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Synergistic effect of low concentration electrolyzed water and calcium lactate to ensure microbial safety, shelf life and sensory quality of fresh pork

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The objectives of this study were to evaluate the effectiveness of low concentration electrolyzed water (LcEW) and other carcass decontaminants against Escherichia coli O157:H7 and Listeria monocytogenes in fresh pork and to conduct the shelf life/sensory study of pork. Pork samples were inoculated with approximately 5 log cfu/g of afore mentioned pathogens and dip treated with distilled water (DW), aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium hypochlorite solution (NaOCl), LcEW, strong acidic electrolyzed water (SAEW), and LcEW + CaL for 5 min at room temperature (23 ± 2 °C). The greatest reduction (3.0–3.2 log cfu/g) was achieved with LcEW + CaL against pathogens and significantly differed (p < 0.05) from other treatments. This combination also extended shelf life of pork up to 6 days at 4 °C storage.
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Synergistic effect of low concentration electrolyzed water and calcium lactate to
ensure microbial safety, shelf life and sensory quality of fresh pork
S.M.E. Rahman
a
,
b
,
1
, Jun Wang
a
,
1
, Deog-Hwan Oh
a
,
*
a
Department of Food Science and Biotechnology and Institute of Bioscience and Biotechnology, Kangwon National University, 192-1 Hyoja 2 dong, Chuncheon, Gangwon 200-701,
Republic of Korea
b
Department of Animal Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
article info
Article history:
Received 15 December 2011
Received in revised form
18 June 2012
Accepted 23 June 2012
Keywords:
Combination of LcEW þCaL
Microbial safety
Shelf life
Sensory quality
Pork meat
abstract
The objectives of this study were to evaluate the effectiveness of low concentration electrolyzed water
(LcEW) and other carcass decontaminants against Escherichia coli O157:H7 and Listeria monocytogenes in
fresh pork and to conduct the shelf life/sensory study of pork. Pork samples were inoculated with
approximately 5 log cfu/g of afore mentioned pathogens and dip treated with distilled water (DW),
aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium hypochlorite solution (NaOCl),
LcEW, strong acidic electrolyzed water (SAEW), and LcEW þCaL for 5 min at room temperature
(23 2
C). The greatest reduction (3.0e3.2 log cfu/g) was achieved with LcEW þCaL against pathogens
and signicantly differed (p<0.05) from other treatments. This combination also extended shelf life of
pork up to 6 days at 4
C storage.
Ó2012 Elsevier Ltd. All rights reserved.
1. Introduction
About 40 percent of all meat consumed in the world is pork,
followed by poultry meat at 30 percent, and beef at 25 percent
(FAO, 2006). Although the consumption of pork products is
increasing, the microbial safety of pork during storage and
marketing remains a concern. Meat products are highly perishable,
and food poisoning can occur as a result of careless processing and
storage (Aymerich, Picouet, & Monfort, 2008). The main ora
responsible for spoilage in fresh meat products during aerobic
storage is the Pseudomonas species and they are dominant in
poultry meat, pork and beef and lamb (Coates, Beattie, Morgan, &
Widders, 1995). Microbial contamination in meat is an important
factor associated with meat quality. It has been found that bacterial
contamination, such as Salmonella Typhimurium, Escherichia coli
O157:H7 and Listeria monocytogenes, impacted meat safety (Cutter,
2000;Dorsa, Cutter, & Siragusa, 1998;Nissen, Alvseike, Bredholt,
Holck, & Nesbakken, 2000). Therefore, to improve the microbial
safety of pork during processing and storage, various processing
techniques have been used for reduction of bacterial contaminants
to extend shelf life (Latha, Sherikar, Waskar, Dubal, & Ahmed, 2009;
Schirmer & Langsrud, 2010;Viana, Gomide, & Vanetti, 2005).
