Meat Science 57 (2001) 419±426
www.elsevier.com/locate/meatsci
Volatile production in irradiated normal, pale soft exudative
(PSE) and dark ®rm dry (DFD) pork under di€erent
packaging and storage conditions
$
D.U. Ahn *, K.C. Nam, M. Du, C. Jo
Department of Animal Science, Iowa State University, Ames, IA 50011-3150, USA
Received 18 July 2000; received in revised form 18 September 2000; accepted 18 September 2000
Abstract
Normal, pale soft exudative (PSE) and dark ®rm dry (DFD) pork Longissimus dorsi muscles were vacuum packaged, irradiated at 0
or 4.5 kGy and stored at 4 C for 10 days. Volatile production from pork loins was determined at Day 0 and Day 10 of storage at 4 C.
With both aerobic and vacuum packaging, irradiation increased the production of sulfur-containing volatiles (carbon disul®de, mercaptomethane, dimethyl sul®de, methyl thioacetate and dimethyl disul®de) in all three pork conditions at Day 0 but did not increase
hexanal ÿ the major indicator volatile of lipid oxidation. The PSE pork produced the lowest amount of total sulfur-containing volatiles
in both aerobically and vacuum-packaged pork at Day 0. The majority of sulfur-containing volatiles produced in meat by irradiation
disappeared during the 10-day storage period under aerobic packaging conditions. With vacuum packaging, however, all the
volatiles produced by irradiation remained in the packaging bag during storage. Irradiation had no relationship with lipid oxidation-related volatiles (e.g. hexanal) in both aerobic and vacuum-packaged raw pork. The DFD muscle was very stable and resistant
to oxidative changes in both irradiated and nonirradiated pork during storage, suggesting that irradiation can signi®cantly increase
the utilization of raw DFD pork and greatly bene®t the pork industry. # 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Meat conditions; Irradiation; Volatiles; Packaging; O€-odor; Lipid oxidation
1. Introduction
The e€ect of irradiation on the catalysis of lipid oxidation and the development of o€-¯avor in normal, pale soft
exudative (PSE) and dark ®rm dry (DFD) pork may differ. Also, the membrane structure of PSE pork is leaky
because of high protein denaturation (Fisher, Hamm, &
Honikel, 1979; Warriss & Brown, 1987). Through the
holes generated by the denatured membrane proteins,
water molecules can easily get into membrane bilayers.
Along with the water, irons and free amino acids con®ned
inside cellular materials under normal conditions may also
migrate into membrane bilayers and promote oxidative
reactions when free radicals are available. Hydroxyl
$
Journal Paper No. J- 18965 of the Iowa Agriculture and Home
Economics Experiment Station, Ames, IA 50011. Project No. 3322,
and supported by the Food Safety Consortium.
* Corresponding author. Tel.: +1-515-294-6595; fax: +1-515-2949143.
E-mail address: duahn@iastate.edu (D.U. Ahn).
radicals can be formed from water molecules in all meat
conditions upon irradiation, and the reaction of hydroxyl
radicals is site speci®c because of their short half-life (10ÿ6
sec) (Diehl, 1995; Thakur & Singh, 1994). Therefore, the
distribution of water and the site where hydroxyl radicals formed are critical for the irradiation-dependent
reaction. The distribution and proportion of free and
bound water in normal, PSE and DFD pork are di€erent
(Forrest, Aberle, Hedrick, Judge, & Merkel 1975). It is
hypothesized that PSE meat would be more susceptible to
oxidative changes and produce more o€-¯avor volatiles
than normal and DFD pork when irradiated.
Volatile compounds responsible for o€-odor in irradiated meat are produced by the impact of radiation on
protein and lipid molecules and are distinctly di€erent
from those characteristics of lipid oxidation. Recent ®ndings in this area (Patterson & Stevenson, 1995) support
and extend this concept. These investigators studied
odor volatiles in irradiated chicken meat and found that
dimethyltrisul®de is the most potent o€-odor compound, followed by cis-3- and trans-6-nonenals, oct-1-
0309-1740/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0309-1740(00)00120-0
420
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
en-3-one and bis(methylthio-)methane. These studies also
provided evidence to support the concept that the changes
that occur following irradiation are distinctly di€erent
from those of warmed-over ¯avor in oxidized meat.
