or V. parahaemolyticus/g) and the sensory properties on freshly sliced shad (Konosirus punctatus), in comparison with SAEW or US alone. Another aim was to develop the response surface model for E. coli and V. parahaemolyticus in the shad treated with the combination of SAEW and US. Single treatments with SAEW (chlorine 15 ppm), SAEW (chlorine 30 ppm), or US for 50 min caused a much-less-than-1-log10 reduction in the number of both E. coli and V. parahaemolyticus in the shad. In contrast, the combination of SAEW (15 or 30 ppm chlorine) and US (50 or 100 min) caused >1-log10 reduction of E. coli numbers (1.04–1.86 log reduction) and V. parahaemolyticus (1.02–1.42 log reduction) in the shad. In addition, the sensory properties of the shad were not changed under the harshest conditions of the combination (SAEW with chlorine at 30 ppm and US for 100 min). Response surface models were developed for the population of E. coli (Y = 6.15322 − 0.024732X
1 − 0.016486X
2 − 0.00015X
1X
2 + 0.00024X
12 + 0.00007X
22) and V. parahaemolyticus (Y = 5.67649 − 0.042598X
1 − 0.014013X
2 + 0.00003X
1X
2 + 0.00006X
12 + 0.00062X
22 ), where Y is the bacterial population (log10 CFU), X
1 is ppm chlorine in SAEW, and X
2 is the duration of treatment (min) with US. The appropriateness of the models was verified by bias factor (B
f; 1.10 for E. coli, 1.03 for V. parahaemolyticus), accuracy factor (A
f; 1.11 for E. coli, 1.05 for V. parahaemolyticus), mean square error (MSE; 0.0087 for E. coli, 0.0028 for V. parahaemolyticus), and coefficient of determination (R
2; 0.976 for E. coli, 0.982 for V. parahaemolyticus). To produce a 1-log10 reduction of E. coli and V. parahaemolyticus, US treatment times for E. coli and V. parahaemolyticus were calculated within the maximum of 54 and 67 min, respectively, at chlorine 10 ppm in SAEW. SAEW chlorine concentrations (ppm) for E. coli and V. parahaemolyticus were calculated within the maximum of 38 and 41 ppm, respectively, at 20 min of US. Therefore, the resulting response surface models for E. coli and V. parahaemolyticus should be further validated on slices of other kinds of raw fish. Ultimately, the response surface quadratic polynomial equations may thus be used for predicting the combined treatments of SAEW and against E. coli and V. parahaemolyticus in raw fish production, processing, and distribution.
Under the current commercial practice, live mussels only have 10 days’ shelf-life. Observed spoilage indices reduce consumers’ acceptance, palatability and shelf-life of modified atmosphere packaged (MAP) live mussels. The aims of this study are to isolate specific spoilage bacteria from modified atmosphere packaged live mussels, evaluate isolates for microbial spoilage indices using qualitative methods and volatile metabolites production. Forty-six hydrogen sulphide producing bacteria were isolated and evaluated for trimethylamine n-oxide (TMAO) reduction, proteolytic and lipolytic activities and hydrogen sulphide production. Twenty-eight isolates were obtained from pouch water and 18 from mussel meat. All the isolates could produce H2S on Iron agar at 25 °C while 30/46 produced H2S at 4 °C and tolerate 0–6% NaCl. Four (4/46) isolates could not hydrolyse mussel protein. Over 80% isolates reduced TMAO to TMA in 3 days with the production of H2S. Results of this study shows hydrogen sulphide producing bacteria isolated from MAP live mussels produce microbial spoilage indices. Isolate with highest enzymatic activities and hydrogen sulphide production was identified as Shewanella baltica using 16S rRNA gene. Axenic culture of the isolate was inoculated into sterile mussel broth. Inoculated sample was further stored at 4 °C for 10 days for spoilage study. Volatile metabolites produced during storage were evaluated using headspace solid phase micro-extraction gas chromatography mass spectrometry (HS-SPME GC/MS). A total of 44 compounds were identified in the sample after 10 days while 27 compounds were identified in inoculated mussel broth. Group of compounds identified are alcohols, aldehydes, phenol, furans, ketone, esters, organic acid, aromatic hydrocarbons, alkanes, nitrogen and sulphur containing compounds. Dimethyl trisulphide, methyl-phenol, 3,5-octadiene and thiohexene were unique to inoculated mussel broth. Understanding spoilage mechanism and attendant spoilage indices will help in designing effective mussel quality protocols and shelf-life extension.
The aquaculture industry has witnessed a continuous rapid growth over the last two decades from a combination of increased seafood consumption and production. These aquatic products filled a niche in the modern demand for alternate sources of protein. Electrolyzed water (EW), a novel non-thermal technique, is currently being used as an environmental-friendly sanitizer, and frozen electrolyzed water ice (EW ice) has emerged as an alternative method for improving the safety and quality of seafood. EW and EW ice whilst reducing microbial contamination also contribute to extending the shelf life of aquatic products compared to conventional sanitizers. This present chapter provides a comprehensive guide to the application of EW and EW ice on aquatic products and offers clear perspectives for a global adoption of EW in the seafood industry.