Constant efforts have been made to create effective and new
technologies for the decontamination of carcasses and meat
products (Huffman, 2002;Zhou, Xu, & Liu, 2010). Several inter-
vention strategies have been developed to reduce the level of
bacteria on pork or other animal carcass surfaces such as washing
and sanitizing with hot or chilled water (Frederick, Miller,
Thompson, & Ramsey, 1994;Özdemir et al., 2006), chlorinated
and electrolyzed water (Ding, Rahman, Purev, & Oh, 2010;Fabrizio
& Cutter, 2004;Park, Hung, & Brackett, 2002), food grade acids
(Dubal et al., 2004;Pipek et al., 2006), salts (Jensen et al., 2003;
Latha et al., 2009), ozone (Jaksch et al., 2004), chlorine dioxide
(Pohlman, Stivarius, McElyea, Johnson, & Johnson, 2002), essential
oil and nisin (Solomakos, Govaris, Koidis, & Botsoglou, 2008). All
these sanitizers act differently on different types of organisms, but
the information is limited on the action of these sanitizers on
articially inoculated specic organisms in meat. Moreover, most of
these sanitizers are made from the dilution of condensed solutions,
which in handling involves some risk and is troublesome. A sani-
tizer named low concentration electrolyzed water (LcEW) that is
not produced from the dilution of a hazardous condensed solution
has been reported in several previous researches as a safe and
promising sanitizer (Ding, Rahman, & Oh, 2011;Rahman, Ding, &
Oh, 2010a,2010b). Thus, LcEW is being used in this study as an
alternative non-thermal sanitizer, and furthermore, it has been
*Corresponding author. Tel.: þ82 33 250 6457; fax: þ82 33 241 0508.
E-mail addresses: ehsan_bau@yahoo.com (S.M.E. Rahman), wangjun@
kangwon.ac.kr (J. Wang), deoghwa@kangwon.ac.kr (D.-H. Oh).
1
S.M.E. Rahman and Jun Wang share the co-rst-authorship.
Contents lists available at SciVerse ScienceDirect
Food Control
journal homepage: www.elsevier.com/locate/foodcont
0956-7135/$ esee front matter Ó2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.foodcont.2012.06.041
Food Control 30 (2013) 176e183
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reported from our previous research that LcEW treatment could
also help to maintain the physicochemical and sensory quality of
fresh chicken breast meat (Rahman, Park, Song, Al-Harbi, & Oh,
2012). Combinations of LcEW and other measures are also possible.
Organic acid salts such as calcium lactate have been used in the
meat industry because of their ability to increase avor, prolong
shelf life, and improve the microbiological safety of products
(Lawrence, Dikeman, Hunt, Kastner, & Johnson, 2003;Naveena,
Sen, Muthukumar, Vaithiyanathan, & Babji, 2006;Selgas, Salazar,
& García, 2009). Meat and meat products are considered to be
a relatively minor source of calcium (Fennema, 1996), so CaL
dipping is useful for enriching these meat products with calcium. In
addition, CaL helps to maintain tenderness and palatability of meat
products (Lawrence et al., 2003). Therefore, we combined
LcEW þCaL and applied in our study to nd any synergistic or
hurdle effect. Accordingly, the present work was undertaken to
study and compare the antimicrobial effect of LcEW alone and its
combination with CaL as a safe and natural sanitizer in handling or
food application comparison with other commercial sanitizers
against background ora and inoculated pathogens associated with
fresh pork. Sensory quality and shelf life of pork at refrigeration
temperature (4
C) was also studied.
2. Materials and methods
2.1. Bacterial cultures
The three strains each of E. coli O157:H7 (B0259, B0297 and
B0299) and L. monocytogenes (ATCC 19115, ATCC 19111 and Scott A)
used in this experiment were obtained from Department of Food
Science, University of Georgia (Grifn, GA, USA), and Health
Research Department (Gyeonggi-do, Republic of Korea), respec-
tively. Stock cultures of each pathogen were transferred into tryptic
soy broth (TSB; Difco, NJ, USA) and incubated for 24 h at 35
C.
Following incubation, 10 mL of each culture was sedimented by
centrifugation (4000g for 10 min at 4
C), washed and resus-
pended in 10 mL of 0.1% peptone water (pH 7.1) to obtain a nal cell
concentration of 10
9
cfu/mL. Subsequently, resulting suspensions of
each strain of the 2 pathogens were combined to construct culture
cocktails. These culture cocktails were used in the following
experiments. The bacterial population in each cocktail culture was
conrmed by plating 0.1 mL portions of appropriately diluted
culture on tryptic soy agar (TSA) plates and incubating the plates at
35
C for 24 h.
