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Email: norashikin@upm.edu.my
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Food Research 5 (Suppl. 1) : 47 - 56 (2021)
Journal homepage: http://www.myfoodresearch.com
Stability of electrolyzed water: from the perspective of food industry
1Khalid, N.I., 1Sulaiman, N.S., 1, 2*Ab Aziz, N., 1Taip, F.S., 3Sobri, S. and
4Nor-Khaizura, M.A.R.
1Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400
Serdang, Selangor, Malaysia.
2Halal Products Research Institute, University Putra Malaysia, 43300 UPM Serdang, Selangor, Malaysia.
3Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra
Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia
4Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400,
UPM Serdang, Selangor, Malaysia.
Article history:
Received: 18 April 2020
Received in revised form:23
July 2020
Accepted: 11 October 2020
Available Online: 3 January
2021
Keywords:
Disinfection,
Electrochemically activated
water,
Electrolysis,
Novel disinfectants,
Sanitation,
Sustainable cleaning
DOI:
https://doi.org/10.26656/fr.2017.5(S1).027
Abstract
Green cleaner and disinfectant can provide a better environment and they can reduce
cleaning cost by eliminating the cost of harsh cleaning chemicals, minimizing cleaning
chemicals storage space, reducing cost for wastewater treatment and reducing logistics
cost for chemical supply. This study explored the personal view of Small and Medium
Enterprises (SMEs) top to bottom workers towards the challenges during cleaning and
disinfection process and their readiness in accepting a green cleaner and disinfectant. In
this work, the advantages and disadvantages of electrolyzed water (EW) as green cleaner
and disinfectant were discussed. A lab-scale batch ion-exchange membrane electrolysis
unit was used to produce acidic electrolyzed water (AcEW) and alkaline electrolyzed
water (AlEW). The stability of AcEW and AlEW was also studied based on its physical
changes (pH, oxidative-reduction potential (ORP), chlorine content and hydrogen
peroxide content) in 7 days of storage, whereby measurements were taken daily. The pH
maintained for both AcEW and AlEW during the 7 days of storage. The ORP maintained
at plateau for the first 5 days of AcEW storage. After 5 days, AcEW showed a decreasing
trend. While ORP for AlEW increases drastically between day 1 and 2. Then, the ORP
reaches a plateau after three days. The amount of free chlorine, total chlorine and
hydrogen peroxide content was 10 mg/L, respectively, on the day of production. However,
all the properties decreased gradually and there were no chlorine and hydrogen peroxide
detected on the 7th day. The results from this study can be used as a guideline to store the
EW and to understand the stability of the EW, which can benefit the SME food
manufacturers.
1. Introduction
Selection of suitable cleaning detergents and
disinfection (or also known as sanitisation in the USA)
for SMEs can be costly and complex. Considering SMEs
financial aspect, they are facing difficulties in finding a
balance between the cleaning detergent cost and its
performance. Food-grade cleaning detergents are easy to
rinse and poses less harm to food contact surfaces and
food products. However, these types of detergents can be
expensive and can be a burden to SME food
manufacturers. Generally, there are three types of
cleaning detergents for the food industry: 1) pure
chemicals, 2) formulated detergents and 3) pure
chemicals with additives. The main components of all
chemicals are always an alkali or an acid. The selection
of the main components is depending on the nature of
food soil in the processing system. Then, after the
cleaning process, the food contact surfaces are
disinfected to inactivate microorganism that is harmful to
humans. Disinfection of food contact surfaces can be
done with moist heat at a range of 90 to 95°C (Tetra Pak
International S.A., 2015), with hot water of 75°C (Heinz
and Hautzinger, 2007; Watkinson, 2008; Hui, 2012;
Khalid et al., 2019) or with chemicals (Khalid et al.,
2016). Food manufacturers commonly use two types of
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cleaning detergents in order to achieve cleanliness.
