Analysis of Neutral Electrolyzed Water anti-bacterial activity on contaminated eggshells with Salmonella enterica or Escherichia coli
Introduction
While the food industry tries to maintain food safe and with high quality, foodborne outbreaks still exist. Salmonella and Escherichia coli have been reported to be the principal pathogens related to foodborne disease outbreaks (CDC, 2010). Salmonella spp has an incidence of 20.9 and 17.2 cases per 100,000 and E. coli 1.82 and 2.2 per 100,000 in the European Union (EU) and US respectively (Food and Authority, 2017). Eggs and poultry are important vehicles for the transmission of Salmonella which has been classified as a food pathogen related to outbreak-associated illnesses (Report, 2011). Among Salmonella serotypes, S. Enteritidis and S. Typhimurium are frequently reported in outbreaks and are present in avian digestive tracts. Eggshells can be contaminated when they come into contact with feces, infested nests, or surrounding environments (Holck et al., 2018; Huang et al., 2008; Humphrey, 1994; Paramithiotis et al., 2017).
The washing process of eggshells of table eggs has not been implemented worldwide. This practice has been adopted in countries like Japan, the US, and Australia (Hutchison et al., 2004; Jones and Musgrove, 2005; Northcutt et al., 2005). The major advantage to egg washing is the decrease in bacterial load on eggshells. However, one of the major concerns about the egg washing process is the possible damage to protective structures like the cuticle (European Food Safety Authority (EFSA), 2005). Non-corrosive effects, low public health impacts, and being environmentally friendly are some important characteristics that disinfectants should have. Several sanitizers have been used or described in egg washing processes like organic acids (National Service for Agroalimentary Public Health [SENASICA], 2011) and chlorine based sanitizers (Northcutt et al., 2005; Soljour et al., 2004; Wang and Slavik, 1998).
The use of Electrolyzed Water (EW) is a promising strategy in the egg washing process. EW is generated by electrolysis of NaCl in water (Cheng et al., 2012) and its use has previously been reported in cutting boards (Venkitanarayanan et al., 1999) spinach (Guentzel et al., 2008), lettuce (Abadias et al., 2008; Koseki et al., 2004), meat (Fabrizio and Cutter, 2004), and strawberries (Udompijitkul et al., 2007) for the control of foodborne diseases. Its bactericidal effects are explained by three characteristics: Oxidation Reduction Potential (ORP), presence of reactive chlorine and oxygen species like hypochlorous acid (HOCl), and pH. High ORP causes modifications in metabolic flux and ATP production. It inhibits glucose oxidation, disrupts protein synthesis, inhibits oxygen uptake and oxidative phosphorylation which is coupled with the leakage of some macromolecules (Huang et al., 2008) and causes damage to cell membranes (Liao et al., 2007). Hypochlorous acid is the main component of EW and it produces a hydroxyl radical that acts on different pathogens (Len et al., 2002, Len et al., 2000; Len et al., 2002). pH is an important factor because bacteria generally grow in a pH range of 4 to 9 (Huang et al., 2008) and changing the pH cause proteins to denature. Based on pH, EW has been historically classified into two groups: acid electrolyzed water (AEW) and basic electrolyzed water (BEW). AEW (pH ̴ 2.0) has been reported in chicken meat (Fabrizio and Cutter, 2004), cutting boards (Venkitanarayanan et al., 1999), and eggs (Ni et al., 2014). Alkaline EW has been used against E. coli (Liao et al., 2007) and on eggs (Ni et al., 2014). There is also a slightly acidic solution (near neutral, pH 6.0–6.5) that has been tested in tomatoes (Deza et al., 2003), lettuce (Guentzel et al., 2008), grapes, peaches (Guentzel et al., 2010), chicken (Rahman et al., 2012), beef (Ding et al., 2010), and eggshells (Cao et al., 2009) as well as against the main foodborne pathogens like Salmonella, E. coli, Listeria monocytogenes and Enterococcus fecalis.
The goal of the present work is to evaluate a Neutral Electrolyzed Water (NEW) with a pH ̴ 7 against Salmonella enterica and Escherichia coli in vitro as well as on artificially contaminated eggshells. Additionally, cuticle and bacterial integrity were evaluated by transmission and scanning electronic microscopy to identify possible damage. To our knowledge, this type of EW has never been previously reported on eggs.
Section snippets
Bacterial strain and inocula
Bacterial strain Salmonella enterica subsp. enterica (ex Kauffmann and Edwards) Le Minor and Popoff serovar Typhi (ATCC 7251) and Escherichia coli (Migula) Castellani and Chalmers (ATCC 11229) were obtained from the American Type Culture Collection. Strains were confirmed by Vitek 2 system (BioMérieux Cat. No. 27630) following the manufacturer instructions. Stock inoculums were sub-cultured overnight on Salmonella-Shigella Agar (Cat. No. 214400, Bioxon. Estado de Mexico, Mexico) or Trypticase
Physicochemical properties
ORP, pH, and Cl2 (mg L−1) values were obtained from 15 different batches. Values are summarized in Table 1. NaCl solution and distilled water showed a slightly neutral pH (5.71 and 5.29 respectively); CAS and NEW showed a pH value of 2.03 and 7.12 respectively. NEW was the only solution that had a high ORP value (907.27 mV), the rest of the solutions had values below 587 mV. NEW was the only solution that contained free chlorine with a concentration value of 60.85 (mg L−1). Free chlorine was
Discussion
In the present study, we analyzed the bactericidal effect of Neutral Electrolyzed Water in addition to their impact on bacterial surfaces of Salmonella enterica and E. coli. We also evaluated the effect of NEW on eggshell integrity.