2.2. Sample preparation
Boneless pork loins (48 h post-slaughter) were obtained from
a retail store in Chuncheon, Korea. External fats and fascia were
removed and then stored in a refrigerator at 4
C prior to use for the
experiment within 3 h. Pork samples were cut into pieces of similar
size (2.5 2.5 cm) using a sterile knife. Before inoculation, each
sample weighed 10 0.2 g.
2.3. Inoculation
To destroy the background microora, pork samples were
surface treated using UV light in a biological safety hood. Surfaces
were evenly exposed to UV light by turning sections every 10 min
for a total time of no more than 30 min (Cutter & Siragusa, 1994).
After applying this treatment, the naturally existing bacterial
population was reduced to an undetectable level (with 10 cfu/g
detection limit). Accordingly, mixed inocula (0.1 mL, more than
10
9
cfu/mL) of E. coli O157:H7 and L. monocytogenes were spread
separately on the top and bottom surface of each piece of fresh pork
using a sterile glass rod to obtain an inoculated level of 10
5
log cfu/g
(Zhang, Kong, Xiong, & Sun, 2009). Then the samples were kept in
a laminar ow hood for 20e30 min at room temperature
(23 2
C) to allow for bacterial attachment. Inoculated samples
without LcEW, SAEW, and LcEW þCaL treatments were used as
control.
2.4. Preparation of treatment solutions
Low concentration electrolyzed water (LcEW), with a pH of
6.8,oxidation reduction potential (ORP) of 700e720 mV and avail-
able chlorine concentration (ACC) of 10 mg/L used in this study was
produced by electrolysis of a dilute NaCl solution (0.9%) in
a chamber without a membrane using an electrolysis device (model
D-7, Dolki Co. Ltd., Wonju, Korea) at a setting of 3 V and 1.47 A.
Strong acid electrolyzed water (SAEW) with a pH of 2.54, ORP of
110 0 e1120 mV was generated using electrolyzed water (EW)
generator (A2-1000, Korean E& S Fist Inc, Seoul, Korea) including
a small amount of salt solution (0.1%) and tap water at a setting of
12 A. with a residual chlorine concentration of about 50 mg/L. As
reported, SAEW was made by EW generator with a membrane to
separate the positive pole and negative pole, which had an acidic
pH, higher ORP value and always initially had a higher residual
chlorine concentration, compared to LcEW (Rahman et al., 2010a).
The sodium hypochlorite solution (NaOCl: pH 9.8, 100 mg/L avail-
able chlorine) was prepared with the addition of 0.1 g of NaOCl(DC
Chemical Co., Seoul, Korea) in 1 L of sterile DW. 3% (v/v) lactic acid
(pH 2.35) solutions were prepared with DW by using LA (90%,
Merck). 3% (w/v) calcium lactate (pH 6.5) solutions were prepared
with DW by using CaL (98%, Yakuri pure chemicals co. ltd., Kyoto,
Japan). Aqueous ozone (5 ppm) was produced on site by an elec-
trochemical process using a green water ozone generator
(GW-1000, Youl chon, Korea). Distilled water was used as control.
The pH, ORP and available chlorine concentration of treatment
solutions (LcEW and SAEW) were measured immediately before
treatment with a dual-scale pH meter (Accumet model 15, Fisher
Scientic Co., Fair Lawn, NJ) with pH and ORP electrodes. The
residual chlorine was determined by a colorimetric method using
a digital chlorine test kit (RC-3F, Kasahara Chemical Instruments
Corp., Saitama, Japan). The detection limit is 0e300 mg/L.
