Food Industry Checking (1)

Available online at www.sciencedirect.com

Food Control 19 (2008) 329–345
www.elsevier.com/locate/foodcont

Review

Application of electrolyzed water in the food industry
Yu-Ru Huang a, Yen-Con Hung b, Shun-Yao Hsu c, Yao-Wen Huang
Deng-Fwu Hwang d,*
b

d,e

,

a
Department of Food Science, National Penghu University, Penghu, Taiwan, ROC
Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of Georgia, Griffin, GA 30223-1797, USA
c
Graduate Institute of Food Science and Technology, National Taiwan University, P.O. Box 23-14, Taipei 106, Taiwan, ROC
d
Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC
e
Department of Food Science and Technology, Center for Food Safety, University of Georgia, Athens, GA 30602-7610, USA

Received 12 February 2007; received in revised form 6 August 2007; accepted 10 August 2007

Abstract
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.
Published by Elsevier Ltd.
Keywords: Electrolyzed water; Disinfectant; Food industry

Contents
1.
2.
3.
4.
5.
6.
7.
8.

*

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Principles and characteristics of electrolyzed water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Systems for generation of electrolyzed water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The advantages and disadvantages of EO water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inactivation of microbes using EO water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inactivation of blood-virus using EO water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inactivation of toxins using EO water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EO water used as a disinfectant in the food industry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.1. Use of EO water for food processing equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2. Use of EO water for vegetables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3. Use of EO water for fruits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.4. Use of EO water for poultry and meat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.5. Use of EO water for seafood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Corresponding author. Tel.: +886 2 24622192x5103; fax: +886 2 24626602.
E-mail address: [email protected] (D.-F. Hwang).

0956-7135/$ - see front matter Published by Elsevier Ltd.
doi:10.1016/j.foodcont.2007.08.012

330
330
331
331
332
334
334
335
335
335
339
339
342

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Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

1. Introduction
Food-borne illnesses are prevalent all over the world.
The toll of that in terms of human life and suffering is enormous. Acute food-borne disease infections and intoxications are much more of a concern to governments and
the food industry today than a few decades ago. From
January 1988 through December 1997, a total of 5170 outbreaks of food-borne disease were reported to the Centers
for Disease Control and Prevention. These outbreaks
caused 163,000 persons to become ill (Bean, Goulding,
Lao, & Angulo, 1996; Olsen, Mackinnon, Goulding, Bean,
& Slutsker, 2000). Food-borne infections are estimated to
cause 76 million illnesses, 300,000 hospitalizations and
5000 deaths annually in the USA (Mead et al., 1999). When
excluding multi-ingredient foods, seafood ranked third on
the list of products which caused food-borne disease
between 1983 and 1992 in the USA (Lipp & Rose, 1997).
Moreover, the top five food categories linked to food poisoning outbreaks in the USA from 1990 to 2003 were seafood, dairy products, eggs, beef, and poultry products
which were responsible for 61% of all outbreaks according
to the Center for Science in the Public Interest (CSPI)’s
database (CSPI, 2006). Globally, the search for effective
and safe protocols and agents for rendering food safety
has been continued to engage the attention of researchers,
food manufacturers and retailers as well as policy makers,
in countries such as the USA, Japan, UK and Taiwan. In
fact, recent outbreaks of food-borne illnesses in Taiwan,
USA and Japan, have raised vast international concern.
The best way to reduce incidences of food-borne diseases is to secure safe food supply. Although Hazard Analysis Critical Control Point (HACCP) system has been
implemented in many food processing establishments, most
outbreaks of food-borne illnesses still occurred in foodservice sectors including institutions, fast food restaurants,
and food stores, where food products had undergone various treatments and should have been rendered as safe
(Chang, 2003). This situation indicates that hazards might
still exist in the food supply systems. Today, food chains
are becoming complicated in handling, processing, transportation, and storage ensuring a safe food supply becomes
a challenge task.
Electrolyzed oxidizing (EO) water, also known as
strongly acidic electrolyzed water (SAEW) or electrolyzed
strong acid aqueous solution (ESAAS), is a novel antimicrobial agent which has been used in Japan for several
years. It has been reported to possess antimicrobial activity
against a variety of microorganisms (Fabrizio & Cutter,
2003; Horiba et al., 1999; Iwasawa & Nakamura, 1993;
Kim, Hung, & Brachett, 2000a, 2000b; Kim, Hung, Brachett, & Frank, 2001; Kimura et al., 2006; Kiura et al., 2002;

Park & Beuchat, 1999; Park, Hung, & Brackett, 2002a;
Venkitanarayanan, Ezeike, Hung, & Doyle, 1999b;
Vorobjeva, Vorobjeva, & Khodjaev, 2003). In recent years,
EO water has gained interest as a disinfectant used in agriculture, dentistry, medicine and food industry. It has been
shown as an effective antimicrobial agent for cutting
boards (Venkitanarayanan, Ezeike, Hung, & Doyle,
1999a), poultry carcasses (Fabrizio, Sharma, Demirci, &
Cutter, 2002; Park et al., 2002a), eggs (Russell, 2003), lettuce (Izumi, 1999; Koseki & Itoh, 2001; Koseki, Yoshida,
Isobe, & Itoh, 2001; Koseki, Fujiwara, & Itoh, 2002; Koseki, Isobe, & Itoh, 2004a; Koseki, Yoshida, Kamitani,
Isobe, & Itoh, 2004c; Park, Hung, Doyle, Ezeike, & Kim,
2001; Yang, Swem, & Li, 2003), alfalfa seeds, sprouts
(Kim, Hung, Brackett, & Lin, 2003; Sharma & Demirci,
2003), pears (Al-Haq, Seo, Oshita, & Kawagoe, 2002),
apples (Okull & Laborde, 2004), peaches (Al-Haq, Seo,
Oshita, & Kawagoe, 2001), tomatoes (Bari, Sabina, Isobe,
Uemura, & Isshiki, 2003; Deza, Araujo, & Garrido, 2003),
strawberry (Koseki, Yoshida, Isobe, & Itoh, 2004b) and
food processing equipments (Ayebah & Hung, 2005; Ayebah, Hung, & Frank, 2005; Kim et al., 2001; Park, Hung,
& Kim, 2002b; Venkitanarayanan et al., 1999a; Walker,
Demirci, Graves, Spencer, & Roberts, 2005a, 2005b). EO
water also has the potential to be more effective and inexpensive than traditional cleaning agents. The greatest
advantage of EO water for the inactivation of pathogenic
microorganisms relies on its less adverse impact on the
environment as well as users’ health because of no hazard
chemicals added in its production. Moreover, it has been
clarified that EO water does no harm to the human body
(Mori, Komatsu, & Hata, 1997). It is more effective, less
dangerous and less expensive than most traditional preservation methods such as glutaraldehyde (Sakurai, Nakatsu,
Sato, & Sato, 2003; Sakurai, Ogoshi, Kaku, & Kobayashi,
2002), sodium hypochlorite and acetic acid (Ayebah et al.,
2005). Many aspects of EO water are elucidated in this
review, including its chemical and physical properties, generation, antimicrobial properties and its applications in
food industries, such as fresh vegetables, fruits, eggs, poultry and seafood.
2. Principles and characteristics of electrolyzed water
EO water was initially developed in Japan (Shimizu &
Hurusawa, 1992). It has been reported to have strong bactericidal effects on most pathogenic bacteria that are
important to food safety. EO water is produced by passing
a diluted salt solution through an electrolytic cell, within
which the anode and cathode are separated by a membrane. By subjecting the electrodes to direct current voltages, negatively charged ions such as chloride and

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

331

Fig. 1. Schematics of electrolyzed water generator and produced compounds.