Thayer, Fox and Lakritz (1993) reported that irradiation
dose, processing temperature and packaging conditions
strongly in¯uence the microbial load and the nutritional
quality of meat. Irradiation-induced oxidative chemical
changes are dose dependent, and the presence of oxygen
has a signi®cant e€ect on the development of oxidation
and odor intensity (Merritt, Angelini, Wierbicki, & Shuts,
1975). Hashim, Resurrecccion, and McWatters (1995)
reported that irradiating uncooked chicken thigh and
breast produced a characteristic ``bloody and sweet''
aroma that remained after the thighs were cooked but
was not detectable after the breasts were cooked. The
chromatograms of raw irradiated meat suggested that
lipid oxidation can be responsible for only part of the
o€-odor in irradiated meat (Ahn, Olsen, Lee, Jo, Wu, &
Chen, 1998; Ahn, Jo, & Olson, 1999a), and other
mechanisms such as radiolysis of proteins played an
important role in the production of o€-odor volatiles in
irradiated meat (Jo & Ahn, 2000).
The objective of this research was to determine the
e€ects of irradiation on volatile characteristics of normal, pale soft exudative and dark ®rm dry pork during
storage with di€erent packaging conditions.
2. Materials and methods
2.1. Sample preparation
Three conditions of pork loin (Longissimus dorsi)
muscles Ð Normal, PSE and DFD Ð were purchased
from a local packing plant, sliced to 3-cm thick steaks and
either packaged in oxygen-permeable zipper bags (46,
2 MIL, Associated Bag Company, Milwaukee, WI) or
vacuum-packaged (ÿ1.0 bar, at 4 C) in oxygenimpermeable nylon/polyethylene bags (9.3 mL O2/m2/24
h at 0 C; Koch, Kansas City, MO) using a Multi Vac
vacuum packager (AG-800, Wolfertschwenden/Allgau,
Germany). Half of the steaks from the oxygen permeable
and oxygen impermeable bags were stored overnight at
4 C and then irradiated using a Linear Accelerator (Circe
IIIR, Thomson CSF Linac, Saint-Aubin, France). The
target doses of irradiation were 0 and 4.5 kGy. The
energy and power level used were 10 MeV and 10 kw,
respectively, and the average dose rate was 92.0 kGy/
min. The max/min ratio was approximately 1.12 for 2.5
kGy and 1.15 for 4.5 kGy. To con®rm the target dose, two
alanine dosimeters per cart were attached to the top and
bottom surfaces of the sample. The alanine dosimeter was
read using a 104 Electron Paramagnetic Resonance
Instrument (Bruker Instruments Inc., Billerica, MA). The
irradiated pork steaks were stored at 4 C for 10 days,
and the volatile characteristics of the steaks were determined after 0 and 10 days of storage. Precept II and
Purge-and-Trap Concentrator 3000 (Tekmer-Dohrmann,
Cincinnati, OH) connected to gas chromatography (GC;
6890, Hewlett-Packard Co., Wilmington, DE) was used
to quantify and characterize the volatiles responsible for
the o€-¯avor in the pork with di€erent irradiation doses
and meat conditions.
2.2. Dynamic headspace GC/mass spectrometry
Volatiles were analyzed using a dynamic headspace
GC/mass spectrometry method. Two grams of minced
pork loin sample was placed in a sample vial (40 ml) and
then one pack of oxygen absorber (Ageless Type Z-100,
Mitsubishi Gas Chemical America, Inc., New York,
NY) was added. Four replications per treatments were
analyzed. The sample vial was ¯ushed (40 C) with
helium gas (99.999%) for 5 s at 40 psi, capped tightly
with a Te¯on-lined, open-mouth cap and placed in a
refrigerated (4 C) sample-tray. The maximum holding
time for samples before volatile analysis was less than
10 h to minimize oxidative changes during the sample
holding time (Ahn, Jo, & Olson, 1999b). Samples were
purged with helium gas (40 ml/min) for 15 min. Volatiles were trapped at 20 C using a Tenax/Silica gel/
Charcoal column (Tekmar-Dorham) and desorbed for 2
min at 220 C. The desorbed volatiles were concentrated
at ÿ100 C using a cryofocusing unit, and then thermally desorbed and injected (30 s) into a capillary GC
column. An HP-624 (7.5 m, 0.25 mm i.d., 1.4 mm nominal) and an HP-1 (52.5 m, 0.25 mm i.d., 0.25 mm nominal,
Hewlett-Packard Co.) were connected using a zero deadvolume column connector (J&W Scienti®c, Folsom, CA).
