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M: Food Microbiology
& Safety
JFS M: Food Microbiology and Safety
Synergistic Effect of Electrolyzed Water
and Citric Acid Against Bacillus Cereus Cells
and Spores on Cereal Grains
YOUNG BAE PARK,JIN YONG GUO, S.M.E. RAHMAN,JUHEE AHN,AND DEOG-HWAN OH
ABSTRACT: The effects of acidic electrolyzed water (AcEW), alkaline electrolyzed water (AlEW), 100 ppm sodium
hypochlorite (NaClO), and 1% citric acid (CA) alone, and combinations of AcEW with 1% CA (AcEW +CA) and AlEW
with 1% CA (AlEW +CA) against Bacillus cereus vegetative cells and spores was evaluated as a function of temper-
ature (25, 30, 40, 50, or 60 ◦C) and dipping time (3 or 6 h). A 3-strain cocktail of Bacillus cereus cells or spores of
approximately 107CFU/g was inoculated in various cereal grains (brown rice, Job’s tear rice, glutinous rice, and bar-
ley rice). B.cereus vegetative cells and spores were more rapidly inactivated at 40 ◦Cthanat25◦C. Regardless of the
dipping time, all treatments reduced the numbers of B.cereus vegetative cells and spore by more than 1 log CFU/g,
except the deionized water (DIW), which showed approximately 0.7 log reduction. The reductions of B.cereus cells
increased with increasing dipping temperature (25 to 60 ◦C). B.cereus vegetative cells were much more sensitive
to the combined treatments than spores. The effectiveness of the combined electrolyzed water (EW) and 1% CA
was considerable in inhibiting B.cereus on cereal grains. The application of combined EW and CA for controlling
B.cereus cells and spores on cereal grains has not been previously reported. Therefore, the synergistic effect of EW
and CA may provide a valuable insight on reducing foodborne pathogens on fruits, vegetables, and cereal grains.
Keywords: Bacillus cereus, cereal grains, citric acid, electrolyzed water, synergistic effect
Introduction
Since food safety and quality has been a high priority over the
last decade, microbial control is in great endeavor for develop-
ing new preservatives and processing technologies. A number of ef-
forts have been implemented, including chemicals (antimicrobials,
food sanitizers, and organic acids), biocontrol (lactic acid bacteria),
modified atmospheres (vacuum packaging, modified-atmosphere
packaging, and controlled-atmosphere packaging), radiations (ul-
traviolet light, gamma rays, microwaves), high hydrostatic pressure
(HHP), and pulsed electric field (PEF), in response to increasing
public awareness and concern on food safety and quality (Francis
and others 1999; Allende and others 2008).
In recent years, the electrolyzed water (EW) has received much
attention as a minimal and nonthermal process with the increas-
ing demand for ready-to-use or ready-to-eat fruits and vegetables
(Park and others 2008; Allende and others 2008). The application of
EW for the microbial control provides many advantages over other
chemical preservatives, including less adverse chemical residue,
and it is cost-effective and environmentally friendly (Kroyer 1995;
Kim and others 2000b; Al-Haq and others 2005). EW is generated
in a special apparatus connected to a power supply by the addi-
tion of water with NaCl, which produces acidic electrolyzed wa-
ter (AcEW) and alkaline electrolyzed water (AlEW ) (Huang and
others 2008). AlEW produced by the cathode has a pH level of
MS 20080922 Submitted 11/18/2008, Accepted 2/23/2009. Authors Guo, Rah-
man, and Oh are with Div. of Food and Biotechnology and author Ahn is
with Div. of Biomaterials Engineering and Inst. of Bioscience and Biotech-
nology, Kangwon Natl. Univ., Chunchon, Gangwon, Republic of Korea.