Development of various novel thermal and nonthermal techniques has shown potential applications in meat processing and preservation. Consumer's demand of meat products with esteemed quality, wholesomeness, and superior safety has led to the commercial introduction of these innovative methods. Accordingly, this treatise outlines the potential of several advanced thermal and nonthermal methods like super‐chilling, ultrarapid freezing, immersion vacuum cooling, hydrofluidization freezing, impingement freezing, electrostatic‐assisted freezing, pressure‐shift freezing, acidic electrolyzed water coupled with high hydrostatic pressure, and nonthermal plasma technique for preserving meat quality and prolongation of shelf stability. This article also highlights the advancements in the packaging technology like use of linear low‐density polyethylene‐based active clay nanocomposite films and resulted benefits for the meat sector. Additionally, consumer responses to various meat products preserved with these technologies are also discussed in this critique. The focal objective of the current discourse is to reconnoiter the aptitude of these novel techniques in meat preservation so that these methods can be adopted at commercial scale in a much broader sense.
Practical applications
For decades, several methods have been adopted for preservation of meat. With technological advancements, meat industry is looking for some modern and economic preservation methods for meat and meat‐based products. In this regard, several nonconventional techniques like super‐chilling, hydrofluidization freezing, impingement freezing, electrostatic‐assisted freezing, and pressure‐shift freezing have shown their potential for effective meat preservation. Therefore, this article will be helpful for the meat industrialists to consider these techniques for commercial preservation of meat and meat products in a more effectual manner.
The optimization of parameters for the effective leaching of thermostable pullulanase from Clostridium thermosulfurogenes SV2-fermented bran was carried out using response surface methodology based on the central composite rotatable design. The design contains a total of 54 experimental trials with the first 32 organized in a fractional factorial design and experimental trials from 33–40 and 51–54 involving the replication of the central points. The design was employed by selecting solvent to wheat bran ratio (S/BB), process temperature, solvent pH, shaking (RPM) and contact time (h) as model factors. Among the five independent variables studied, the S/BB, solvent pH and shaking were found to be significant. S/BB ratio of 9.0, 200 RPM shaking and solvent pH 6.0 were identified as optimum for the leaching of thermostable pullulanase from the strain SV2-fermented bran.
Summary Microflora adhering to surfaces of processing lines in a shrimp factory and a fish pro- cessing plant was identified in situ and adhesion of mixed culture of Listeria monocytogenes and Gram-negative bacteria on stainless steel surfaces (untreated, polished and glass bead- ed) was studied ex situ. The predominant genus attached to the surfaces was Pseudomonas spp. (66 %) in the shrimp factory and Enterobacteriaceae (27 %) in the fish factory. Shrimp juice was used as an enrichment broth during the study of adhered bacteria. Three diffe- rent Gram-negative strains and a mixture of Pseudomonas spp. were selected to study their attachment together with L. monocytogenes to stainless steel surfaces. Highest numbers of the attached bacteria were obtained after the contamination with a mixed culture of L. mo- nocytogenes and Serratia liquefaciens. A lower number of bacteria adhered to stainless steel surfaces when mixed cultures of L. monocytogenes and Pseudomonas fluorescens or Aeromonas spp. were tested. No significant differences (p
The objective of this study was to investigate
the combined effect of temperature (15-35oC), pH (3-9),
and dipping time (1-5 min) on the inactivation of
Staphylococcus aureus in broth treated with low
concentration electrolyzed water (LcEW). Reductions of
1.44-7.12 log CFU/mL were observed in different
combinations of the 3 factors. Also, a quadratic equation
for S. aureus inactivation kinetic was developed by
multiple regression analysis using response surface
methodology. The predicted values were shown to be
significantly in good agreement with experimental values
as a result of the level of significance was p<0.0001.
Besides, the developed model was validated by fitting with
literature data and the results showed that the predictions
had a good agreement with the observed data with a
satisfied determination of coefficient (R2=0.963).
a b s t r a c t A microbiological risk assessment was conducted on Vibrio parahaemolyticus in order to estimate the risk of getting infected by consuming cooked shrimps (Penaeus monodon) for Malaysians. This study was based on the risk assessment framework developed by the Codex Alimentarius Commission. The risk estimate was calculated by using the data generated from this study and assumptions based on data taken from reports produced by the Ministry of Health Malaysia and from other studies. The @RISK software package, version 4.5 (2005 Palisade USA) in combination with Microsoft Ò Excel were used to run the simulations. All of the calculations were performed by the Monte Carlo method of simulations from specified input distributions and appropriately combining the sampled values to generate the corresponding output distributions. All simulations, consisting of 10,000 iterations were undertaken. The estimated illness per year was 123 people (aged from 18 to 59 years) for Malaysians. The 90% of distribution of illness due to the consumption of cooked shrimps lies between 49 and 197 cases per year. The incidence rate of illness/100,000 population/year (aged between 18 and 59 years) is 1.3 while 90% distribution lies between 0.5 and 2. In the case of shrimp that were cooked during meal preparation, the hazard has been significantly reduced. It is important to pay attention to temperature control during harvesting and post-harvest handling. It is also required to prevent cross-contamination during handling and preparation of shrimps and adequate cooking before consumption. Ó 2012 Published by Elsevier Ltd.
