PROCESSING AND PRODUCTS
Double-Packaging Is Effective in Reducing Lipid Oxidation
and Off-Odor Volatiles of Irradiated Raw Turkey Meat1
K. C. Nam and D. U. Ahn2
Department of Animal Science, Iowa State University, Ames, Iowa 50011-3150
ABSTRACT The effects of double packaging on lipid
oxidation, color, and volatile production were determined
to establish a modified packaging method to improve
quality changes in irradiated raw turkey meat. Sliced raw
turkey breast and thigh meats were aerobically, vacuumor double (vacuum and aerobic)-packaged, electron beam
irradiated at 2.5 kGy, and then stored under refrigerated
temperature. For the double-packaged samples, the outer
vacuum bags were removed after 5, 7, or 9 d of refrigerated storage. 2-Thiobarbituric acid-reactive substances
(TBARS) values, volatile compounds, and color values of
the samples were determined after 10 d of storage.
Irradiation and aerobic packaging promoted production of aldehydes (propanal and hexanal) related to lipid
oxidation in turkey breast and thigh meats. Vacuumpackaged irradiated samples retained S-volatile com-
pounds (methanethiol, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide), mainly responsible for the
irradiation off-odor, during storage. Exposure of doublepackaged irradiated turkey meats to aerobic conditions
by removing outer vacuum bags a few days before the
test was effective in controlling both lipid oxidation-dependent (aldehydes) and radiolytic off-odor (S-compounds) volatiles. The a* values of raw turkey breast
and thigh meats increased by irradiation regardless of
packaging conditions. The a* value of double-packaged
meats was lower than that of the vacuum-packaged meats
but was not significant. Thus, the use of double-packaging
alone was not enough to reduce the pink color of irradiated raw turkey meat. When lipid oxidation and irradiation off-odor should be minimized without any additional
additives, however, double packaging is an excellent
method to be used for turkey meats.
(Key words: double packaging, irradiation, lipid oxidation, off-odor, turkey meat)
2003 Poultry Science 82:1468–1474
INTRODUCTION
Irradiation is a feasible method for controlling pathogenic and putrefying microorganisms in raw meat. The
quality changes in irradiated meat, however, are a concern for the meat industry and the consumer. Previous
reports indicate that irradiation increases lipid oxidation
in aerobically packaged meat, and several off-odor volatile compounds are newly generated or increased in meat
after irradiation (Patterson and Stevenson, 1995; Ahn et
al., 2001). Ahn et al. (2000b) suggested that volatile compounds responsible for off-odor in irradiated meat are
produced by the radiolysis of protein and lipid molecules
and are distinctively different from those of lipid oxidation.
The color of meat is one of the most important quality
parameters that determines consumer acceptance of meat.
2003 Poultry Science Association, Inc.
Received for publication February 11, 2002.
Accepted for publication December 18, 2002.
1
Journal Paper No. J-19732 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project No. 3706, and supported by State of Iowa funds.
2
To whom correspondence should be addressed: duahn@iastate.edu.
Reports show that turkey breast meat becomes pink after
irradiation (Millar et al., 1995; Nam and Ahn, 2002). The
increased pink color in irradiated raw turkey breast is
more intense and stable under vacuum than aerobic conditions (Luchsinger et al., 1996; Nam and Ahn, 2002).
Although irradiated meat can be microbiologically safer
than nonirradiated meat, consumers will not buy irradiated meat unless its quality, including color and odor,
is acceptable.
The color and odor changes in meat by irradiation are
highly dependent upon packaging conditions. Lipid oxidation is a significant problem in irradiated meat when
it is stored aerobically, because oxygen is essential for
lipid oxidation and plays an important role in determining the secondary reactions of free radicals with meat
components (Merritt et al., 1975; Katusin-Razem et al.,
1992). Off-odor, however, is more problematic in vacuumpackaged meats (Ahn et al., 2000a), because sulfur com-
Abbreviation Key: a* = redness; b* = yellowness; L* = lightness; MDA
= malonedialdehyde; TBARS = 2-thiobarbituric acid reactive substances;
TBA = thiobarbituric acid; TCA = trichloroacetic acid; V5-A5 = vacuum
packaged for 5 d then aerobically packaged for 5 d; V7-A3 = vacuum
packaged for 7 d then aerobically packaged for 3 d; V9-A1 = vacuum
packaged for 9 d then aerobically packaged for 1 d.