Author Park is with Div. of Health Research & Planning, Gyeonggi-do
Research Inst. of Health & Environment, Pajang-dong 324-1, Gyeonggi-
do, 440-290, Republic of Korea. Direct inquiries to author Oh (E-mail:
deoghwa@kangwon.ac.kr).
approximately 11 and an oxidation-reduction potential (ORP) of
–795 mV, while AcEW from the anode has free Cl2and HOCl
(pH 2.4 to 2.6, ORP =1150 mV). EW has been introduced in agri-
culture, livestock management, medical sterilization, and food san-
itation (Venkitanarayanan and others 1999; Kim and others 2000a,
2000b). Many researchers have reported the antimicrobial effi-
cacy of EW against foodborne pathogens, including Escherichia
coli O157:H7, Salmonella enteritidis,L.monocytogenes,Campy-
lobacter jejuni,Enterobacter aerogenes,andStaphylococcus au-
reus, on alfalfa, lettuce, cabbage, seafood, and meat (Izumi 1999;
Venkitanarayanan and others 1999; Kim and others 2000b; Koseki
and others 2001; Fabrizio and Cutter 2004; Park and others 2004; Al-
Haq and others 2005; Abbasi and Lazarovits 2006; Huang and others
2006, 2008; Udompijitkul and others 2007).
Bacillus cereus is a Gram-positive, rod-shaped, β-hemolytic,
spore-forming bacterium, causing emetic and diarrheal food poi-
soning (Granum and Lund 1997). The emetic syndrome is caused
by heat-stable toxins, while the diarrheal syndrome is caused by
heat-labile enterotoxins (Altayar and Sutherland 2006; Fricker and
others 2007). B.cereus is ubiquitous in soil, causing contamination
problems in a variety of foods. Cereal grains are likelyto be contam-
inated with B.cereus intheprocessingunitsfromfarmtofork(Fang
and others 1997; Haque and Russell 2005). Ankolekar and others
(2009) found that foodborne illness in the United States was caused
due to B. cereus with rice as the vehicle would be most likely as-
sociated with the diarrheal-type syndrome. Thus, an outbreak of B.
cereus infection has been directly linked to the consumption of con-
taminated cereal grains. However, there is little information with
regard to a synergistic inhibitory effect of EW and other common
preservatives against B.cereus vegetative cells and spores on cereal
grains. Therefore, the objective of this study was to investigate the
inhibitory effect of EW, as compared to that of sodium hypochlorite
C
2009 Institute of Food Technologists RVol. 74, Nr. 4, 2009—JOURNAL OF FOOD SCIENCE M185
doi: 10.1111/j.1750-3841.2009.01139.x
Further reproduction without permission is prohibited
M: Food Microbiology
& Safety
Effect of electrolyzed water against
Bacillus cereus
...
(NaClO) and citric acid (CA), against B. cereus vegetative cells and
spores on various cereal grains. CA (low pH) and hypochlorite solu-
tion (free chlorine) are widely used in the food industry as preser-
vative, acidulant, and flavoring agent (Nielsen and Arneborg 2008;
Pao and Petracek 2008).
Materials and Methods
Bacterial strains and culture condition
Strains of B. cereus ATCC 12480, ATCC 13061, and ATCC 14579
were cultivated aerobically in trypticase soy broth supplemented
(TSB; Difco, Detroit, Mich., U.S.A.) at 30 ◦C for 24 h. After 2 suc-
cessive cultivations in TSB, the cultures were centrifuged twice at
1500 rpm for 10 min. The pellets were resuspended to 0.01 M ster-
ile phosphate buffer solution. The harvested cocktail suspensions
were diluted to proper concentration for inoculation into various
cereal rice grains.
Spore production
Nutrient agar (NA; Oxoid, Hampshire, U.K.) containing 5 mg/L
of manganese sulfate (MnSO4.H2O) was used as a sporulation
medium (Christiansson and others 1997). One milliliter of the ac-
tively growing culture of B.cereus vegetative cells was serially di-
luted in 0.1% sterile peptone water, surface plated (0.1 mL) on
NA, and incubated at 30 ◦C until more than 90% sporulation was
observed by microscopic examination. Spores were collected by
flooding the surface with sterile distilled water and scraping the
colonies with a sterile glass spreader.