hydroxide in the diluted salt solution move to the anode to
give up electrons and become oxygen gas, chlorine gas,
hypochlorite ion, hypochlorous acid and hydrochloric acid,
while positively charged ions such as hydrogen and sodium
move to the cathode to take up electrons and become
hydrogen gas and sodium hydroxide (Hsu, 2005). Two
types of water are produced simultaneously. EO water,
with low pH (2.3–2.7), high oxidation–reduction potential
(ORP, >1000 mV), high dissolved oxygen and contains free
chlorine (concentration depends on the EO water machine
setting), is produced from anode side. However, electrolyzed reduced (ER) water, with high pH (10.0–11.5), high
dissolved hydrogen, and low ORP (ÿ800 to ÿ900 mV), is
produced from the cathode side. ER water with strong
reducing potential can be used to remove dirt and grease
from items such as cutting boards and other kitchen utensils (Hsu, 2005).
The principle of producing electrolyzed water is shown
in the Fig. 1 with the following:
Positivepole : 2H2 O ! 4Hþ þ O2 " þ4eÿ
2NaCl ! Cl2 " þ2eÿ þ 2Naþ
Cl2 þ H2 O ! HCl þ HOCl
Negativepole : 2H2 O þ 2eÿ ! 2OHÿ þ H2 "

water generators, made by the HoshizakiÒ Company,
allows the users to select amperages and/or voltages, while
the machines change brine flow rate accordingly. The third
type of EO water generators, made by the ToyoÒ and the
Nippon IntekÒ companies, allows the users to select a preset chlorine concentration level of EO water from a display
panel and the machines change brine flow rate and amperages and/or voltages automatically (Hsu, 2003).
Hsu (2003) investigated relationship among water flow
rate, water temperature and salt concentration on electrolysis efficiency, and separation efficiency of an EO water
generator. He made following conclusions: (1) electric
potential (7.9–15.7 V) and power consumption (16–
120 W) of electrolysis cell were not affected by water flow
rate, water temperature or salt concentration in the feed
solution; (2) electric current changed with water temperature and water flow rate; and (3) electrolysis efficiency of
the electrolysis cell and separation efficiency of the ion
exchange membrane were significantly decreased by the
increases in water flow rate and salt concentration in the
feed solution. Later, Hsu (2005) also reported that ORP
decreased with increases in water follow rate and free chlorine increased with increases of salt concentration and
decrease of water flow rate.

2NaCl þ 2OHÿ ! 2NaOH þ Clÿ
4. The advantages and disadvantages of EO water
3. Systems for generation of electrolyzed water
Commercial EO water generators can be divided into
three major types based on their automatic control systems. The first type of EO water generators, made by the
ARVÒ and the AmanoÒ companies, allows the users to
select brine flow rate while the machines adjust voltages
and/or amperages automatically. The second type of EO

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. On the other hand, sodium
hypochlorite was proved to have a strong toxicity, such as
skin irritation, membrane irritation, acute toxicity, and so
on (Mori et al., 1997; Sekiya, Ohmori, & Harii, 1997;
Shigeto et al., 2000). Currently used hatchery sanitizers

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Y.-R. Huang et al. / Food Control 19 (2008) 329–345

(formaldehyde gas and glutaraldehyde) are noxious to
humans and chicks, and may pose a serious health risk
(Russell, 2003). Furthermore, the use of formaldehyde
gas and glutaraldehyde are gradually being limited because
of the adverse effects this chemical has on the environment.
Sakurai et al. (2003) also stated that EO water provides a
useful means of cleaning and disinfecting digestive endoscopes between patients. It is safe for the human body
and for the environment. In addition, the cost of using
EO water is much less expensive (5.3 yen/L) compared with
glutaraldehyde (1200 yen/L) (Sakurai et al., 2003).
When EO water comes into contact with organic matter,
or is diluted by tap water or reverse osmosis (RO) water, it
becomes ordinary water again. Thus, it’s less adverse
impact on the environment as well as users’ health. Moreover, compared with other conventional disinfecting techniques, EO water reduces cleaning times, is easy to
handle, has very few side effects, and is relative cheap
(Tanaka et al., 1999). Chemicals used for cleaning and disinfection are expensive and represent an operating expense
for the dairy producer. Once the initial capital investment
is made to purchase an EO water generator, the only operating expenses are water, salts and electricity to run the unit
(Walker et al., 2005b).
The main disadvantage of EO water is that the solution
rapidly loses its antimicrobial activity if EO water is not
continuously supplied with H+, HOCl and Cl2 by electrolysis (Kiura et al., 2002). EO water is gaining a reputation in
various fields as a more capable disinfectant than conventional chemical disinfectants. However, problems, such as
chlorine gas emission, metal corrosion, and synthetic resin
degradation, due to its strong acidity and free chlorine content have been a matter of concern. Although metal corrosion and synthetic resin degradation occurred, they were
not serious on hemodialysis equipment (Tanaka et al.,
1999). Ayebah and Hung (2005) also indicated that EO
water did not have any adverse effect on stainless steel,
it can still be safely used as a sanitizer to inactivate
bacteria on food contact surfaces made from stainless
steel in food processing. After disinfection, washing food
equipment with sterile water can completely avoid metal
corrosion. During the EO water generation process,
chlorine ions are generated, and thus chlorine gas is emitted. This necessitates the use of standard-type extractor
fan.
5. Inactivation of microbes using EO water
As shown in Table 1, many studies have been conducted
in evaluating the bactericidal activity of EO water. EO
water possess antimicrobial activity on a variety of microorganisms including Pseudomonas aeruginosa (Kiura et al.,
2002; Vorobjeva et al., 2003), Staphylococcus aureus (Park
et al., 2002b; Vorobjeva et al., 2003), S. epidermidis, E. coli
O157:H7 (Kim et al., 2000a, 2000b; Park, Hung, & Chung,
2004; Venkitanarayanan et al., 1999b), Salmonella Enteritidis (Venkitanarayanan et al., 1999b), Salmonella Typhimu-

rium (Fabrizio & Cutter, 2003), Bacillus cereus (Len, Hung,
Erickson, & Kim, 2000; Sakashita, Iwasawa, & Nakamura,
2002; Vorobjeva et al., 2003), Listeria monocytogenes (Fabrizio & Cutter, 2003; Park et al., 2004; Vorobjeva et al.,
2003), Mycobacterium tuberculosis (Iwasawa & Nakamura,
1993), Campylobacter jejuni (Park et al., 2002a), Enterobacter aerogenes (Park et al., 2002b) and Vibrio parahaemolyticus (Huang et al., 2006a; Kimura et al., 2006). EO water
can also reduce germination of many fungal species, such
as Alternaria spp., Bortrytis spp., Cladosporium spp., Colletotrichum spp., Curvularia lunata, Didymella bryonaie,
Epicoccum nigrum, Fusarium spp., Helminthosporium spp.,
Pestalotia spp., Phomopsis longicolla, Rhodosporidium toruloides, Stagonospora nodorum, Thielaviopsis basicola, Trichoderma spirale, Acidovorax avenae subsp., Erwinia
chrysanthemi, Pantoea ananatis, Pseudomonas syringae
(Buck, Iersel, Oetting, & Hung, 2002), Aspergillus spp.
(Buck et al., 2002; Suzuki et al., 2002b), Botryosphaeria
berengeriana (Al-Haq et al., 2002), Monilinia fructicola
(Al-Haq et al., 2001; Buck et al., 2002), Penicillium expansum (Okull & Laborde, 2004) and Tilletia indica (Bonde
et al., 1999).
In general, bacteria generally grow in a pH range of 4–9.
Aerobic bacteria grow mostly at ORP range +200 to
800 mV, while anaerobic bacteria grow well at ÿ700 to
+200 mV. The high ORP in the EO water could cause
the modification of metabolic fluxes and ATP production,
probably due to the change in the electron flow in cells.
Low pH may sensitize the outer membrane of bacterial
cells to the entry of HOCl into bacterial cells (McPherson,
1993). HOCl, the most active of the chlorine compounds,
appears to kill the microbial cell through inhibiting glucose
oxidation by chlorine-oxidizing sulfhydryl groups of certain enzymes important in carbohydrate metabolism. Other
modes of chlorine action that have been proposed are: (1)
disruption of protein synthesis; (2) oxidative decarboxylation of amino acids to nitrites and aldehydes; (3) reactions
with nucleic acids, purines, and pyrimidines; (4) unbalanced metabolism after the destruction of key enzymes;
(5) induction of deoxyribonucleic acid (DNA) lesions with
the accompanying loss of DNA-transforming ability; (6)
inhibition of oxygen uptake and oxidative phosphorylation, coupled with leakage of some macromolecules; (7)
formation of toxic N-chlorine derivatives of cytosine; and
(8) creation of chromosomal aberrations (Marriott & Gravani, 2006).
A theory for inactivation of bacteria based on the high
oxidation potential of EO water causing damage of cell
membranes was reported by Liao, Chen, and Xiao
(2007). The chemical process of oxidation occurs when
oxygen contacts with other compounds causing them to
lose electrons and further causing the compounds to break
down and change functions. In the case of microbes, oxidation could damage cell membranes, create disruption in cell
metabolic processes and essentially kill the cell. The bactericidal effects of EO water on Staphylococcus saprophyticus,
Micrococcus luteus and Bacillus sphaericus can be seen by