Sodium hydroxide is commonly used as an alkaline-
based detergent to remove the carbohydrate-based
fouling deposit for cleaning, and disinfectant (e.g.,
sodium hypochlorite) is used for disinfection (Walton,
2008). Alkaline-based cleaning chemical is commonly
used for cleaning food-contact surfaces. Acid cleaning
cycle (e.g., acetic acid) is added onto food contact
surfaces that process food (commonly dairy products)
that contain mineral such as calcium, phosphorous, and
riboflavin (Walton, 2008).
Even though there are formulated cleaning
detergents which can cater function of multiple cleaning
and disinfection chemicals, there is still a need to find a
green cleaner as we are becoming increasingly health
and eco-conscious. Thus, the demand for sustainable
initiatives also grows. One of the green cleaner available
today is the electrolyzed water (EW). EW is one of the
green alternatives solution for both cleaning and
disinfection chemicals whereby EW can be produced
through the electrolysis process of salt solution only. As
the electrolysis cell with an ion-selective membrane is
subjected to current, two types of solution are produced.
Acidic electrolyzed water (AcEW) is produced at anode.
AcEW contains hydrogen peroxide, H2O2 (Rico et al.,
2007; Stanga, 2010), ozone gas, O3 (Guzel-Seydim et al.,
2004; Stanga, 2010; Meireles et al., 2016), hypochlorous
acid, HOCl, hyphochloric acid, HCl (Meireles et al.,
2016) and hypochlorite ion, ClO¯ (Meireles et al., 2016).
All of these components make AcEW to be a powerful
sanitiser in disinfecting many types of foodborne
pathogens such as Salmonella (Venkitanarayanan et al.,
1999; Fabrizio and Cutter, 2004), Escherichia coli
(Venkitanarayanan et al., 1999; Ozer and Demirci, 2006)
and Listeria monocytogenes (Venkitanarayanan et al.,
1999; Ozer and Demirci, 2006). Whereas alkaline
electrolyzed water (AlEW) contains sodium hydroxide; a
grease-cutting cleaner produced at cathode. In contact
with NaOH, fouling deposit will swell and assist the dirt
removal (Khalid et al., 2016).
Most of the SME factories have small factory areas
which allow them to have limited storage area. Bulk
purchasing of cleaning detergents can reduce the total
cleaning cost, but the limited storage area becomes a
hindrance. Moreover, SMEs only use a small amount of
cleaning detergents which leads to more cleaning
detergents becoming expired. Treatment or disposal of
the expired chemicals will only contribute to a negative
effect on the environment and increase the operating
cost. EW is seen as a potential in solving the storage
problem as it can be produced on-site and does not need
any storage area (Khalid, Ab Aziz, Thani et al., 2020).
The research is aimed to identify the potential of EW
as green cleaner and disinfectant in the food industry
SMEs. The effect of storage duration on chemical
properties of acidic electrolyzed water (AcEW) and
alkaline electrolyzed water (AlEW) was also studied.
The results obtained from this work can be used as a
guideline for SMEs to apply and store the EW
reasonably.
2. Materials and methods
2.1 Identifying the potential of EW as green cleaner in
the food industry
Face to face unconstructed interviews (impromptu)
were conducted in an SME meat processing factory
(factory X) in Selangor, Malaysia. The factory produced
different types of burgers (beef, lamb and chicken). The
manufacturing process of the factory includes weighing,
flaking, mincing, pre-mixing, mixing, burger forming,
blast freezing, packing and frozen storage (Khalid,
Saulaiman, Nasiruddin et al., 2019). Questions related to
cleaning and sanitation process were asked during the
interviews. The interview was not transcribed. However,
notes were taken during the interview. The purpose of
this interview is to understand the difficulties of SME
food manufacturer in implementing good cleaning
practices. The questions included the selection of
cleaning and disinfection detergents, storage for cleaning
apparatus and chemical storage conditions. A short visit
during cleaning was also conducted. Moreover, the
potential application of EW in the food industry for
replacing commercial cleaning chemicals was also asked
during the interview. Several workers related to cleaning
and sanitation process were interviewed with 1)
production manager, 2) quality assurance/quality control
(QA/QC) manager, 3) production worker 1, and 4)
production worker 2.