Ramped oven temperature was used to improve volatile
separation. The initial oven temperature, 0 C was held for
2.50 min. After that the oven temperature was increased to
10 C at 2.5 C per min, increased to 80 C at 10 C/min,
increased to 150 C at 20 C/min and then increased to
180 C at 10 C/min. Constant column pressure at 20 psi
was maintained. The ionization potential of the mass
selective detector was 70eV and the scan range was 33.1±
300 m/z. Identi®cation of volatiles was achieved by
comparing mass spectral data of samples with those of
the Wiley library (Hewlett-Packard Co.). Standards,
when available, were used to con®rm the identi®cation
by the mass selective detector. The area of each peak
was integrated using ChemStation software (HewlettPackard Co.), and the total ion counts104 was reported as an indicator of volatiles generated from the meat
samples.
2.3. Statistical analysis
The e€ects of irradiation on the volatiles of normal,
PSE and DFD pork with di€erent packaging and storage
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
421
three pork conditions. Among the volatiles produced by
irradiation, mercaptomethane, dimethyl disul®de,
methyl thioacetate and dimethyl disul®de Ð sulfurcontaining volatile compounds Ð were the major ones.
The productions of butane, mercaptomethane, dimethyl
sul®de, methyl thioacetate and dimethyl sul®de were the
highest in irradiated normal pork and the lowest in
irradiated PSE pork in most cases. Carbon disul®de,
another sulfur-containing volatile compound, was
found in both irradiated and nonirradiated pork, but its
concentration also increased signi®cantly after irradiation in all three pork conditions. The production of
carbon disul®de was the highest in irradiated PSE pork
and the lowest in nonirradiated DFD pork. The total
content of sulfur-containing volatiles in irradiated normal pork was about 2-fold higher than the contents in
the PSE or DFD pork, suggesting that normal pork
would produce stronger irradiation odor than PSE or
DFD pork. The greater production of sulfur-containing
volatiles in irradiated normal pork compared with the
PSE or DFD pork could be related to the water content/activity of the meat, but cannot prove it at this
time were analyzed statistically by analysis of variance
using SAS1 software (SAS Institute, 1985). The StudentNewman-Keuls multiple range test was used to compare
di€erences in volatile content among irradiated meats
within a packaging and storage combination (P<0.05).
The e€ect of irradiation, meat condition, packaging and
storage on each volatile was also determined statistically.
Mean values, S.E.M. and probabilities for treatment
e€ects were reported.
3. Results and discussion
3.1. Volatiles of aerobically packaged pork
Irradiation had a signi®cant impact on the amount
and pro®le of volatiles in pork. At Day 0, aerobically
packaged irradiated pork produced a greater number of
volatiles than the nonirradiated pork (Table 1). Butane,
propane, mercaptomethane, dimethyl sul®de, methyl
thioacetate and dimethyl disul®de, not detected in nonirradiated pork, were produced by irradiation in all
Table 1
Relative production of volatiles of aerobically packaged pork Longissimus dorsi muscle at 0 days of storage at 4 Ca
Volatile compound
Peak area (pAs) 10
Butane
Acetaldehyde
Propane
Mercaptomethane
Pentane
Furan
Ethanol
Dimethyl sul®de
Carbon disul®de
3-Methyl pentane
1-Hexene
Hexane
1-Propanol
Diacetyl
2-Butanone
3-Methyl butanal
1-Heptene
Heptane
2-Pentanone
Methyl thioacetate
Pentanal
Dimethyl disul®de
1-Octene
Octane
2-Octene
3-Octene
Hexanal
Nonane
Total volatiles
a
0 kGy
4.5 kGy
Normal
PSE
0
962
0
0
321
41
956
0
185
31
29
170
117
323
283
28
26
148
93
0
74
0
139
1226
32
5
16
37
5242
0
688
0
0
224
51
692
0
130
0
0
145
6
141
431
0
0
124
119
0
66
0
137
1353
0
0
0
29
4390
DFD
S.E.M.