Electrolyzed oxidizing water has been estimated that it has strong bactericidal activity and has been widely used as a disinfectant for inactivating microbial organisms. The combined effects of temperature (15–35C), chlorine concentration of electrolyzed oxidizing water (30–70 ppm) and treatment time (1–5 min) on the reduction of Listeria monocytogenes in lettuce were investigated. Reductions of 1.39–2.79 log10 cfu/g were observed in different combinations of the three factors. Also, a quadratic equation for L. monocytogenes inactivation kinetic was developed by multiple regression analysis using response surface methodology. The predicted values were shown to be significantly in good agreement with experimental values because the adjusted determination coefficient () was 0.9578 and the level of significance was P < 0.0001. Besides, average mean deviation (E%), bias factor (Bf) and accuracy factor (Af), which are validation indicators of the model were 0.0218, 1.0003 and 1.0220, respectively. Thus, predicted model showed a good correlation between the experimental and predicted values, indicating success at providing reliable predictions of L. monocytogenes growth in lettuce.PRACTICAL APPLICATIONSElectrolyzed oxidizing water is an important sanitizer, and nowadays it has been widely used in food industry. Lettuce is regarded as a “healthier” food, which is one of the most popular vegetables consumed, whereas many outbreaks caused by L. monocytogenes have been reported until now. According to the model developed in this study, inactivation of L. monocytogenes in lettuce treated with EO water could be predicted by inputting a certain group of environmental factors.
The optimization of parameters for the effective leaching of thermostable pullulanase from Clostridium thermosulfurogenes SV2-fermented bran was carried out using response surface methodology based on the central composite rotatable design. The design contains a total of 54 experimental trials with the first 32 organized in a fractional factorial design and experimental trials from 33-40 and 51-54 involving the replication of the central points. The design was employed by selecting solvent to wheat bran ratio (S/BB), process temperature, solvent pH, shaking (RPM) and contact time (h) as model factors. Among the five independent variables studied, the S/BB, solvent pH and shaking were found to be significant. S/BB ratio of 9.0, 200 RPM shaking and solvent pH 6.0 were identified as optimum for the leaching of thermostable pullulanase from the strain SV2-fermented bran.
The Method of Least Squares Linear Models Matrix Formulas for Least Squares Geometry of Least Squares Analysis of Variance for One Regressor Least Squares for Two Regressors Geometry of the Analysis of Variance for Two Regressors Orthogonalizing the Second Regressor, Extra Sum of Squares Principle Generalization to p Regressors Bias in Least-Squares Estimators Arising from an Inadequate Model Pure Error and Lack of Fit Confidence Intervals and Confidence Regions Robust Estimation, Maximum Likelihood, and Least Squares Appendix 3A. Iteratively Reweighted Least Squares Appendix 3B. Justification of Least Squares by the Gauss?Markov Theorem; Robustness Appendix 3C. Matrix Theory Appendix 3D. Nonlinear Estimation Appendix 3E. Results Involving V(?) Exercises
This study was conducted to develop a model to describe the effect of antimicrobials [potassium sorbate (PS), potassium lactate (PL), and combined PL and sodium diacetate (SDA, PLSDA)] on the growth parameters of Listeria monocytogenes such as specific growth rate (SGR) and lag phase periods (LT) in air-dried raw sausages as a function of storage temperature (4, 10, 16, and 25°C). Results showed that the SGR of L. monocytogenes was dependent on the storage temperature and level of antimicrobials used. The most effective treatment was the 4% PLSDA, followed by the 2% PLSDA and 4% PL and 0.2% PS exhibited the least antimicrobial effect. Increased growth rates were observed with increasing storage temperatures from 4 to 25°C. The growth data were fitted with a Gompertz equation to determine the SGR and LT of the L. monocytogenes. Six polynomial models were developed for the SGR and LT to evaluate the effect of PS (0.1, 0.2%) and PL (2, 4%) alone and PLSDA (2, 4%) on the growth kinetics of L. monocytogenes from 4 to 25°C.