7.91 ± 0.05
7.89 ± 0.10
5.89 ± 0.40
5.10 ± 1.40
8.36 ± 0.08
8.03 ± 0.03
8.03 ± 0.03
8.03 ± 0.03
6.72 ± 0.02
7.98 ± 0.06
7.98 ± 0.04
7.98 ± 0.04
7.98 ± 0.04

Gram-positive
Listeria monocytogenes
Listeria monocytogenes
Listeria monocytogenes
Listeria monocytogenes
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Bacillus cereus
Bacillus cereus (spores)
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
–
–
–
–
0
0
0
3.92 ± 0.11
3.76 ± 0.02
–
0
0
0

–
–
–
–
–
–
0
0
0
0
0
0
0
<1
<1
0
0
0
–
–
–
–
–
–
–
–
–
0
–
–
–

–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–

0, Complete inactivation of bacterial culture; –, not measured.

7.98 ± 0.04
8.04 ± 0.07
7.74 ± 0.08
7.76 ± 0.08
5.20 ± 1.0
5.11 ± 1.60
8.04 ± 0.07
8.21 ± 0.04
7.63 ± 0.06
8.12 ± 0.02
8.01 ± 0.04
7.80 ± 0.03
7.90 ± 0.04
7.42 ± 0.26
7.47 ± 0.13
7.42 ± 0.26
7.47 ± 0.13
8.23 ± 0.03
1.34 ± 0.37
1.23 ± 0.33
5.36 ± 0.80
2.66 ± 1.10
–
–
–
–
–
–
–
–
–

<1.0
<1.0
1.06 ± 0.15
<1.0
5.13 ± 1.20
3.46 ± 1.40
–
–
–
–
–
–
–
–
–
–
–
–

5 min

0
0
5.12 ± 0.80
0
–
–
–
–
–
–
–
–
–

0
0
0
0
3.37 ± 0.70
0
–
–
–
–
–
–
–
–
–
–
–
–

10 min

0
0
4.60 ± 1.10
0
–
–
–
–
–
–
–
–
–

0
0
0
0
3.32 ± 0.50
0
–
–
–
–
–
–
–
–
–
–
–
–

15 min

2.63
2.63
2.60
2.60
2.84
2.53
2.79
3.18
2.84
2.84
2.53
2.79
3.18

2.36
2.37
2.48
2.45
2.30
2.60
2.84
2.84
2.84
2.84
2.84
2.84
2.84
2.95
2.67
2.67
2.57
2.84
1160
1158
1150
1150
1125
1178
1163
1116
1125
1125
1178
1163
1116

1153
1155
1153
1151
1155
1150
1125
1125
1125
1125
1125
1125
1125
1072
1092
1092
1082
1125

ORP (mV)

pH

1 min

0s

30 s

EO water property

Surviving bacterial population after exposing time (mean log CFU/mL)

Gram-negative
Escherichia coli O157:H7
Escherichia coli O157:H7
Salmonella Enteritidis
Salmonella Enteritidis
Salmonella Typhimurium
Salmonella Typhimurium
Pseudomonas aeruginosa
Escherichia coli
Citrobacter freundii
Flavobacter sp.
Proteus vulgaris
Alcaligenes faecalis
Aeromonas liquefaciens
Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni
Enterococcus faecalis

Bacterial species

Table 1
A comparison of bactericidal effects on bacterial strains treated with electrolyzed oxidizing water

43.0
48.5
50
50
43
53.1
26.9
11.3
43
43
53.1
26.9
11.3

86.3
82.3
83.5
82.0
50
50
43
43
43
43
43
43
43
25.7
53.9
53.3
51.6
43

Free chlorine
(mg/L)

4
23
4
25
23
23
23
23
23
23
23
23
23

4
23
4
23
4
25
23
23
23
23
23
23
23
4
23
4
23
23

Temperature (°C)

Venkitanarayanan et al. (1999b)
Venkitanarayanan et al. (1999b)
Fabrizio and Cutter (2003)
Fabrizio and Cutter (2003)
Vorobjeva et al. (2003)
Park et al. (2002b)
Park et al. (2002b)
Park et al. (2002b)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Park et al. (2002b)
Park et al. (2002b)
Park et al. (2002b)

Venkitanarayanan et al. (1999b)
Venkitanarayanan et al. (1999b)
Venkitanarayanan et al. (1999b)
Venkitanarayanan et al. (1999b)
Fabrizio and Cutter (2003)
Fabrizio and Cutter (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Vorobjeva et al. (2003)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Vorobjeva et al. (2003)

Ref.

Y.-R. Huang et al. / Food Control 19 (2008) 329–345
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Y.-R. Huang et al. / Food Control 19 (2008) 329–345

using a scanning electron microscope. The cells treated
with electrolyzed acidic water had wrinkled cell wall with
round pores in which the cytoplasmic structures were
flushed out (Osafune, Ehara, & Ito, 2006).
Little reports on the effects of chlorine, pH and ORP
values of the EO water in inactivation of pathogens are
available. Kim et al. (2000b) have developed chemically
modified water from deionized water with the same properties (i.e., pH, chlorine and ORP) as EO water without using
electrolysis. Their results suggested that ORP of EO water
might be the primary factor responsible for the bactericidal
effect. However, Koseki et al. (2001) noted that the ORP is
not the main factor of antimicrobial activity because the
higher ORP of ozonated water did not show higher disinfectant effect than lower ORP of EO water. They further
defined that free chlorine of EO water, mainly hypochlorous acid (HOCl), produces hydroxyl radical (OH) that
acts on microorganisms. Ozone solution produces OH,
too. The higher OH produced by higher HOCl concentration in EO water means the better the disinfectant efficacy
than ozone solution. Len et al. (2000) reported that the relative concentrations of aqueous molecular chlorine, HOCl,
hypochlorite ion (OClÿ) and chlorine gas (Cl2) were also
the factors that accounted for the bactericidal potency.
At pH 4, EO water with the maximum concentration of
HOCl had the maximum microbicidal activity.
Park et al. (2004) investigated the effects of chlorine and
pH on efficacy of EO water for inactivating E. coli O157:H7
and L. monocytogenes. It was demonstrated that EO water
is very effective for inactivating E. coli O157:H7 and L. monocytogenes in a wide pH range (between 2.6 and 7.0), if sufficient free chlorine (>2 mg/L) is present. For each chlorine
content, bactericidal activity and ORP increased with
decreasing pH. Based on fluorescent and spectroscopic
measurements, Liao et al. (2007) reported that the ORP
of EO water could damage the outer and inner membranes
of E. coli O157:H7. The redox state of the glutathione disulfide–glutathione couple (GSSG/2GSH) can serve as an
important indicator of redox environment. There are many
redox couples in a cell that work together to maintain the
redox environment. The inactivation mechanism hypothesized was that ORP could damage the redox state of
GSSG/2GSH and then penetrate the outer and inner membranes of cell, giving rise to the release of intracellular components and finally cause the necrosis of E. coli O157:H7.
Thus, the antimicrobial effect of EO water derives from
the combined action of the hydrogen ion concentration,
oxidation–reduction potential and free chlorine.
Storage conditions can affect chemical and physical
properties of EO water. When stored under an open, agitated and diffused light condition the EO water had the
highest chlorine loss rate. Under open condition, chlorine
loss through evaporation followed first-order kinetics.
The rate of chlorine loss was increased abound 5-fold with
agitation, but it was not significantly affected by diffused
light (Len, Hung, & Chung, 2002). EO water exposed to
the atmosphere could reduce more chlorine and oxygen