Normal
PSE
136
506
87
3024
581
72
233
682
422
48
74
323
19
43
513
45
125
284
0
402
103
612
112
1305
32
31
16
32
9862
76
1093
142
676
206
93
98
136
1162
97
25
247
25
36
53
27
71
196
0
36
55
30
103
1139
32
26
0
19
5899
DFD
4
c
bc
c
d
ab
b
a
b
cd
b
b
b
a
a
bc
ab
c
b
a
c
ab
b
a
b
bc
c
bc
c
d
b
b
a
b
cd
c
b
b
0b
b
ab
b
d
b
a
c
ab
b
a
b
c
0
1818
0
0
286
58
789
0
65
0
0
167
72
363
182
17
0
71
17
0
31
0
144
1297
23
0
0
0
5400
c
a
c
d
ab
ab
a
b
d
c
b
b
b
a
c
ab
d
b
b
c
b
b
a
b
bc
a
bc
b
a
a
ab
b
a
b
b
a
a
c
b
a
a
a
a
b
a
a
a
a
a
a
b
b
a
c
b
a
b
b
a
a
b
ab
c
b
c
ab
b
ab
b
c
ab
b
a
a
b
87
356
77
1345
144
72
52
562
352
0
0
160
0
26
145
32
33
86
0
295
25
130
48
526
18
0
0
0
4571
b
c
b
b
b
ab
b
a
b
c
b
b
c
b
c
ab
c
b
b
b
b
b
b
b
c
8
153
10
80
67
9
80
45
67
6
6
29
10
37
59
7
9
35
9
24
13
38
16
144
7
3
9
13
419
Di€erent letters within a row are di€erent (P<0.05). n=4. PSE, pale, soft, exudative; DFD, dark, ®rm, dry; S.E.M., standard error of the mean.
422
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
to linoleic acid, was detected only in irradiated and nonirradiated normal meat. Changes in other volatiles in all
three pork conditions after irradiation were either small
or inconsistent. Most sulfur and carbonyl compounds
have low odor thresholds and were considered as important to irradiation odor (Angelini, Merritt, Mendelshon,
& King 1975). Batzer and Doty (1955) reported that
methyl mercaptan and hydrogen sul®de were important
to irradiation odor, and Patterson and Stevenson (1995)
found that dimethyl trisul®de was the most potent o€odor compound, followed by cis-3- and trans-6-nonenals, oct-1-en-3-one, and bis(methylthio-)methane in
irradiated chicken meat. Dimethyl trisul®de was detected in irradiated pork loin in our previous work (Ahn, Jo,
& Olson, 1999a), but no noticeable amount of dimethyl
trisul®de was found in this study. This indicated that the
sulfur-containing compounds would be the major volatile components responsible for the characteristic odor in
irradiated pork. This study also provided evidence to
support the concept that the changes that occur following irradiation are distinctly di€erent from those of
warmed-over ¯avor in oxidized meat.
After 10 days of storage in the aerobic packaging
condition, the amount of total volatiles decreased by
point. Hashim et al. (1995) characterized the odor of
irradiated meat as a bloody and sweet and Heath,
Owens, Tesch and Hannah (1990) described it as a hot
fat, burned oil, or burned feathers odor.
The amount of acetaldehyde was the highest in nonirradiated DFD but the lowest in irradiated DFD pork.
Propane was the highest in irradiated PSE pork. The
content of pentane, hexane and heptane, a group of chemicals presumably associated with radiolytic degradation of lipids, was higher in irradiated normal pork than
in nonirradiated normal pork and also was higher than
the irradiated and nonirradiated PSE and DFD pork,
respectively. As previously reported (Ahn, Olson, Jo,
Love, & Jin, 1999), the concentrations of alkenes such
as 1-hexene and 1-heptene in pork from a same meat
condition Ð except for 1-hexene in DFD pork Ð
increased signi®cantly after irradiation, but the amounts
were small. Octane content in irradiated DFD pork was
lower than in any other irradiated or nonirradiated pork.
The amounts of ethanol, 1-propanol, diacetyl and 2-pentanone in all three pork conditions decreased signi®cantly
after irradiation, but the amounts were small compared
with the sulfur-containing compounds. Hexanal, an o€¯avor volatile typically associated with oxidative changes
Table 2
Relative production of volatiles of aerobically packaged pork Longissimus dorsi muscle after 10 days of storage at 4 Ca
Volatile compound
0 kGy
4.5 kGy
Normal
PSE
38
197
0
246
26
64
0
139
50
22
224
15
76
217
21
39
121
166
0
35
46
459
14
13
42
30
2300
26
164
0
205
0
61
0
11
103
0
324
35
188
139
0
0
59
57
0c
35
271
601
22
24
181
41
2500
DFD
S.E.M.
