ArticlePDF Available

Synergistic Effect of Electrolyzed Water and Citric Acid Against Bacillus Cereus Cells and Spores on Cereal Grains

Authors:

Abstract and Figures

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 temperature (25, 30, 40, 50, or 60 degrees C) and dipping time (3 or 6 h). A 3-strain cocktail of Bacillus cereus cells or spores of approximately 10(7) CFU/g was inoculated in various cereal grains (brown rice, Job's tear rice, glutinous rice, and barley rice). B. cereus vegetative cells and spores were more rapidly inactivated at 40 degrees C than at 25 degrees 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 degrees 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.
Content may be subject to copyright.
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 Cthanat25C. 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, 2009JOURNAL 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 40C) 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 60C) 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-
etativecellsandsporesat40C 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 Cthanat23C. 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 SCIENCEVol. 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, 2009JOURNAL 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 SCIENCEVol. 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.
References
Abbasi PA, Lazarovits G. 2006. Effect of acidic electrolyzed water on the viability of
bacterial and fungal plant pathogens and on bacterial spot disease of tomato. Can
J Microbiol 52:915–23.
Al-Haq MI, Sugiyama J, Isobe S. 2005. Applicationsof electrolyzed water in agriculture
and food industries. Food Sci Technol Res 11:135–50.
Allende A, Tomas-Barberan FA, Gil MI. 2008. Minimal processing for healthy tradi-
tional foods. Trends Food Sci Technol 17:513–9.
Altayar M, Sutherland AD. 2006. Bacillus cereus is common in the environment but
emetic toxin producing isolates are rare. J App Microbiol 100:7–14.
Ankolekar C, Rahmati T, Labbe RG. 2009. Detection of toxigenic Bacillus cereus and
Bacillus thuringiensis spores in U.S. rice. Int J Food Microbiol 128:460–6.
Brul S, Coote P. 1999. Preservative agents in foods: mode of action and microbial re-
sistance mechanisms. Int J Food Microbiol 50:1–17.
Christiansson A, Ekelund K, Ogura H. 1997. Membrane filtration method for enumer-
ation and isolation of spores of Bacillus cereus from milk. Int Dairy J 7:743–8.
Driks A. 2004. The Bacillus spore coat. Am Phytopathol Soc 94:1249–51.
Fabrizio KA, Cutter CN. 2004. Comparison of electrolyzed oxidizing water with other
antimicrobial interventions to reduce pathogens on fresh pork. Meat Sci 68:463–8.
Fang SW, Chu SY, Shih DYC. 1997. Occurrence of Bacillus cereus in instant cereal prod-
ucts and their hygienic properties. J Food Drug Anal 5:139–44.
Francis GA, Thomas C, O’Breirne D. 1999. The microbiological safety of minimally
processed vegetables. Int J Food Sci Technol 34:1–22.
Fricker M, Messelhauber U, Busch U, Scherer S, Ehling-Schulz M. 2007. Diagnostic
real-time PCR assays for the detection of emetic Bacillus cereus strains in foods and
recent food-borne outbreaks. Appl Environ Microbiol 73:1892–8.
Granum PE, Lund T. 1997. Bacillus cereus and its food poisoning toxins. FEMS Micro-
biol Lett 157:223–8.
Haque A, Russell NJ. 2005. Phenotypic and genotypic characterisation of Bacillus
cereus isolates from Bangladeshi rice. Int J Food Microbiol 98:23–34.
Huang Y-R, Hsieh H-S, Lin S-Y, Lin S-J, Hung Y-C, Hwang D-F. 2006. Application
of electrolyzed oxidizing water on the reduction of bacterial contamination for
seafood. Food Con 17:987–93.
Huang Y-R, Hung Y-C, Hsu S-Y, Huang T-W, Hwang D-F. 2008. Application of elec-
trolyzed water in the food industry. FoodCon 19:329–45.
Izumi H. 1999. Electrolyzed water as a disinfectant for fresh-cut vegetables. J Food Sci
64:536–9.
Kim C, Hung YC, Brackett RE. 2000a. Roles of oxidation-reduction potential in elec-
trolyzed oxidizing and chemically modified water for the inactivation of food-
related pathogens. J Food Prot 63:19–24.