1468
DOUBLE PACKAGING AND IRRADIATED TURKEY MEAT QUALITY
pounds, the main volatiles responsible for off-odor in
irradiated meat, are highly volatile and easily evaporate
under aerobic conditions during storage. However, sulfur
compounds stay in meat during storage under vacuum
conditions (Ahn et al., 2001).
Modifying packaging conditions may minimize the
quality deterioration of irradiated meat. An appropriate
combination of aerobic- and vacuum-packaging conditions can be effective in minimizing lipid oxidation and
off-odor volatiles in irradiated turkey breast during storage. It may also be effective in reducing pink color in
irradiated meat. The term double packaging was used in
this study to describe a packaging method in which meat
pieces were first individually packaged in oxygen-permeable bags and then a few of them were vacuum packaged
in a larger vacuum bag. After a certain period of storage,
the outer vacuum bag was removed, and the meat was
stored until the last day of storage. The concept of double
packaging was developed as an attempt to minimize odor
and color problems in irradiated raw meat without adding any additives. Current Food and Drug Administration—USDA regulations allow no additives added to
meat before irradiation. When a new petition is approved,
however, this double-packaging concept can be used in
combination with other additives such as antioxidants in
raw and ready-to-eat cooked meat products.
The objective of this study was to determine the effectiveness of double-packaging conditions on lipid oxidation, volatiles, and color of irradiated turkey breast and
thigh meat during refrigerated storage.
MATERIALS AND METHODS
Sample Preparation and Irradiation
Large White turkeys (n = 32; 16 wk old) were slaughtered, then carcasses were chilled in ice water for 3 h and
drained in a cold room. Breast and leg muscles were
deboned from the carcasses 24 h after slaughter. Skin and
visible fat were removed. Breast or thigh muscles from
eight birds were pooled and used as a replication. The
muscles were sliced into 2 cm thick steaks and individually packaged in oxygen-permeable bags3 (polyethylene,
4 × 6, 2 mil) or oxygen-impermeable vacuum bags4 (nylonpolyethylene, 9.3 mL O2/m2 per 24 h at 0°C). The meat
samples were irradiated at 2.5 kGy using a linear accelerator5 with 10 MeV of energy, 10 kW of power level, and 88.1
kGy/min of average dose rate. Nonirradiated vacuumpackaged samples were used as a control. Alanine dosimeters were attached to the top and bottom surfaces of a
sample and were read using a 104 Electron Paramagnetic
Resonance Instrument6 to check the absorbed dose. For
3
Associated Bag Company, Milwaukee, WI.
Koch, Kansas City, MO.
5
Circe IIIR; Thomson CSF Linac, Saint-Aubin, France.
6
Bruker Instruments, Inc., Billerica, MA.
7
Brinkman Instrument, Inc., Westbury, NY.
8
Hunter Associated Labs, Inc., Reston, VA.
9
Takmar-Dohrmann, Cincinnati, OH.
10
Hewlett-Packard Co., Wilmington, DE.
4
1469
the double-packaged samples, the outer vacuum (V) bags
were removed after 5 d (V5-A5), 7 d (V7-A3), or 9 d (V9A1) of refrigerated storage in a cold room (4°C). Lipid
oxidation, color, and volatile compounds of the samples
were determined after 0 and 10 d of storage.