Normal
PSE
80
235
37
524
33
112
749
216
64
22
199
21
73
379
27
49
145
0
194
45
53
745
18
18
104
38
4180
91
357
34
394
29
77
336
246
103
31
321
25
143
200
93
60
172
0
45
51
97
766
20
19
360
53
4123
DFD
4
Peak area (pAs) 10
Butane
Acetaldehyde
Mercaptomethane
Pentane
Furan
Ethanol
Dimethyl sul®de
Carbon disul®de
3-Methyl pentane
1-Hexene
Hexane
1-Propanol
Diacetyl
2-Butanone
3-Methyl butanal
1-Heptene
Heptane
2-Pentanone
Methyl thioacetate
Pentanal
1-Octene
Octane
2-Octene
3-Octene
Hexanal
Nonane
Total volatiles
a
b
b
a
b
b
b
b
b
c
bc
ab
ab
a
c
b
a
a
b
b
b
b
b
b
b
c
b
c
c
b
b
b
a
a
a
b
27
434
0
171
0
70
0
112
110
0
211
29
515
173
34
0
54
62
0c
22
27
670
19
0
0
0
2724
b
a
b
a
b
b
c
a
c
b
b
b
b
b
b
b
b
a
ab
a
b
a
ab
b
b
b
bc
a
a
c
a
b
a
a
a
a
ab
a
b
b
a
a
b
c
a
a
a
c
bc
b
a
a
a
44
257
0
256
26
32
873
215
75
0
312
17
127
707
18
55
162
0
79
29
88
711
25
0
36
37
4184
b
ab
a
b
a
ab
c
b
a
bc
a
a
c
b
b
b
a
a
10
50
9
92
2
56
102
25
21
2
50
6
32
45
7
11
18
12
2
6
21
130
4
3
90
6
192
Di€erent letters within a row are di€erent (P<0.05). n=4. PSE, pale, soft, exudative; DFD, dark, ®rm, dry; S.E.M., standard error of the mean.
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
423
DFD pork after 10 days of storage in aerobic conditions. Irradiation did not increase hexanal production in
all three pork conditions, but the storage time did in
aerobically packaged pork (Table 2). Luchsinger et al.
(1996) showed that 2-thiobarbituric acid reactive substances (TBARS) values of both chilled and frozen boneless pork chops were stable, regardless of display day, dose
and irradiation sources. Ahn et al. (1998) reported that
hexanal is the volatile compound that best represents the
lipid oxidation status in meat. This indicated that DFD
pork is less susceptible to oxidative changes during storage. The amount of 3-methyl pentane in irradiated
DFD pork also increased during storage.
30±60% in all pork but irradiated DFD pork. As in 0day pork, mercaptomethane, dimethyl sul®de and
methyl thioacetate were found only in irradiated pork,
and 2-pentanone in nonirradiated pork (Tables 1 and
2). This indicated that storage time had no e€ect on the
production of these compounds. Propane and dimethyl
disul®de, found in irradiated meat at Day 0, were not
detected after 10 days of storage in aerobic conditions.
