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Radiation Physics and Chemistry 81 (2012) 1107–1110
Contents lists available at SciVerse ScienceDirect
Radiation Physics and Chemistry
journal homepage: www.elsevier.com/locate/radphyschem
Effect of high-dose irradiation on quality characteristics of ready-to-eat
chicken breast
Hyejeong Yun a, Kyung Haeng Lee b, Hyun Jung Lee a, Ju Woon Lee c, Dong Uk Ahn d, Cheorun Jo a,n
a
Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 305-764, South Korea
Department of Food Science and Nutrition, Chungju National University, Jeungpyung 368-701, South Korea
c
Radiation Food Science and Biotechnology, Korea Atomic Energy Research Institute, Jeoungeup 580-785, South Korea
d
Department of Animal Science, Iowa State University, Ames, IA 50011-3150, USA
b
a r t i c l e i n f o
abstract
Article history:
Received 2 June 2011
Accepted 30 October 2011
Available online 7 November 2011
High-dose (higher than 30 kGy) irradiation has been used to sterilize specific-purposed foods for safe
and long-term storage. The objective of this study was to investigate the effect of high-dose irradiation
on the quality characteristics of ready-to-eat chicken breast in comparison with those of the low-dose
irradiation. Ready-to-eat chicken breast was manufactured, vacuum-packaged, and irradiated at 0, 5,
and 40 kGy. The populations of total aerobic bacteria were 4.75 and 2.26 Log CFU/g in the samples
irradiated at 0 and 5 kGy, respectively. However, no viable cells were detected in the samples irradiated
at 40 kGy. On day 10, bacteria were not detected in the samples irradiated at 40 kGy but the number of
bacteria in the samples irradiated at 5 kGy was increased. The pH at day 0 was higher in the samples
irradiated at 40 kGy than those at 0 and 5 kGy. The 2-thiobarbituric acid reactive substance (TBARS)
values of the samples were not significantly different on day 0. However, on day 10, the TBARS value
was significantly higher in the samples irradiated at 40 kGy than those at 0 and 5 kGy. There was no
difference in the sensory scores of the samples, except for off-flavor, which was stronger in samples
irradiated at 5 and 40 kGy than control. However, no difference in off-flavor between the irradiated
ones was observed. After 10 days of storage, only the samples irradiated at 40 kGy showed higher offflavor score. SPME-GC–MS analysis revealed that 5 kGy of irradiation produced 2-methylbutanal and
3-methylbutanal, which were not present in the control, whereas 40 kGy of irradiation produced
hexane, heptane, pentanal, dimethly disulfide, heptanal, and nonanal, which were not detected in the
control or the samples irradiated at 5 kGy. However, the amount of compounds such as allyl sulfide and
diallyl disulfide decreased significantly in the samples irradiated at 5 kGy and 40 kGy.
& 2011 Elsevier Ltd. All rights reserved.
Keywords:
High-dose irradiation
Ready-to-eat chicken
Volatile compound
Quality
1. Introduction
Irradiation technology is well known to be the most effective
method for sterilization of food products. Recently, research has
focused on using irradiation technology for the development of
specific-purposed food products, including space, military, elderly,
and immuno-compromised patient foods. The food products in this
category should be safe to consume even after a long storage period
(Bourland, 2008). When developing space foods, approximately
40–50 kGy of high-dose irradiation is applied to ensure sterilization
of radiation-resistant bacteria and fungi (Bourland, 2008; NASA,
2003). However, high-dose irradiation, especially higher than
10 kGy, can lead to physicochemical changes and significantly
deteriorate sensory properties of foods, including taste, flavor, texture,
and color (Kim et al., 2006). To prevent or minimize quality changes
in food products after high-dose irradiation, the combination of
ascorbic acid, calcium salt, color agent from paprika, and an advanced
packaging method has been introduced (Lacroix and Ouattata, 2004)
but not implemented well.
Ready-to-eat chicken breast products are popular poultry meat
dishes worldwide. However, the hygienic quality and safety of
these products during distribution and storage is not well established due to potential contamination of pathogens or spoilage
bacteria from fresh vegetables, soy sauce, and raw chicken breast.
In this study, low- and high-dose irradiation (5 and 40 kGy) of
ready-to-eat chicken breast was performed, and the physicochemical, microbiological, and sensory quality characteristics
were compared after storage for 10 day at 4 1C.