Analysis of 2-Thiobarbituric Acid
Reactive Substances Values
Lipid oxidation was determined by 2-thiobarbituric
acid-reactive substances (TBARS) method (Ahn et al.,
1998). Minced sample (5 g) was placed in a 50-mL test
tube and homogenized with 15 mL of deionized, distilled
water using a Brinkman Polytron Type PT 10/357 for
15 s at high speed. The meat homogenate (1 mL) was
transferred to a disposable test tube (13 × 100 mm), and
butylated hydroxytoluene (7.2%, 50 µL) and thiobarbituric acid (TBA)-trichloroacetic acid (TCA) [20 mM TBA
and 15% (wt/vol) TCA] solution (2 mL) were added. The
mixture was vortexed and then incubated in a 90°C water
bath for 15 min to develop color. After being cooled for
10 min in cold water, the samples were vortexed and
centrifuged at 3,000 × g for 15 min at 5°C. The absorbance
of the resulting upper layer was read at 531 nm against
a blank prepared with 1 mL deionized, distilled water
and 2 mL TBA-TCA solution. The amounts of TBARS
were expressed as milligrams of malonedialdehyde
(MDA) per kilogram of meat.
Color Measurement
The CIE color values were measured on the sample
surface using a LabScan color meter8 that had been calibrated against black and white reference tiles covered
with the same packaging materials as used for samples.
The CIE lightness (L*), redness (a*), and yellowness (b*)
values were obtained using an illuminant A (light source).
An average value from both top and bottom locations on
a sample surface was used for statistical analysis.
Analysis of Volatile Compounds
A purge-and-trap apparatus9 (Precept II and Purge &
Trap Concentrator 3000) connected to a gas chromatograph-mass spectrometer10 was used to analyze volatiles
produced in samples (Ahn et al., 2001). Minced sample
(3 g) was placed in a 40-mL sample vial, and the vials
were then flushed with helium gas (40 psi) for 5 s. The
maximum holding time of a sample in a refrigerated (4°C)
loading tray was less than 4 h to minimize oxidative
changes during the waiting period before starting the
analysis (Ahn et al., 1999). The meat sample was purged
with helium gas (40 mL/min) for 11 min at 40°C. Volatiles
were trapped using a Tenax-charcoal-silica column9 and
desorbed for 2 min at 220°C, focused in a cryofocusing
module (−90°C), and then thermally desorbed into a column for 30 s at 220°C.
An HP-624 column (7.5 m, 0.25 mm i.d., 1.4 µm nominal), an HP-1 column10 (52.5 m, 0.25 mm i.d., 0.25 µm
1470
NAM AND AHN
nominal), and an HP-Wax column (7.5 m, 0.250 mm i.d.,
0.25 µm nominal) were connected using zero dead-volume column connectors11 and used for volatile analysis.
Ramped oven temperature was used to improve volatile
separation. The initial oven temperature of 0°C was held
for 2.50 min. After that, the oven temperature was increased to 15°C at 2.5°C per min, increased to 45°C at
5°C per min, increased to 110°C at 20°C per min, and
then increased to 200°C at 10°C per min and was held for
5.25 min at that temperature. Constant column pressure at
20.5 psi was maintained. The ionization potential of the
mass selective detector10 (Model 5973) was 70 eV, and
the scan range was 18.1 to 350 m/z. Identification of
volatiles was achieved by comparing mass spectral data
of samples with those of the Wiley Library.10 Standards,
when available, were used to confirm the identification
by the mass selective detector. The area of each peak was
integrated using ChemStation software,10 and the total
peak area (pA × s × 104) was reported as an indicator of
volatiles generated from the meat samples.
Statistical Analysis
A completely randomized design was used to determine the effects of double packaging on color, lipid oxidation, and volatile profiles of the irradiated samples during storage.
Data were analyzed by the procedure of generalized
linear model using SAS software (SAS Institute, 1995):
Student-Newman-Keul’s multiple-range test was used to
compare the mean values of treatments. Means and standard error of the means (SEM) are reported (P < 0.05).
RESULTS AND DISCUSSION
Lipid Oxidation
Irradiation promoted lipid oxidation of turkey meat,
but the increased lipid oxidation was problematic only
when the irradiated meat was aerobically packaged and
stored (Table 1). The differences in TBARS between aerobically and vacuum- or double-packaged turkey breast
meat were minimal at d 0, but the TBARS of aerobically
packaged turkey breast meat became significantly higher
than those of vacuum-packaged meat after 10 d of storage.
The TBARS of double-packaged meat was between the
aerobically packaged and vacuum-packaged meats and
showed an increasing trend as the exposure time to aerobic conditions increased.