Kim C, Hung Y-C, Brackett RE. 2000b. Efficacy of electrolyzed oxidizing (EO) water
and chemically modified water on different types of foodborne pathogens. Int J
Food Microbiol 61:199–207.
Kim H, Kang Y, Beuchat LR, Ryu JH. 2008. Production and stability of chlorine diox-
ide in organic acid solutions as affected by pH, type of acid, and concentration of
sodium chlorite, and its effectiveness in inactivating Bacillus cereus spores. Food
Microbiol 25:964–9.
Koseki S, Fujiwara K, Itoh K. 2001. Decontamination of lettuce using acidic elec-
trolyzed water. J Food Sci 64:652–8.
Kroyer GT. 1995. Impact of food processing on the environment: an overview. Leben-
son Wiss Technol 28:547–52.
Lambert RJ, Stratford M. 1999. Weak-acid preservatives: modelling microbial inhibi-
tion and response. J App Microbiol 86:157–64.
Lee KS, Bumbaca D, Kosman J, Setlow P, Jedrzejas MJ. 2008. Structure of a protein–
DNA complex essential for DNA protection in spores of Bacillus species. Proc Nat
Acad Sci 105:2806–11.
Leuschner RGK, Weaver AC, Lillford PJ. 1999. Rapid particle size distribution analysis
of Bacillus spore suspensions. Coll Surf B 13:47–57.
Liao LB, Chen WM, Xiao XM. 2007. The generation and inactivation mechanism of
oxidation–reduction potential of electrolyzed oxidizing water. J Food Eng 78:1326–
32.
Lin C-S, Wu C, Yeh J-Y, Saalia FK. 2005. The evaluation of electrolysed water as an
agent for reducing micro-organisms on vegetables. Int J Food Sci Technol 40:495–
500.
Moussa-Boudjemaa B, Gonzalez J, Lopez M. 2006. Heat resistance of Bacillus cereus
spores in carrot extract acidified with different acidulants. Food Con 17:819–
24.
Nielsen MK, Arneborg N. 2008. The effect of citric acid and pH on growth
and metabolism of anaerobic Saccharomyces cerevisiae. Food Microbiol 24:101–
5.
Pao S, Petracek PD. 2008. Shelf life extension of peeled oranges by citric acid treat-
ment. Food Microbiol 14:485–91.
Park H, Hung Y-C, Brackett RE. 2002a. Antimicrobial effect of electrolyzed water for
inactivating Campylobacter jejuni during poultry washing. Int J Food Microbiol
72:77–83.
Park H, Hung Y-C, Kim C. 2002b. Effectiveness of electrolyzed water as a sanitizer for
treating different surfaces. J Food Prot 65:1276–80.
Park BK, Oh MH, Oh D-H. 2004. Effect of electrolyzed water and organic acids on
the growth inhibition of Listeria monocytogenes on lettuce. Kor J Food Preserv 11:
530–7.
Park E-J, Alexanderm E, Taylor GA, Costa R, Kang D-H. 2008. Fate of foodborne
pathogens on green onions and tomatoes by electrolysed water. Lett Appl Micro-
biol 46:519–25.
Riesenman PJ, Nicholson WL. 2000. Role of the spore coat layers in Bacillus subtilis
spore resistance to hydrogen peroxide, artificial UV-C, UV-B, and solar UV radia-
tion. Appl Environ Microbiol 66:620–6.
Rode LJ. 1968. Correlation between spore structure and spore properties in Bacillus
megaterium. J Bacteriol 95:1978–86.
Roszak DB, Colwell RR. 1987. Metabolic activity of bacterial cells enumerated bydirect
viable count. Appl Environ Microbiol 53:2889–983.
Setlow P. 2005. The bacterial spore: nature’s survival package. Culture 26:1–4.
Setlow P, Johnson EA. 2001. Spores and their significance. In: Doyle MP, Buchat LR,
Montville TJ, editors. Food microbiology: fundamentals and frontiers. Washington,
D.C.: American Society for Microbiology, p 33–69.
Smelt JPPM, Hellemons JC, Wouters PC, van Gerwen SJC. 2002. Physiological and
mathematical aspects in setting criteria for decontamination of foods by physical
means. Int J Food Microbiol 78:57–77.