than that kept to a closed systems for a longer time (Hsu
& Kao, 2004). Fabrizio and Cutter (2003) reported that
EO water stored at 4 °C was more stable than stored at
25 °C.
The effectiveness of chlorine as a bactericidal agent is
reduced in the presence of organic matter due to the formation of combined available chlorines. At an identical chlorine concentration, the combined available chlorines had
much lower bactericidal activity than the free form
(Oomori, Oka, Inuta, & Arata, 2000). For practical application, EO water usually must be used in the presence of
amino acids or proteins containing materials produce a
combined form. Although the electrolyzed solution is not
a newly discovered disinfectant, it is important to examine
its bactericidal effect on different bacteria (Table 1).
6. Inactivation of blood-virus using EO water
Researchers also indicated that EO water has antiviral
potency on blood borne pathogenic viruses including hepatitis B virus (HBV), hepatitis C virus (HCV) (Morita
et al., 2000; Sakurai et al., 2003; Tagawa et al., 2000) and
human immunodeficiency virus (HIV) (Kakimoto et al.,
1997; Kitano et al., 2003; Morita et al., 2000). EO water
contained only 4.2 mg/L of free chlorine (pH 2.34, ORP
1053 mV) had a greater efficacy against hepatitis B virus
surface antigen (HBsAg) and HIV-1 than sodium hypochlorite (Morita et al., 2000). The possible mechanisms
underlying the EO water disinfection against blood-borne
viruses might include (1) inactivation of surface protein;
(2) destruction of virus envelope; (3) inactivation of viral
nucleic acids encoding for enzymes; and (4) destruction
of viral RNA (Morita et al., 2000). Hanson, Gor, Jeffries,
and Collins, 1989 demonstrated that dried HIV is relatively
resistant against disinfectants compared with wet HIV. In
an insightful work, Kitano et al. (2003) stated that EO
water has an inactivation potential against the infectivity
of dried HIV-1. They found that the viral reverse transcript
(RT) and the viral RNA in HIV-1 are targets of EO water.
Sakurai et al. (2003) reported experiments with HBC and
HCV-contaminated endoscopes, and concluded that neither HBV nor HCV was detected after the endoscopes were
cleaned manually with a brush and disinfected with EO
water. Viral DNA was not detected from any endoscope
experimentally contaminated with viral-positive mixed sera
(Lee et al., 2004; Tagawa et al., 2000). Thus, EO water
directly inactivates viruses and its clinical application is recommended. Effectiveness of EO water in preventing viral
infection in the food field needs to be further studied.
7. Inactivation of toxins using EO water
Staphylococcal food poisoning results from the consumption of a food in which enterotoxigenic staphylococci
have grown and produced toxins. Within 1–6 h after ingestion of staphylococcal enterotoxin (SEs)-contaminated
foods, victims experience nausea, abdominal cramps, vom-

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

iting, and diarrhea (Archer & Young, 1988; Garthright,
Archer, & Kvenberg, 1988). Although EO water has been
proved to be effective against Staphylococcus aureus, trace
amounts of enterotoxin produced by the bacteria may
remain active after disinfection. Suzuki, Itakura, Watanabe, and Ohta (2002a) reported that exposure of 70 ng, or
2.6 pmol, of staphylococcal enterotoxin A (SEA) in 25 lL
of phosphate buffer saline (PBS) to a 10-fold volume of
EO water, or 64.6 · 103-fold molar excess of HOCl in EO
water, caused a loss of immuno-reactivity between SEA
and a specific anti-SEA antibody. Native PAGE indicated
that EO water caused fragmentation of SEA, and amino
acid analysis indicated a loss in amino acid content, in particular Met, Tyr, Ile, Asn, and Asp. EO water denatures
SEA through an oxidative reaction caused by OH radicals
and reactive chlorine. Thus, EO water might be useful as a
preventive measure against food-borne disease caused by
SEA.
Suzuki et al. (2002b) also reported that EO water could
sterilize Aspergillus parasiticus and eliminate the mutagenicity of aflatoxin AFB1 by the OH radical originating
from HOCl. Exposing A. parasiticus at an initial density
of 103 spores in 10 lL to a 50-fold volume (500 lL) of
EO water containing 390 lmol HOCl for 15 min at room
temperature resulted in a complete inhibition of fungal
growth. Three nanomoles of AFB1 showed a high mutagenicity for both Salmonella Typhimurium TA98 and TA100
strains, but this mutagenicity was reduced markedly after
exposure to 20-fold molar amount of HOCl in the EO
water in both TA98 and TA100. However, foods contain
compounds such as proteins, lipids, vitamins, minerals,
color, etc., and concerning food soundness, it may not necessarily be appropriate to apply EO water to wash food
materials.
8. EO water used as a disinfectant in the food industry
8.1. Use of EO water for food processing equipment
EO water has been used as a disinfectant for food processing equipment (Table 2). Venkitanarayanan et al.
(1999a) reported EO water could be used as an effective
method for eliminating food-borne pathogens on cutting
boards. EO water (pH of 2.53, ORP of 1178 mV and chlorine of 53 mg/L) could also reduce Enterobacter aerogenes
and S. aureus on glass, stainless, steel, glazed ceramic tile,
unglazed ceramic tile and vitreous china surfaces. Immersion of these surfaces in EO water for 5 min with agitation
(50 rpm) reduced populations of E. aerogenes and S. aureus
on the tested surfaces to <1 CFU/cm2 (Park et al., 2002b).
Listeria monocytogenes is a food-borne pathogen that can
lead to potentially life-threatening listeriosis in high-risk
populations. Listeriosis outbreaks have been associated
with processed foods and the formation of L. monocytogenes biofilms in the processing environment is an important
source for secondary contamination (Carpentier & Chassaing, 2004).

335

Frank and Koffi (1990) and Lee and Frank (1991) earlier reported that L. monocytogenes biofilms are resistant
to chlorine, acid anionic and quaternary ammonium sanitizers, so that inadequate cleaning and sanitation of food
processing surfaces may lead to spread of the pathogen
throughout the entire processing plant. Kim et al. (2001)
investigated the resistance of L. monocytogenes biofilms
on stainless steel surfaces to EO water (pH of 2.60, ORP
of 1160 mV and chlorine of 56 mg/L) and found that a
300-s treatment on a stainless steel surface, could reduce
the L. monocytogenes from 1.9 · 1010 CFU/82.5 cm2 to
below detection levels (5 CFU/coupon). However, it took
300 s of exposure to 200 mg/L chlorine solution to achieve
the same result. Ayebah et al. (2005) recently inactivated
L. monocytogenes biofilms on stainless steel surfaces with
a combination of ER and EO water. They found that ER
water alone did not significantly reduce the L. monocytogenes biofilms. Treatment with EO water for only 30–120 s
reduced the viable bacteria populations in biofilms by
4.3–5.2 log CFU per coupon (2 by 5 cm), whereas the combined treatment of ER water followed by EO water could
produce an additional reduction by 0.3–1.2 log CFU per
coupon.
Stainless steel has been the most commonly used material for food contact surfaces in the food industry. Ayebah
and Hung (2005) reported that EO water (pH of 2.42, ORP
of 1077 mV and free chlorine of 50 mg/L) and modified EO
water (pH of 6.12, ORP of 774 mV and free chlorine of
50 mg/L) did not have any adverse effect on stainless steel
for a period of 8 days.
The effect of EO water in reducing bacteria in the pipelines of the milking system has been investigated (Walker
et al., 2005a, 2005b). A 10 min wash with 60 °C ER water
followed by a 10 min wash with 60 °C EO water successfully removed all detectable bacteria from the non-porous
milk contact surfaces and ATP residue tests were negative. These results indicated that EO water has the potential to be used as a cleaning and sanitizing agent for
cleaning in place (CIP) cleaning of on-farm milking
systems.
8.2. Use of EO water for vegetables
Electrolyzed water has been used to inactivate pathogens
on fresh produce (Table 3). Izumi (1999) has demonstrated
that EO water is usable for cleaning fresh-cut carrots, bell
peppers, spinach, Japanese radish and potatoes. The precut produces, treated with EO water (pH 6.8, 20 mg/L free
chlorine) by dipping, rinsing or dipping/blowing, showed a
bacterial reduction by 0.6–2.6 logs CFU/g. The EO water
containing 50 mg/L chlorine had a stronger bactericidal
effect than that containing 15 or 30 mg/L chlorine. The
treatment did not cause discoloration of fresh-cut produces.
Rinsing EO water (50 mg/L) treated fresh-cut produces
with fresh water did not increase the bacterial reduction
due to the additive effects of the sequential treatment.
Koseki et al. (2004b) reported that cucumbers washed with