Irradiated turkey thigh meat showed a greater degree
of lipid oxidation than breast meat (Table 1). The TBARS
of aerobically packaged irradiated turkey thigh meat were
about four times higher than those of the breast meat.
According to our experience with sensory tests, a considerable proportion of consumers could detect rancid offodor when the TBARS value is 1 mg MDA/kg meat or
11
J&W Scientific, Folsom, CA.
higher. When irradiated turkey thigh meat was aerobically packaged and stored for 10 d, lipid oxidation was
a problem. Vacuum-packaged thigh meat was within the
critical limit (< 1.0 mg MDA/kg meat). If lipid oxidation
is the major quality concern, vacuum or V9-A1 double
packaging (9 d vacuum packaging and then 1 d aerobic
packaging) is desirable for the refrigerated storage of irradiated turkey breast and thigh meats.
Color Changes
Raw turkey breast meat was more pink after irradiation
(Table 2). The a* values of raw turkey breast meat increased significantly after irradiation irrespective of packaging types. Nam and Ahn (2002) reported that the turkey
breast meat color becomes more pink due to formation
of carbon monoxide-myoglobin and that pink color indicates a defect if it persists after cooking. The pink color
generated by irradiation was more stable under vacuum
than under aerobic conditions (Lynch et al., 1991; Nam
and Ahn, 2002). Although the a* values of irradiated turkey breast meats decreased under all packaging conditions during the storage, the vacuum-packaged meat had
higher a* values than aerobically packaged meat after 10
d of storage. The a* values of double-packaged meats
were lower than those of the vacuum-packaged meats,
but the differences were not significant. Therefore, the
use of double packaging alone was not enough to reduce
the pink color of irradiated turkey meat to the level of
nonirradiated meat. The L* values of turkey breast decreased after irradiation but gradually increased during
storage regardless of packaging conditions. The b* value
of aerobically packaged turkey breast increased after irradiation and then remained high during storage.
The redness of raw turkey thigh meat also increased
significantly after irradiation regardless of packaging conditions (Table 3). Double-packaged thigh meats had lower
a* values than vacuum-packaged meats, but the difference was not significant as in breast meats. The b* value
of aerobically packaged irradiated turkey thigh meat was
significantly higher than that of the vacuum-packaged
thigh.
Off-Odor Volatiles
Many volatile compounds were newly generated, or
the amounts of volatiles already present in nonirradiated
raw turkey breast increased significantly by irradiation
(Table 4). The amount of total volatiles in irradiated turkey breast was higher than that of the vacuum-packaged
nonirradiated control at d 0. The amounts of S-compounds and hexanal also increased significantly after irradiation. The biggest difference between aerobically and
vacuum-packaged irradiated turkey breast was found in
S-compounds. The amount of dimethyl sulfide in aerobically packaged turkey breast meat was higher than that
in vacuum-packaged meat, whereas dimethyl disulfide
and dimethyl trisulfide were much higher in vacuumpackaged than in aerobically packaged irradiated meat
1471
DOUBLE PACKAGING AND IRRADIATED TURKEY MEAT QUALITY
TABLE 1. 2-Thiobarbituric acid reactive substance values of irradiated raw turkey meat
under different packaging conditions during refrigerated storage1
Nonirradiated
Storage
Vacuum
Irradiated
Aerobic
V5-A5
V7-A3
V9-A1
Vacuum
SEM
(mg MDA/kg meat)
Breast
Day 0
Day 10
SEM
0.25c
0.29d
0.02
0.63ay
2.34ax
0.12
0.48by
1.68bx
0.05
0.48by
1.35bx
0.11
0.48by
0.96cx
0.04
0.52by
0.71cx
0.04
0.03
0.11
Thigh
Day 0
Day 10
SEM
0.39by
0.55cx
0.02
1.09ay
8.17ax
0.72
0.58b
3.42bx
0.35
0.58b
2.14bc
0.22
0.58b
1.26cx
0.08
0.53by
0.90cx
0.06
0.01
0.53
Different letters within a row are significantly different (P < 0.05), n = 4.
Different letters within a column with same meat are significantly different (P ≤ 0.05).