a b s t r a c t Bacillus sporothermodurans is a milk spoilage bacterium producing resistant endospores that survive ultra-high temperature treatment. The inactivation of B. sporothermodurans LTIS27 spores by combined hydrostatic pressure and heat treatments was studied. A central composite experimental design was used to evaluate the effect of pressure (300e500 MPa), temperature (30e50 C), and pressure-holding time (10e30 min) on the inactivation of spores in distilled water and skim milk. The inactivation observed was shown to fit well with the values predicted by the quadratic equation, since R adj 2 were 0.970 and 0.977 in distilled water and milk, respectively. By analyzing the response surface plots, the inacti-vation was shown to be higher in distilled water than in milk under all the conditions tested. This was probably due to a protective effect of milk against inactivation by pressure. The optimum process parameter values for a 5-log cycle reduction of spores were calculated as 477 MPa/48 C for 26 min and 495 MPa/49 C for 30 min in water and in milk, respectively. This study shows the efficiency of hydrostatic pressure in combination with moderate temperature to inactivate B. sporothermodurans spores. Such treatments could be applied by the dairy industry to ensure the commercial sterility of UHT milk.
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 investigate the efficacy of acidic electrolyzed water (AEW) against Vibrio parahaemolyticus on shrimp. The shrimp was initially inoculated with V. parahaemolyticus(7–8 log CFU/g), and treated with AEW (AEW1 containing 51 mg/L of chlorine or AEW2 containing 78 mg/L of chlorine) or organic acids (2% AA and 2%LA) for 1 min or 5 min under different treated conditions. The effect of AEW was better than that of organic acids, the number of survival V. parahaemolyticus cells on shrimp was reduced by 0.9 log CFU/g after treatment for 5 min with AEW without vibration, while 1.0 log CFU/g bacteria cells reduced with vibration. No significant difference (p > 0.05) was observed between AEW and organic acids in the bactericidal activity with or without vibration. The effective order of temperatures on bactericidal activities of AEW was 50 °C > 20 °C > 4 °C, and a 3.1 log CFU/g reduction of V. parahaemolyticus cells on shrimp was detected with treatment of AEW at 50 °C. Mild heat greatly enhanced efficacy of electrolyzed water against V. parahaemolyticus. Basic electrolyzed water (BEW) (50 °C) pretreatment combined with AEW (50 °C) treatment remarkably reduced bacterial cells by 5.4 log CFU/g on shrimp after treatment for 5 min. There was a significant change in physicochemical properties (pH, ORP, ACC) of AEW, after it was used to wash shrimp (P < 0.05). This study suggests that BEW (50 °C) pretreatment followed by AEW (50 °C) treatment could be a possible method to effectively control V. parahaemolyticus contamination on shrimp.
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 5min; 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 5min 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 30d against total aerobic bacteria on raw shrimp at 2min. 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 5min, 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.
The lethal effect of high pressure on microorganisms is influenced by a number of factors in relation to the technological variables, microorganisms and food matrix, which have to be considered when designing high pressure processes. The present work aimed to develop and validate a model of the inactivation of Salmonella enterica on dry-cured ham by high pressure processing (HPP), as a function of the technological parameters: intensity, length and fluid temperature. Dry-cured ham inoculated with S. enterica was treated at different HPP conditions (at 347 to 852MPa; for 2.3 to 15.75min; at 7.6 to 24.4°C) following a central composite design. Bacterial inactivation was assessed in terms of logarithmic reductions of Salmonella counts on selective media. According to the best fitting and most significant polynomial equation, pressure and time were the most important factors determining the inactivation extent. Temperature showed significant influence through its interaction with both pressure and holding time. The model was validated with results obtained from further experiments within the range of the experimental domain. The accuracy factor and bias factor were within the proposed acceptable values indicating the suitability of the model for predictive purposes, for instance to predict the process criteria to meet the lethality safety standards. The results of this work may help food processors to select optimum processing conditions of HPP to ensure the microbiological safety of pressure-treated foods.
The effects of high pressure (400–600MPa) and moderate heat (60–80°C) treatments at various process times (10–20min) on the reduction of Bacillus cereus As 1.1846 spores, suspended in milk buffer were investigated. In the present work, response surface methodology (RSM) was employed, and a quadratic equation of high hydrostatic pressure inactivation was built with RSM. By analyzing response surface plots and corresponding contour plots and by solving the quadratic equation, experimental values were shown to be significantly in agreement with predicted values, since the adjusted determination coefficient (RAdj2) was 0.9752 and the level of significance was P
For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10min. EO water achieved additional 0.7logCFU/cm2 reduction than tap water on E. coli after 1min treatment and additional treatment time did not achieved additional reduction. EO water treatment also reduced V. parahaemolyticus, by 1.5logCFU/cm2 after 5min treatment and achieved 2.6logCFU/cm2 reduction after 10min. The pathogenic bacteria were not detected in EO water after soaking treatment. In addition, EO water could effectively disinfect the platform of fish retailer in traditional markets and fish markets.
Background: Glutaraldehyde (GA) is currently considered to be the best disinfectant for endoscope disinfection. However, GA poses high risks for medical staff involved in the process and also to the environment. Strongly acidic electrolyzed water (SAEW) has been recently re-evaluated for its potent bactericidal effect and environmental safety.
