JOURNAL OF FOOD SCIENCE
CHEMISTRY/BIOCHEMISTRY
Volatiles Production and Lipid Oxidation in
Irradiated Cooked Sausage as Related to
Packaging and Storage
D. U. Ahn, D. G. Olson, C. Jo, J. Love, and S. K. Jin
ABSTRACT
Irradiation dose affected production of volatiles in vacuumand aerobic-packaged cooked pork sausage, but its effect
on TBARS was minor. Storage increased production of
volatiles and changed their composition only in aerobic-packaged sausage. Among volatile components, 1-heptene and
1-nonene were influenced most by irradiation dose, and aldehydes by packaging type. TBARS and volatiles of vacuumpackaged irradiated cooked sausage did not correlate well.
However, TBARS had very high correlation with amount of
aldehydes, total volatiles, ketones and alcohols with long retention times in aerobic-packaged pork sausage. Heptene
and 1-nonene could be indicators for irradiation; and propanal,
pentanal, and hexanal for oxygen-dependent changes of
cooked meat.
Key Words: irradiation, TBARS, volatiles, packaging, pork
sausage
INTRODUCTION
IRRADIATION IS AN EFFECTIVE METHOD FOR MICROORGANISM CONtrol in raw meat and is permitted for use in both poultry and red meat.
A major concerns, however, is its effect on meat quality. Irradiationinduced oxidative chemical changes are dose-dependent, and the presence of oxygen affects the rate of oxidation (Katusin-Razem et al.,
1992). Lee et al. (1996) reported that pre-rigor beef irradiated with an
absorbed dose of 2.0 kGy and stored at 2⬚C in modified atmosphere
packaging (25% CO2 and 75% N2), did not show increased lipid
oxidation. Al-Kahtani et al. (1996) and Hampson et al. (1996), however, have shown that irradiation at 1.5- to 10-kGy dosages increased
thiobarbituric acid (TBARS) values and decreased thiamin and tocopherol levels in turkey breast and fish muscles. Results have indicated
that irradiation accelerated lipid oxidation of raw and cooked meat
only when they were stored in oxygen-permeable bags after irradiation (Ahn et al., 1997, 1998b).
Hashim et al. (1995) showed that irradiating uncooked 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. It was long been known that the precursors
of undesirable odor compounds in irradiated meat were water soluble
and contained nitrogen and/or sulfur. Methyl mercaptan and sulfur
dioxide formed from sulfur (S)-containing compounds (e.g., glutathione) also contributed to irradiation odor. Patterson and Stevenson
(1995) reported that dimethyltrisulfide is the most potent off-odor
compound, and dietary tocopherol and ascorbic acid reduced the development of off-odor in irradiated raw chicken meat. However, others reported that irradiation had no detrimental effect on flavor of
vacuum-packaged raw and cured meat, and electron beam treatment
The authors are affiliated with the Dept. of Animal Science, Iowa State Univ.,
Ames, IA 50011-3150. Direct inquiries to Dr. D. U. Ahn.
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JOURNAL OF FOOD SCIENCE—Volume 64, No. 2, 1999
had little effect on odor and flavor of reheated meat with sous-vide
treatment (Shamsuzzaman et al., 1992).
Irradiated raw pork, regardless of packaging, produced more volatiles than nonirradiated patties and developed a characteristic aroma shortly after irradiation (Ahn et al., 1998a). The gas chromatography (GC)
profiles of irradiated raw meat showed that irradiation produced many
unidentified volatiles that were not major peaks of lipid oxidation. The
chromatograms of raw irradiated meat suggested that substances that
imparted the characteristic irradiation aroma had low molecular weights,
and were highly volatile and difficult to separate (Ahn et al., 1997,
1998a). Although lipid oxidation still may be responsible for part of the
characteristic aroma in irradiated meat, other mechanisms, such as radiolysis of proteins, could be important in its production.
The effects of irradiation on lipid oxidation in cooked meat would
be quite different from those in raw meat. Cooked meat is highly
susceptible to lipid oxidation because the cooking process denatures
antioxidant components, damages cell structure, and exposes membrane lipids to the environment. Raw meat has very strong antioxidant
effects unless it is heated, denatured, or contains added prooxidants.
Cooked meat, however, is highly susceptible to lipid oxidation (Ahn
et al., 1993). Irradiation studies have been mainly focused on the
antimicrobial and certain quality aspects of raw meat and little information on lipid oxidation of irradiated cooked or further processed
meat products has been reported.
The objective of this research was to determine the effects of irradiation dose on lipid oxidation and volatiles production in cooked
sausages as related to packaging and storage time.