2.2 Preparation of electrolyzed water
A laboratory-scale batch electrolysis unit was used to
generate acidic electrolyzed water (AcEW) and alkaline
electrolyzed water (AlEW). The electrolysis unit (Figure
1) was designed and constructed at the Department of
Process and Food Engineering, Faculty of Engineering,
Universiti Putra Malaysia, Malaysia. Both the cathode
and anode chambers were made of acrylic glass that
allowed visual observation during the electrolysis
process. The chamber can be filled with electrolyte up to
6 litres (3 litres per chamber). The chambers are
separated by a polyester UF membrane which allowed
ion exchange during the electrolysis process. DC power
supply (PSW, 0 – 30 V, 0 – 36 A, GW Instek, Taiwan) is
used to control the voltage. In this work, 3.4 L diluted
sodium chloride solution (R&M Chemicals, United
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Kingdom) was poured into the electrolysis unit (1.7 L
salt solution in each chamber). Both the cathode and
anode which were made of stainless steel 316 were
installed and the chamber was closed. Then, current
approximately in the range of 2.0 to 2.2 A was subjected
to the electrolysis unit. At the end of the electrolysis
process, AcEW and AlEW were collected at anode and
cathode chambers, respectively.
2.3 Stability of electrolyzed water
After electrolysis, the changes towards the chemical
properties (pH, oxidation-reduction potential (ORP), free
chlorine, total chlorine and hydrogen peroxide content)
of EW were tested. Then, 100 mL of AcEW and 100 mL
of AlEW were stored in a dark brown tightly-screwed
closed bottle at room temperature (25-30°C). The
amount of pH, ORP, free chlorine, total chlorine and
hydrogen peroxide content of EW were measured at
every 24 hrs for 7 days according to previous researchers
(Hsu and Kao, 2004; Cui, et al., 2009; Khalid et al.,
2018). For every 24 hrs, the bottles were opened for
approximately 5 mins for analytical measurements. The
experiment was repeated for 3 times and each repetition
was carried out at different week.
2.4 Analytical measurement of electrolyzed water
Free and total chlorine test strips 0 – 10 mg/L (Hach,
Unites State) were used to estimate the free chlorine and
total chlorine content in electrolyzed water. The
hydrogen peroxide test strip 0 – 10 mg/L (Macherey-
Nagel, Germany) was used to estimate the content of
hydrogen peroxide. The pH was measured using a
portable pH/mV/ISE meter equipped with pH electrode
(Fisher Scientific, USA). Oxidation-reduction potential
(ORP) was measured using a portable pH/mV/ISE meter
equipped with redox electrode (Boeco, Germany). Table
1 shows the reactions involved during the electrolysis
process (Al-Haq et al., 2005; Rahman et al., 2016). As
shown in Table 1, chlorine and hydrogen peroxide are
only generated at the anode chamber which contributes
to the AcEW’s properties. Thus, the pH, ORP, free
chlorine, total chlorine and hydrogen peroxide are
measured for AcEW. Whereas, only pH and ORP were
measured for the AlEW.
3. Results and discussion
3.1 Background of the impromptu interview
Factory x, a meat processing factory was used in this
work. Factory x was chosen as the case study due to the
prior research conducted by (Hasnan et al., 2019).
Hasnan et al. (2019) proposed a spine plant layout design
for the factory x. The suggested spine plant layout that
was proposed by Hasnan et al., (2019) was expected to
improve the food hygiene and reduce the travelled
distances inside this small-scale meat processing factory.