Staack N, Ahrn´
e L, Borch E, Knorr D. 2008. Effects of temperature, pH, and controlled
water activity on inactivation of spores of Bacillus cereus in paprika powder bynear-
IR radiation. J Food Eng 89:319–24.
Udompijitkul P, Daeschel MA, Zhao Y. 2007. Antimicrobial effect of electrolyzed oxi-
dizing water against Escherichia coli O157:H7 and Listeria monocytogenes on fresh
strawberries (Fragaria x ananassa). J Food Sci 72:M397–406.
Venkitanarayanan KS, Ezeike GO, Hung Y-C, Doyle MP. 1999. Efficacy of electrolyzed
oxidizing water for inactivating Escherichia coli O157:H7, Salmonella enteritidis,
and Listeria monocytogenes. Appl Environ Microbiol 65:4276–9.
Vitro R, Sanz D, Alvarez I, Raso CJ. 2005. Inactivation kinetics of Yersinia enterocolitica
by citric acid and lactic acid at different temperatures.Int J Food Microbiol 103:251–
7.
Wang H, Feng H, Luo Y. 2004. Microbial reduction and storage quality of fresh-cut
cilantro washed with acidic electrolyzed water and aqueous ozone. Food Res Int
37:949–56.
Young SB, Setlow P. 2003. Mechanisms of killing of Bacillus subtilis spores by
hypochlorite and chlorine dioxide. J Appl Microbiol 95:54–67.
Vol. 74, Nr. 4, 2009JOURNAL OF FOOD SCIENCE M189
... Some examples of the very recently fresh vegetable sanitisation techniques which have been used or studied for fresh produce are: different types of electrolysed water (EW) (Afari, Hung, King, & Hu, 2016;Yang, Feirtag, & Diez-Gonzalez, 2013;Zhang, Cao, Hung, & Li, 2016); 0.8%e5% H 2 O 2 (Lopez-Galvez, Ragaert, Palermo, Eriksson, & Devlieghere, 2013;Lu, Joerger, & Wu, 2014;Van Haute, Tryland, Veys, & Sampers, 2015); 1%e2% organic acid (Tirawat, Phongpaichit, Benjakul, & Sumpavapol, 2016;Bermúdez-Aguirre & Barbosa-C anovas, 2013); and also some combinations of these methods, such as combination of 100 mg/L EW with 1% citric acid (CA) (Park, Guo, Rahman, Ahn, & Oh, 2009), combination of 1% organic acids with 2% H 2 O 2 (Lopez- Galvez et al., 2013). However, these techniques use too high concentration of sanitisers, which can't satisfy the requirement for processing fresh organic produce. ...
... In our study the FAC was only 4 mg/L. Park et al. (2009) evaluated the effect of 1% CA and combined effect of EW (100 mg/L) with 1% CA on grain, and found an approximately 2 log CFU/g reduction for Bacillus Cereus cells and spores. However, in another report, CA 3% was used to inactivate E. coli O157:H7 on fresh-cut lettuce, no inactivation was achieved after 15 min (Bermúdez-Aguirre & Barbosa-C anovas, 2013). ...
Article
Potential organic compatible sanitisers including electrolysed water (EW, 4 mg/L free available chlorine (FAC)), citric acid (0.6%), H 2 O 2 (1%), and their combinations were applied on organic and conventional fresh-cut lettuce (Lactuca sativa Var crispa L.) to evaluate their effects on microbiological safety, physi-cochemical parameters and sensory analysis (including raw sample and boiled sample). The combination of 1% H 2 O 2 with 0.6% citric acid led to the highest reductions of microbial loads (2.26 log CFU/g for aerobic mesophilic count (AMC) and 1.28 log CFU/g for yeasts and moulds); however, it also caused the highest electrolyte leakage rate (3.11% vs. 0.91% for control). The combination of EW with 1% H 2 O 2 achieved 1.69 and 0.96 log CFU/g reductions for AMC and yeasts and moulds, respectively with elec-trolyte leakage rate of 1.41%. In terms of the content of polyphenolic compounds, firmness, colour and raw material sensory analysis, there were no significant differences among different treatments, and between organic and conventional counterparts. The results suggest that 1% H 2 O 2 combined with 4 mg/L EW is a promising approach for treating organic fresh-cut lettuce.