Sample preparation and inoculation
The 4 types of cereal grains, including brown rice (BR), Job’s tear
rice (JR), glutinous rice (GR), and barley rice (BaR), were purchased
from a local market. Approximately 7 to 7.5 log CFU/g of B.cereus
spores and vegetative cells were inoculated in each cereal grains.
The inoculated samples were placed on a sterile perforated tray, air-
dried in a laminar flow hood at 25 ◦C for 30 min, and packaged in
sterile Ziploc Rbags (Bangkok, Thailand). The pouches were stored
at 4 ◦C prior to use within 1 wk.
Experimental design
Two experiments were carried out using a completely random-
ized block design. In experiment 1, BR was inoculated with B.cereus
vegetative cells or spores at approximately 2.3 ×107CFU/g. The in-
oculated samples were treated with 7 different treatments, includ-
ing deionized water (DIW), 100 ppm sodium hypochlorite (NaClO),
AcEW,AlEW,1%CA,1%CAinAcEW(AcEW+CA), and 1% CA in
AlEW (AlEW +CA), at two different temperatures (25 and 40◦C) for
different dipping times (3 and 6 h). In experiment 2, BR, JR, GR,
and BaR were inoculated with B.cereus vegetative cells or spores at
approximately 1.8 ×107CFU/g and treated with 7 different treat-
ments (DW, 100 ppm NaClO, AcEW, AlEW, 1% CA, AcEW +CA, and
AlEW +CA) at different temperatures (25, 30, 40, 50, and 60◦C) for
3 h dipping time.
Preparation of treatment solutions
EW was produced from 0.1% NaCl solution using a flow-type
electrolysis generator A2 (EN’S & ST’S, Seoul, Korea) set at 16 A,
consisting of AcEW and AlEW. When a stable amperage was reached
after 15 min, AcEW and AlEW were collected from the anode com-
partment and the cathode compartment. The sodium hypochlorite
(NaClO) solution was prepared with the addition of 0.1 g of NaClO
(DC Chemical Co., Seoul, Korea) in 1 L of sterile distilled water. The
crystalline CA (Yakuri Pure Chemicals Co., Kyoto, Japan) was dis-
solved in 1 L of sterile distilled water or EW to obtain a final con-
centration of 1% CA solution (w/v). Sterile deionized water (DIW)
wasusedascontrol.
Treatment of cereal grain samples
The inoculated cereal grain samples (10 g each) were treated with
50 mL of the chemical solution alone (DIW, NaClO, AcEW, AlEW, or
CA) or with the mixture of CA and EW. The treatments were dipped
in a water bath (Vision Scientific Co. Ltd., Buchon-si, Kyunggi-do,
Korea) at 25, 30, 40, 50, and 60 ◦C for 3 and 6 h. After dipping, the
treatment solutions were removed by gentle pressing with cheese-
cloth, and the treatments were used for microbial analysis.
Microbial analysis
Duplicate samples treated (10 g each) were aseptically mixed
with 90 mL of 0.1% sterile peptone water. The mixtures were stom-
ached (Interscience, St. Nom-La-Breteche, France) for 1.5 min. Di-
lutions of mixed slurries were serially (1:10) diluted with 0.1% sterile
peptone water. The sample dilutions (0.1 mL) were plated on both
brain heart infusion agar (BHI, Difco) and mannitol egg polymyxin
agar (MYP, Difco). The agar plates were incubated to enumerate the
populations of B.cereus at 30 ◦Cfor24h.
Statistical analysis
All analyses were conducted in duplicates with 3 replicates of
each experiment. Data were analyzed using the statistical analysis
system (SAS; SAS Inst. Inc., Cary, N.C., U.S.A.). An analysis of vari-
ance (ANOVA) was used to evaluate the treatment, dipping time,
cell type, and temperature as fixed effects. Duncan multiple range
tests was used to determine the significant difference at P<0.05.
