Meat Science 61 (2002) 49–54
www.elsevier.com/locate/meatsci
Raw-meat packaging and storage affect the color and odor of
irradiated broiler breast fillets after cooking
M. Du, S.J. Hur, D.U. Ahn*
Department of Animal Science, Iowa State University, Ames, IA 50011-3150, USA
Received 16 April 2001; received in revised form 18 July 2001; accepted 18 July 2001
Abstract
Raw breast fillets were divided into two groups and either vacuum or aerobically packaged. The fillets in each group were subdivided equally into two groups and then irradiated at 0 or 3 kGy using a Linear Accelerator. After 0, 3 and 7 days of storage at
4 C, fillets were cooked in an 85 C water bath (cook-in-bag) to an internal temperature of 74 C. Oxidation-reduction potential
(ORP) of raw fillets was measured before cooking, and color and sensory characteristics were analyzed after cooking. Irradiation
decreased the ORP of meat, but the potential in aerobically packaged fillets increased during storage. After cooking, color a*-value
of irradiated fillets was higher than that of the non-irradiated. Irradiation of raw meat also changed color L* and b* values after
cooking. Aerobic storage reduced the redness of cooked meat induced by irradiation. Irradiated raw broiler fillets stored for 0 day
and 3 day under aerobic conditions before cooking produced a oxidized chicken-like odor. The odor, however, disappeared after 7
days of storage under aerobic conditions before cooking. For raw broiler samples stored under vacuum conditions, significant
differences in color and odor between irradiated and non-irradiated fillets remained throughout the 7-day storage period after
cooking. Irradiation had only a minor influence on lipid oxidation of raw breast fillets as indicated by low TBARS values. This
study indicates that the effect of irradiation on color and odor of broiler breast fillets after cooking can be reduced significantly
through shelf-display of raw fillets under aerobic conditions. Storage under vacuum conditions before cooking is not effective in
reducing irradiation-induced changes in the color and odor of breast fillet after cooking. # 2002 Elsevier Science Ltd. All rights
reserved.
Keywords: Color; Broiler; Breast fillet; Irradiation; Storage; Odor
1. introduction
Irradiation is effective in controlling pathogeninduced food poisoning (Rajkowski & Thayer, 2000;
Serrano, Murano, Shenoy, & Olson, 1997). However,
ionizing radiation generates free radicals that may
induce lipid peroxidation and other chemical changes
(Branka, Branka, & Dusan, 1992; Wong, Herald, &
Hachmeister, 1995). Irradiation induces changes in
volatile profile and lipid oxidation in meat homogenates, and pork patties and lions (Ahn et al., 1998; Jo,
Jin, & Ahn, 2000). The color of meat was also changed
by irradiation (Millar, Moss, & Stevenson, 2000;
Nanke, Sebranek, & Olson, 1998). Irradiation increased
the color a* value of breast meat, and irradiated meats
appeared redder than the non-irradiated (Millar et al.,
* Corresponding author. Tel.: +1-515-294-6595; fax: +1-515-2949143.
E-mail address: duahn@iastate.edu (D.U. Ahn).
2000). The redness induced by irradiation in cooked
breast meat could easily be misconstrued as undercooked by consumers, and thus, cause quality problems.
Further, irradiation produces characteristic irradiation
odor in meats. Irradiating raw meat could produce offodor, which stayed in meat even after cooking (Heath,
Owens, Tesch, & Hannah, 1990). The color and odor in
cooked irradiated breast fillets are important because
they determine the ultimate consumer acceptance of
irradiated meat. However, few reports about the effect
of packaging and storage of irradiated raw meat on the
color and odor of the meat after cooking have been
published.
Ahn et al. (2000) indicated that the off-odor detected
in irradiated meat was related to sulfur compounds
produced by irradiation process. Millar et al. (2000)
suggested that color changes induced by irradiation
were related to carbon monoxide (CO) production
during irradiation. If this is the case, aerobic display of
irradiated raw meat could be conducive to reducing the
0309-1740/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0309-1740(01)00161-9
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M. Du et al. / Meat Science 61 (2002) 49–54
adverse changes in color and odor after irradiation,
because sulfur compounds and CO can escape during
aerobic display. Therefore, the objective of this study
was to determine the effect of refrigerated storage of
irradiated raw broiler breast fillets on the color and
irradiation odor of the fillets after cooking.