... Furthermore, the disinfection efficacy of SAEW on spores largely depended on ACC and treatment time, which was consistent with a previous study (Yang et al., 2021). Moreover, EW in combination with other technologies, including mild heat (Hussain et al., 2019), HPP (Wang et al., 2017), citric acid (Park et al., 2009), and ultrasonication (Lv et al., 2020), has been utilized to improve the inactivation efficacy on bacterial spores. However, the available literature on the inactivation mechanism of spores by SAEW remains limited. ...
Article
This study aimed to investigate the inactivation mechanism of Bacillus cereus spores by slightly acidic electrolyzed water (SAEW). Spore inactivation efficacy of SAEW at different available chlorine concentrations (ACC, 20, 60 and 100 mg/L), as well as spore structures change, coat damage, mutagenesis, and inner membrane (IM) properties were examined. The viability of treated spores with lysozyme addition and spore germination induced by germinant was also examined. The results showed that SAEW could reach maximal 5.81 CFU/mL log reduction with ACC of 100 mg/L for 20 min treatment. Scanning and transmission electron photomicrographs indicated that SAEW treatment rendered spore surface ruptured, IM damage and core contents loss. No mutants were generated in survivors of SAEW treated-spores. SAEW significantly weakened spore viability in high salt medium, losing its ability to retain pyridine-2,6-dicarboxylic acid (DPA) at 85 °C. SAEW-treated spores germinated with l-alanine or inosine induction were mostly stained with propidium iodide (PI) but could not recover via lysozyme addition. Furthermore, SAEW treatment inhibited spore germination in the induction of germinant (mixture of l-alanine and inosine or dodecylamine). These findings indicated that SAEW inactivated spore primarily by damaging the spore IM.
... As reported by Fenner et al. [18], Proteus mirabilis and S. aureus were more sensitive than Mycobacterium avium subsp. avium, Enterococcus faecium, and Pseudomona saeruginosa toward EW. Park et al. [19] also found that Bacillus cereus vegetative cells were much more sensitive to the combined treatments of EW and citric acid than spores. Therefore, more attention should be paid to the difference in sensitivity of microorganisms to EW when EW is used in food preservation. ...
Article
Full-text available
Pseudomonas is considered as the specific spoilage bacteria in meat and meat products. The purpose of this study was to evaluate the inactivation efficiency and mechanisms of slightly acidic electrolyzed water (SAEW) against Pseudomonas deceptionensis CM2, a strain isolated from spoiling chicken breast. SAEW caused time-dependent inactivation of P. deceptionensis CM2 cells. After exposure to SAEW (pH 5.9, oxidation–reduction potential of 945 mV, and 64 mg/L of available chlorine concentration) for 60 s, the bacterial populations were reduced by 5.14 log reduction from the initial load of 10.2 log10 CFU/mL. Morphological changes in P. deceptionensis CM2 cells were clearly observed through field emission-scanning electron microscopy as a consequence of SAEW treatment. SAEW treatment also resulted in significant increases in the extracellular proteins and nucleic acids, and the fluorescence intensities of propidium iodide and n-phenyl-1-napthylamine in P. deceptionensis CM2 cells, suggesting the disruption of cytoplasmic and outer membrane integrity. These findings show that SAEW is a promising antimicrobial agent.
... The agents responsible for bactericidal effect in NEW can be attributed to its ORP, pH and the concentration of chlorine related substances, including Cl 2 , HClO, and ClO À (Hati et al., 2012;Park, Guo, Rahman, Ahn, & Oh, 2009;Rahman, Khan, & Oh, 2016). LCNEW was an effective method to control microorganism in pure cultures, and it had a broad spectrum antibacterial effect. ...