Methods: Through the aspiration channel of the scopes, upper GI endoscopes and colonoscopes were experimentally contaminated with Pseudomonas aeruginosa, Mycobacterium avium and hepatitis B surface antigen positive blood. Four disinfection methods were tested: manual washing only, soaking in 3% GA for 5 and 10 min, and a 10-s soak in SAEW with 50 or 100 mL of aspiration.
Results: Direct plating culture was positive for Pseudomononas contamination after manual washing only (1/5) and after a 5-min soak in 3% GA. Complete disinfection, confirmed by enrichment culture and polymerase chain reaction (PCR) of Pseudomonas and hepatitis B surface antigen positive blood on the contaminated upper GI endoscope was obtained after a 10-min soak in GA and after using SAEW (0/5). Mycobacterum avium are rather resistant against SAEW as determined by broth culture and PCR (1/5).
Conclusion: Strongly acidic electrolyzed water is a valuable disinfectant for endoscopes.
The effects of processing and postprocess storage conditions on the incidence and survival of Listeria monocytogenes on crawfish (Procambaris sp.), crabmeat (Callinectus sapidus), and smoked salmon (Salmo salar) were evaluated. L. monocytogenes was recovered from 3% of whole boiled market crawfish samples and 17% of frozen vacuum-packaged partially cooked crawfish tail meat, but not from boiled crabmeat or smoked salmon. Contamination was most likely due to postprocess handling as commonly used methods of cooking (5 min boil or 20 min steep) reduced L. monocytogenes to nondetectable levels in laboratory-contaminated crawfish. In postprocess storage temperature abuse studies, cooked whole crawfish were inoculated internally and externally with 3.0 log CFU of L. monocytogenes per g and incubated at 22 or 30°C for 6 h. The greatest increase in numbers of cells, 1.9 log CFU/g (determined by standard plate count), occurred at 30°C on externally contaminated crawfish. There was little change in numbers of L. monocytogenes during cold storage (6°C, 5 days; −20°C, 15 days). There was little change in cell numbers associated with products stored at 22 or −20°C. At 6°C, numbers of cells associated with crabmeat increased by 3.8 log MPN/g after 6 days; however, there was no increase in numbers of cells associated with salmon. The results show that the survival and growth characteristics of L. monocytogenes are dependent on storage time and temperature and the nature of the seafood product.
Background: It is well known that strongly acidic electrolyzed water (SAEW) has a potent bactericidal effect. We examined residual viruses on endoscopes that were used in hepatitis B virus (HBV)-positive and hepatitis C virus (HCV)-positive patients and evaluated the effectiveness of SAEW in cleaning/disinfecting the endoscopes.
Methods: A random sample of endoscopes used in 109 endoscopies on HBV-positive patients and 107 endoscopies on HCV-positive patients, who underwent upper gastrointestinal endoscopy for various reasons was taken to determine the degree of HBV and HCV contamination. Samples were taken using 10 mL of physiological saline injected through the forceps channel of each endoscope and collected at the distal end to be assayed using polymerase chain reaction (PCR). After examination, each endoscope was treated with air aspiration, then 200 mL of tap water that contained an enzyme detergent was absorbed, and SAEW was aspirated after cleaning with a brush. After each procedure, PCR was used for comparison and to identify any residual viruses.
Results: In saline collected after air aspiration, viruses were detected in 39/109 endoscopes used in HBV patients and in 20/107 endoscopes used in HCV patients. In the saline aspirated with tap water containing an enzyme detergent, HBV was detected in 12/109 endoscopes and HCV was detected in 6/107 endoscopes. However, neither HBV nor HCV was detected after the endoscopes were cleaned manually with a brush and disinfected with SAEW.
Conclusion: Endoscopes contaminated with HBV and HCV are effectively cleaned and disinfected by SAEW.
This study examined the concentration of cetylpyridinium chloride (CPC) required to control Listeria monocytogenes on the surfaces of raw and cooked, peeled and shell-on shrimp. Shrimp (5 g) were inoculated by immersion into a 24 h culture of L. monocytogenes (decimally diluted in PBS) for 1 min, followed by air drying for 1 h, to yield between 6.2 log and 7.0 log CFU/g. The raw and cooked shell-on samples had higher L. monocytogenes counts than the peeled shrimp groups after this inoculation process. The shrimp samples were treated by soaking in different concentrations of CPC (0.05, 0.1, 0.2, 0.4, 0.6, 0.8, or 1.0%) solutions for 1 min, with or without a water rinse for 1 min. The samples were bagged, stored at 4 °C for 24 h, and then plated onto Oxford selective media for determination of log CFU/g. All CPC treatments (0.05% to 1.0%) that were followed by a water rinse reduced L. monocytogenes counts on cooked shrimp by about 2.5 log CFU/g. Conversely, treatments not followed by a water rinse reduced L. monocytogenes counts on cooked shrimp by 3 log CFU/g with 0.1, 0.2, or 0.4% CPC, 5 log CFU/g with 0.6% CPC, 6 log CFU/g with 0.8% CPC, and 7.0 log CFU/g with 1.0% CPC. These results indicate that a soaking treatment of CPC has a strong potential to eliminate or reduce L. monocytogenes on the surfaces of shrimp.