Results and Discussion
The inhibitory efficacy of EW against B.cereus vegetative cells
and spores on BR was evaluated at various temperatures and
different dipping times. The inoculated BR samples treated with
DIW, 100 ppm NaClO, AcEW, AlEW, 1% CA, AcEW +CA, and AlEW
+CA were dipped at 25 and 40 ◦C for 3 and 6 h (Figure 1 and
2). The DIW treatments reduced the numbers of B.cereus vegeta-
tive cells and spores by 0.65 to 1.76 log CFU/g, while other treat-
ments reduced those of B.cereus vegetative cells and spores by 0.76
to 3.87 log CFU/g at 25 ◦Cfor3h(Table1and2).Thecombi-
nation of EW with 1% CA (AcEW +CA and AlEW +CA) most ef-
fectively reduced the populations of B.cereus vegetative cells and
spores, as compared to the DIW treatment, followed by CA treat-
ment. CA, AcEW +CA, and AlEW +CA treatments reduced the
numbers of B.cereus vegetative cells by 2.01, 2.45, and 2.37 log
CFU/g, respectively, at 25 ◦C for 3 h (Figure 1a) and reduced the
numbers of B.cereus spores by 1.35, 1.79, and 1.74 log CFU/g, re-
spectively (Figure 1b). No significant differences in log reduction
were observed between the dipping times of 3 and 6 h. Thus, the
shorter dipping time (3 h) was used for the following successful
experiment because the extended dipping time is not practical in
food applications. For all treatments, the numbers of B.cereus veg-
etativecellsandsporesat40◦C were more effectively reduced
than those at 25 ◦C. All treatments at 40 ◦C reduced the num-
bers of B.cereus vegetativecellsandsporesbymorethan2log
CFU/g (Figure 2). This is in agreement with the result from Venki-
tanarayanan and others (1999), who reported that there was EW
showed greater antimicrobial activity at 45 ◦Cthanat23◦C. Sim-
ilar to the treatments at 25 ◦C, the combined treatments (AcEW +
CA and AlEW +CA) most significantly reduced the numbers of B.
cereus vegetative cells and spores, followed by the CA treatment
M186 JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 4, 2009
M: Food Microbiology
& Safety
Effect of electrolyzed water against
Bacillus cereus
...
(Figure 2). Vegetative cells were more susceptible to the treatments
than spores. Kim and others (2000b) reported that JAW EO water
(pH 2.5, ORP 1123 mV, Cl 10 mg/L) generally reduced B. cereus pop-
ulation by 3 log10 CFU/mL after a 30-s treatment. Increasing the
treatment time to 120 s enhanced the reduction of B. cereus spores
by EO water to 1.4 log10 CFU/mL. They also cited that ROX EO wa-
ter (pH 2.6, ORP 1160 mV, Cl 56 mg/L) resulted in complete in-
activation of the B. cereus vegetative cells after a 30-s treatment.
Increasing treatment time to 120 s enhanced inactivation of spores
by 3.5 to 6 log10 CFU/mL. Spore structure and chemistry may play
an important role in the resistance to treatments. Certain bacteria
undergo distinct physical and metabolic adaptations in response
to unfavorable nutritional and environmental conditions, a phe-
nomenon known as the sporulation (Smelt and others 2002). The
spore is in cryptobiosis during the dormant period and remains its
potential food spoilage (Roszak and Colwell 1987; Leuschner and
others 1999; Young and Setlow 2003; Setlow 2005). The resistance
of bacterial spores under external stresses is primarily due to their
ultra-structure, composing of core, cortex, and coat (Rode 1968;
Riesenman and Nicholson 2000; Setlow and Johnson 2001; Young
and Setlow 2003; Driks 2004; Lee and others 2008). The numbers
A
0
1
2
3
4
5
6
7
8
DIW NaClO AcEW AlEW CA AcEW+CA AlEW+CA
Surviving population of vegetative cells
(log CFU/g) .