10 min
20 min
10 min
20 min
5 min
10 min
5 min
20 min
10 min
10 min
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
5 min
5 min and
0.5 min
1 min
2 min
0.5 min
1 min
2 min
1 min
5 min

Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Kitchen cutting board
Glass
Glass
Stainless steel
Stainless steel
Glazed ceramic tile
Glazed ceramic tile
Unglazed ceramic tile
Unglazed ceramic tile
Vitreous china
Vitreous china
Glass
Glass
Stainless steel
Stainless steel
Glazed ceramic tile
Glazed ceramic tile
Unglazed ceramic tile
Unglazed ceramic tile
Vitreous china
Vitreous china
Stainless steel
Stainless steel
Stainless steel
Stainless steel
Stainless steel
Stainless steel
Stainless steel
Stainless steel

Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Listeria monocytogenes
Listeria monocytogenes
Listeria monocytogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Enterobacter aerogenes
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms
Listeria monocytogenes biofilms

Indicator

++
++
+++
+++
++
+++
+++
+++
++
++
++
+++
++
+++
++
+++
++
+++
++
+++
+
+++
+
+++
+
+++
+
+++
+
+++
++
++
++
++
++
++
+++
+++

Effectiveness

2.50
2.56
2.58
2.56
2.46
2.51
2.29
2.50
2.38
2.33
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.53
2.40
2.40
2.40
2.38
2.38
2.38
2.6
2.6

pH
1163
1165
1161
1162
1154
1157
1147
1156
1156
1150
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1178
1163
1163
1163
1169
1169
1169
1160
1160

ORP (mV)

EO water property

87
80
87
90
87
93
45
72
66
52
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
53
47
47
47
84
84
84
56
56

Free chlorine (mg/L)

Temperature (°C)
23
23
35
35
45
45
55
23
35
45
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23

Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Venkitanarayanan et
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Ayebah et al. (2005)
Ayebah et al. (2005)
Ayebah et al. (2005)
Ayebah et al. (2005)
Ayebah et al. (2005)
Ayebah et al. (2005)
Kim et al. (2001)
Kim et al. (2001)

Ref.

al.
al.
al.
al.
al.
al.
al.
al.
al.
al.

(1999a)
(1999a)
(1999a)
(1999a)
(1999a)
(1999a)
(1999a)
(1999a)
(1999a)
(1999a)

+++, bacterial reduction being more than 6 log CFU/ per unit; ++, bacterial reduction being between 2 and 6 log CFU/ per unit; +, bacterial reduction being less than 2 log CFU/ per unit.

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

50 rpm

Immersion condition

Processing materials

Table 2
Inactivation of food-borne pathogens on food processing materials by electrolyzed oxidizing water

336
Y.-R. Huang et al. / Food Control 19 (2008) 329–345

Immersion condition

EO 4 min
EO 4 min
EO 4 min
EO 4 min
EO 4 min
EO 5 min
EO 5 min
EO 5 min
EO 5 min+23 °C ER 5 min
EO 5 min+23 °C ER 5 min
EO 5 min+23 °C ER 5 min
EO 10 min
EO 1 min+23 °C ER 1 min
EO 5 min
EO 5 min+ EO 5 min
20 °C ER 5 min+ EO 5 min
EO 5 min
EO 5 min+ EO 5 min
20 °C ER 5 min+ EO 5 min
EO 1 min
EO 5 min
1 min EO
5 min EO
1 min EO
5 min EO
1 min EO
5 min EO
1 min EO
5 min EO
1 min EO
5 min EO
20 °C ER 1 min +1 or 5 min
20 °C ER 5 min +1 or 5 min
50 °C ER 1 min +1 or 5 min
50 °C ER 5 min +1 or 5 min
20 °C ER 1 min +1 or 5 min
20 °C ER 5 min +1 or 5 min
50 °C ER 1 min +1 or 5 min
50 °C ER 5 min +1 or 5 min
1 min EO
3 min EO
1 min EO
3 min EO
3 hr

Vegetables

Carrot
Spinach
Bell pepper
Japanese radish
Potato
Cucumber
Cucumber
Cucumber
Cucumber
Cucumber
Cucumber
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Lettuce
Alfalfa seeds
EO
EO
EO
EO
EO
EO
EO
EO

Aerobic bacteria counts
Aerobic bacteria counts
Aerobic bacteria counts
Aerobic bacteria counts
Aerobic bacteria counts
Aerobic bacteria counts
Coliform bacteria
Fungi
Aerobic bacteria counts
Coliform bacteria
Fungi
Aerobic bacteria counts
Aerobic bacteria counts
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Salmonella sp.
Salmonella sp.
Salmonella sp.
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Salmonella sp.
Salmonella sp.
Salmonella sp.
Salmonella sp.
Salmonella sp.
Salmonella sp.
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7
Salmonella sp.
Salmonella sp.
Salmonella sp.
Salmonella sp.
Escherichia coli O157:H7
Escherichia coli O157:H7
Listeria monocytogenes
Listeria monocytogenes
Salmonella sp.

Indicator

Table 3
Inactivation of food-borne pathogens on vegetables by electrolyzed oxidizing water

++
+++
+
+
+
++
+++
+++
+++
+++
+++
+++
+++
++
++
++
++
++
++
+
++
+
++
+++
++++
+
++
+
++
+++
+++
++
++
+++
+++
++
++
+++
+++
++++
++++
+++
++++
++

Effectiveness

6.8
6.8
6.8
6.8
6.8
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.6
2.5
2.5
2.5
2.5
2.4

–
–
–
–
–
1130
1130
1130
1130
1130
1130
1140
1140
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1030
1030
1030
1030
1081

ORP (mV)

EO water property
pH
20
20
20
20
20
32
32
32
32
32
32
30
30
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
45
45
45
45
84

Free chlorine (mg/L)
23
23
23
23
23
23
23
23
23
23
23
23
23
20
20
20
20
20
20
4
4
20
20
50
50
4
4
20
20
50
50
4
4
4
4
4
4
4
4
22
22
22
22
23

Temperature (°C)
Izumi (1999)
Izumi (1999)
Izumi (1999)
Izumi (1999)
Izumi (1999)
Koseki et al. (2004b)
Koseki et al. (2004b)
Koseki et al. (2004b)
Koseki et al. (2004b)
Koseki et al. (2004b)
Koseki et al. (2004b)
Koseki et al. (2001)
Koseki et al. (2001)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Koseki et al. (2004c)
Park et al. (2001)
Park et al. (2001)
Park et al. (2001)
Park et al. (2001)
Kim et al. (2003)
(continued on next page)

Ref.

Y.-R. Huang et al. / Food Control 19 (2008) 329–345
337

338

++++, bacterial reduction being more than 4 log CFU/ per unit; +++, bacterial reduction being between 2 and 4 CFU/ per unit; ++, bacterial reduction being between 1 and 2 CFU/ per unit;
+, bacterial reduction being less than 1 log CFU/ per unit. –, not measured.