1
MDA = malonedialdehyde; V5-A5 = vacuum packaged for 5 d then aerobically packaged for 5 d; V7-A3 =
vacuum packaged for 7 d then aerobically packaged for 3 d; V9-A1 = vacuum packaged for 9 d then aerobically
packaged for 1 d.
a–c
x,y
TABLE 2. Color values of irradiated raw turkey breast meat under different
packaging conditions during refrigerated storage1
Nonirradiated
Storage
L* value
Day 0
Day 10
SEM
a* value
Day 0
Day 10
SEM
b* value
Day 0
Day 10
SEM
Irradiated
Vacuum
Aerobic
V5-A5
V7-A3
V9-A1
50.2x
44.9by
0.6
46.8y
52.8ax
1.1
45.5y
50.3abx
1.4
45.5y
49.8abx
1.3
45.5
48.6b
1.3
2.5b
1.9c
0.3
8.4ax
4.4by
0.3
8.4ax
5.9ay
0.4
8.4ax
5.0aby
0.5
13.3bx
7.7by
0.3
15.0ax
9.5ay
0.4
12.6bx
9.4ay
0.5
12.6bx
7.6by
0.5
Vacuum
SEM
48.0
51.4ab
1.1
1.2
1.0
8.4ax
5.7ay
0.4
8.7ax
6.1ay
0.2
0.4
0.3
12.6bx
8.2aby
0.5
13.1bx
7.4by
0.3
0.4
0.4
Different letters within a row are significantly different (P < 0.05), n = 4.
Different letters within a column with same color value are significantly different (P < 0.05).
1
L* = lightness; a* = redness; b* = yellowness; V5-A5 = vacuum packaged for 5 d then aerobically packaged
for 5 d; V7-A3 = vacuum packaged for 7 d then aerobically packaged for 3 d; V9-A1 = vacuum packaged for
9 d then aerobically packaged for 1 d.
a–c
x,y
TABLE 3. Color values of irradiated raw turkey thigh meat under different
packaging conditions during refrigerated storage1
Nonirradiated
Storage
L* value
Day 0
Day 10
SEM
a* value
Day 0
Day 10
SEM
b* value
Day 0
Day 10
SEM
Irradiated
Vacuum
Aerobic
V5-A5
V7-A3
V9-A1
Vacuum
SEM
43.9a
39.0
1.5
37.2b
43.1
1.9
33.8by
40.9x
1.4
33.8by
41.7x
1.6
33.8by
42.2x
1.3
37.1by
43.8x
1.2
1.6
1.4
10.5b
11.0b
0.6
19.3ax
11.2by
0.9
16.7ax
13.5ab
0.4
16.7ax
12.9ab
1.1
16.7ax
12.6aby
1.2
17.0ax
14.1ay
1.0
1.0
0.7
14.5bx
12.2by
0.4
21.3ax
16.6ay
1.0
13.3b
14.7ab
0.5
13.3b
13.4ab
1.1
13.3b
12.5b
0.5
15.9bx
11.4by
0.7
0.8
0.9
Different letters within a row are significantly different (P ≤ 0.05), n = 4.
Different letters within a column with same color value are significantly different (P ≤ 0.05).
1
L* = lightness; a* = redness; b* = yellowness; V5-A5 = vacuum packaged for 5 d then aerobically packaged
for 5 d; V7-A3 = vacuum packaged for 7 d then aerobically packaged for 3 d; V9-A1 = vacuum packaged for
9 d then aerobically packaged for 1 d.
a,b
x,y
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NAM AND AHN
TABLE 4. Volatiles profile of irradiated raw turkey breast meat
at d 0 under different packaging conditions
Nonirradiated
Compound
Vacuum
Irradiated
Aerobic
(pA × s × 10 )
0b
288a
3,315a
22,973a
549
590a
543a
2,153b
2,492a
0b
1,848b
0b
0b
915a
780b
36,448a
Vacuum
SEM
342a
0b
3,034a
4,312b
575
662a
582a
16,600a
2,604a
677a
2,776a
575a
575a
883a
5,266a
39,535a
12
11
224
1,652
36
34
30
3,395
153
41
218
18
18
74
877
4,214
4
0b
0b
253b
3,963b
124
0b
34b
0b
0b
0b
827c
0b
0b
328b
0b
5,531b
2-Methyl-1-propene
Butane
Pentane
Dimethyl sulfide
Hexane
1-Heptene
Heptane
Dimethyl disulfide
Toluene
1-Octene
Octane
2-Octene
3-Methyl-2-heptene
Hexanal
Dimethyl trisulfide
Total
Different letters within a row are significantly different (P ≤ 0.05), n = 4.