2. Materials and methods
2.1. Sample preparation
Fifty boiler chickens were raised on corn-soybean
meal based diet for 6 weeks, and then slaughtered
according to USDA regulation. Broiler breast fillets
were separated and randomly divided into two groups,
either vacuum or aerobically packaged, and then electron-beam irradiated at 0 or 3.0 kGy using a Linear
Accelerator (Circe IIIR; Thomson CSF Linac, SaintAubin, France). The energy and power level used were
10 MeV and 10 kW, respectively, and the average dose
rate was 88.3 kGy/min. The maximum and minimum
absorbed doses were 3.38 kGy and 2.96 kGy (max/min
ratio was 1.14). To confirm the target dose, two alanine
dosimeters per cart were attached to the top and bottom
surface of a sample. The alanine dosimeter was read
using a 104 Electron Paramagnetic Resonance Instrument (Bruker Instruments Inc., Billerica, MA, USA).
Ten raw breast fillets from each different packaging/
irradiation combination were sampled at 0, 3 and 7 days
of storage at 4 C and cooked in an 85 C water bath to
an internal temperature of 74 C. ORP of samples were
measured before cooking, and aerobically packaged
breast fillets were repackaged in vacuum bags. Color
and odor of fillets were measured after cooking.
2.2. Color measurement
The surface color of breast meat was measured in
package using a Hunter LabScan colorimeter (Hunter
Laboratory, Inc., Reston, VA) and expressed as color
L* (lightness), a* (redness) and b* (yellowness) values.
The surface color of skin side was used for measurement. Same packaging materials were used to cover a
white standard plate to eliminate the influence of
packaging material on meat color. The inside color of
fillets was measured after transversely cutting fillets in
half. The scanning wavelength ranging from 400 to 720 nm
was used for measuring the reflectance of breast fillets.
2.3. Sensory evaluation
Sensory evaluation was conducted at 0, 3, 7 days of
storage for aerobic packaged fillets, and only at 7 days
for vacuum packaged fillets. A triangle test was used to
differentiate the odor of the irradiated and non-irra-
diated broiler breast fillets. Twenty trained sensory
panelists were used for evaluation. Sensory panelists
were trained by smelling the irradiated cooked broiler,
and let them familiarize with irradiation off-odor and
the methodology of triangle test. Panelists were presented with two sets of samples: Each set was composed
of three capped scintillation vials that contain cooked
meat samples. Two of the three vials contained 2 g of
minced non-irradiated cooked breast meat, and the
other vial contained 2 g of irradiated samples. Vials
were labeled with random three-digit numbers and presented to panelists in random sequence. Sensory panelists were asked to remove the cap and sniff the sample,
and then select an odd sample among each set. Two sets
of samples were presented to each panelist at the same
time.
2.4. ORP measurement
The ORP in the center of breast fillets was measured
by using a platinum electrode attached to a pH/ion
meter (Accumet 25, Fisher Scientific, Fair Lawn, NJ).
ORP was recorded 2 min after inserting the electrode
into the center of a breast fillet.
2.5. Statistical analysis
The effects of irradiation and storage on the color,
ORP and TBARS of broiler breast were analyzed statistically by GLM using the SAS1 software (SAS Institute, 1989). Student–Newman–Keuls multiple range test
was used to compare differences among mean values (P
< 0.05). Mean values and S.E.M. were reported.
For the analysis of sensory data, the significance in
odor difference was determined by the total correct
choices by panelists (chose odd, irradiated sample
among the three samples in one set). For triangle tests,
19 correct choices out of 40 total choices were needed
for a significant at P < 0.05 level, and 21 correct choices
out of 40 total choices for significant at P < 0.05 level
(Roessler, Pangborn, Sidel, & Stone, 1978).