2. Materials and methods
2.1. Sample preparation
n
Corresponding author. Tel.: þ82 42 821 5774; fax: þ 82 42 825 9754.
E-mail address: cheorun@cnu.ac.kr (C. Jo).
0969-806X/$ - see front matter & 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.radphyschem.2011.10.024
Chicken breast (Orpum Co. Ltd., Sangju, Korea) and ingredients
were purchased from a local market. The amount of ingredients
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H. Yun et al. / Radiation Physics and Chemistry 81 (2012) 1107–1110
per 1 kg of chicken breast used were hot pepper paste (75 g), red
pepper powder (75 g), soy sauce (100 g), sugar (75 g), garlic
(50 g), fresh onion (750 g), and black pepper (2.5 g). All ingredients were mixed with the chicken breast, heated on a preheated
pan (approximately 170 1C) for 20 min, and cooled for 1 h at
ambient temperature. Approximately 100 g of the sample was
vacuum-packaged in a polyethylene/nylon bag (2 ml O2/m2/24 h
at 0 1C, Kuk Young Export Packaging Co., Daejeon, Korea) and
irradiated at 5 and 40 kGy using a gamma irradiator (Advanced
Radiation Technology Institute, Jeongeup, Korea). Non-irradiated
samples were also prepared as a control. Irradiated and nonirradiated control samples were then stored at 4 1C for 10 day.
2.2. Microbiological, chemical, and sensory analyses
The experiment was performed in triplicate. Media for the
enumeration of total aerobic bacteria was tryptic soy agar (Difco
Laboratories, Sparks, MD, USA). For pH, the homogenized samples
were measured using a pH meter (Orion520A; Orion Research
Inc., Boston, MA, USA). The development of lipid oxidation was
measured as 2-thiobarbituric acid reactive substance (TBARS)
value using the method described by Jung et al. (2010). Measurements of volatile basic nitrogen were performed according to
Kruk et al. (2011). Volatile compounds were measured by solidphase microextraction (SPME) gas chromatograph/mass spectrometry (GC/MS) according to Sohn et al. (2009). Sensory evaluation
of irradiated samples for color, odor, taste, texture, and overall
acceptance was performed on a 9 point hedonic scale using 15
untrained panelists. The sensory session was carried out 2 times
per day.
2.3. Statistical analysis
The data were collected and analyzed by SAS software (version
8.02; SAS Institute, Cary, NC, USA). Mean values and standard
errors of the mean (SEM) were reported, and the significance was
defined at Pr0.05. Differences among mean values were analyzed by Student–Newman–Keul’s multiple range test.
3. Results and discussion
After manufacturing the ready-to-eat chicken breast, the
initial number of contaminated microorganisms was 4.75 log
CFU/g, but 2 log reduction was achieved by irradiation at 5 kGy
(Table 1). When the samples were exposed to 40 kGy of irradiation, no viable cells were observed. On day 10, non-irradiated
control showed similar levels of microorganisms as day 0. On the
other hand, the samples irradiated at 5 kGy showed increase in
the number of microorganisms over the 10-day storage, but still
1 log lower than that of the control. The samples irradiated at
40 kGy showed no viable cells even after 10 day at 4 1C. From the
results, it can be assumed that specific-purposed foods should be
irradiated at a high-dose (40 kGy) due to the observed microbial
growth in the samples irradiated at 5 kGy.
The pH of the control samples (5.73) were not different from
those irradiated at 5 kGy but was statistically different from that
irradiated at 40 kGy (5.83). No difference was found in the pH of
the chicken breast after storage, which is in agreement with a
study by Lee and Kim (2004). Generally, the pH of meat increases
as the level of oxidation increases (Holly et al., 1994). When
irradiation passes through matters such as solutions or foods,
energy is absorbed, leading to ionization or excitation of atoms
and molecules and ultimately induce chemical changes (Stewart,
2001). The pH of an aqueous system can affect the end result of
irradiation. Acidic medium (excess H þ ) favors the disappearance
of aqueous electrons (eaq
), whereas alkaline medium favors their
formation (Brewer, 2004).
The analysis of TBARS values was carried out to assess lipid
oxidation development of the samples. On day 0, there was no
significant difference found among the treatments (Table 1).