The amounts of other volatiles such as acetaldehyde, mercaptomethane, furan and ethanol signi®cantly decreased in
all three pork conditions after 10 days of storage, but the
decrease of mercaptomethane was the most signi®cant
(Table 2). The amount of methyl thioacetate in irradiated
DFD pork, and that of octane in all pork except irradiated DFD, also decreased signi®cantly over the 10day storage in aerobic conditions. The content of dimethyl sul®de was the only sulfur compound that increased
signi®cantly after 10 days of storage in aerobic conditions. This result suggests that some of these compounds escaped from the packaging bags and others
converted to other compounds via the chemical or
enzymatic reactions during storage. Hexanal was produced in all three pork conditions, except nonirradiated
3.2. Volatiles of vacuum-packaged pork
Volatile pro®les of vacuum-packaged pork at Day 0
(Table 3) were similar to those of the aerobically packaged
pork (Table 1) except for minor di€erences. In addition to
butane, propane, mercaptomethane, dimethyl sul®de,
methyl thioacetate and dimethyl disul®de, a few other
volatiles were detected only in vacuum-packaged irradiated pork at Day 0 (Tables 1 and 3). The productions
Table 3
Relative production of volatiles of vacuum-packaged pork L. dorsi muscle at 0 days of storage at 4 Ca
Volatile compound
Peak area (pAs) 104
Butane
Acetaldehyde
Propane
Mercaptomethane
Pentane
Furan
Ethanol
Dimethyl sul®de
Carbon disul®de
3-Methyl pentane
1-Hexene
Hexane
1-Propanol
Diacetyl
2-Butanone
3-Methyl butanal
1-Heptene
Heptane
2-Pentanone
Methyl thioacetate
Pentanal
Dimethyl disul®de
1-Octene
Octane
2-Octene
3-Octene
Nonane
Total volatiles
a
0 kGy
4.5 kGy
Normal
PSE
0
1261
0
0
235
54
761
0
0
0
0
115
43
204
201
17
14
95
46
0
46
0
119
18
13
0
0
4142
0
877
0
0
332
62
587
0
82
0
0
131
64
72
232
0
0
105
53
0
60
0
78
992
0
0
18
3735
c
ab
b
c
bc
a
d
d
b
b
b
b
a
ab
bc
b
b
a
b
c
b
ab
b
c
d
DFD
c
bc
b
c
ab
a
d
bc
b
b
b
a
b
a
c
b
b
a
c
b
ab
b
b
b
d
0
1651
0
0
160
59
667
0
55
0
0
88
42
181
103
22
0
57
0
0
25
0
66
619
138
0
0
3933
c
a
b
c
c
a
d
cd
b
b
b
b
a
b
bc
b
b
b
b
c
b
b
a
b
c
d
S.E.M.
Normal
PSE
96
326
86
2185
419
77
104
759
189
0
53
183
16
0
120
41
97
178
0
187
57
239
328
1089
28
20
39
6916
67
699
15
739
436
68
95
354
124
45
43
204
24
0
134
114
871
189
0
153
60
55
81
1163
29
21
26
5709
a
c
a
a
a
b
b
a
b
a
a
cd
c
b
b
b
a
b
a
a
a
ab
b
a
a
a
DFD
b
bc
a
bc
a
b
c
ab
a
a
a
bc
c
ab
a
a
a
b
a
c
b
a
b
a
ab
b
64
462
85
1408
190
52
0
978
145
0
0
135
0
44
196
26
38
91
0
137
27
145
66
849
21
0
0
5159
b
c
a
b
c
b
a
ab
b
b
b
d
bc
ab
bc
b
b
b
a
b
b
ab
b
b
c
c
3
161
13
247
33
6
51
29
18
2
4
14
6
13
25
8
45
14
3
16
7
4
31
112
14
1
5
201
Di€erent letters within a row are di€erent (P<0.05). n=4. PSE, pale, soft, exudative; DFD, dark, ®rm, dry; S.E.M., standard error of the mean.
424
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
increased signi®cantly. Among the sulfur compounds,
the increase of dimethyl sul®de in irradiated pork during the 10-day storage was the most dramatic (4- to 6fold increase from the Day 0, Tables 3 and 4), but those
of methyl thioacetate and dimethyl disul®de were also
signi®cant. Irradiated normal pork produced the highest
amount of total sulfur-containing volatile compounds
and DFD pork had the lowest of the three pork conditions. The amounts of acetaldehyde and 2-butanone in
irradiated meat increased but that of ethanol in nonirradiated pork decreased after storage. Hexanal was
found in both irradiated and nonirradiated normal and
PSE pork, and the production of nonane increased signi®cantly after 10 days of storage in vacuum-packaged
pork (Table 4).
of butane, mercaptomethane, dimethyl sul®de and
dimethyl disul®de were the highest in irradiated normal
pork and the lowest in irradiated PSE pork as in aerobically packaged pork at Day 0 (Table 1). Irradiation
increased the production of 1-hexene, 3-octene and
nonane in normal and PSE pork. But irradiation
decreased the amounts of ethanol, 1-propanol, diacetyl
and 2-pentanone signi®cantly. Irradiated normal pork
produced the highest amounts of butane, carbon disul®de and 1-octene; nonirradiated DFD pork had the
highest acetaldehyde; irradiated DFD pork produced the
lowest pentane, ethanol and 1-propanol; and irradiated
PSE pork had the highest 3-methyl butanal. Hexanal was
not detected from any of the vacuum-packaged pork
(Table 3).