a–c
at d 0. All of these S-compounds are regarded as major
volatiles responsible for the characteristic irradiation offodor and are different from rancid odor produced by
lipid oxidation products. Hashim et al. (1995) showed
that irradiating raw chicken breast and thigh produced
a characteristic “bloody and sweet” aroma that remained
after the thighs were cooked, but was not detectable after
the breasts were cooked. Ahn et al. (2000a) described the
irradiation odor in raw pork as a “barbecued corn-like”
odor. Ahn et al. (2000b) reported that S-containing volatiles, such as 2,3-dimethyl disulfide produced by the radiolytic degradation of sulfur amino acids, were responsible for the off-odor in irradiated pork, and their amounts
were highly dependent upon irradiation dose. They also
assumed that the off-odor volatiles in irradiated pork
were the result of compounding effects of volatiles from
lipid oxidation and radiolysis of various amino acid side
chains (Ahn et al., 2001). Jo and Ahn (2000) also found
that 2,3-dimethyl disulfide was produced from irradiated
oil emulsion containing methionine.
Irradiated turkey thigh meat had higher total volatiles
compared with breast meat, but their volatile profiles
were similar to those of breast meat (Tables 4 and 5). The
amount of hexanal in turkey thigh meat was much higher
than that in turkey breast, which was consistent with the
TBARS results (Table 1). Several hydrocarbons such as
2-methyl-l-propene, butane, 1-octene, and octane were
detected more in irradiated vacuum-packaged turkey
thigh meat than in aerobically packaged meat. Significantly more dimethyl disulfide or dimethyl trisulfide was
TABLE 5. Volatiles profile of irradiated raw turkey breast meat
at d 10 under different packaging conditions
Irradiated1
Nonirradiated
Compound
Butane
Methanethiol
Pentane
Propanal
Dimethyl sulfide
Hexane
Heptane
Dimethyl disulfide
Toluene
1-Octene
Octane
2-Octene
3-Methyl-2-heptene
Hexanal
Dimethyl trisulfide
Total
Vacuum
Aerobic
0c
0b
293d
0b
4,275b
125c
32b
31c
6d
0b
1,115c
0b
527b
174b
0c
6,583c
0c
0b
4,486b
797a
0b
762b
737a
0c
0d
0b
825c
0b
0b
8,628a
0c
17,237b
V5-A5
V7-A3
V9-A1
Vacuum
SEM
(pA × s × 104)
525ab
467a
0b
0b
5,502a
3,683bc
0b
0b
907b
3,127ab
700b
1,001a
584a
587a
0c
0c
752c
728c
0b
0b
1,292c
1,984b
0b
0b
0b
0b
7,539a
2,857b
0c
0c
17,804b
14,437b
602a
523b
2,981c
0b
10,420a
696b
0b
1,764b
1,086b
0b
2,289ab
0b
0b
1,208b
847b
22,419b
0c
1,509a
4,038bc
0b
10,724a
1,113a
0b
4,395a
1,398a
1,061a
2,676a
715a
885a
1,398b
1,670a
31,582a
34
128
340
1
2,048
53
60
238
38
15
150
14
22
930
72
2,282
Different letters within a row are significantly different (P < 0.05), n = 4.