2.5. Dip wash treatments and microbiological analysis of meat
samples
Inoculated and uninoculated pork samples (10 g) were placed in
sterile containers and immersed in treatment solutions (DW, AO,
3% LA, 3% CaL, NaOCl, LcEW, SAEW, and LcEW þCaL) at room
temperature (23 2
C). Unwashed meat samples were used as
control. To evaluate the effect of dipping time on the reduction of
microorganisms, each 10 g piece of uninoculated pork was dipped
for 0, 1, 3, 5, 7, and 10 min, respectively and nally 5 min dipping
was chosen for subsequent experiment. Following treatments, all
samples were aseptically excised and immediately placed in
a stomacher bag (Nasco Whirl-Pak, Janesville, WI, USA) containing
90 mL of BPW and homogenized for 2 min with a Seward stomacher
(400 Circulator, Seward, London, UK). After homogenization, 1 mL
aliquots of the sample were serially diluted in 9 mL of sterile
buffered peptone water and 0.1 mL of sample or diluents was
spread-plated onto each selective medium. Total bacterial counts
were determined by plating appropriately diluted samples onto
Tryptic Soy Agar (TSA). Yeasts and molds were plated on Potato
Dextrose Agar (PDA; Difco). Two selective media of Sorbitol Mac-
Conkey agar (SMAC; Difco) and Oxford Agar Base (OAB; Difco) were
used for the enumeration of E. coli O157:H7 and L. monocytogenes,
respectively. All plates were incubated at 37
C for 24 h, except for
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183 177
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yeasts and molds at 25
C for 3e5 d and expressed as log cfu/g. All
independent trials were replicated 3 times.
2.6. Shelf-life study
After treatment of uninoculated pork with LcEW, SAEW, and
LcEW þCaL; the samples were placed in polyethylene air-
permeable plastic bags (Robertson, 1993) and stored at 4
C for
12 days. Microbiological (Total Viable Count And Yeast and Mold)
analysis was carried out immediately after treatment and subse-
quently at storage intervals of 2, 4, 6, 8, 10, and 12 days. The end of
the shelf-life arrived when the population of a group of microor-
ganisms reached an unacceptable level of 6e7 log cfu/g (Zhou
et al., 2010) or when the sensory panel rejected the samples.
2.7. Evaluation of the sensory quality during the shelf-life
Sensory evaluation of pork was carried out to estimate the shelf-
life by a four member sensory panel using a six point standardized
scale for color and a four point standardized scale for odor (Latha
et al., 2009).
2.8. pH measurement
Values of pH were measured in triplicate in all meat samples
stored at 4
C by inserting the pH electrode (Model 720A, Orion/
Research, Boston, MA) directly into meat homogenates (1:10
dilution).
2.9. Lipid oxidation
Lipid oxidation was assessed by the 2-thiobarbituric acid (TBA)
method of Witte, Krause, and Bailey (1970). TBARS values were
calculated from a standard curve of malonaldehyde and expressed
as mg malonaldehyde/kg meat.
2.10. Statistical analyses
All experiments were repeated three times, and the values
represent the means of duplicate determinations for each sample.
Data were expressed as the means standard deviation (SD). The
results were analyzed using the SPSS statistical package (SPSS Inc.,
Chicago, IL) and the signicance of difference was dened at
p<0.05.
3. Results and discussion
The Physicochemical properties (pH, ORP, and ACC) of treatment
solutions (DW, AO, 3% LA, 3% CaL, NaOCl, LcEW, SAEW, and
LcEW þCaL) used in this study are presented in Table 1. The effect
of dipping times (1, 3, 5, 7, and 10 min) on the reduction of total
viable counts (TVC) on pork treated with DW, LcEW, and SAEW are
shown in Fig. 1. From these results, treatments exposed for 5 min
showed signicant difference (p<0.05) in reducing total bacteria
from the dipping times of 1 and 3 min, but there was no signicant
difference (p>0.05) from the dipping times of 7 and 10 min. Also 7
and 10 min dipping resulted in changing fresh color (visual esti-
mation) of pork. According to these results, 5 min dipping would be
the most appropriate to minimize the quality deterioration (color),
thus, it was chosen for the subsequent treatments which were done
at room temperature. In contrast, Park et al. (2002) and Fabrizio,
Sharma, Demirci, and Cutter (2002) examined the use of EO
water to inactivate Campylobacter jejuni or Salmonella spp. on
poultry. In these studies, it was determined that EO water was more
effective when the contact times were increased to >10 and 40 min,
respectively. Also, our previous report revealed that 10 min treat-
ment with LcEW at room temperature could signicantly reduce
the natural background microora and extend the shelf life of fresh
chicken breast meat (Rahman et al., 2012).