60 min EO
Alfalfa seeds

Alfalfa seeds

10 min EO & sonication & seed coat
removal
10 min EO & sonication & seed coat
removal
15 min EO
Alfalfa sprouts

Salmonella sp.

++

2.6

1076

66.8

23

Stan and Daeschel
(2003)
Stan and Daeschel
(2003)
23
70
1079
2.5
++

Kim et al. (2003)
23
84
1081
2.4
++

10 min EO & seed coat removal
10 min EO & seed coat removal
Alfalfa sprouts
Alfalfa sprouts

Alfalfa sprouts

10 min EO & sonication
10 min EO & sonication
Alfalfa sprouts
Alfalfa sprouts

Non-Salmonella
microflora
Salmonella sp.

Kim et al. (2003)
23
84
1081
2.4
+++

Kim et al. (2003)
Kim et al. (2003)
23
23
84
84
1081
1081
2.4
2.4
++
++

Kim et al. (2003)
Kim et al. (2003)
23
23
84
84
1081
1081
2.4
2.4
++
+

Temperature (°C)

23
84

Free chlorine (mg/L)
ORP (mV)

1081
3 hr
Alfalfa seeds

pH

2.4
++

EO water property
Effectiveness
Indicator
Immersion condition
Table 3 (continued)

Vegetables

Non-Salmonella
microflora
Salmonella sp.
Non-Salmonella
microflora
Salmonella sp.
Non-Salmonella
microflora
Salmonella sp.

Ref.

Kim et al. (2003)

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

ER water (pH of 11.3, ORP of ÿ870 mV) for 5 min and
then soaked in EO water (pH of 2.6, ORP of 1130 mV
and free chlorine of 30 mg/L) for 5 min showed a reduction
in aerobic mesophiles. This treatment had at least
2 log CFU per cucumber greater reduction than that only
soaked in EO water (30 mg/L free chlorine), ozonated water
(5 mg/L ozone) or sodium hypochlorite solution (NaOCl,
150 mg/L free chlorine) for 10 min. In studies on sequential
wash treatment, Koseki et al. (2001) also found that a 2log CFU/g reduction in aerobic bacteria counts for both
the lettuce treated with ER water for 1 min followed by
the treatment with EO water for 1 min and the lettuce treated with acidic EO water alone for 10 min; however,
repeated EO water treatment did not show a significant
increase of bacterial reduction. Koseki et al. (2004c) used
mildly heated (50 °C) ER water to treat lettuce for 5 min,
and then used chilled (4 °C) EO water to treat for 1 or
5 min. They found the treatment could reduce both E. coli
O157:H7 and Salmonella at a level of 3–4 log CFU/g.
Wang, Feng, and Luo (2004) washed fresh-cut cilantro with
ozonated water for 5 min followed with a EO water (pH of
2.45, ORP of 1130 mV and free chlorine of 16.8 mg/L) for
5 min and found that the sequential wash is effective in
reducing initial microbial count and slowing microbial
growth during storage.
Lettuce with smooth surfaces have been used for the
investigation of the effectiveness of EO water on bacterial
reduction. Park et al. (2001) observed that shaking lettuce
with EO water (45 mg/L free chlorine) at 100 rpm for 3 min
significantly decreased mean populations of E. coli
O157:H7 and L. monocytogenes by 2.41 and 2.65 log CFU
per lettuce leaf, respectively, when compared with sterile
H2O treatment. The result was in agreement with that of
Izumi (1999) who pointed out that EO water (50 mg/L of
free chlorine) treatment of shredded lettuce did not significantly affect the quality characteristics such as color and
general appearance. Yang et al. (2003) suggested that
fresh-cut lettuce dipped in EO water (pH 7) containing
300 mg/L of free chlorine for 5 min could not only keep
the best visual quality but also achieve a 2-log CFU/g
reduction for S. Typhimurium, E. coli O157:H7 and
L. monocytogenes.
Koseki and Itoh (2001) suggested that the best temperature for distribution of fresh-cut vegetables with reduced
microbial population is 1 °C. Ice is an inexpensive material
for preserving fresh produces and fish. Koseki, Fujiwara,
and Itoh (2002) treated lettuce with frozen EO water (pH
of 2.5, ORP of 1148 mV and free chlorine of 20.5 mg/L)
and stored in a styrene-foam container for 24 h. The results
indicated that a 1.5-log CFU/g aerobic bacteria counts
reduction on lettuce was due to an increased chlorine gas
concentration from frozen EO water. In order to check
the effectiveness of Cl2 concentration and volume or weight
ratio of vegetables to frozen EO water, Koseki, Isobe, and
Itoh (2004a) prepared a EO-ice by freezing EO water at
ÿ40 °C. The EO water with 20, 50, 100 and 200 mg/L of
free chlorine could generate ice with 30, 70, 150 and

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

240 mg/L of Cl2, respectively. EO-ice generating 70–
240 mg/L Cl2 significantly reduced L. monocytogenes by
1.5 log CFU/g during 24 h storage. EO-ice generating 70–
150 mg/L of Cl2 reduced E. coli O157:H7 cell counts by
2.0 log CFU/g. Although higher concentration with
240 mg/L of Cl2 showed a significantly higher reduction
of E. coli O157:H7 by 2.5 log CFU/g, accompanied by physiological disorder resembling leaf burn. The weight ratio of
EO-ice to lettuce was >10. Chlorine at a level below 150 mg/
L did not affect the surface color of the lettuce.
Sprouts have been associated with a number of foodborne illnesses in recent years. E. coli O157:H7, Salmonella
spp. and B. cereus have been responsible for several sproutassociated outbreaks worldwide (Taormina, Beuchat, &
Slusker, 1999). Sprouts are produced under warm and
humid condition, pathogens can grow rapidly during seed
germination increasing the likelihood of infections.
Beuchat, Ward, and Pettigrew (2001) reported populations
of Salmonella exceeding 106 CFU/g could occur on alfalfa
sprouts produced from contaminated seeds. Although the
use of 20,000 mg/L Ca(OCl)2 for treatment of seeds
intended for sprout production has been recommended
(NACMCF, 1999), the use of high concentrations of
Ca(OCl)2 both generated worker safety concerns and
significantly reduced seed germination rates (70% versus
90–96%) (Kim et al., 2003). Studies have demonstrated that
64.5 mg/L free chlorine in EO water treatment reduced
E. coli O157:H7 population on alfalfa sprouts (initial population was about 6 log CFU/g) by 1.05 log CFU/g (91.1%)
for 2 min treatment, while the reduction was by
2.72 log CFU/g (99.8%) for 64 min treatment. EO water
treatment did not cause any visible damage to the sprouts
(Sharma & Demirci, 2003). Kim et al. (2003) reported that
treatment of seeds with 20,000 mg/L Ca(OCl)2 reduced
the population of Salmonella and non-salmonella to undetectable levels on culture media, but an amount >6 log
CFU/g of Salmonella was still recovered from sprouts generated from these seeds. However, the combination of EO
water (84 mg/L free chlorine) and sonication treatment had
a better reduction on Salmonella and non-salmonella populations than that by using EO water alone. Removal of
seed coats by sonication might have detached cells that
were attached or entrapped in sprouts, thus making the
pathogen more susceptible to the EO water. The combined
treatment achieved 2.3 and 1.5 log CFU/g greater reductions than EO water alone in populations of Salmonella
and non-salmonella microflora, respectively (Kim et al.,
2003).
8.3. Use of EO water for fruits
Postharvest decay of fruits causes economic loss to the
fruit industry. In studies on surface sterilization of fruits,
Al-Haq et al. (2001) found that EO water could prevent
peach from decay and it could be used as an important
alternative to liquid sterilants. Al-Haq et al. (2002) later
found that EO water immediately reacted with Botryosp-