V5-A5 = vacuum packaged for 5 d then aerobically packaged for 5 d; V7-A3 = vacuum packaged for 7 d
then aerobically packaged for 3 d; V9-A1 = vacuum packaged for 9 d then aerobically packaged for 1 d.
a–d
1
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DOUBLE PACKAGING AND IRRADIATED TURKEY MEAT QUALITY
TABLE 6. Volatiles profile of irradiated raw turkey thigh meat
at d 0 under different packaging conditions
Nonirradiated
Compound
Vacuum
Irradiated
Aerobic
(pA × s × 10 )
358b
521a
658b
7,234b
12,076a
0b
1,491b
688a
1,536b
1,136b
1,138a
1,484a
0b
4,584b
0b
0b
4,455
0b
37,366b
Vacuum
SEM
446a
594a
1,010a
10,414a
11,203a
702a
2,295a
723a
1,864a
1,795a
2,339a
1,676a
1,147a
6,544a
651a
681a
3,243
1,289a
48,616a
20
44
45
705
1,350
26
77
38
80
91
1,769
117
23
422
10
12
1,480
464
3,830
4
2-Methyl-1-propene
Butane
1-Pentene
Pentane
Dimethyl sulfide
1-Hexene
Hexane
Benzene
1-Heptene
Heptane
Dimethyl disulfide
Toluene
1-Octene
Octane
2-Octene
3-Methyl-2-heptene
Hexanal
Dimethyl trisulfide
Total
0c
0b
0c
548c
3,039b
0b
379c
0b
0c
62c
0b
0b
0b
1,894c
0b
0b
1,338
0b
7,262c
Different letters within a row are significantly different (P < 0.05), n = 4.
a–c
detected in irradiated thigh meats with vacuum packaging than in irradiated turkey breast.
The volatiles profile of irradiated turkey breast meat
was highly dependent upon packaging conditions during
irradiation and storage (Table 5). The greatest amounts
of total volatiles and hydrocarbons such as toluene, 1octene, and octane were detected in vacuum-packaged
turkey breast meat. The amount of dimethyl sulfide was
significantly increased, and methanethiol was newly generated under V9-A1 double-packaging and vacuum-packaging conditions. Considerable proportions of dimethyl
disulfide and dimethyl trisulfide (26 and 32% of 0 d values, respectively), however, still remained in the meat
under vacuum-packaging conditions after 10 d of storage
(Table 5). These changes in the composition of S-compounds during storage suggested that dimethyl disulfide
and dimethyl trisulfide might be degraded into dimethyl
sulfide during storage under V9-A1 double-packaging
and vacuum-packaging conditions.
Under aerobic conditions, almost all S-compounds disappeared during the 10-d storage period. Therefore, aerobic packaging was more effective than vacuum packaging
in reducing volatiles responsible for the irradiation offodor. However, aerobic packaging promoted lipid oxidation in meats as evidenced by the increased amounts of
propanal and hexanal as well as TBARS (Tables 1 and 4
to 7). When lipid oxidation and irradiation off-odor were
considered, double packaging of turkey breast meat was
more desirable than aerobic or vacuum packaging alone.
The volatile characteristics of double-packaged turkey
breast were somewhere between the aerobically and vacuum-packaged meats depending upon the number of
days in vacuum and aerobic conditions. Among the double-packaged treatments, V7-A3 double-packaged (vacuum conditions for 7 d and then aerobic conditions for
3 d) turkey breast meat was the most desirable in reducing
irradiation off-odor and lipid oxidation. After 10 d of
storage, the amount of dimethyl disulfide in V7-A3 double packaging was only 29% of the vacuum packaging,
and the other S-volatiles (methanethiol, dimethyl sulfide,
and dimethyl trisulfide) were not detected. The amounts
of propanal and hexanal also decreased to 0 and 33% of
the aerobically packaged turkey breast, respectively. Turkey breast with V5-A5 double packaging (5 d of vacuum
packaging and then 5 d of aerobic conditions) produced
significant amounts of lipid oxidation products such as
propanal and hexanal, and V9-A1 double packaging had
large amounts of S-compounds in the meat.