3.1. Decontamination of fresh pork
After sanitizing treatments in 5 min dipping, the populations of
TVC in the pork samples were 4.61, 4.31, 3.83, 3.67, 3.63, 3.57, 3.33,
3.21, and 2.41 log cfu/g for the control, DW, AO, 3% LA, 3% CaL,
NaOCl, LcEW, SAEW, and LcEW þCaL treatments, respectively
(Fig. 2). The greatest reduction was achieved with LcEW þCaL. This
combination treatment reduced the microbial load in the pork by
2.20 log cfu/g, compared to the unwashed control, whereas
washing with DW resulted in the lowest reduction by 0.30 log cfu/g.
Yeasts and molds had a more or less similar pattern to that of total
aerobic bacteria (Fig. 3). Initial populations of yeasts and molds in
the pork samples were 1.97, 1.76, 1.40, 1.25, 1.22, 1.13, 1.01, 0.90, and
0.40 log cfu/g for the control, DW, AO, 3% LA, 3% CaL, NaOCl, LcEW,
SAEW, and LcEW þCaL treatments, respectively. The LcEW þCaL
treatment caused the most effective reduction (p<0.05) of yeasts
and molds in the pork by 1.57 log cfu/g compared to the unwashed
control, whereas washing with DW only showed a reduction of
0.21 log cfu/g. These results demonstrate that combination of LcEW
with CaL is an effective sanitizer for microbial decontamination in
meat. Reduction in TVC by 0.98 log units was observed in the
present study for 3% CaL treated pork, which is in agreement with
the ndings of Latha et al. (2009),Mendonca, Molins, Kraft, and
Walker (1989) and Ahmed et al. (2003), whereas they used other
salt treatments. Latha et al. (2009) also observed TVC reduction by
about 2.32 log cfu/g on pork carcasses after hot water treatment
with slight to moderate changes in color while, we found
2.20 log cfu/g reduction of TVC in fresh pork treated by LcEW and
3% CaL combinedly without changing in color. Muhlisin et al. (2010)
reported that sodium acetate and calcium lactate lowered
(p<0.05) the aerobic and anaerobic bacterial counts in high oxygen
modied atmosphere packaging (OxyMAP) and nitrogen modied
atmosphere packaging (NitroMAP) which is in agreement with
Lawrence et al. (2003) who reported reduced antimicrobial plate
counts in beef longissimus dorsi owing to the effect of calcium salts.
The sodium and calcium salts of lactic acid are approved for use in
meat products as direct food ingredients (Anonymous, 1987)
Table 1
Physicochemical properties of treatment solutions.*
Treatment solutions pH ORP
a
(mV) ACC
b
(mg/L)
DW
c
7.0 0.1 412 18 0.3 0.1
AO
d
6.6 0.1 1245 25 5.2 0.2 mg
O
3
/L of water
3% LA
e
2.35 0.2 613 10 ND
k
3% CaL
f
6.51 0.05 290 20 ND
NaOCl
g
10.6 0.2 630 15 100 4.5
LcEW
h
6.8 0.2 700 10 10 0.1
SAEW
i
2.54 0.3 1130 20 50 2.2
LcEW þCaL
j
6.82 0.08 245 20 1.0 0.1
* Values are mean standard deviation, n¼3.
a
Oxidation reduction potential.
b
Available chlorine concentration.
c
Distilled water.
d
Aqueous ozone.
e
Lactic acid (3%).
f
Calcium lactate (3%).
g
Sodium hypochlorite solution.
h
Low concentration electrolyzed water.
i
Strong acidic electrolyzed water.
j
Low concentration electrolyzed water þ3% Calcium lactate.
k
Not detected.
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183178
Author's personal copy
because they are derived from lactic acid, naturally present in the
animal tissues. Chen and Shelef (1992) found that CaL is equally
effective in controlling growth of aerobes and anaerobes in meats.