Article
The sanitising effect of low concentration neutralised electrolysed water (LCNEW, pH: 7.0, free available chlorine (FAC): 4 mg/L) combined with ultrasound (37 kHz, 80 W) on food contact surface was evaluated. Stainless steel coupon was chosen as attachment surface for Escherichia coli ATCC 25922, Pichia pastoris GS115 and Aureobasidium pullulans 2012, representing bacteria, yeast and mold, respectively. The results showed that although LCNEW itself could effectively reduce survival population of E. coli ATCC 25922, P. pastoris GS115 and low concentration A. pullulans 2012 in planktonic status, LCNEW combined with ultrasound showed more sanitising efficacy for air-dried cells on coupons, with swift drops: 2.2 and 3.1 log CFU/coupon reductions within 0.2 min for E. coli ATCC 25922 and P. pastoris GS115, respectively and 1.0 log CFU/coupon reductions within 0.1 min for A. pullulans 2012. Air-dried cells after treatment were studied by atomic force microscopy (AFM)/optical microscopy (OM) and protein leakage analyses further. All three strains showed visible cell damage after LCNEW and LCNEW combined with ultrasound treatment and 1.41 and 1.73 mg/mL of protein leakage were observed for E. coli ATCC 25922 and P. pastoris GS115, respectively after 3 min combination treatment, while 6.22 mg/mL of protein leakage for A. pullulans 2012 after 2 min combination treatment. For biofilms, LCNEW combined with ultrasound also significantly reduced the survival cells both on coupons and in suspension for all three strains. The results suggest that LCNEW combined with ultrasound is a promising approach to sanitise food equipment.
... Many studies have shown that EW can efficiently inactivate pathogens (Luo & Oh, 2016;Park, Guo, Rahman, Ahn, & Oh, 2009;Yang, Feirtag, & Diez-Gonzalez, 2013;. However, there are only a few reports on its mechanism of action. ...
Article
Electrolysed water (EW) is an activated liquid with a high oxidation-reduction potential. EW causes oxidative damage to pathogenic microorganisms and as a result, may have utility in the food industry. The molecular mechanism of EW's action is not understood. In this study, we exposed Escherichia coli ATCC 25922 to a sub-lethal concentration of EW and examined structural and metabolic changes. Atomic force microscopy revealed that EW caused damage to E. coli membranes. To understand the metabolic responses to EW perturbations in of E. coli, multivariate data analysis of NMR spectroscopy demonstrated that EW significantly influenced the metabolic state. This included reducing nucleotide and amino acid biosynthesis, suppressing energy-associated metabolism, altering osmotic adjustment, and promoting fatty acid metabolism. The results enrich our understanding of E. coli metabolic changes caused by EW perturbation and support the effectiveness of the NMR metabolomics as a valuable tool to analyse and evaluate such a complex biological system.
... A number of studies demonstrate that NEW has a strong antibacterial ability against a variety of foodborne pathogens, such as Salmonella enteritidis, Listeria monocytogenes, Bacillus cereus, and Escherichia coli O157:H7 in fruit and vegetables, and food processing equipment (Gil, Gómez-López, Hung, & Allende, 2015;Len, Hung, Erickson, & Kim, 2000;Liu et al., 2018;Luo, Kim, Wang, & Oh, 2016;Park, Guo, Rahman, Ahn, & Oh, 2009;Xuan et al., 2016). However, the NEW used was mainly produced by current commercial NEW-producing units with NaCl or NaCl mixed with HCl as electrolytes. ...
Article
A novel method was used to produce near neutral pH electrolysed water (NEW) by developing a portable electrochemical sanitising unit that uses diluted sodium chloride and sodium bicarbonate solution (6 mM) as electrolytes. The unit produced NEW at pH 5.70 to 7.1, an oxidation-reduction potential of 802.2-933.8 mV, and free available chlorine (FAC) of 3.3-70 mg/L. NEW produced by the unit with NaCl 10 g/L showed stronger bactericidal effects than NEW produced by mixing the anode and cathode product from commercial unit's (P < 0.05): 2.03 log colony forming units (CFU)/mL reductions compared with 1.66 log CFU/mL reductions. To further understand the sanitising result, electron spin resonance and flow cytometry were performed. The results showed NEW produced by the developed unit induced 82.2% injured cells compared with 54.4% by NEW without detected free radicals. Overall, the current efficiency and power consumption were increased during NEW generation for NEW using sodium bicarbonate compared with sole NEW. The developed NEW generator is a promising sanitising unit for consumers and food industry to control foodborne pathogens.