Irradiated turkey thigh meats produced more volatiles
than breast meat after 10 d of storage, and lipid oxidation
was a greater concern in irradiated turkey thigh than in
breast (Table 7). Greater amounts of propanal and hexanal
were produced in irradiated turkey thigh than in breast,
and 3-methyl butanal, pentanal, and heptanal, which
were not found in irradiated breast meat, were also detected in aerobically packaged irradiated thigh meat. Unlike in breast meat, aerobically packaged turkey thigh
meat had more total volatiles than vacuum-packaged
meat. The amounts and profiles of S-compounds in irradiated turkey thigh meat at d 10 were similar to those in
breast. As in turkey breast, irradiated vacuum-packaged
turkey thigh meat contained large amounts of S-compounds, and aerobically packaged thigh meats had lipid
oxidation problems at d 10. Turkey thigh meat with V7A3 double packaging (7 d vacuum packaging and then
3 d aerobic conditions) had less S-compounds than vacuum-packaged meat and had smaller lipid oxidation
products than aerobically packaged meat. The amounts of
dimethyl sulfide and dimethyl disulfide in V7-A3 doublepackaged irradiated thigh meat were 50 and 35% of the
1474
NAM AND AHN
TABLE 7. Volatiles profile of irradiated raw turkey thigh meat
at d 10 under different packaging conditions
Irradiated1
Nonirradiated
Compound
Vacuum
Aerobic
V5-A5
V7-A3
V9-A1
Vacuum
SEM
(pA × s × 10 )
509b
512b
0c
0c
13,036b
7,269c
2,545b
1,642c
2,804c
11,865b
2,488a
1,754b
0b
0b
0b
0b
b
827
693bc
958
826
3,958b
1,371c
c
473
792c
547c
824b
0b
0b
2,439bc
4,954ab
0c
0c
0b
0b
62,278b
23,349c
0b
0b
0c
0c
92,861b
55,677c
765a
494b
6,166c
0d
14,629b
1,403bc
0b
0b
821b
953
661cd
1,582b
1,029a
0b
4,499a
0c
0b
13,064d
0b
906b
46,978c
0c
1,920a
3,562d
0d
23,587a
1,096c
0b
0b
613c
617
0d
4,476a
968a
657a
2,785bc
0c
0b
3,283e
0b
1,696a
45,266c
26
45
615
334
1,145
113
10
27
37
66
272
131
34
30
527
23
38
2,809
51
54
3,408
4
Butane
Methanethiol
Pentane
Propanal
Dimethyl sulfide
Hexane
Butanal
3-Methyl butanal
1-Heptene
Heptane
Pentanal
Dimethyl disulfide
Toluene
1-Octene
Octane
2-Octene
3-Methyl-2-heptene
Hexanal
Heptanal
Dimethyl trisulfide
Total
0c
0c
708e
0d
3,461c
290d
0b
0b
0d
69
0d
10d
0d
0b
1,755c
443b
616a
65e
0b
0c
7,421d
495b
0c
20,199a
6,146a
256c
1,778b
901a
922a
1,227a
1,283
11,149a
0d
562c
0b
2,650bc
914a
604a
82,197a
1,512a
0c
142,798a
Different letters within a row are significantly different (P < 0.05), n = 4.
V5-A5 = vacuum packaged for 5 d then aerobically packaged for 5 d; V7-A3 = vacuum packaged for 7 d
then aerobically packaged for 3 d; V9-A1 = vacuum packaged for 9 d then aerobically packaged for 1 d.
a–e
1
vacuum-packaged irradiated meat, respectively, and no
methanethiol or dimethyl trisulfide was detected. The
amounts of propanal, pentanal, and hexanal in V7-A3
double-packaged irradiated turkey thigh meat were 26,
12, and 28%, respectively, of the aerobically packaged
irradiated thigh meat, and 3-methyl butanal and heptanal
were not detected. Therefore, exposing the double-packaged irradiated turkey meat to aerobic conditions by removing the outer vacuum bag 3 d before selling or consuming is desirable to reduce S-volatiles and minimize
lipid oxidation in turkey breast meats. For irradiated
thigh meat, at least 5 d exposure to aerobic conditions is
needed to remove off-odor volatiles. Exposure of the thigh
meat to aerobic conditions for 5 d or longer, however,
caused lipid oxidation. Therefore, double packaging
alone was not enough to solve both the lipid oxidation
and off-odor problems simultaneously in irradiated
thigh meat.
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