However, irradiation at 40 kGy showed a significantly higher
TBARS value than other treatments after 10 day of storage.
The content of volatile basic nitrogen (VBN) ranged between
20.16 and 22.59 mg%, and the samples irradiated at 40 kGy were
higher than those at 0 and 5 kGy (Table 1), regardless of storage
time. Generally, VBN is used to measure freshness of meat-based
foods (less than 20 mg% in packed meats), and high protein foods
with high contamination by microorganisms have high VBN
values (Davies and Board, 1998). The higher VBN value of the
high-dose-irradiated samples was not due to contamination by
microorganisms but instead by chemical radiolysis of meat
protein molecules to small N-containing molecules.
The volatile compounds produced from ready-to-eat chicken
breast were identified by SPME–GC/MS immediately after irradiation at 5 and 40 kGy (Table 2). Irradiation increased the production of volatile compounds, including hexane, heptane, propanal,
2-methyl-butanal, 3-methyl-butanal, benzene, ally methyl sulfide, pentanal, toluene, dimethyl disulfide, hexanal, heptanal,
nonanal, benzaldehyde, and total volatiles, compared to that of
the control. After 10 day of storage, the amounts of hexane,
heptane, propanal, 2-methyl-butanal, 3-methyl-butanal, benzene,
ally methyl sulfide, pentanal, toluene, dimethyl disulfide, and
hexanal increased by approximately 2–5 fold. In contrast, the
amounts of heptanal and nonanal decreased or not detected in the
control and irradiated samples on day 10. Generally, irradiation
produced characteristic volatile compounds in meats such as
1-pentene, 1-hexene, 1-heptene, and dimethyl disulfide, which
Table 1
Effect of low- and high-dose irradiation on total aerobic bacteria, pH, TBARS, and volatile basic nitrogen of ready-to-eat chicken breast stored at 4 1C for 10 day.
Irradiation dose (kGy)
0
5
40
SEM
Total aerobic bacteria (log CFU/g)
pH
Storage day
Storage day
SEM
0
10
4.75x
2.26yb
ND1z
0.083
4.74x
3.30ya
NDz
0.1025
0.036
1.157
-
0
10
5.73y
5.73y
5.83x
0.25
5.79
5.79
5.82
0.019
SEM
0.025
0.024
0.018
Values with different letters (a–b) within the same row differ significantly (Po 0.05).
Values with different letters (x–z) within the same column differ significantly (P o0.05).
1
ND: Viable cell was not detected with detection limit at o 101.
TBARS (mg/g of malondialdehyde)
Volatile basic nitrogen (mg%)
Storage day
Storage day
SEM
0
10
2.70
2.61
2.85b
0.105
2.57y
2.58y
3.67ax
0.129
0.695
0.094
0.162
SEM
0
10
20.16y
20.35y
22.59x
0.305
18.67y
20.35y
22.40x
0.517
0.619
0.187
0.349
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H. Yun et al. / Radiation Physics and Chemistry 81 (2012) 1107–1110
1109
Table 2
Major volatile compounds (area count 104) produced from irradiated ready-to-eat chicken breast.