MATERIALS & METHODS
Sample preparation
Fresh lean pork (95%) was purchased from a local meat packing
plant and ground twice through a 9-mm plate. Sausage was prepared
from lean ground pork, backfat (10% of lean meat), salt (2%), ice
(7.5%), and 1% soy protein concentrate (90% protein). No spices
were added to aviod any potential antioxidant effects or complication
of volatile profiles. The sausage was cooked in a smokehouse with
steam to an internal temperature of 75°C and chilled in ice water. Half
of the cooked sausages were vacuum-packaged (-1.0 bar) using a
Multi Vac vacuum packager (AG-800, Wolfertschwenden/Allgau,
Germany) in impermeable nylon/polyethylene bags (O2 permeability,
9.3 mL O2/m2/24h at 0⬚C; Koch, Kansas City, MO), and the other half
in oxygen-permeable bags. After packaging, they were electron irradiated from a Linear Accelerator (Circe IIIR, Thomson CSF Linac,
Saint-Aubin, France) to an absorbed dose of 0, 2.5, or 4.5 kGy (dose
rate was 107 kGy/min). The sausages were at 4⬚C during irradiation
and stored for up to 8 days at 4⬚C.
The degree of lipid oxidation and volatiles in cooked sausages was
determined after 0, 4, and 8 days storage. Lipid oxidation was determined by the thiobarbituric acid reactive substances (TBARS) method
as previously described (Ahn et al., 1998b). A purge-and-trap apparatus connected to a GC was used to trap and quantify the volatile
compounds produced in cooked pork sausage during irradiation and
storage.
Volatiles analysis
Precept II and Purge-and-Trap Concentrator 3000 (Tekmar-Dohrmann, Cincinnati, OH) were used to purge and trap the volatiles potentially responsible for off-odor in irradiated cooked pork sausage. A
GC (Model 6890, Hewlett Packard Co., Wilmington, DE) equipped
with a flame ionization detector was used to analyze volatiles after
thermally desorbing the trapped volatiles. In preparation for volatiles
analysis, sausage (2g) was weighed into a sample vial (40 mL), an
oxygen absorber (Ageless type ZPT-50, Mitsubishi Gas Chemical
America, Inc., New York) was added, and the vial was capped tightly
with a Teflon-lined open-mouth cap and was placed in a refrigerated
(3⬚C) sample tray. The sample was purged by using an auto sampling
unit (Precept II) equipped with a robotic arm. The sample was heated
to 32⬚C and then purged with helium gas (40 mL/min) for 11 min.
Volatiles were trapped by using a Tenax/silica gel/charcoal column
(Tekmar-Dohrmann, Cincinnati, OH) and desorbed for 1 min at 220⬚C.
All transfer lines connecting Precept II, the Concentrator 3000 and the
GC inlet, were maintained at 135⬚C.
A split inlet (split ratio, 49:1) was used to inject volatiles into a
DB-Wax capillary GC column (0.25 mm i.d. ⫻ 60 m, and 0.25 ␮m
film thickness, Hewlett Packard), and ramped oven temperature conditions (32⬚C for 2 min, increased to 40⬚C at 2⬚C/min, increased to
50⬚C at 5⬚C/min, increased to 70⬚C at 10⬚C/min, increased to 140⬚C at
20⬚C/min, increased to 200⬚C at 30⬚C/min, and held for 4.5 min) were
used. Inlet temperature was 180⬚C, and detector temperature was
280⬚C. Helium was the carrier gas with a constant column flow of 1.2
mL/min. Detector air, H2, and make-up gas (He) flow rates were 300
mL/min, 30 mL/min, and 28 mL/min, respectively.
Individual peaks were tentatively identified by retention times of
volatile standards. Standard kits (aldehydes, ketones, alcohols, hydrocarbons, and alkenes C6-C10) were purchased from Chromatography Research Supplies (Addison, IL), and 49 standards (9 aldehydes, 11 alcohols, 13 ketones, and 16 hydrocarbones) were used to
identify peaks in meat volatiles. A few peaks that could not be identified with the standards were identified using a Mass Selective (MS)
detector (Model 5973, Hewlett Packard Co., Wilmington, DE). GCMS was performed with column and other purge-and-trap/GC conditions as described. The ionization potential of MS was 70 eV, and the
scan range was 50 to 550 m/z. The identification of volatiles was
achieved by comparing mass spectral data with those of the Wiley
library (Hewlett Packard Co., Wilmington, DE). The area of each peak
was integrated by using ChemStation software (Hewlett Packard Co.,
Wilmington, DE), and the total peak area (pA*sec) was reported as an
indicator of generated volatiles.
Statistical analysis
Analysis of variance (ANOVA) was used to determine the effects
of irradiation dose and storage time on volatiles and lipid oxidation of
irradiated cooked pork sausage with different packaging conditions.