3 h dipping time
6 h dipping time
B
0
1
2
3
4
5
6
7
8
DIW NaClO AcEW AlEW CA AcEW+CA AlEW+CA
Surviving population of spores .
(log CFU/g) .
3 h dipping time
6 h dipping time
Figure 1 --- Effects of EW, NaClO, and CA, either alone or in
combination, on the inactivation of
B
.
cereus
vegetative
cells (A) and spores (B)onBR treated at 25 ◦C for 3 and
6 h dipping periods. The initial populations were approx-
imately 7.45 log CFU/g for vegetative cells (A) and 7.26
log CFU/g for spores (B).
of B.cereus vegetative cells were reduced by 5 and 4.94 log CFU/g,
respectively, for AcEW +CA and AlEW +CA treatments at 40 ◦Cfor
3 h, whereas those of B.cereus spores were reduced by 3.26 and 3.18
log CFU/g. Since no significant difference in the reduction between
dipping times, a dipping time of 3 h was used for the remainder of
the study.
The effect of antimicrobial treatments at various temperatures
was investigated in BR, JR, GR, and BaR inoculated with B.cereus
vegetative cells and spores (Table 1 and 2). In Table 1, AcEW +CA
and AlEW +CA treatments most effectively reduced the number
of B.cereus cells and spores on BR at all dipping temperatures. No
Bacillus cereus vegetative cells (<100 CFU/g) were detected in BR
by AcEW +CA and AlEW +CA treatments at 60 ◦Cfor3h.Thelog
reductions of B. cereus vegetative cells for all treatments were signif-
icantly increased with increasing dipping temperature (P<0.05).
Higher temperatures and water activity (aw) values significantly re-
duced the numbers of B. cereus spores. For Paprika powder with an
awvalue of 0.88 heated to approximately 95 to 100 ◦C, the load of
B. cereus spores was reduced by 4.5 log10 CFU/g within 6 min
(Staack and others 2008). CA showed better reduction in the
numbers of B. cereus vegetative cells and spores than AcEW,
A
0
1
2
3
4
5
6
7
8
DIW NaClO AcEW AlEW CA AcEW+CA AlEW+CA
Surviving population of vegetative cells
(log CFU/g) .
3 h dipping time
6 h dipping time
B
0
1
2
3
4
5
6
7
8
DIW NaClO AcEW AlEW CA AcEW+CA AlEW+CA
Surviving population of spores
(log CFU/g)
3 h dipping time
6 h dipping time
Figure 2 --- Effects of EW, NaClO, and CA, either alone or in
combination, on the inactivation of
B
.
cereus
vegetative
cells (A) and spores (B)onBR treated at 40 ◦C for 3 and
6 h dipping periods. The initial populations were approx-
imately 7.45 log CFU/g for vegetative cells (A) and 7.26
log CFU/g for spores (B).
Vol. 74, Nr. 4, 2009—JOURNAL OF FOOD SCIENCE M187
M: Food Microbiology
& Safety
Effect of electrolyzed water against
Bacillus cereus
...
Table 1 ---Reductionain the population of
B
.
cereus
vegetative cells and spores on BR and JR treated with EW, NaClO, and CA, either alone or in combination
at different dipping temperatures for 3 h.
B
.
cereus
vegetative cellb
B
.