After the implementation of the new plant layout, a short
visit was conducted. The improved plant layout itself
solely cannot improve the hygienic environment of the
factory. Thus, during the visit’s meeting, the topic
regarding improving the cleaning and sanitation of
factory x was discussed. The group meeting was
attended by the production manager and the QA/QC
manager. They explained the cleaning and sanitation
difficulties that they were facing. The meeting took
about one and a half hours. Notes were taken during the
meeting. After the meeting, two production workers
were interviewed individually. The individual interview
took about 30 mins each. During the interview and
discussion, notes were taken. The finding was
determined based on the notes taken and the observation
Figure 1. Schematic diagram of the laboratory-scale batch
electrolysis unit: a) front-side view (complete set-up), b) front
-side view c) right view, d) top-side view and e) perspective
view.
Anode Cathode
2NaCl = Cl2 (g) + 2e- + 2Na+
2H2O(l) = 4H+ (aq) + O2 (g) + 4e-
Cl2 + H2O (l) = HCl + HOCl
H2O = H+ + ∙OH + e-
∙OH + ∙OH = H2O2
2 H2O2 (l) + 2e- = 2OH- + H2 (g)
2NaCl + 2OH- = 2NaOH + Cl-
• Acidic electrolyzed water is obtained
• Chlorine species (HCl, HOCl) are generated
• Hydrogen peroxide is generated (H2O2)
• Alkaline electrolyzed water is obtained
• Sodium hydroxide (NaOH) is generated
Table 1. Reactions involve during the electrolysis process (Al-Haq et al., 2005; Rahman et al., 2016)
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during the visit. The themes and similarity of the notes
were analysed.
3.2 Challenges of cleaning from Small and Medium
Enterprise (SME) perspectives
Based on the group discussion (meeting) and
individual reflection of production workers, four major
problems were identified which are: 1) difficulty in
selecting the cleaning and disinfection chemical, 2)
limited knowledge in cleaning and disinfection process,
3) budget constraints and 4) limited storage area. First, in
implementing a cleaning program, the selection of good
cleaning detergents is very difficult for SMEs. They
claim that food-grade detergents are expensive and
eventually can become a burden. Thus, they tend to
purchase a cheap cleaning detergent without any proper
material safety data sheet (MSDS).
Second, they believe visual cleanliness is the only
indicator which can validate their cleaning programs.
Most of the SMEs are unaware of cleaning indicators for
food industries which are physical (visual, touch and
smell), microbiological and chemical cleanliness (Khalid
et al., 2019). These indicators are also known as cleaning
target for some food industries. These three cleanliness
indicators are important to ensure the products are safe
and do not contaminate microbiologically, physically
and chemically (Walton, 2008). Moreover, a clean
environment contributes to a more healthy and safe
working environment for workers. Maintaining
cleanliness in food manufacturing premise is of the
utmost importance to create a safe, enjoyable,
comfortable, and stress-free environment for workers in
the food industry (Khalid et al., 2019).
Third, food SMEs have a limited budget which
constraints them in implementing a good cleaning
process. They tend to skip the costly cleaning process
such as hot water rinsing. Hot water rinsing is used to
melt the invisible fat layer which is commonly found in
meat processing area (Khalid and Ab Aziz, 2019). SMEs
try to avoid boiler utilization as it will increase the
operating and maintenance cost (Khalid and Ab Aziz,
2019). This hot water rinsing increases the cleaning
performance and also capable to act as disinfectant in
inactivating foodborne pathogens (Heinz and Hautzinger,
2007; Watkinson, 2008; Hui, 2012; Khalid et al., 2019).
An expensive disinfectant chemical can be replaced with
this hot water rinsing process at 75°C (Heinz and
Hautzinger, 2007; Watkinson, 2008; Hui, 2012; Khalid
et al., 2019). This will reduce the operating cost.
However, most of food SMEs do not know about this
and continue to purchase expensive disinfectant
chemicals. Then, when they were asked if they are
willing to accept other cleaning chemical solution, they
stated that they are open for the suggestion as long as the
alternative cleaning solution is cheap and effective.
Thus, EW, which is environmentally friendly and cheap
can be accepted in SME factories.