Pork samples were inoculated with approximately 5 log cfu/g of
L. monocytogenes and E. coli O157:H7 and treated with DW, AO, 3%
LA, 3% CaL, NaOCl, LcEW, SAEW, and LcEW þCaL. Sanitizing
treatment of the inoculated pork signicantly reduced the micro-
bial populations. After treatment, the initial populations of
L. monocytogenes in the pork samples were 5.07, 4.58, 3.99, 3.68,
3.60, 3.46, 3.25, 3.12, and 1.90 log cfu/g for the control, DW, AO, 3%
LA, 3% CaL, NaOCl, LcEW, SAEW, and LcEW þCaL treatments,
respectively (Fig. 4). In fact, the LcEW þCaL showed the greatest
reduction (p<0.05) of the population of L. monocytogenes by
3.17 log cfu/g compared to the unwashed control, whereas washing
with DW produced the lowest reduction by 0.49 log cfu/g. However,
E. coli O157:H7 had a similar pattern to L. monocytogenes. After
treatment, the populations of E. coli O157:H7 in pork samples were
5.03, 4.63, 4.02, 3.66, 3.59, 3.51, 3.30, 3.12,and 2.03 log cfu/g for the
control, DW, AO, 3% LA, 3% CaL, NaOCl, LcEW, SAEW, and
LcEW þCaL treatments, respectively (Fig. 5). LcEW þCaL signi-
cantly reduced (p<0.05) the populations of E. coli O157:H7 by
3.0 log cfu/g compared to the unwashed control, while washing
aab
bbc bc bc cc
d
0
1
2
3
4
5
log cfu/g
Treatments
Total viable count
Fig. 2. Surviving population of total viable count on fresh pork after washing with distilled water (DW), aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium
hypochlorite (NaOCl), low concentration electrolyzed water (LcEW), strong acidic electrolyzed water (SAEW), and LcEW þCaL relative to an unwashed control. Vertical bars
represent mean standard deviation (SD), n¼6. Bars labeled with different letters among treatments indicate a signicant difference (p<0.05).
aab b
ccc
a
b
bc ccc
a
b
bc ccc
0
1
2
3
4
5
0135710
Total viable count (log cfu/g)
Dipping time (min)
a
DW
a
LcEW
c
c
a
b
b
c
b
b
c
a
b
b
c
c
D
W
L
c
E
W
SAEW
Fig. 1. Surviving population of total viable count on fresh pork after washing with distilled water (DW), low concentration electrolyzed water (LcEW) and strong acidic electrolyzed
water (SAEW) at different dipping times (min). Vertical bars represent mean standard deviation (SD), n¼6. Bars labeled with different letters in the same treatment indicate
a signicant difference (p<0.05).
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183 179
Author's personal copy
with DW reduced the populations by 0.40 log cfu/g. So many
research works have been published to date, examining the effects
of various intervention technologies to decontaminate fresh meat
and meat products. For instance, Latha et al. (2009) revealed that
the application of salts resulted in reduction of 2.88 and
3.29 log cfu/g for L. monocytogenes and E. coli respectively on pork
carcasses. On the other hand, effectiveness of EO water has been
reported against populations of E. coli,L. monocytogenes,C. coli,
C. jejuni, and S. Typhimurium associated with pork, chicken and
other meat surfaces which can result in reductions in those path-
ogens ranging from 0.48 to 3.0 log cfu/g (Fabrizio & Cutter, 2004,
2005;Fabrizio et al., 2002;Kim, Hung, & Russell, 2005;Park
et al., 2002). Recent studies have reported greater reductions
being achieved by combining interventions such as hot water and
organic acid washing (Castillo, Lucia, Mercado, & Acuff, 2001).
There is growing interest in the development of novel combina-
tions of natural antimicrobials and other food preservation systems
to improve the quality and safety of meat. Generally, bio-
preservation and natural antimicrobials provide an excellent
opportunity for such combined preservation systems. For example,
oregano essential oil, combined with MAP, were studied as hurdles
in the storage of fresh meat and a longer shelf life was observed
over that of the same packaging alone (Chouliara, Karatapanis,
Savvaidis, & Kontominas, 2007).
3.2. Shelf-life and sensory quality
The changes in microbial populations during the shelf-life study
are shown in Fig. 6. Combined treatment with LcEW and 3% CaL was
found to effectively control the growth of aerobic bacteria, yeast
and fungi during storage at 4
C for 12 days, when compared to
unwashed controls. All the untreated and treated pork samples
were stored at refrigeration temperature and shelf-life as well as
sensory scores of meat was assessed at intervals (Figs. 6e8). The
a
ab
bbc bc bc cc
d
0
0.5
1
1.5
2
2.5
log cfu/g
Treatments
Yeast and mold
Fig. 3. Surviving population of yeast and mold on fresh pork after washing with distilled water (DW), aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium
hypochlorite (NaOCl), low concentration electrolyzed water (LcEW), strong acidic electrolyzed water (SAEW), and LcEW þCaL relative to an unwashed control. Vertical bars
represent mean standard deviation (SD), n¼6. Bars labeled with different letters among treatments indicate a signicant difference (p<0.05).