3. Results and discussion
3.1. Color values
Table 1 shows the surface color of breast meat after
different durations of storage before cooking. The color
a* value of cooked breast fillets from raw meats irradiated and stored in vacuum was significantly higher
than that from the non-irradiated. For the fillets irradiated and stored in aerobic conditions, however, only
the meat from 0 day storage showed significant difference in color a* value between irradiated and nonirradiated after cooking. This result suggested that the
51
M. Du et al. / Meat Science 61 (2002) 49–54
irradiated and non-irradiated meats stored for 0 day,
and irradiated meat stored for 7 days (Table 1). Nanke
et al., (1999) showed that both color a* and b* values of
irradiated pork, beef and turkey decreased during aerobic storage, but they did not measure the color change
after cooking. Jo et al., (2000) reported that the Hunter
color a* value of irradiated cooked pork sausage
decreased during aerobic storage.
Table 2 shows the Hunter color values of the inside
surface of breast fillets. Without storage before cooking
(0 day), irradiated fillets had higher a* values than nonirradiated samples. But after 3 days or more of aerobic
storage before cooking, the difference in color a* values
became small and was not statistically significant. The
decrease of color a* value after aerobic display could be
caused by the evaporation of carbon monoxide (CO)
because the redness of irradiated meat could be associated with CO production during irradiation (Millar et
al., 2000). The color b* values of cooked meat from
vacuum packaged nonirradiated fillets were higher than
those from irradiated. The difference in color L* value
between aerobically and vacuum packaged was significant only in cooked fillets from nonirradiated raw
fillet stored 0 day.
Fig. 1 showed the reflectance spectra of cooked breast
fillets from the meats stored for 7 days before cooking.
Irradiated fillets in vacuum bags had lower reflectance
values than that of non-irradiated at 500 and 570 nm,
and 400 and 430 nm ranges, which is typical for irradiated meats. However, no typical reflectance spectra of
irradiated meat were found in the irradiated fillets
stored under aerobic conditions for 7 days before cooking. The spectra of aerobically packaged fillets with or
without irradiation were very similar, indicating that the
effect of irradiation on cooked meat color disappeared
color changes induced by irradiation in raw fillets were
maintained in cooked meat only when the meats were
stored in vacuum conditions. There were no significant
changes in color a* values of cooked fillets from raw
meat stored under vacuum for different durations
before cooking. For the cooked fillets from raw meat
stored for 3 and 7 days under aerobic conditions, however, the difference in color a* values between irradiated
and non-irradiated samples disappeared. This result
showed that irradiation and then storage under aerobic
conditions could eliminate the influence of irradiation
on the redness of cooked meat color. Although many
studies report the increase of redness in raw and cooked
meat after irradiation (Du, Ahn, Nam, & Sell, 2000;
Luchsinger et al., 1996; Millar et al., 2000; Nanke, Sebranek, & Olson, 1998, 1999), this is the first report
showing that aerobic display of raw meat before cooking can reduce the redness after cooking. Because consumers would consider the redness in cooked meat as
undercooked, it is important to prevent irradiationinduced redness in cooked meat. Aerobic display of raw
meat for 7 days after irradiation could be a good
method to prevent the redness of irradiated meat after
cooking. There were no difference between irradiated
and non-irradiated samples for color L* and b* values
except for color b* value in vacuum packaged fillet at
day 0 (Table 1). Packaging conditions of non-irradiated
raw breast fillets significantly influenced the color b*
value of cooked fillet after 7 days of storage. The b*
value of cooked breast fillets showed decreasing trends
as the display time before cooking was increased
(Table 1). The color L* values of cooked breast fillets
from raw meats irradiated and stored in vacuum were
lower than those in aerobic conditions. However, the
differences were significant only in cooked fillets from
Table 1
The surface color of cooked broiler breast fillet stored for different period of time before cookinga
Packaging
0 day
0 kGy
Hunter color a* value
Aerobic
Vacuum
S.E.M.
6.16 b
6.93 b
0.28
S.E.M.
3 kGy
6.87 ay
8.46 ax
0.31
3 days
0 kGy
0.34
0.35
5.60 y
7.14 bx
0.27
S.E.M.
3 kGy
5.74 y
8.47 ax
0.31
7 days
0 kGy
0.14
0.38
5.44 y
7.10 bx
0.20
S.E.M.