The effects of cultivation medium compositions including tapioca, fishmeal, CaCO3 and (NH4)2SO4 for the growth of Bacillus thuringiensis YMB 96-1988 were accessed by using response surface methodology (RSM). The two-level (24-1) fractional factorial designs (FFD) which involve two concentrations of each nutrient, and the paths of steepest ascent were effective in searching for the major factors of the bacteria growth. This allows the fitting of a first order linear model to the data. In this study, supplementary CaCO3 showed a negative effect on the spore production based on the first order regression coefficients derived from SAS programme. Subsequently, a 23 central composite design (CCD) was used for allocation of treatment combinations. Preliminary studies showed that tapioca and fishmeal is believed to be the major factors for the growth of B. thuringiensis. Estimated optimum compositions for the production of spores by B. thuringiensis are as follows: tapioca, 5.01%; fishmeal 5.86%; (NH4)2SO4 0.06% and resulted in a maximum spore count of 8.56 2 108/ml was obtained. This value is close to the 8.35 2 108/ml spore density as counted from actual experimental observations.
Raw fish is prone to the risk of microbial outbreaks due to contamination by pathogenic microorganisms, such as Escherichia coli O157:H7 and Listeria monocytogenes. Therefore, it is essential to treat raw fish to inactivate pathogenic microorganisms. Electrolyzed Oxidizing Water (EO) is a novel antimicrobial agent containing acidic solution with a pH of 2.6, Oxidation Reduction Potential (ORP) of 1150 mV, and 70–90 ppm free chlorine, and alkaline solution with a pH of 11.4 and ORP of −795 mV. This study was undertaken to evaluate the efficacy of acidic EO water treatment and alkaline EO water treatment followed by acidic EO water treatment at various temperatures for the inactivation of E. coli O157:H7 and L. monocytogenes Scott A on the muscle and skin surfaces of inoculated salmon fillets. Inoculated salmon fillets were treated with acidic EO water at 22 and 35 °C and 90 ppm free-chlorine solution as control at 22 °C for 2, 4, 8, 16, 32, and 64 min. The acidic EO water treatments resulted in a reduction of L. monocytogenes Scott A population in the range of 0.40 log10 CFU/g (60%) at 22 °C to 1.12 log10 CFU/g (92.3%) at 35 °C. Treatment of inoculated salmon fillets with acidic EO water reduced E. coli O157:H7 populations by 0.49 log10 CFU/g (67%) at 22 °C and 1.07 log10 CFU/g (91.1%) at 35 °C. The maximum reduction with chlorine solution (control) was 1.46 log10 CFU/g (96.3%) for E. coli O157:H7 and 1.3 log10 CFU/g (95.3%) for L. monocytogenes Scott A at 64 min. A response surface model was developed for alkaline treatment followed by acidic EO water treatment to predict treatment times in the range of 5–30 min and temperatures in the range of 22–35 °C for effective treatment with alkaline EO water followed by acidic water, alkaline and acidic water treatments. Response surface analysis demonstrated maximum log reductions 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. Data collected from the treatments was used to develop empirical models as a function of treatment times and temperature for prediction of population of E. coli O157:H7 and L. monocytogenes Scott A. Correlations (R2) of 0.52 and 0.77 were obtained between model predicted and experimental log10 reduction for E. coli O157:H7 and L. monocytogenes Scott A reductions, respectively. These results clearly indicated that EO water has a potential to be used for decontamination of raw fish.
The combined effects of different temperatures (10.5–24.5 °C), pH level (5.5–7.5), sodium chloride levels (0.25–6.25%) and sodium nitrite levels (0–200 ppm) on the predicted growth rate and lag-time of Leuconostoc mesenteroides under aerobic and anaerobic conditions was studied. The response surface (RS) model developed provided reliable estimates of the three kinetic parameters studied, with a bias factor between 0.86 and 1.18 and an accuracy factor between 1.13 and 1.31, in aerobic and anaerobic conditions, respectively. For both conditions, SEP values ranged between 15.62% and 27.63%. The developed models are a valuable tool, enabling its application for shelf-life estimation of a food product.