a
b
ccd cd dde de
e
0
1
2
3
4
5
6
log cfu/g
Treatments
L. monocytogenes
b
c
cd
c
d
d
d
d
e
e
d
d
e
e
Fig. 4. Surviving population of L. monocytogenes on fresh pork after washing with distilled water (DW), aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium
hypochlorite (NaOCl), low concentration electrolyzed water (LcEW), strong acidic electrolyzed water (SAEW), and LcEW þCaL relative to an unwashed control. Vertical bars
represent mean standard deviation (SD), n¼6. Bars labeled with different letters among treatments indicate a signicant difference (p<0.05).
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183180
Author's personal copy
end of the shelf-life was considered to occur when the total aerobic
count was 7 log cfu/g and the total yeast count was 5 log cfu/g
(Alegria et al., 2010;Debevere, 1996, pp. 37e64; Gómez-López,
Devlieghere, Ragaert, & Debevere, 2007). The results of our study
revealed that onset of spoilage occurred after 12 days of storage for
treated (LcEW þCaL) pork with corresponding increases in the TVC
to 6.98 0.30 and YM to 5.2 0.28 log cfu/g, respectively. While, in
control samples spoilage was evidenced after 6 days of storagewith
corresponding increases in the TVC to 7.12 0.26 and YM to
5.18 0.25 log cfu/g, respectively. Thus, LcEW and CaL combination
treated pork meat samples could be stored for 12 days at refriger-
ation temperature, indicating that overall increase in shelf-life of 6
days in comparison with untreated pork meat samples. Whereas,
Latha et al. (2009) observed enhanced shelf-life of 7 days for pork
samples treated with salt combination compared to untreated
samples stored at 4
C. Similar ndings had been recorded by
Ahmed et al. (2003).Sawaya et al. (1995) also noted an increase in
shelf-life by 6e7 days at chill temperature (4
C) in broiler carcasses
a
ab
bbc bc ccd cd
d
0
1
2
3
4
5
6
log cfu/g
Treatments
E. coli
O157:H7
Fig. 5. Surviving population of E. coli O157:H7 on fresh pork after washing with distilled water (DW), aqueous ozone (AO), 3% lactic acid (LA), 3% calcium lactate (CaL), sodium
hypochlorite (NaOCl), low concentration electrolyzed water (LcEW), strong acidic electrolyzed water (SAEW), and LcEW þCaL relative to an unwashed control. Vertical bars
represent mean standard deviation (SD), n¼6. Bars labeled with different letters among treatments indicate a signicant difference (p<0.05).
Storage time (d)
024681012
Total viable count (log cfu/g)
0
2
4
6
8
10
Control
LcEW
SAEW
LcEW + CaL
Storage time (d)
024681012
Yeast and mold (log cfu/g)
0
2
4
6
8
10
Fig. 6. Effects of various treatments on total viable count, and yeast and mold of pork
samples stored at refrigeration temperature. Values shown are mean standard
deviation (SD), n¼6. The error bars indicate 95% condence intervals.
Storage time (d)
024681012
Color scores
0
1
2
3
4
5
6
7
Control
LcEW
SAEW
LcEW + CaL
Fig. 7. Color scores of treated and untreated pork samples. Six point scale for color:
1¼extremely bright red, 2 ¼moderately bright red, 3 ¼slightly bright red,
4¼slightly discolored, 5 ¼moderately discolored and 6 ¼extremely discolored.
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183 181
Author's personal copy
pretreated with lactic acid. Recent studies suggest that the use of
CaL may also enhance the shelf life of meat products during
refrigerated storage (Devatkal & Mendiratta, 2001).
Sensorial quality of the pork samples was evaluated bya sensory
panel throughout the storage period. The mean scores of sensory
attributes (color and odor) for untreated and treated pork are
shown in Figs. 7 and 8. Incipient spoilage changes in control, LcEW,
SAEW and LcEW þCaL treated samples with slight discoloration
and slight off odor were evident on days 4, 6 and 8 respectively.