3 kGy
5.55 y
8.77 ax
0.54
0.23
0.53
Hunter color b* value
Aerobic
Vacuum
S.E.M.
19.15
20.00
0.36
19.23
19.65
0.60
0.50
0.50
17.65
18.72
0.42
17.38
18.56
0.40
0.448
0.373
16.55 y
18.11 x
0.40
17.00
18.57
0.45
0.35
0.49
Hunter color L* value
Aerobic
Vacuum
S.E.M.
85.33 x
82.57 by
0.58
86.11 x
84.77 ay
0.40
0.45
0.55
85.29
83.45
0.66
85.51
83.78
0.58
0.645
0.604
85.61
84.30
0.45
85.62 x
83.19 y
0.66
0.37
0.71
a
a–d Means within a row with no common letter differ significantly (p < 0.05;. n=10). x–y Means within a column with no common letter differ
significantly (P < 0.05;. n=10).
52
M. Du et al. / Meat Science 61 (2002) 49–54
during the 7-day storage of raw breast fillets under
aerobic conditions.
The ORP change after irradiation might also influence irradiation-induced color changes in both aerobically and vacuum packaged raw meat at day 0
(Table 3). Irradiation decreased the ORP of breast fillets. This could be due to the electrons absorbed in
meats during electron beam irradiation. Shahidi, Pegg,
and Shamsuzzaman (1991) suggested that irradiation
decreased the ORP of sodium ascorbate solution, which
agrees with our results. However, the ORP of irradiated
breast fillets quickly increased during storage. After 3
and 7 days of storage, the ORP, especially that of aerobically packaged fillets, was significantly higher than
that of non-irradiated fillets. The reason for the accelerated ORP changes in irradiated fillets is not clear, but
could be related to the membrane damages induced by
irradiation, which could have increased oxygen permeability through the membranes. Compared with breast
fillets under aerobic storage before cooking, small
changes in ORP were observed with vacuum packaged
samples. For vacuum packaged fillets, the irradiated
samples maintained lower ORP than non-irradiated
samples throughout the storage periods although the
difference was significant only at day 0. Low ORP may
reduce metmyoglobin to myoglobin and keep irons in
reduced form, and thus, increase the stability of redness
Fig 1. The reflectance spectra of the inside of cooked breast fillets
after 7 days of storage before cooking.
Table 2
The inside color of cooked broiler breast fillet aerobically displayed for different period of time before cookinga
Package
0 day
S.E.M.
0 kGy
Hunter color a* value
Aerobic
Vacuum
S.E.M.
3 kGy
7.19 by
8.61 bx
0.27
3 days
0 kGy
9.15 a
9.80 a
0.31
0.33
0.25
6.34 y
7.20 bx
0.23
S.E.M.
3 kGy
7.08 y
9.01 ax
0.37
7 days
0 kGy
0.27
0.34
6.07 y
7.27 bx
0.32
S.E.M.
3 kGy
6.77 y
9.79 ax
0.37
0.36
0.33
Hunter color b* value
Aerobic
Vacuum
S.E.M.
19.06
18.79 a
0.28
18.03
17.51 b
0.32
0.36
0.23
18.15 a
18.06 a
0.30
16.47 b
16.27 b
0.28
0.28
0.30
17.36
18.62 a
0.57
17.96
17.70 b
0.33
0.61
0.25
Hunter color L* value
Aerobic
Vacuum
S.E.M.
88.56 x
86.82 y
0.37
87.12
87.46
0.66
0.57
0.50
84.76
86.19 a
0.54
84.62
84.23 b
0.65
0.72
0.45
77.79
82.55
2.50
82.63
82.69
0.53
2.51
0.46
a
a–d Means within a row with no common letter differ significantly (P < 0.05;. n=10). x–y Means within a column with no common letter differ
significantly (P < 0.05;. n=10.)
Table 3
The oxidation-reduction potential (ORP) of raw broiler breast fillets after different duration of storagea
Package
0 day
0 kGy
ORP (mV)
Aerobic
Vacuum
S.E.M.
a
200
212 b
16.4
S.E.M.
3 kGy
274 x
367 ay
30.8
3 days
0 kGy
29.3
18.9
1 bx
93 y
19.3
S.E.M.