Chapter
Food safety is a burning issue in the present world. Safe sanitizers are obligatory for maintaining quality of food and increasing the shelf life of fresh produce and other agricultural products. Food industries have been using electrolyzed water (EW) as a unique sanitizer for the past two decades which has excellent results to reduce the microbial count. Hurdle technology, e.g., combination of EW with ultrasonication, short-term heat treatment, organic acids, and salts, found to have more effective results in reducing microorganisms which overcame the little shortcomings with EW like corrosiveness and maintained organoleptic qualities. In this chapter, we are going to discuss the production of EW and its combination with ultrasonication, short-term heat treatment, organic acids, and salts to produce a novel sanitizer.
Chapter
An overabundance of environmental extremities classically called abiotic stresses has been the integral part of plant’s growth and development. Since then plants are also well adapted with its full genetic potential in two responses: susceptibility and resistance. These are coordinated with the expression of genes in up/down regulation according to genotypic plasticity at varying degrees as well as durations. Among the stressors most of those are perceived through root system of plants directly from soil like drought, salinity, metals and metalloids, pH variability, chemicals toxicity, hypoxia/anoxia etc. With the expression potential of gene(s) and its induction roots are also able to epigenetic regulation in tolerance of the stress factors where without interference of DNA sequence are also most important. Epigenetic regulation is also inheritable in nature but rather than any alteration of DNA sequence it involves the nuclear protein (histone) amendment as well as chemical modifications like methylation. In roots tissues certain conserved DNA sequences in chimeric manner in a precise and stringent regulation process tunes the responses to stresses that differs from rest of the flanking sequences. With the most modern–state-of art including high throughput sequencing at different platforms epigenetic regulation in roots genomics has reached a significant milestones to characterize stress. Thus, breeding with roots genomics now has set an alternative approach where world environmental climatic changes are ameliorated or minimize in crops to a significant extent. This chapter would encase various aspects of roots epigenetic responses to abiotic stresses in overall aspects of technology and its usefulness in crop sustenance.
Article
Full-text available
The aim of this study was to prepare electro-activated solutions (EAS) from calcium lactate, calcium ascorbate, and an equimolar mixture of these two salts to obtain their corresponding acids and to study their physicochemical characteristics, in particular, pH, titratable acidity, pKa, and antioxidant activity. Indeed, the solutions were electro-activated in a reactor comprising three compartments (anodic, central, and cathodic) separated by anionic and cationic exchange membranes, respectively. The electric current intensities used were set at 250, 500, and 750 mA for a maximum period of 30 min. In general, the EAS obtained at 750 mA for 30 min showed the lowest pH (2.16, 2.08, 1.94) and pKa (3.13, 3.07, 2.90) values and the highest titratable acidity (0.107, 0.102, 0.109 mol/L) for calcium lactate, the mixture, and calcium ascorbate, respectively. In addition, the obtained results have demonstrated that the pH, titratable acidity, and pKa of the EAS varied proportionally and significantly (p < 0.001) with the duration of the experiment and the intensity of the electric current applied. To evaluate the migration of calcium (Ca²⁺) between the central and the cathodic compartments of the reactor, the concentration of Ca²⁺ was determined especially in the cathodic section by inductively coupled plasma optical emission spectroscopy (ICP-OES). The results showed that the migration of Ca²⁺ varied proportionally with the electric current intensity. In this context, analysis by Fourier transform infrared (FTIR) spectroscopy, high-performance liquid chromatography (HPLC), and differential scanning calorimetry (DSC) have confirmed the production of lactic acid and ascorbic acid compared to standards. In addition, analysis by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging technique confirmed high antioxidant activities of >90 and >83% for calcium ascorbate and the mixture, respectively, in comparison to the standard ascorbic acid (85%). Overall, this research has clearly demonstrated the eventual potential of electro-activation to produce highly reactive organic acids from their conjugated salts. These EAS can become excellent antimicrobial and sporicidal agents in the food processing industry.