However, marked spoilage with greenish discoloration and
noticeable off odor was seen on the 6th and the 12th day in control
and combination treated samples respectively. Sensory scores like
color (2.5 0.20) and odor (1.5 0.30) were within the acceptable
limit (Figs. 7 and 8). More or less similar shelf-life based on
sensorial properties has been described by others (Ahmed et al.,
2003;Dubal et al., 2004;Latha et al., 2009).
3.3. pH and TBARS value
The pH of the fresh untreated meat was 5.7 and it slowly
increased during storage (Fig. 9). This increase in pH during storage
could be due to degradation of proteins and production of amines
(Gill, 1983). Onset of spoilage was associated with pH rising in meat
during storage. Treatment of the fresh meat with LcEW þCaL
combination did not alter the pH much, and increases during
storage for 12 days were only 0.17 pH units. Incipient spoilage in the
control samples was manifest after 6 days of storage at 4
C with
corresponding increases in the pH to >6.0. Our results are also in
agreement with Tan and Shelef (2002).Holmer et al. (2009) cited
that higher pH and longer aging periods will result in increased
microbial proliferation and decreased shelf-life. Furthermore, as pH
increased, TVC increased, and these results are similar to those of
Rousset and Renerre (1991) that indicated bacterial counts were 10-
to 100-fold greater on high pH (¼6.20) meat than normal pH
(¼5.55) meat at various aging durations. Changes in Thiobarbituric
acid reactive substances (TBARS) values (mean S. D.) during
storage for 12 days at 4
C have shown in Fig.10. No or little changes
were observed in the refrigerated untreated meat before or at onset
of spoilage (6 days), but values increased on further storage. The
smallest changes during the 12-day storage were seen in
LcEW þCaL treatment, followed by LcEW treatment and the
highest increases in TBARS values were observed consistently
control samples. A similar trend was observed by Tan and Shelef
(2002). However, the acceptable limit of 1e2 mg malonaldehyde/
kg meat was revealed by Witte et al. (1970).
4. Conclusion
The slightly acidic low concentration electrolyzed water is novel
and no studies to that examine the effect of LcEW and its combi-
nation with calcium lactate to decontaminate fresh pork. The
decontamination of fresh pork by LcEW þCaL reduced the surface
microbial counts immediately after the treatment and retarded
microbial growth during storage. The results of the current study
are very promising, although carried out in laboratory condition.
Amongst the treatments, combination treatment showed highest
retardation of growth and multiplication of all inoculated patho-
gens, reduced the total viable counts as well as substantially
increasing the shelf-life of pork meat at refrigeration temperatures
compared with LcEW and SAEW treatment alone. Further works
need to be performed in a commercial slaughter plant to ascertain
the effects of LcEW þCaL. Also it can be elucidated by combining
LcEW with other organic acid salts i.e. sodium and potassium
lactate and applying in various meat and meat products with
different treatment method and time.
Storage time (d)
024681012
Odor scores
0
1
2
3
4
5
Control
LcEW
SAEW
LcEW + CaL
Fig. 8. Odor scores of treated and untreated pork samples. Four point odor scale:
1¼no off odor, 2 ¼slightly off odor, 3 ¼moderately off odor and 4 ¼extremely off
odor.
Stora
g
e time
(
d
)
024681012
pH value
5.4
5.6
5.8
6.0
6.2
6.4
6.6
6.8
Control
LcEW
SAEW
LcEW + CaL
Fig. 9. Changes in pH (mean SD) of treated and untreated pork samples during
storage at refrigeration temperature.
Storage time (d)
024681012
TBARS (mg MA/kg)
0
1
2
3
4
5
6
Control
LcEW
SAEW
LcEW + CaL
Fig. 10. Changes in TBARS (mean S. D.) of treated and untreated pork samples during
storage at refrigeration temperature.
S.M.E. Rahman et al. / Food Control 30 (2013) 176e183182
Author's personal copy
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S.M.E. Rahman et al. / Food Control 30 (2013) 176e183 183
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... However, potatoes washed at 60 • C with US treatment have shown color changes [29]. Other studies have reported that dipping in electrolyzed water for 3 min has the best sanitizing effect [31][32][33]. The present study also showed that washing for 3 min with SAEW + US at 10 times the sample volume at 25 • C was the most effective treatment condition to reduce the population of EPEC in fresh-cut carrot. ...
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