cereus
sporeb
25 ◦C30
◦C40
◦C50
◦C60
◦C25
◦C30
◦C40
◦C50
◦C60
◦C
Treatment BR JR BR JR BR JR BR JR BR JR BR JR BR JR BR JR BR JR BR JR
DIW 0.72e1.20c1.91cNTd2.59d2.53d2.63d2.71d5.10a5.00c0.65e0.87d1.76dNTd1.77d1.84d1.38d1.2c1.14e1.68bc
NaClO 1.07d2.29b2.37bNTd2.71d2.81d2.69d3.87c5.40a5.28bc 1.26bc 1.86b2.09cNTd2.13c2.23c1.65c1.77b1.4d1.81b
AcEW 1.22c2.13b2.46bNTd3.27c3.58c3.39c3.77c5.37a5.78ab 1.19c1.77b1.83dNTd1.85d2.60b1.72c1.70b1.60c1.68bc
AlEW 1.08cd 1.29c2.10cNTd2.67d2.79d2.84d2.59d5.16a5.13c0.98d1.35c1.92cd NTd1.95cd 1.99d1.61c1.34c1.31de 1.59c
CA 2.01b2.22b3.49aNTd4.43b3.47c4.56b3.95c5.45a6.16a1.35b1.83b2.51bNTd2.47b2.63b2.42b1.76b1.85b1.68bc
AcEW +CA 2.45a2.78a3.67aNTd5.00a4.59a5.44a5.35aNDcNDc1.79a3.15a3.17aNTd3.26a3.62a3.05a2.80a3.01a2.38a
AlEW +CA 2.37a2.64a3.63aNTd4.94a4.23b5.37a4.87bNDcNDc1.74a3.08a3.22aNTd3.18a3.47a2.96a2.68a3.04a2.27a
aMeans with different superscript letters within a column are significantly different at P<0.05.
bThe initial populations were approximately 7.45 log CFU/g for vegetative cells and 7.26 log CFU/g for spores.
cND denotes that the viable cells were not detected below the detection limit (100 CFU/g).
dNT denotes that JR was not tested at 30 ◦C.
AlEW, and NaClO alone (Table 1). In general, antimicrobial
activity is more effective under acidic condition (Vitro and others
2005; Moussa-Boudjemaa and others 2006; Nielsen and Arneborg
2008). The type of acid used to produce ClO2also affects its
lethal activity against B. cereus spores. Kim and others (2008)
found the reduction of spores after treatment with citric acid-based
ClO2 solution (pH 3) for 5 min was 3.4 logCFU/mL. CA may in-
hibit microbial growth by altering the permeability of cytoplasmic
membrane and chelating divalent metal ions (Brul and Coote 1999;
Lambert and Stratford 1999). The low pH may change the func-
tions of the cytoplasmic membrane, which controls the permeabil-
ity between the internal cell and the external cell environment, and
eventually inhibits microbial growth on food systems. When com-
pared to the AlEW treatment, B.cereus cells were more effectively
inhibited by the AcEW treatment, which might result from high
ORP value, low pH, and hypochlorous contained in AcEW. The re-
sult confirms previous reports suggesting that a pH level (approxi-
mately 2.5), ORP value (1160 mV), free chlorine (approximately 70
ppm), hypochlorous acid (HOCl), and radicals (O−,Cl
−,andOH
−)
are mostly responsible for microbial inactivation in AcEW (Kim and
others 2000a; Park and others 2002a; Liao and others 2007). Nu-
merous studies have demonstrated that AcEW had better bacteri-
cidal activity against foodborne pathogens than AlEW (Koseki and
others 2001; Park and others 2002b, 2008; Lin and others 2005).
AcEW may increase the susceptibility of microorganisms due to
the oxidation of unsaturated fatty acids in cell membranes and the
change in membrane permeability, resulting in an increase elec-
trolytic leakage (Wang and others 2004). A similar reduction pat-
tern was observed for all treatments on JR samples (Table 1). For all
treatments, the numbers of B.cereus vegetative cells on JR and BR
were reduced by more than 5 log CFU/g at 60 ◦C . As compared to
the individual treatments (NaClO, AcEW, AlEW, and CA), the com-
bined treatments (AcEW +CA and AlEW +CA) were more effec-
tively inhibited B.cereus vegetative cells and spores at all dipping
temperatures. The combined treatments reduced the populations
of B.cereus vegetative cells to below the detection limit, indicating
a synergistic antimicrobial effect of EW and CA. The observation is
in agreement with previous report that EW combined with 1% CA
showed much greater antimicrobial effect against L.monocytogenes
on lettuce than individual treatments (Park and others 2004). The
reductions of vegetative cells for all treatments were increased with
increasing temperature, while those of spores were not significantly
increased over 50 ◦C(P>0.05). The poor color and texture were
Table 2 --- Reductionain the population of
B
.
cereus
vege-
tative cells and spores on BaR and GR treated with EW,
NaClO, and CA, either alone or in combination at different
dipping temperatures for 3 h.