Our published results and our studies for optimization of process conditions to inactivate Bacillus subtilis by high hydrostatic pressure and mild heat using response surface methodology indicated that the optimum process parameters for a six-log-cycle reduction of B. subtilis were obtained as temperature, 46 °C; pressure, 479 MPa; and pressure holding time, 14 min. Based on the results, response surface methodology (RSM) was employed in the present investigation, the effects of food constituents like soybean protein, soybean oil, sucrose, and pH of food matrix on the B. subtilis reduction during high pressure and moderate heat was studied, and a quadratic polynomial predictive model for the effects of food constituents and pH of food matrix on B. subtilis reduction during high pressure and moderate heat was built with RSM accurately. The experimental results showed that the efficiencies of B. subtilis reduction in milk buffer and food matrix designed in the present work, under the condition of high pressure treatment process parameters described above, had some differences. The soybean protein (P < 0.0001), sucrose (P < 0.0001), and pH (P = 00006) significantly affected reduction of B. subtilis. The effect of soybean oil on reduction of B. subtilis was not significant (P = 0.8363). The adequacy of the predictive model equation for predicting B. subtilis reduction in food matrix by high pressure and moderate heat was verified effectively using experimental test date that was not used in the development of the model.
Electrolyzed oxidizing (EO) water has been regarded as a new sanitizer in recent years. Production of EO water needs only water and salt (sodium chloride). EO water have the following advantages over other traditional cleaning agents: effective disinfection, easy operation, relatively inexpensive, and environmentally friendly. The main advantage of EO water is its safety. EO water which is also a strong acid, is different to hydrochloric acid or sulfuric acid in that it is not corrosive to skin, mucous membrane, or organic material. Electrolyzed water has been tested and used as a disinfectant in the food industry and other applications. Combination of EO water and other measures are also possible. This review includes a brief overview of issues related to the electrolyzed water and its effective cleaning of food surfaces in food processing plants and the cleaning of animal products and fresh produce.
The Nernst equations between the oxidation-reduction potential (ORP), the concentration of hypochlorous acid and chlorine and the value of pH in electrolyzed oxidizing water (EOW) were developed in three parts, which were in agreement in the measured values. The role of ORP in EOW for killing Escherichia coli O157:H7 was studied. The inactivation effect of EOW on E. coh O157:H7 was also studied by spectroscopy measurements, and the inactivation mechanism was proposed. (c) 2006 Elsevier Ltd. All rights reserved.
The safety of electrolyzed seawater was evaluated by measuring the production rate of organic halogen compounds and the occurrence of reverse mutations. Aquaculture feedwater and wastewater were collected from a fish-culturing facility, and available chlorine of approximately 1.0 mg/L was generated to ensure a disinfectant effect. More than 90% of the generated organic halogen compounds were bromoform. The amount of bromoform was far less than the reference values for drinking water standards in Japan and the U.S., provided that the electrolyzation was performed within the range of normal use. The reverse mutation assay of electrolyzed seawater showed no mutagenicity. Electrolyzed seawater with available chlorine at an adequate level for disinfection can be used safely and effectively in various aspects of aquaculture.
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.
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.
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.
The effect of NaCl concentration (5.0 115.0 g/l). pH value (4.0-7.2), temperature (1-35 degrees C) and NaNO2 concentration (0 200 mg/l) on the growth responses of Listeria monocytogenes, in laboratory medium was investigated. The growth curves generated within this matrix of conditions were fitted using the function of Baranyi and Roberts (1994) and the growth responses modelled using a quadratic polynomial to produce response surfaces. Growth curves could then be regenerated for any set of conditions within the experimental matrix and values predicted for the growth rate, doubling time, lag time and time to 1000-fold increase. The model was validated using data from published literature and was found to give realistic predictions for doubling times in foods, including meat and meat products, milk, dairy products and vegetables. Predictions from this model (Baranyi and Roberts. 1994) compared favourably with those from the models of Buchanan and Phillips (1990), Murphy et al. (1996) and the Food MicroModel.
We reported the high effectiveness of electrolyzed strong acid aqueous solution (ESAAS) in cleaning hemodialysis lines. Although ESAAS has a strong bactericidal action, one concern is its strong acidity. It has a pH of 2.3-2.7, more than 1,000 mV in oxidation-reduction potential (ORP), and 10-50 ppm of available chlorine. The possibility of metal corrosion, degradation of synthetic resins, chorine gas emission, or dissolving calcium carbonate (CaCO3) deposits due to ESAAS's acidity was tested using in vitro experiments. The bactericidal and antiviral effects of various ESAAS's were also tested. Metal corrosion and synthetic resin degradation, although they occurred, were not serious. There were no problems with chlorine gas emission and dissolving of CaCO3 deposits. Each type of ESAAS showed almost the same bactericidal and antiviral effect, but in some cases differences were observed.