Article
The aim of this study was to assess the effect of γ-irradiation on the microbial inactivation of selected foodborne pathogens (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli 0157:H7, and Salmonella Typhimurium) in combination with 2.5% sodium citrate, 0.5% sodium carbonate and 0.75% citric acid as food additives in frozen and powdered infant formula (IF). The study demonstrated that γ-irradiation alone was more efficient against pathogens in frozen IF. A hurdle technology with sodium carbonate induced a high radiosensitization in powdered and frozen IF against all pathogens, compared to other additives that induced a lower radiosensitization effect. Contrarily to other pathogens, spore-producing B. cereus was more radiosensitized in powdered IF by carbonate, citrate, and citric acid, with radiosensitivity values up to 4.1. E. coli was strongly radiosensitized in presence of carbonate and citrate in frozen IF with values up to 2.4. This study demonstrated that the use of food additives – mainly sodium carbonate – in combination with γ-irradiation can be a good way to reduce the time of irradiation treatment to assure the safety of the IF product.
Article
Full-text available
Microbial control of postharvest diseases has been extensively studied and appears to be a viable technology. Food safety must be ensured at each postharvest processing step, including handling, washing of raw materials, cleaning of utensils and pipelines, and packaging. Several commercial products are available for this purpose. The time is ripe for developing new techniques and technologies. The use of electrolyzed water (EW) is the product of a new concept developed in Japan, which is now gaining popularity in other countries. Little is known about the principle behind its sterilizing e#ect, but it has been shown to have significant bactericidal and virucidal and moderate fungicidal properties. Some studies have been carried out in Japan, China, and the USA on the pre-and postharvest application of EW in the field of food processing. EW may be produced using common salt and an apparatus connected to a power source. As the size of the machine is quite small, the water can be manufactured on-site. Studies have been carried out on the use of EW as a sanitizer for fruits, utensils, and cutting boards. It can also be used as a fungicide during postharvest processing of fruits and vegetables, and as a sanitizer for washing the carcasses of meat and poultry. It is cost-e#ective and environment-friendly. The use of EW is an emerging technology with considerable potential.
Article
Full-text available
This study was conducted to determine the inactivation effect of electrolyzed water and organic acids either alone or in combination on L. monocytogenes or natural microflora on lettuce. Acidic electrolyzed water completely inactivated L. monocytogenes in broth system within 60 sec, but alkalin electrolyzed water caused approximate 1.7 log CFU/g reduction. However, acidic electrolyzed water reduced only 2.5 log CFU/g of L. monocytogenes on lettuce, and similar antimicrobial effect was observed with alkalin electrolyzed water. In the meantime, acidic and alkaline electrolyzed water caused approximately 2 log CFU/g reduction compared to control, whereas both electrolyzed water combined with organic acids ranged from 2.6 to 3.7 log CFU/g reduction. Among the organic acids, both electrolyzed water combined with citric acid showed the strongest synergistic antimicrobial effect to reduce L. monocytogenes on lettuce as well as total counts, yeast and molds. When antimicrobials, alone or in combination were treated into L. monocytogenes inoculated lettuce at for designed periods, the combined alkalin electrolyzed water with citric acid showed the greatest potential to inhibit growth of the bacteria. According to Scanning Electron Microscopy(SEM), the treatment of electrolyzed alkali water in combination with citric acid highly reduced the growth of the L. monocytogenes compared to single treatment and resulted in causing the destruction of cell membrane.
Article
The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AlEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCl solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was nor damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.
Article
From July 1992 to June 1993, 155 instant cereal products were purchased from 24-hour stores, supermarkets and grocery stores in Taipei area and examined for Bacillus cereus, coliform bacteria, Escherichia coli and aerobic plate count. The results showed that B. cereus was found on 32% of instant cereal products examined. The isolation rates of B. cereus in regular instant cereal and cereal mix were 26% and 38%, respectively. Count range of B. cereus in all positive samples was 3 - 93 MPN/g. Aerobic plate counts of these two categories ranged between 5 - 2.3 × 10 4 CFU/g and 5 - 4.2 × 10 3 CFU /g, respectively. Among all samples, only one cereal mix sample was illegally contaminated with E. coli , while 8 samples contained coliform bacteria. Coliform was isolated from 2 of 74 (2.7%) regular instant cereal products, but isolated from 6 of 81 (7.4%) cereal mix products, except those of only one cereal mix were beyond sanitary standard. All of 44 B. cereus isolates had strong hemolysin activity, but only 4 isolates were capable of producing diarrheagenic enterotoxin.