Last but not least is the limited storage area. Bulk
purchasing of cleaning chemicals can reduce the total
cleaning chemicals cost. However, the storage area of
SMEs is quite small. Most of the SME factories were set
-up in a small and limited factories area. Thus, they have
small chemical storage area which they have to store all
unused (unopened bottles) chemicals, used chemicals,
expired chemicals and cleaning apparatus (brushes,
sweep, sponge etc.). Disposal of expired chemicals can
be costly. Thus, they eventually decided to store the
expired cleaning chemicals. EW which can be generated
on-site does not need big space for storage and does not
require further wastewater treatment. These are the key
criteria which enhance the acceptance of EW in SME for
cleaning and sanitation.
3.3 Electrolyzed water as an affordable and green
cleaner
Electrolyzed water is claimable as a green and cheap
cleaner with high potential as detergents for both
cleaning and disinfection (Al-Haq et al., 2005; Rahman
et al., 2016). Based on the interviews with SMEs, they
are willing to accept this technology as the cost using
EW is low because the only operating expenses are
water, salts, and electricity in order to run the
electrolyzing unit (Al-Haq et al., 2005; Rahman et al.,
2016). However, the cost for initial capital investment to
purchase the EW generator is not considered when
calculating the cost. To date, there is no report made on
the cost advantages regarding the usage of electrolyzed
water in food industries. The actual cost advantage needs
to be determined (Dev et al., 2014). The actual cost
should consider the price of the initial purchase of EW
generator, the shelf life of the EW generator, shelf life of
electrode’s materials (material for cathode and anode for
electrolysis) and the membrane’s shelf life. There are
two main corrosive components in electrolyzed water
which are salt and chlorine (Khalid, Sulaiman, Ab Aziz
et al., 2020). Corrosion will reduce the electrode’s
material performance by reducing the current flow (Hsu
et al., 2015, Khalid, Sulaiman, Ab Aziz et al., 2020).
Eventually, the brown precipitate formed due to
corrosion can attach to the membrane and eventually
limiting the ion-exchange process (Khalid, Sulaiman, Ab
Aziz et al., 2020). Frequent replacement of electrodes
and membrane is needed. Therefore, future analysis may
include short- and long-term cost analyses.
Alkaline electrolyzed water (AlEW) contains sodium
hydroxide (Table 1); a grease-cutting cleaner which is
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able to remove oil, grease and fat. Detergency test using
AlEW shows that it is able to eliminate 100% of the
animal and vegetable oil formed on the steel’s surface
effectively (Shirota and Isaka, 2001). Since the
properties of the AlEW are not affected by the heat
effect, cleaning using AlEW at a higher temperature will
contribute to higher cleaning efficiency (Dev et al.,
2014). AlEW is also able to remove protein-based soil.
For milking system that used cleaning-in-place (CIP)
program for cleaning, AlEW has proven its potential to
replace the sodium hydroxide (NaOH) (Dev et al., 2014;
Wang et al., 2016). Whereas, acidic electrolysed water
(AcEW) can be used to replace acidic-based detergent
(Dev et al., 2014; Wang et al., 2016). Dev et al. (2014)
and Wang et al. (2016) applied AcEW during cleaning-
in-place (CIP) process to clean the milking system as
fouling deposit consists of some minerals. Their
experimental works show that AcEW can replace the
acid-based detergent and the sanitiser for CIP process of
the milking system.
3.4 Electrolyzed water as environmentally friendly
cleaning medium
Utilizing EW during cleaning is better for the
environment, worker’s safety and food safety as EW is
less toxic than petroleum-based cleaning chemical
(Colangelo et al., 2015; Gil et al., 2015; Rood et al.,
2018). Food manufacturer acceptance of EW as cleaning
medium, however, will likely depend on how well they
can overcome the stigma that EW can cause equipment
surface corrosion. Cleaning food equipment directly with
salt solution can damage and reduce the shelf life of the
equipment. This is one of the worries raised from SMEs
when EW was suggested as an alternative green cleaner
(Khalid, Ab Aziz, Thani et al., 2020). However, Ayebah
and Hung (2005) reported that EW is less corrosive to
stainless steel. Carbon steel, copper, aluminium and
stainless steel had a fair, good and outstanding corrosion
resistance in EW, respectively. Ayebah and Hung (2005)
also indicated that AcEW water did not have any adverse
effect on stainless steel. Stainless steel is the safest and
suitable material for food contact surface manufacturing.