3 kGy
27 ax
124 y
5.4
7 days
0 kGy
6.3
19
26b x
114 y
10.1
S.E.M.
3 kGy
66 ax
138 y
3.5
5.7
9.0
a–d Means within a column with no common letter differ significantly (P < 0.05; n=20). x–y Means within a row with no common superscript
differ significantly (P < 0.05; n=20).
M. Du et al. / Meat Science 61 (2002) 49–54
in meat fillets. If this is the case, the rapid increase in
ORP for irradiated fillets during aerobic display before
cooking should be associated with the decrease of
redness after cooking.
For the fillets stored under vacuum conditions before
cooking, a significant difference in odor between the
irradiated and non-irradiated was observed even after 7
days of storage (Table 4). For the fillets aerobically
stored before cooking, however, the difference in odor
decreased as storage time increased (Table 4). After 7
days of aerobic display, the difference in odor between
irradiated and non-irradiated fillets was not significant,
as indicated by low number of correct choices of sensory
panelists. This result indicated that 7 days of aerobic
display before irradiation can largely remove the effect
of irradiation on the odor of cooked breast fillets.
Hashim, Resurreccion, and McWatters (1995) evaluated
the sensory characteristics of irradiated refrigerated and
frozen chicken and found that irradiated raw chicken
had higher fresh chickeny, bloody and sweet aromatic
aroma intensities than nonirradiated samples. Cooked
chicken had more chickeny flavor than raw meat, and
no other sensory attributes of cooked chicken meat were
affected by irradiation (Hashim et al., 1995). Heath et
al. (1990) reported that irradiating raw chicken at high
dose produced an irradiated odor, which remained after
cooking, but not for breast meat. Hanis et al. (1989),
however, reported that heat treatment removed irradiation odor. The reason for failing to detect irradiation
odor after cooking could be due to the low sensitivity of
their sensory evaluation method. In our study, it was
clearly shown that irradiation odor was kept in breast
meat after cooking, except for samples that had been
stored for 7 days under aerobic condition before cooking
(Table 4).
Aerobic display of irradiated breast fillets may
increase lipid oxidation. Therefore, the TBARS values
of cooked breast fillets from the raw meat displayed
aerobically for 7 days were analyzed. The TBARS
values of aerobically packaged samples after cooking
were only 0.64 0.14 for irradiated, and 0.54 0.11 for
non-irradiated samples. As for vacuum packaged samples, the TBARS values were only 0.49 0.06 for
Table 4
Triangle test for the irradiation odor of cooked broiler breast fillets
after different periods of storage before cooking
Storage time
0 day
3 day
7 day
No.of correct pick
Aerobic packaging
Vacuum packaging
32a
–c
24b
–
17
30a
a
Means significant difference at 0.01 (minimum correct picks for a
significant level at 0.01 are 21 among 40 panelists)
b
Means significant difference at 0.05 (minimum correct picks for a
significant level at 0.05 are 19 among 40 panelists)
c
Sensory evaluation was not conducted.
53
irradiated and 0.41 0.04 for non-irradiated samples.
As indicated by TBARS analysis, there was no big jump
of lipid oxidation even in irradiated raw meat after 7
days of aerobic storage. Thus, aerobic storage of irradiated chicken breast fillets before cooking could be a
good method to reduce irradiation-induced odor and
color changes.
4. Conclusion
Our results show that the changes in color and odor
induced by irradiation in vacuum packaged raw broiler
fillets was maintained after cooking. Breast meat fillets
cooked shortly after irradiation were redder in color
and produced more chickeny flavor than non-irradiated
meat. Aerobic storage of irradiated broiler breast fillets
before cooking reduced the redness and irradiation odor
of breast meat after cooking. Thus, this study suggests
that aerobic display of irradiation raw meat could be
employed as a method to prevent irradiation-induced
color and odor changes in broiler breast fillets after
cooking.
Acknowledgements
Journal paper number J- 19285 of the Iowa Agriculture and Home Economics Experiment Station,
Ames, IA 50011-3150. Project No. 6504, and supported
by the Hatch Act and S-292 Regional Project.
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