Article
Knowledge of the homogeneity of a spore crop is an essential criteria for the subsequent investigation of their properties. Two methods of analysis have been compared; particle size distributions of Bacillus spores suspensions were analysed by laser light scattering with a Malvern Mastersizer; and scanning transmission electron microscopy (STEM) was used to record images of 50–100 individual spores. With an image particle sizing analysis software the dimensions (length, breadth, perimeter) of single spores were determined. Good agreement between the average individual spore dimensions determined by electron microscopy and those obtained by light scattering was evident. The Mastersizer was convenient and rapid to use but the image analysis provided the opportunity to distinguish between spores, vegetative cells and other particles. Spore suspensions were further separated from vegetative cells by centrifugation in continuous and discontinuous Percoll (modified colloidal silica) density gradients (1.09–1.13 g/ml). Electron microscopy revealed an adhesion of colloidal silica particles to the spore surface which could only be partially removed by repetitive washing. High silica contents were therefore detected by X-ray microanalysis. Percoll did not effect differential scanning calorimetric analysis of spores.
Article
The microbial spoilage of peeled oranges was caused predominantly by Gram negative bacteria Enterobacter agglomerans, and Pseudomonas spp., end yeasts Cryptococcus albidus, Rhodotorula glutinis, and Saccharomyces cerevisiae. infusion of fruits with citric acid solution (0.1, 0.25, 0.5, and 1.0% w/v) during the peeling process reduced the surface pH of peeled fruits (from 6.0 to <4.6) and extended their shelf life in comparison with fruits infused with water only. Regardless of treatment method (dipping or infusion), maximal shelf life extension was attained with 0.5% w/v citric acid for 4 degrees C storage or 1.0% w/v citric acid for 8 and 21 degrees C storage. Infusion of 0.5% w/v citric acid extended shelf life of both peeled whole and chunked fruits. The extension of shelf life resulted primarily from the inhibition of spoilage bacteria. (C) 1997 Academic Press Limited.
Article
For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10min. EO water achieved additional 0.7logCFU/cm2 reduction than tap water on E. coli after 1min treatment and additional treatment time did not achieved additional reduction. EO water treatment also reduced V. parahaemolyticus, by 1.5logCFU/cm2 after 5min treatment and achieved 2.6logCFU/cm2 reduction after 10min. The pathogenic bacteria were not detected in EO water after soaking treatment. In addition, EO water could effectively disinfect the platform of fish retailer in traditional markets and fish markets.
Article
The efficacy of electrolysed oxidizing water in reducing micro-organisms on vegetables was evaluated. Formation of brown spots on leafy and fruit vegetables could be avoided when they were soaked in acidic electrolysed oxidizing (AC) water for less than 9 and 15 min, respectively. Soaking in alkaline electrolysed (AK) water for 30 min did not affect the appearance of the vegetables. The effectiveness of water or AK water on aerobic plate count (APC) reduction was limited (0.5 log CFU g−1). However, soaking in AC water alone effectively reduced APC values of leafy vegetables and fruit vegetables by 1.0–1.5 log CFU g−1. Soaking in AC water followed by AK water further reduced APC by 0.5 and 0.7 log CFU g−1 on leafy cabbage and green pepper, respectively. Continuous changing of electrolysed water with either shaking or ultrasonication can effectively reduce APC by 2–2.5 log CFU g−1. Electrolysed oxidizing water was significantly more effective than water in eliminating micro-organisms on vegetables.
Article
A process to decontaminate paprika powder using variable near-infrared (IR) radiation was tested using a closed sample holder allowing water to be retained in the powder. The reduction in the concentration of Bacillus cereus spores and changes in water activity (aw) and colour were measured during IR heating. High heat flux was applied initially to heat the powder rapidly to the desired temperature, followed by low heat flux to maintain the temperature for a given time. The water activity (aw) value of the powder could be maintained within the bulk of the closed sample, but the surface aw value decreased during heating. Due to carotenoid sensitivity to temperature, surface and overall colour values declined, though remaining acceptable values of medium red and red, respectively. For powder with an aw value of 0.88 heated to 95–100 °C, the load of B. cereus spores was reduced by 4.5 log10 CFU/g within 6 min; the final spore concentration remained approximately 2 log10 CFU/g due to tailing. Reducing pH to 4.0 from 4.5 did not significantly affect the reduction of the B. cereus spore concentration.