The changes of volatiles in pork after10 days of storage
in vacuum packaging were di€erent from those in aerobic
packaging. Total volatile content of nonirradiated pork
decreased but that of the irradiated pork increased signi®cantly (Table 4). Unlike in aerobically packaged pork,
the amounts of all sulfur-containing volatile compounds
except for mercaptomethane and carbon disul®de
3.3. Correlations
The production of volatiles was strongly in¯uenced by
meat condition and irradiation. Storage time had less
e€ect than meat condition and irradiation on the content of many volatile compounds, but packaging of raw
Table 4
Relative production of volatiles of vacuum-packaged pork Longissimus dorsi muscle after 10 days of storage at 4 Ca
Volatile compound
0 kGy
4.5 kGy
Normal
PSE
0c
272
0
0
205
13
269
0
211
110
0
130
130
123
346
16
0
65
329
0
31
0
30
718
0
0
22
42
3062
0
57
0
0
96
0
131
0
124
149
0
88
38
152
308
0
0
45
124
0
34
0
196
566
0
0
26
50
2184
DFD
S.E.M.
Normal
PSE
331
367
111
1692
637
29
397
4877
292
104
89
290
68
63
760
91
191
273
0
410
79
358
141
880
30
25
128
58
12771
271
278
110
1655
382
34
100
1612
186
71b
35
201
20
23
196
129
66
137
0
259
48
235
537
882
25
17
78
48
7635
DFD
4
Peak area (pAs) 10
Butane
Acetaldehyde
Propane
Mercaptomethane
Pentane
Furan
Ethanol
Dimethyl sul®de
Carbon disul®de
3-Methyl pentane
1-Hexene
Hexane
1-Propanol
Diacetyl
2-Butanone
3-Methyl butanal
1-Heptene
Heptane
2-Pentanone
Methyl thioacetate
Pentanal
Dimethyl disul®de
1-Octene
Octane
2-Octene
3-Octene
Hexanal
Nonane
Total volatiles
a
ab
c
b
cd
b
ab
b
b
ab
c
bc
a
a
b
c
d
c
a
b
b
c
c
b
c
b
ab
c
c
b
c
b
d
c
b
b
c
a
c
c
b
a
b
c
d
c
b
b
b
c
b
b
c
b
ab
c
0
135
0
0
109
0
0
0
77
68
0
144
13
29
208
0
0
42
50
0
0
0
17
515
0
0
0
17
1424
c
b
c
b
d
c
b
b
c
b
c
bc
b
b
c
c
d
c
c
b
b
c
c
b
c
b
bc
c
a
a
a
a
a
a
a
a
a
ab
a
a
b
b
a
b
a
a
c
a
a
ab
b
a
a
a
a
a
a
ab
a
a
b
a
b
b
b
b
b
b
b
bc
a
b
b
c
a
b
b
a
a
b
ab
ab
b
197
108
68
1684
309
25
62
3562
204
39
10
173
13
117
322
17
37
83
0
374
25
473
139
799
20
10
0
10
8880
b
b
b
a
bc
a
b
a
b
b
c
bc
b
a
b
c
c
bc
c
a
b
a
c
a
c
b
c
b
20
42
8
116
42
2
68
454
16
18
6
22
15
15
66
11
7
18
13
61
5
41
23
90
3
2
19
8
413
Di€erent letters within a row are di€erent (P<0.05). n=4. PSE, pale, soft, exudative; DFD, dark, ®rm, dry; S.E.M., standard error of the mean.