HOCl is the main component of NEW and its presence has been linked to EW bactericidal effects (Len et al., 2000; Venkitanarayanan et al., 1999). NEW showed a neutral pH that allows its use on different foods without affecting physical or organoleptic characteristics
Declaration of competing interest
Sandra Martinez-Vidal works at Esteripharma S.A. de C.V.
Acknowledgments
This work was supported by Consejo Nacional de Ciencia y Tecnologia (CONACYT) [grant number 221000].
We are very thankful to Ajia Sugahara and Jose A. Montero-Santamaria for providing language help and discussion of the manuscript.
Author contributions
Jocelyn Medina-Gudiño, Andres Rivera-Garcia and Liliana Santos-Ferro conducted the experiments; Juan C. Ramirez-Orejel, David Paez-Esquiliano, Sandra Martinez-Vidal and Eduardo Andrade-Esquivel conducted the experiments and interpreted the results; Lourdes T. Agredano-Moreno and Luis F. Jimenez-Garcia took the electron microscopy pictures and Jose A. Cano-Buendia conceived and designed the experiment, led the discussion of the results and wrote the manuscript. All authors read and approved the
References (43)
- et al.
Efficacy of neutral electrolyzed water (NEW) for reducing microbial contamination on minimally-processed vegetables
Int. J. Food Microbiol.
(2008) - et al.
Efficacy of electrolyzed oxidizing water for the microbial safety and quality of eggs
Poult. Sci.
(2004) - et al.
Efficiency of slightly acidic electrolyzed water for inactivation of Salmonella enteritidis and its contaminated shell eggs
Int. J. Food Microbiol.
(2009) - et al.
Electrolyzed oxidizing water for microbial decontamination of food
Microb. Decontam. Food Ind. Nov. Methods Appl.
(2012) - et al.
Efficacy of neutral electrolyzed water to inactivate Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus on plastic and wooden kitchen cutting boards
J. Food Prot.
(2007) - et al.
Modelling of Escherichia coli O157:H7 growth at various storage temperatures on beef treated with electrolyzed oxidizing water
J. Food Eng.
(2010) - et al.
Comparison of electrolyzed oxidizing water with other antimicrobial interventions to reduce pathogens on fresh pork
Meat Sci.
(2004) - et al.
Spraying hatching eggs with electrolyzed oxidizing water reduces eggshell microbial load without compromising broiler production parameters
Poult. Sci.
(2009) - et al.
Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water
Food Microbiol.
(2008) - et al.
Postharvest management of gray mold and brown rot on surfaces of peaches and grapes using electrolyzed oxidizing water
Int. J. Food Microbiol.
(2010)
Comparison of UV-C and pulsed UV light treatments for reduction of Salmonella, Listeria monocytogenes, and Enterohemorrhagic Escherichia coli on eggs
J. Food Prot.
Application of electrolyzed water in the food industry
Food Control
Contamination of egg shell and contents with Salmonella enteritidis: a review
Int. J. Food Microbiol.
An assessment of the microbiological risks involved with egg washing under commercial conditions
J. Food Prot.
In vitro inactivation of Escherichia coli, Staphylococcus aureus and Salmonella spp. using slightly acidic electrolyzed water
J. Biosci. Bioeng.
Correlation of eggshell strength and Salmonella enteritidis contamination of commercial shell eggs
J. Food Prot.
Changes in eggshell surface microstructure after washing with cetylpyridinium chloride or trisodium phosphate
J. Food Prot.
Effect of mild heat pre-treatment with alkaline electrolyzed water on the efficacy of acidic electrolyzed water against Escherichia coli O157:H7 and Salmonella on Lettuce
Food Microbiol.
Ultraviolet spectrophotometric characterization and bactericidal properties of electrolyzed oxidizing water as influenced by amperage and pH
J. Food Prot.
The generation and inactivation mechanism of oxidation-reduction potential of electrolyzed oxidizing water
J. Food Eng.
Food recalls and warnings due to the presence of foodborne pathogens — a focus on fresh fruits, vegetables, dairy and eggs
Curr. Opin. Food Sci.
Cited by (20)
A combined approach using slightly acidic electrolyzed water spraying and chitosan and pectin coating on the quality of the egg cuticle, prevention of bacterial invasion, and extension of shelf life of eggs during storage
2022, Food ChemistryCitation Excerpt :Subsequently, a second assessment of the condition of the eggshells (unwashed or SAEW sprayed) was carried out using scanning electron microscopy. Many studies showed the picture of eggs with and without cuticles obtained by transmission electron microscopy (Liu et al., 2022; Medina-Gudiño et al., 2020). Medina-Gudiño et al. (2020) assessed the integrity of egg cuticles after treatment with neutral electrolytic water (NEW, pH = 7.12) and 2% citric acid solution (CAS, pH = 2.03) by cuticle staining and scanning electron microscopy.
Recent trends and applications of electrolyzed oxidizing water in fresh foodstuff preservation and safety control
2022, Food ChemistryCitation Excerpt :Additionally, SAEW could effectively maintain the quality of fresh eggs during storage, which exhibited lower yolk pH, albumen pH and weight loss, as well as a higher yolk index and haugh unit. Similarly, Medina-Gudiñoa et al. (2020) reported that NEW treatment (pH = 7.12, ACC = 60.85 mg/L, and ORP = 907.27 mV) for 30 s could cause a reduction of S. enterica by more than 5.56 log CFU/mL in vitro and over 1.45 log CFU/mL on inoculated eggshells. As for E. coli, NEW could reduce the populations by more than 3.28 log CFU/mL in vitro and over 6.39 log CFU/egg on eggshells.
- 1
Both authors contributed equally to this study.