B
.
cereus
vegetative cellb
B
.
cereus
sporeb
25 ◦C40
◦C25
◦C40
◦C
Treatment BaR GR BaR GR BaR GR BaR GR
DIW 1.29d1.76d2.10c2.33e1.18d0.74c1.76c1.16d
NaClO 2.05bc 2.55c2.40c2.88d1.68bc 1.36b1.97c2.17b
AcEW 1.98bc 2.85bc 2.76c3.90c1.96b1.31b2.88b2.49b
AlEW 1.87c1.85d2.31c2.61de 1.29c0.76c2.04c1.72c
CA 2.06bc 3.14b3.40b4.37b1.75bc 1.49b2.94b2.40b
AcEW 2.55a3.87a4.30a5.05a2.84a2.41a3.62a3.42a
+CA
AlEW 2.42ab 3.57a4.21a4.89a2.64a2.10a3.57a3.33a
+CA
aMeans with different superscript letters within a column are significantly
different at P<0.05.
bThe initial populations were approximately 7.16 log CFU/g for vegetative cells
and 7.32 log CFU/g for spores.
M188 JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 4, 2009
M: Food Microbiology
& Safety
Effect of electrolyzed water against
Bacillus cereus
...
observed on BR and JR treated greater than 50 ◦C (data not shown).
According to the results, the dipping temperatures of 25 and 40 ◦C
were selected for all treatments on GR and BaR.
In Table 2, B.cereus vegetative cells and spores for all treatments
on GR and BaR were reduced in the same manner as those on BR
and JR. The combined treatments (AcEW +CA and AlEW +CA) syn-
ergistically reduced the numbers of B.cereus vegetative cells and
spores. The numbers of B.cereus vegetative cells on BaR were re-
duced by 4.30 and 4.21 log CFU/g, respectively, for AcEW +CA and
AlEW +CA treatments at the dipping temperature of 40 ◦C, while
those of B.cereus spores were reduced by 3.62 and 3.57 log CFU/g
(Table 2). The least reductions were observed at the DIW treatments
as compared to other treatments. The combined treatments were
most effective in inhibiting B.cereus vegetative cells and spores at
the dipping temperature of 40 ◦C, followed by CA treatment. More
than 5 log reduction of B.cereus vegetative cells was achieved at the
dipping temperature of 40 ◦C in AcEW +CA treatment (Table 2).
The AcEW alone showed better antimicrobial activity against
B.cereus vegetative cells and spores than the AlEW alone, while
no significant difference in inhibiting B.cereus vegetative cells and
spores was observed between the combined treatments, AcEW +
CA and AlEW +CA.
Conclusions
The combined treatments showed significant potential for in-
hibiting B.cereus cells and spores in cereal grains. The applica-
tion of EW in combination with other preservatives may provide a
significant improvement in terms of food quality and microbiolog-
ical safety. Moreover, emerging trends in the EW processing are to
explore synergistic ways of inactivating vegetative cells and spores,
which may improve the effectiveness of EW by providing additional
barriers to microbial growth. However, the use of combined EW
and other preservatives could result in adverse perception on food
quality. The results of various studies and the data presented in this
study support the use of EW in combination with CA for the sanita-
tion of cereal grains, fruits, and vegetables without compromising
the safety of foods. Hence, further studies are needed to develop an
effective application of combined EW with other preservatives with
regard to food safety as well as food quality.
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