Compound name
Storage (day)
0
10
0 kGy
5 kGy
40 kGy
SEM1
0 kGy
5 kGy
40 kGy
SEM
Hexane
Heptane
Carbon disulfide
Propanal
1-Propanethiol
Thietane
2-methyl-Butanal
3-methyl-Butanal
Benzene
Allyl Methyl Sulfide
Pentanal
Toluene
Dimethyl disulfide
Hexanal
n-Propyl trans-1-propenyl sulfide
Allyl sulfide
Heptanal
Nonanal
Allyl propyl disulfide
Diallyl disulfide
Benzaldehyde
0.00b
0.00b
450.66a
87.60ay
345.77ay
1806.47ay
0.00cy
0.00by
0.00b
102.81by
0.00b
102.81by
0.00b
9.92b
48.01ay
337.60ay
0.00b
0.00b
103.21ay
263.41ay
3.93c
0.00b
0.00by
322.93by
99.37by
213.04by
740.97by
24.5by
27.31by
0.00b
203.83ay
0.00b
175.01b
0.00b
46.59by
55.23ay
358.60ay
0.00b
0.00b
90.56by
196.73by
18.77b
36.39ay
33.04ay
133.18cy
128.72ay
23.54c
58.53cy
78.92ay
89.69ay
24.29ay
209.70a
22.95ay
317.57ay
30.10a
290.85ay
18.36by
87.40by
29.82ax
74.59ax
40.62cy
108.91cy
100.02ay
1.835
1.079
12.933
2.185
8.375
91.516
0.819
1.921
0.642
10.571
0.575
24.114
1.649
12.119
3.009
16.941
1.11
2.773
3.513
13.332
2.695
0.00b
0.00b
497.73a
144.40cx
525.53ax
2360.96ax
24.56cx
40.95cx
0.00b
201.65bx
0.00b
259.56bx
0.00b
67.93c
120.57bx
569.24bx
0
0
220.33ax
438.43ax
15.86b
0.00b
15.38bx
452.48ax
195.62bx
300.41bx
996.66bx
43.71bx
58.46bx
0.00b
431.45ax
0.00b
289.60b
0.00b
140.91bx
156.65ax
765.91ax
0
0
183.25bx
324.03bx
22.51b
105.91ax
151.08ax
285.90bx
320.40ax
0.00c
88.78cx
146.99ax
149.38ax
68.27ax
194.12b
58.45ax
655.02ax
33.55a
744.72ax
88.99bx
229.09cx
0y
0y
107.80cx
196.10cx
186.78ax
5.817
7.348
20.953
5.056
9.616
23.215
1.597
1.828
0.991
12.362
6.644
32.992
0.722
16.057
9.707
29.287
0
0
9.16
10.518
9.733
Total
3662.20ay
2573.44by
1937.19cy
5487.70ax
4377.03bx
3811.33cx
Values with different letters (a–b) within the same day differ significantly (Po 0.05).
Values with different letters (x–y) within the same irradiation dose differ significantly (Po 0.05).
1
Standard errors of the mean (n¼ 15).
Table 3
Sensory evaluation of the ready-to-eat chicken breast after low- and high-dose
irradiation.
Storage (day)
Sensory parameter1
Irradiation dose (kGy)
0
5
40
SEM1
0
Color
Odor
Taste
Off-flavor
Texture
Acceptability
5.6
5.1
5.5
4.1b
5.4
5.5
6.4
3.7
4.9
5.4a
4.8
5.0
5.4
3.7
4.6
5.3a
5.5
4.9
0.427
0.468
0.503
0.510
0.357
0.477
10
Color
Odor
Taste
Off-flavor
Texture
Acceptability
5.0
4.7
4.6
4.5b
4.9
4.5
5.9
4.6
4.3
4.4b
4.8
4.8
5.6
3.1
3.3
6.6a
4.8
3.6
0.340
0.562
0.442
0.601
0.355
0.406
both doses than that of the control (Table 3). After 10 day, the
flavor difference between the control and the samples irradiated
at 5 kGy disappeared, but the samples irradiated at 40 kGy had
significantly higher off-odor than control and 5 kGy irradiated
ones. Based on the results, it can be assumed that high-dose
irradiation of ready-to-eat chicken breast may have impaired
sensory quality. However, other sensory parameters, including
overall acceptance, were not significantly different. This may have
been due to masking flavors derived from different ingredients
that were added during the manufacturing process. Nevertheless,
some protective measures against off-odor production by
the samples treated with high-dose irradiation are necessary.
Sohn et al. (2009) reported that the combination of a-tocopherol
and charcoal pack reduced the off-odor intensity in ground beef
irradiated at 10 kGy during storage at 4 1C for 7 day.
Acknowledgment
Values with different letters (a–b) within the same row differ significantly
(Po 0.05).
1
Standard errors of the mean (n¼ 30).
are found only in irradiated raw meat (Ahn et al., 2000). These
volatile compounds of irradiated meat are associated with lipid
oxidation products and/or radiolytic degradation of lipids, amino
acids, and proteins (Jo and Ahn, 1999). However, the majority of
the compounds formed by irradiation disappeared or were
reduced to very low levels during 5 day of storage under aerobic
conditions.
Sensory evaluation revealed that there were no differences in
all the sensory parameters determined by irradiation dose or
storage time, except for off-flavor (Table 3). On day 0, the
intensity of off-flavor was higher in the irradiated samples at
This work was supported by a grant from the Next-Generation
BioGreen 21 Program (no. PJ0081330), Rural Development
Administration, Republic of Korea.
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