This study investigates the properties of electrolyzed oxidizing (EO) water for the inactivation of pathogen and to evaluate the chemically modified solutions possessing properties similar to EO water in killing Escherichia coli O157:H7. A five-strain cocktail (10(10) CFU/ml) of E. coli O157:H7 was subjected to deionized water (control), EO water with 10 mg/liter residual chlorine (J.A.W-EO water), EO water with 56 mg/liter residual chlorine (ROX-EO water), and chemically modified solutions. Inactivation (8.88 log10 CFU/ml reduction) of E. coli O157:H7 occurred within 30 s after application of EO water and chemically modified solutions containing chlorine and 1% bromine. Iron was added to EO or chemically modified solutions to reduce oxidation-reduction potential (ORP) readings and neutralizing buffer was added to neutralize chlorine. J.A.W-EO water with 100 mg/liter iron, acetic acid solution, and chemically modified solutions containing neutralizing buffer or 100 mg/liter iron were ineffective in reducing the bacteria population. ROX-EO water with 100 mg/liter iron was the only solution still effective in inactivation of E. coli O157:H7 and having high ORP readings regardless of residual chlorine. These results suggest that it is possible to simulate EO water by chemically modifying deionized water and ORP of the solution may be the primary factor affecting microbial inactivation.
Predictive microbiology provides a powerful tool to aid the exposure assessment phase of ‘quantitative microbial risk assessment’. Using predictive models changes in microbial populations on foods between the point of production/harvest and the point of eating can be estimated from changes in product parameters (temperature, storage atmosphere, pH, salt/water activity, etc.). Thus, it is possible to infer exposure to Listeria monocytogenes at the time of consumption from the initial microbiological condition of the food and its history from production to consumption. Predictive microbiology models have immediate practical application to improve microbial food safety and quality, and are leading to development of a quantitative understanding of the microbial ecology of foods.
The effectiveness of electrolyzed (EO) water for killing Campylobacter jejuni on poultry was evaluated. Complete inactivation of C. jejuni in pure culture occurred within 10 s after exposure to EO or chlorinated water, both of which contained 50 mg/l of residual chlorine. A strong bactericidal activity was also observed on the diluted EO water (containing 25 mg/l of residual chlorine) and the mean population of C. jejuni was reduced to less than 10 CFU/ml (detected only by enrichment for 48 h) after 10-s treatment. The diluted chlorine water (25 mg/l residual chlorine) was less effective than the diluted EO water for inactivation of C. jejuni. EO water was further evaluated for its effectiveness in reducing C. jejuni on chicken during washing. EO water treatment was equally effective as chlorinated water and both achieved reduction of C. jejuni by about 3 log10 CFU/g on chicken, whereas deionized water (control) treatment resulted in only 1 log10 CFU/g reduction. No viable cells of C. jejuni were recovered in EO and chlorinated water after washing treatment, whereas high populations of C. jejuni (4 log10 CFU/ml) were recovered in the wash solution after the control treatment. Our study demonstrated that EO water was very effective not only in reducing the populations of C. jejuni on chicken, but also could prevent cross-contamination of processing environments.
The effects of electrolyzed oxidizing (EO) water on reducing Listeria monocytogenes contamination on seafood processing surfaces were studied. Chips (5 x 5 cm(2)) 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.
Clostridium sporogenes is considered to be a non-toxingenic equivalent of proteolytic Clostridium botulinum, and it also causes food spoilage. The effects of temperature (16.6-33.4 degrees C), pH value (5.2-6.8) and concentration of sodium chloride (0.6-7.4%) on the growth parameters of C. sporogenes spores were investigated. The growth curves generated within different conditions were fitted using Baranyi function. Two growth parameters (growth rate, GR; lag-time, LT) of the growth curves under combined effects of temperature, pH and sodium chloride were modeled using a quadratic polynomial equation of response surface (RS) model. Mathematical evaluation demonstrated that the standard error of prediction (%SEP) obtained by RS model was 1.033% for GR and was 0.166% for LT for model establishing. The %SEP for model validation were 43.717% and 5.895% for GR and LT, respectively. The root-mean-squares error (RMSE) was in acceptable range which was less than 0.1 for GR and was less than 8.0 for LT. Both the bias factor (B(f)) and accuracy factor (A(f)) approached 1.0, which were within acceptable range. Therefore, RS model provides a useful and accurate method for predicting the growth parameters of C. sporogenes spores, and could be applied to ensure food safety with respect to proteolytic C. botulinum control.
In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 degrees C) to 0.7 min (100 degrees C) in apple juice, 14.1 (90 degrees C) to 1.0 min (100 degrees C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 degrees C) to 1.2 min (100 degrees C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 degrees C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.
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.
Inactivation of Bacillus sporothermodurans LTIS27 spores by high hydrostatic pressure and moderate heat studied by response surface methodology
- C Aouadhi
- H Smonin
- H Prévost
- M De Lamballerie
- A Maaroufi
- S Mejri
Aouadhi, C., Smonin, H., Prévost, H., de Lamballerie, M., Maaroufi, A., & Mejri, S.
(2013). Inactivation of Bacillus sporothermodurans LTIS27 spores by high hydrostatic pressure and moderate heat studied by response surface methodology. LWT e Food Science and Technology, 50, 50e56.