339

haeria berengeriana that presented on the first few layers
of the pear surface and could not control growth of bacteria that entered into the fruit deeper than 2 mm. No chlorine-induced phytotoxicity on the treated fruit was
observed. Both EO water containing 200 and 444 mg/L
free chlorine significantly reduce the populations of
E. coli O157:H7, S. enteritidis and L. monocytogenes on
the surfaces of tomatoes without affecting sensory quality
(Bari et al., 2003; Deza et al., 2003).
Patulin is a mycotoxin mainly found in apples and their
products that are contaminated with the common storagerot fungus Penicillium expansum (Brian, Elson, & Lowe,
1956; Harwig, Chen, Kennedy, & Scott, 1973). The uses
of 100% and 50% EO water containing 60 mg/L free chlorine could decrease P. expansum viable spore populations
by greater than 4 and 2 log units of aqueous suspension
and wounded apples (Okull & Laborde, 2004). EO water
did not control brown rot in wound-inoculated fruits, but
reduced disease incidence. In contrast to the present results
for smooth fruits, on treatment of the surface of the strawberry with 30 mg/L free chlorine EO water and 150 mg/L
NaOCl, aerobic mesophiles were reduced by less than
1 log CFU per strawberry after washing in ER water (pH
of 11.3, ORP of ÿ870 mV) for 5 min and then with EO
water (pH of 2.6, ORP of 1130 mV and free chlorine of
30 mg/L) for 5 min, EO water (30 mg/L free chlorine), ozonated water (5 mg/L ozone) and sodium hypochlorite solution (NaOCl, 150 mg/L free chlorine) for 10 min,
respectively. These results can be attributed to the surface
structure of the strawberry fruit. There are many achenes
(seeds) that render its surface structure uneven and complex (Koseki et al., 2004b). These studies showed that the
efficacy of EO water as a sanitizing agent was dependent
on the surface structure of fruit treated.
8.4. Use of EO water for poultry and meat
Egg shell can serve as a vehicle for transmission of
human pathogens. Due to the fecal matter in the nesting
place, the wash water during manipulation, or during packaging process, the shell may become contaminated with
E. coli O157:H7, Salmonella sp., L. monocytogenes and Yersinia enterocolitica (Gabriela, Maria, Lidia, & Ana, 2000;
Moore & Madden, 1993; Schoeni & Doyle, 1994). Elimination of pathogens in hatchery facilities has been usually
done by applying of formaldehyde and glutaraldehyde gas
or fogging hydrogen peroxide. However, these disinfectants
may pose high risk for human and chick health. Russell
(2003) found that EO water (pH of 2.1, ORP of 1150 mV
and free chlorine of 8 mg/L) with an electrostatic spraying
system could completely eliminate S. Typhimurium, S. aureus and L. monocytogenes on egg shells.
Efficacy of EO water in reducing pathogens on poultry
has been investigated in recent years (Table 4). Park et al.
(2002a) reported that for chicken wings (50 ± 5 g) inoculated with Campylobacter jejuni, soaking in EO water
(pH of 2.57, ORP of 1082 mV and free chlorine of

10 min EO
30 min EO
10 min EO
30 min EO
45 min EO
45 min EO
45 min EO
45 min EO
40 min EO
15 s spray with EO
15 s spray with EO
15 s spray with EO
15 s spray with EO
15 s spray with EO
15 s spray with EO
10 s spray with ER & 10 s
spray with EO
10 s spray with ER & 10 s
spray with EO
15 min EO
15 min spray with EO
15 min spray with EO
15 min spray with EO

Chicken wing
Chicken wing
Chicken wing
Chicken wing
Broiler carcasses
Broiler carcasses
Broiler carcasses
Broiler carcasses
Chicken carcasses
Pork belly
Pork belly
Pork belly
Pork belly
Pork belly
Pork belly
Cattle hide

Listeria monocytogenes
Aerobic bacteria counts
Listeria monocytogenes
Listeria monocytogenes

Enterobacteriaceae counts

Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni
Aerobic bacteria counts
Salmonella Typhimurium
Escherichia coli
Coliform bacteria
Campylobacter jejuni
Aerobic bacteria counts
Escherichia coli
Coliform bacteria
Salmonella Typhimurium
Listeria monocytogenes
Campylobacter coli
Aerobic bacteria counts

Indicator

++
+
+
+

++++

+++
+++
+++
+++
++
+
++
++
+++
++
++
++
++
++
++
+++

Effectiveness

2.3
2.3
2.3
2.3

2.4

2.5
2.5
2.6
2.6
2.6
2.6
2.6
2.6
2.8
2.6
2.6
2.6
2.6
2.6
2.6
2.4

pH

1150
1150
1150
1150

–

1082
1082
1092
1092
1150
1150
1150
1150
1165
1150
1150
1150
1150
1150
1150
–

ORP (mV)

EO water property

45
45
45
45

70

51.6
51.6
53.3
53.3
50
50
50
50
39.5
50
50
50
50
50
50
70

Free chlorine (mg/L)

25
25
25
25

60

23
23
4
4
4
4
4
4
23
23
23
23
23
23
23
60

Temperature (°C)

Fabrizio
Fabrizio
Fabrizio
Fabrizio

and
and
and
and

Cutter
Cutter
Cutter
Cutter

(2005)
(2005)
(2005)
(2005)

Bosilevac et al. (2005)

Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Park et al. (2002a)
Fabrizio et al. (2002)
Fabrizio et al. (2002)
Fabrizio et al. (2002)
Fabrizio et al. (2002)
Kim et al. (2005)
Fabrizio and Cutter (2004)
Fabrizio and Cutter (2004)
Fabrizio and Cutter (2004)
Fabrizio and Cutter (2004)
Fabrizio and Cutter (2004)
Fabrizio and Cutter (2004)
Bosilevac et al. (2005)

Ref.

++++, bacterial reduction being more than 4 log CFU/ per unit; +++, bacterial reduction being between 2 and 4 CFU/ per unit; ++, bacterial reduction being between 1 and 2 CFU/ per unit;
+, bacterial reduction being less than 1 log CFU/ per unit. –, not measured.

Frankfurter
Frankfurter
Frankfurter
Ham

Cattle hide

Immersion condition

Materials

Table 4
Inactivation of food-borne pathogens on poultry and meat by electrolyzed oxidizing water

340
Y.-R. Huang et al. / Food Control 19 (2008) 329–345

64 min EO
64 min EO
64 min EO
64 min EO
1 min EO
5 min EO
10 min EO
1 min EO
5 min EO
10 min EO
1 min EO
1 min EO
5 min EO
10 min EO
1 min EO
5 min EO
10 min EO
5 min EO (150 rpm)
5 min EO (150 rpm) & CO
5 min EO (150 rpm)
5 min EO (150 rpm) & CO
5 min EO

Salmon fillet

Salmon fillet

Salmon fillet

Salmon fillet

Tilapia
Tilapia
Tilapia
Tilapia

Tilapia

Tilapia

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Dirty fish retailer in fish market

Tuna fillet

Tuna fillet

Tuna fillet

Tuna fillet

Stainless steel containing seafood
residue
Ceramic title containing seafood residue
Floor tile containing seafood residue
5 min EO
5 min EO

Immersion condition

Materials

Listeria monocytogenes
Listeria monocytogenes

Escherichia coli
Escherichia coli
Escherichia coli
Vibrio
parahaemolyticus
Vibrio
parahaemolyticus
Vibrio
parahaemolyticus
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Aerobic bacteria
counts
Listeria monocytogenes

Listeria monocytogenes

Listeria monocytogenes

Escherichia coli

Escherichia coli

Indicator

Table 5
Inactivation of food-borne pathogens on seafood fields by electrolyzed oxidizing water

+++
++

+++

++

++

+

++

++

++

++

+++

+++

++

++++

++

++

+
++
++
++

++

+

++

+

Effectiveness

2.5
2.5

2.5

2.2

2.2

2.5

2.5

2.7

2.7

2.7

2.5

2.5

2.5

2.2

2.4

2.4

2.4
2.4
2.4
2.4

2.6

2.6

2.6

2.6

1150
1150

1150

1135

1135

1105

1105

1090

1090

1090

1120

1120

1120

1145

1159

1159

1159
1159
1159
1159

1150

1150

1150

1150

ORP (mV)

EO water property
pH

50
50

50

100

100

50

50

50

50

50

100

100

100

200

120

120

120
120
120
120

90

90

90

90

Free chlorine
(mg/L)

23
23

23

23

23

23

23

23

23

23

23

23

23

23

23

23

23
23
23
23

35

22

35

22

Temperature
(°C)

Liu et al. (2006b)
Liu et al. (2006b)
(continued on next page)

Liu et al. (2006b)

Huang et al. (2006b)

Huang et al. (2006b)

Huang et al. (2006b)

Huang et al. (2006b)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Huang et al. (2006a)

Ozer and Demirci
(2006)
Ozer and Demirci
(2006)
Ozer and Demirci
(2006)
Ozer and Demirci
(2006)
Huang et al. (2006a)
Huang et al. (2006a)
Huang et al. (2006a)
Huang et al. (2006a)

Ref.