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
425
Table 5
Statistical signi®cance of e€ects of meat condition, irradiation dose, storage time and packaging on volatile production from pork L. dorsi musclea
Volatile compound
Butane
Acetaldehyde
Propane
Mercaptomethane
Pentane
Furan
Ethanol
Dimethyl sul®de
Carbon disul®de
9623-Methyl pentane
1-Hexene
Hexane
1-propanol
Diacetyl
2-Butanone
3-Methyl butanal
1-Heptene
Heptane
2-Pentanone
Methyl thioacetate
Pentanal
Dimethyl disul®de
1-Octene
Octane
2-Octene
3-Octene
Hexanal
Nonane
Total volatiles
a
Probability
Meat condition (d.f.=2)
Irradiation (d.f.=1)
Storage (d.f.=1)
Packaging (d.f.=1)
0.0001
0.17
0.02
0.0001
0.0001
0.0001
0.0001
0.19
0.86
0.0001
0.01
0.01
0.0001
0.0005
0.02
0.0001
0.0001
0.0001
0.0001
0.001
0.0001
0.0002
0.0001
0.04
0.0001
0.03
0.0005
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0002
0.0001
0.0001
0.01
0.62
0.002
0.0001
0.0001
0.0001
0.13
0.0001
0.0001
0.0001
0.0001
0.0001
0.03
0.0001
0.05
0.11
0.0001
0.49
0.20
0.002
0.0001
0.0001
0.0001
0.0001
0.001
0.88
0.0001
0.25
0.09
0.24
0.0001
0.001
0.004
0.57
0.03
0.004
0.38
0.0001
0.17
0.006
0.31
0.003
0.08
0.0009
0.007
0.02
0.02
0.0001
0.0001
0.99
0.0004
0.12
0.0001
0.01
0.43
0.77
0.65
0.02
0.07
0.05
0.15
0.0001
0.21
0.0001
0.14
0.41
0.93
0.0008
0.81
0.52
0.05
0.99
0.05
0.47
0.01
0.80
0.006
0.22
0.56
n=36 for meat condition e€ect; n=48 for irradiation, storage and packaging e€ect.
meat had the least e€ect on most of the volatiles found in
this study. Among the volatiles found in irradiated and
nonirradiated pork (Tables 1±4), the production of all
the volatile compounds except for acetaldehyde, dimethyl sul®de and carbon disul®de were in¯uenced by meat
condition; 3-pentanol, 3-methyl pentane, 2-butanone, 1octene, octane, 3-octene and hexanal were in¯uenced by
irradiation; and pentane, ethanol, dimethyl sul®de, carbon disul®de, 1-propanol, 3-methyl butanal, heptane,
methyl thioacetate, dimethyl disul®de and total volatiles
were in¯uenced by storage time. Butane, propane, mercaptomethane, dimethyl sul®de, hexane, heptane, 2octene, and hexanal in pork were in¯uenced by packaging methods. Irradiation was the only factor that
in¯uenced the production of all ®ve sulfur-containing
volatile compounds in pork. The production of hexanal,
the major volatile related to oxidative changes in meat,
was not in¯uenced by irradiation but by meat condition,
storage and packaging methods (Table 5). Ahn, Jo and
Olson (1999a) also reported that irradiation did not
increase lipid oxidation in meat, and Nam, Ahn, Du, Jo,
and Jo (2000) and Nam, Du, Jo, and Ahn (2000)
showed that irradiation and storage time had no e€ect
on the TBARS of vacuum- and aerobic-packaged normal, PSE and DFD pork.
4. Conclusion
Irradiation increased the production of sulfur-containing volatiles (carbon disul®de, mercaptomethane,
dimethyl sul®de, methyl thioacetate and dimethyl disul®de), but not lipid oxidation products (aldehydes), in all
three pork conditions regardless of packaging conditions.
With vacuum packaging, lipid oxidation and volatile
production of irradiated PSE and irradiated DFD pork
were not di€erent from normal pork. Most of the sulfurcontaining volatiles produced in meat by irradiation
escaped during storage under aerobic packaging conditions. The DFD muscle was very stable and resistant to
oxidative changes. Irradiation and storage of meat in
vacuum packaging may be desirable for long-term storage but may reduce the acceptance of irradiated meat
because of the sustaining o€-odor volatiles. Therefore,
irradiation of DFD pork in aerobic packaging for shortterm storage can be an option for the increased utilization
426
D.U. Ahn et al. / Meat Science 57 (2001) 419±426
of pork. Among the three meat conditions, DFD pork,
highly susceptible to microbial spoilage due to high pH
conditions, could bene®t the most from irradiation
because spoilage microorganisms along with pathogens
will be dramatically reduced by irradiation. The shelf
life of DFD meat Ð the most limiting factor for the
utilization of DFD meat Ð can be extended signi®cantly with the same or smaller levels of volatile
changes than in irradiated normal and PSE pork.
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