Stainless steel shows an outstanding corrosion resistance
in EW (Khalid, Sulaiman, Ab Aziz et al., 2020). Rinsing
is a very important step in protecting the shelf life of the
equipment material to avoid corrosion and to remove the
chemical residue. After disinfection, washing the food
equipment with sterile water can completely avoid metal
corrosion (Ayebah and Hung, 2005). The effectiveness
of rinsing can be measured by monitoring the
conductivity (Stanga 2010). Conductivity is a measure of
the concentration of the dissolved mineral in water
(Etienne, 2006; Stanga, 2010). Moreover, EW reverts
back to the original state when in contact with organic
matter or if it is diluted by tap water, osmosis water or
distilled water (Hati et al., 2012), thus reducing cost for
wastewater treatment.
3.5 Storage of acidic electrolyzed water
Figure 2 shows properties (pH, ORP, free chlorine,
total chlorine and hydrogen peroxide) of AcEW during
the 7 days of storage. There were two main factors which
can reduce the chemical properties of EW which are
exposed to the atmosphere and long duration of storage
(Hsu and Kao, 2004; Khalid et al., 2018). In this work,
seven days of storage was set as storage time assuming
the food industries generate EW (using an EW generator)
once a week for weekly consumption. From the SMEs
perspective, daily usage of EW generator might be costly
as it requires electrical energy to operate. Moreover, the
weekly operation of the EW generator will be more
convenient for the workers. Moreover, the common
design of EW generator has a storage tank for EW.
During the sanitation process, the tank is used to
maintain a high flow rate of EW supply. Therefore, it is
important to determine the EW stability (AcEW and
AlEW) during storage. As shown in Figure 2 (a), the pH
of AcEW remained stable during the seven days of
storage. Maintaining the acidic pH is very important to
ensure that the AcEW can be used as acidic cycle
chemicals. Acidic chemicals such as acetic acid and
phosphoric acid are commonly used for dairy cleaning
(Watkinson, 2008). Acids are generally used to remove
mineral scales such as hard water and millstones scales.
While the ORP as shown in Figure 2 (b) maintains at a
plateau for the first 5 days of storage. After 5 days, the
AcEW shows a decreasing profile. Both pH and ORP are
important properties to maintain as these properties
contribute to AcEW antimicrobial properties. The high
ORP (Kim et al., 2000; Liao et al., 2007; Huang et al.,
2008), low pH (McPherson, 1993; Huang et al., 2008),
chlorine content (Park et al., 2004; Liu, Duan and Su,
2006; Huang et al., 2008) and hydrogen peroxide content
(Rico et al., 2007) are important chemical characteristics
that contribute to antimicrobial properties of AcEW.
Since aerobic and anaerobic bacteria can grow optimally
at an ORP range of +200 to 800 mV and -700 to +200
mV, respectively. Thus, our target is to maintain our
AcEW more than 800 mV. At higher ORP, the metabolic
fluxes and ATP production of bacteria are modified
(Huang et al., 2008). The pH ranging from 4 to 9 is
optimal growth for bacteria. Our target is to maintain our
AcEW to be lower than the pH of 4.