Y.-R. Huang et al. / Food Control 19 (2008) 329–345
341

342

23
40
1125
2.6
Listeria monocytogenes
Above 5 clean food processing gloves

5 min EO

++++

23
40
1125
2.6
Listeria monocytogenes
5 min EO
Nitrile (disposable) containing seafood residue

+++

23
40
1125
2.6
Listeria monocytogenes
5 min EO
Latex (disposable) containing seafood residue

+++

23
40
1125
2.6
++
Listeria monocytogenes
5 min EO
Nitrile containing seafood residue

++++, bacterial reduction being more than 4 log CFU/ per unit; +++, bacterial reduction being between 2 and 4 CFU/ per unit; ++, bacterial reduction being between 1 and 2 CFU/ per unit;
+, bacterial reduction being less than 1 log CFU/ per unit.

Su

Su

Su

Su

Su
23
40
1125
2.6
Listeria monocytogenes
5 min EO

++

Temperature (°C)

23
40

Free chlorine (mg/L)
ORP (mV)

1125
Listeria monocytogenes
5 min EO

Natural rubber latex glove containing seafood
residue
Natural latex glove containing seafood residue

pH

2.6

EO water property
Effectiveness
Indicator
Immersion condition
Materials

Table 5 (continued)

+++

Ref.

Liu and
(2006b)
Liu and
(2006b)
Liu and
(2006b)
Liu and
(2006b)
Liu and
(2006b)
Liu and
(2006b)

Su

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

50 mg/L) with 100 rpm agitation for 30 min has achieved
reduction by 3 log CFU/g. Since pathogens were attached
to a water-skin interfaces and further entrapped in folds,
crevices and follicles, no viable cell of C. jejuni was recovered in EO water after treatment. Kim, Hung, and Russell
(2005) recommended to spray-wash chicken with ER water
before defeathering and evisceration to reduce the potential
cross-contamination. However, combining immersion with
spray-washing did not significantly improve the bactericidal effect of EO water as compared to the immersion-only
treatment. Fabrizio et al. (2002) reported that spray-washing with EO water, ozone, 2% acetic acid (AA) or 10% trisodium phosphate (TSP) did not show any significant
microbicidal effectiveness. However, spray-washing with
ER water followed by immersion in EO water had a better
effectiveness than spraying with AA and TSP followed by
immersion in chlorine solution at the end of a 7-day refrigerated storage.
Fabrizio and Cutter (2004) had recently examined the
spray-washing with EO water for 15 s to disinfect pork bellies inoculated with feces containing L. monocytogenes,
S. Typhimurium and Campylobacter coli. This study demonstrated that a 15-s spraying with EO water (pH of 2.4,
ORP of 1160 mV and free chlorine of 50 mg/L) had the
ability to reduce the populations of L. monocytogenes,
S. Typhimurium and C. coli (1.23, 1.67 and 1.81, respectively) on the pork surfaces and inferred that longer contact
times might strengthen the disinfection effectiveness. For
sterilizing hides of cattle before slaughtering, Bosilevac,
Shackelford, Brichta, and Koohmaraie (2005) reported
that sequentially applied ER water and EO water containing 70 mg/L free chlorine at 60 °C for a 10-s spraying could
reduce aerobic bacteria counts by 3.5 log CFU/100 cm2 and
reduced Enterobacteriaceae counts by 4.3 log CFU/
100 cm2. Recently, Fabrizio and Cutter (2005) dipped or
sprayed frankfurters and ham inoculated with L. monocytogenes with EO water (pH of 2.3, ORP of 1150 mV and
free chlorine of 45 mg/L) and/or ER water for 30 min.
No significant difference (p < 0.05) between treatments on
Hunter L*, a*, b* values for frankfurters and ham at the
end of 7 days storage at 4 °C was found. The results indicated that EO water has no detrimental ‘‘bleaching’’ effects
on the surface of tested read-to-eat meats.
8.5. Use of EO water for seafood
Using EO water for inactivating bacteria in raw seafood
have been reported (Table 5). Ozer and Demirci (2006)
found that treating raw salmon with EO water (pH of
2.6, ORP of 1150 mV and free chlorine of 90 mg/L) at
35 °C for 64 min resulted in a 1.07 log CFU/g (91.1%)
and 1.12 log CFU/g (92.3%) reduction in E. coli O157:H7
and L. monocytogenes, respectively. Recently, Liu and Su
(2006) stated that gloves used in handling food for protection of the worker and seller could become a carrier of
pathogens through the contact of raw materials or contaminated surfaces. However, applications of EO water follow-

Y.-R. Huang et al. / Food Control 19 (2008) 329–345

ing a thorough cleaning greatly reduced L. monocytogenes
population on gloves and seafood processing plants.
Soaking inoculated gloves in EO water (pH of 2.6, ORP
of 1125 mV and free chlorine of 40 mg/L) at room
temperature for 5 min completely eliminated L. monocytogenes on gloves (>4.46 log CFU/cm2) (Liu & Su, 2006). The
treatment by immersion in EO water containing 50 mg/L
chlorine for 5 min significantly reduced L. monocytogenes
on tested surfaces (3.73 log/25 cm2 on stainless steel sheet,
4.24 log/25 cm2 on ceramic tile and 1.52 log/25 cm2 on
floor tile) (Liu, Duan, & Su, 2006). Huang et al. (2006a)
also reported that EO water was a very effective sanitizer
used for cleaning fish contacting surfaces in traditional grocery stores and fish markets, so that secondary bacterial
contamination could be prevented. EO water was especially effective in reducing the population of E. coli and
V. parahaemolyticus contamination on tilapia.
In order to prolong the shelf life of yellow-fin tuna
(Thunnus albacares) during refrigerated and frozen storage,
combination of EO water and CO gas were applied.
Huang, Shiau, Hung, and Hwang (2006b) reported that
tuna treated with a combination of EO water containing
100 mg/L chlorine and CO gas could immediately result
in the lowest APC. EO water containing 50 mg/L or
100 mg/L chlorine combined with CO gas treatment in
tuna fish steak would be an effective method for enhancing
the hygienic quality and freshness for tuna meat and
extending refrigerated storage time. The efficiency of EO
water on the growth and toxicity of the dinoflagellates
Alexandrium minutum, Alexandrium catenella and Gymnodinium catenatum has been studied in our laboratory. It
was found that EO water very effectively killed toxic dinoflagillates and destroyed toxicity.
9. Conclusions
Since EO water is considered to be a solution containing
HOCl, the application of EO water can be fitted into the
regulations for hypochlorous (HOCl). In 2002, Japan had
officially approved EO water as a food additive (Yoshida,
Achiwa, & Katayose, 2004). Electrolyzed water generator
has also been approved for applications in the food industry by the US Environmental Protection Agency (EPA)
(Park et al., 2002b).
Although EO water has advantages as a disinfectant for
use in many food products, relevant topics in EO water
deserve future research. These may include the methods
for expanding the usages of EO water in food processing
plant and the application in HACCP and SSOP systems.
Since bactericidal effects of the EO water may be reduced
in the presence of organic matter due to the formation of
monochloramines, techniques to avoid these matters need
to be researched. Furthermore, the sensory characteristics
of food processed may be affected by degradation of contaminants in the food during the application of EO water
need to be further studied.

343

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