During the 4 days of storage, the free and total
chlorine content maintained at 10 mg/L (Figure 2 (c) and
Figure (d) respectively). After 4 days, the total and free
chlorine were found to be reduced gradually. However,
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the reduction rate was inconsistent for each repetition
(large error bar). Large error bar indicates the large
standard deviation. This might happen because the
exposure to the atmosphere during daily measurement
might reduce the total and free chlorine content. Every
day, the bottle was opened for approximately 5 mins for
physical properties measurements. When measurement
time took less than 5 mins, the bottles were closed
immediately. However, if the measurement time was
delayed, the time the AcEW bottles were opened can be
more than 5 mins. This mostly happens because the ORP
meter takes some time to reach its accurate values. Thus,
the exposure to the atmosphere might reduce the chlorine
content inside AcEW. On day 7, there was almost no
chlorine available in the AcEW. At lower pH of 2.3 to
2.7, the outer membrane of bacteria will break down,
allowing hypochlorous acid (HOCl) to enter the inner
membrane of the bacteria (Huang et al., 2008). HOCl is
one of the most active compounds in chlorine compound.
HOCl is highly oxidative and can deactivate the
foodborne pathogens. HOCl reacts with DNA, induces
the DNA-protein interactions, produces pyrimidine
oxidation products and adds chloride to DNA bases
(Birben et al., 2012). Thus, it is very important to
maintain the chlorine content in AcEW.
Figure 2 (e) shows the properties of hydrogen
peroxide during the 7 days of storage. The decrement
pattern for H2O2 properties is similar to free and total
chlorine (Figure 2 (c) and Figure 2 (d) respectively). The
H2O2 maintained at 10 mg/L until day 3 and after that,
the H2O2 level decreased drastically. On day 7, there
were 0, 4 and 1 mg/L H2O2 (1st, 2nd and 3rd repetition,
respectively) that were detected in AcEW. Thus, it is
very important to minimize the opening time of the
bottles during storage. These results have proven that
AcEW can be used as a good cleaner (acidic cycle
chemicals) and disinfectant chemical as well. Hydrogen
peroxide (H2O2) has a strong detaching ability and kills
bacteria without causing corrosion (Stanga, 2010). H2O2
also does not generate off-odours typical chlorine
derivatives such as chlorophenols and chloramines
(Stanga, 2010). None of the prior studies has reported the
effect of H2O2 content in AcEW. The small size of H2O2
enables it to clean the membrane effectively as it can
pass through small filtration membranes and enhances
the biofilm removal and disinfection process (Stanga,
2010). By considering the pH, ORP, chlorine content and
hydrogen peroxide content, the AcEW was at its best
performance for 3 days.
3.6 Storage of alkaline electrolyzed water
Figure 2. Effect of storage on the chemical and physical properties of the AcEW: a) pH, b) ORP, c) free chlorine, d) total chlo-
rine and e) hydrogen peroxide.
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Figure 3 shows the properties (pH, ORP) of AlEW
during the 7 days of storage. Studies on storage of AlEW
have not been well conducted as compared to AcEW (;
Hsu and Kao, 2004; Ciu et al., 2009; Hsu et al., 2015) as
most literature were focusing on the chlorine changes
after storage time. Storage might affect the cleaning or
removal performance of AlEW. The AlEW contains
NaOH which is one of the detergent components used
widely for cleaning food equipment surfaces (Walton,
2008; Khalid et al., 2016). The AlEW has the ability to
act as NaOH and functions well in cleaning food
processing equipment (Wang et al., 2016). The AlEW
has been used to replace the alkaline wash in works by
Dev et al. (2014) and Wang et al. (2016). AlEW has
shown to give the same effect as NaOH during the
alkaline wash. Alkaline detergent is good in removing
organic soil (fat, protein and carbohydrate). When the
fouling deposit is in contact with AlEW, the fouling
deposit swell. The removal is easier after the swelling
stage (Wang et al., 2016). The cohesive strength between
the fouling deposits itself will be lesser and the adhesive
strength between the surface and fouling deposit reduces
(Liu et al., 2006; Law et al., 2009; Ho et al., 2010), thus,
enabling the removal of fouling deposit. The alkaline
cleaning step is important to ensure the removal of
physical deposit. The remaining fouling deposit might
act as a barrier and reduce the disinfection agent
performance at the later stage of the disinfection process.
Most cleaning chemicals are alkaline in nature. The
cleaning removal action (saponification, chelation and
dispersion of fouling deposit) occurs effectively at an
alkaline pH level. Moreover, alkaline performs best
when soil can be hydrolyzed or saponified especially for
fat-based fouling deposit such as grease, oils and fats. In
this work, the efficiency of AlEW depends on the pH
and ORP. Figure 3 shows that the pH of AlEW was
stable during 7 days of storage.
Aerobic and anaerobic bacteria can grow optimally
at the ORP range of +200 to 800 mV and -700 to +200
mV, respectively. At lower ORP (<-700 mV), the
metabolic fluxes and ATP production of bacteria can be
modified, which eventually kills the bacteria (Kim et al.,
2000; Liao et al., 2007; Huang et al., 2008). Lower ORP
(<-700 mV) is non-ideal for microbes’ growth. However,
the ORP increased drastically between day 1 and 2. On
the first day, the ORP was -829 mV, -831 mV and -837
mV (1st, 2nd and 3rd repetition, respectively). The ORP
reduced to 54 mV, -8 mV and -25 mV (1st, 2nd and 3rd
repetition, respectively). After that, the ORP of AlEW
reached a plateau after day 3. On day 7, the ORP of
AlEW were 162 mV, 180 mV and 202 mV (1st, 2nd and
3rd repetition, respectively). Thus, the results have
shown that AlEW can be used as alkaline cycle
chemicals and disinfectants chemicals. The ORP
properties of AlEW are the only antimicrobial properties
which reduced drastically during storage. However, since
the pH was still high, AlEW can still be effectively used
as a disinfection chemical.
4. Conclusion
Green cleaners and disinfection deliver
environmental benefits and at the same time can create
operational cleaning efficiencies which highly benefit the
SMEs manufacturers. This paper aimed to identify the
potential of EW as green cleaner and disinfectant in
SMEs food industry. Based on the impromptu interview
with the workers, SME is facing difficulties to
implement good cleaning and sanitation process due to
the difficulty in selecting cleaning and disinfection
chemical, limited knowledge in cleaning and disinfection
process, budget constraints and limited storage area.
SME manufacturers are facing difficulties to select
suitable cleaning and disinfection detergent which suits
them in terms of operational cost and storage area.
Previous studies on EW show its potential as a green
cleaner as it can be generated on-site, takes up less
storage area, cheap and does not require wastewater
treatment. In this study, the effect of storage duration on
chemical properties of AcEW and AlEW was studied for
7 days. The chemical properties of EW will be reduced
as time increased. It is a common practice to use fresh
EW immediately after electrolysis to ensure the chemical
properties (pH, ORP, free chlorine, total chlorine and
hydrogen peroxide content) of EW are at its maximum.
However, the common design of EW generator has a
storage tank for EW. The tank is used to maintain a high
flow rate of EW supply during the sanitation process.
Figure 3. Effect of storage on the chemical and physical properties of a) pH and b) ORP of the AlEW.
54 Khalid et al. / Food Research 5 (Suppl. 1) (2021) 47 - 56
eISSN: 2550-2166 © 2020 The Authors. Published by Rynnye Lyan Resources
FULL PAPER
Hence, it is important to identify the stability of AlEW
and AcEW during storage. In this work, the AcEW can
be stored for 3 days while maintaining all its original
properties (pH, ORP, free chlorine, total chlorine and
hydrogen peroxide content). AlEW can be stored for 7
days as its pH showed no changes during the 7 days of
storage. In order to maintain the physical properties of
EW, food manufacturers must tightly close the EW
bottles and keep it in a dark bottle to avoid exposure to
the atmosphere. The results obtained from this work can
be used as a guideline for SMEs to apply and store the
EW reasonably. For future work, interviews with several
food SMEs companies on the acceptance of EW as
sanitation solution alternatives should be done.
Conflicts of interest
The authors have declared no conflict of interest.
Acknowledgement
The authors would like to acknowledge the financial
support provided by Universiti Putra Malaysia (9548500)
Putra IPS grant.
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