The volatiles data of samples from different packaging types were
analyzed independently by SAS software (SAS Institute, Inc., 1989).
Correlation coefficients between volatile components and TBARS
were calculated. The Student-Newman-Keuls multiple range test was
used to compare differences among means. Mean values and standard
errors of the mean (SEM) were reported. Significance of differences
was defined at P⬍0.05.
RESULTS & DISCUSSION
Volatiles production
In vacuum-packaged cooked sausage, irradiation dose affected
(P ⬍ 0.05) the production of volatiles but the effects of storage time
were not significant (Table 1). At Day 0, amounts of 1-heptene, 2propanone, and 1-nonene increased as irradiation dose increased.
The production of hexanal, 1-pentanol, and 1-heptanol decreased (P
⬍ 0.05) with increased irradiation dose. Except for 1-pentene⫹hexane
and nonanal, changes in the amount and profile of volatiles in the
sausages were not significant. The changes in 1-pentene⫹hexane
and nonanal during storage were not consistent with storage time.
Amounts of propanal and pentanal were influenced by irradiation at
Day 8 but changes were not consistent with irradiation dose (Table
1). Irradiated sausages (2.5 or 4.5 kGy) produced more total volatiles than nonirradiated except for those irradiated at 4.5 kGy and
stored 8 days. Amounts of total volatiles during storage were mainly
influenced by 1-pentene⫹hexane, 2-methylpentanal, and trimethylhexane but changes were not consistent with storage time. Ahn et al.
(1997, 1998b) reported that the amount of total volatiles was not
consistently influenced by storage time but was increased (P⬍0.05)
by irradiation.
In aerobic-packaged irradiated cooked pork sausage, irradiation
dose and storage time affected (P⬍0.05) the production and composition of volatiles (Table 2). The amounts of 1-heptene and 1-nonene
increased (P⬍0.05) as irradiation dose increased as in vacuum-packaged sausages. Cooked pork sausage irradiated at 2.5 kGy produced
higher amounts of 1-pentanol and 1-heptanol than those at 0 and 4.5
kGy at Day 0 but the amount of 1-pentanol, 1-hexanol, and 1-heptanol
decreased as irradiation dose increased at Day 4 and Day 8. In Day 0
samples, irradiation greatly increased (P⬍0.05) the production of 1pentene⫹hexane but had no effect on Day 4 and Day 8 samples.
Amounts of propanal, pentanal, 2-methyl pentanal, and hexanal were
not influenced by irradiation dose but increased (P⬍0.05) during
storage. After 4 days storage in aerobic-packaging these aldehydes
became the major volatile compounds of irradiated cooked pork sausage. Amounts were two- to four-fold higher than that of the Day 0
samples. Other volatiles such as 1-pentene⫹hexane, 1-pentanol, 1hexanol, and 1-heptanol also increased (P⬍0.05) during storage in
aerobic packaging (Table 2).
Among the volatile components, the amounts of 1-heptene and 1nonene were the only compounds influenced (P⬍0.001) by irradiation dose. Therefore, they could be indicators for irradiation treatment
in cooked pork sausage. The production of 2-methylpentanal and
trimethylhexane was influenced (P⬍0.001) by storage (Table 3) but
changes were not consistent with storage time (Tables 1-2). The production of 1-pentene+hexane, aldehydes (propanal, pentanal, hexanal,
and nonanal), ketones, alcohols, and total volatiles were influenced
(P⬍0.05) by both storage time and packaging (Table 3).
More than 1,000 compounds have been identified as flavor/aroma
components in cooked meat. They are produced by thermal degradation of sugars, amino acids, and nucleotides as well as the Maillard
reaction and lipid oxidation (Shahidi et al., 1986; Specht and Baltes,
1994). Many researchers (Chang and Peterson, 1977; Min et al.,
1979; Wasserman, 1979; Ruther and Baltes, 1994) have reported that
lactones, aromatic and nonaromatic heterocyclic compounds, sulfurcontaining compounds, and furan compounds are important contributors to meaty aroma notes of cooked meat. The volatile compounds
responsible for off-odors in irradiated meat have long been hypothesized to be produced by changes in the protein and lipid molecules and
different from those of lipid oxidation. The major volatile components
found in irradiated cooked pork sausage analyzed by the purge-andtrap/GC method we used were lipid oxidation-related compounds,
most of which were aldehydes, alcohols, ketones, and alkenes with
low carbon numbers.
The major reason our samples had relatively simple volatile compounds was probably because of the low temperature purge (40⬚C)
we used. Exhaustive distillation of meat at high temperature would
not produce the kind of volatile compounds found in cooked sausages that affect sensory quality. Little if any sulfur-containing compounds, pyrazines, or furans were detected in the irradiated cooked
pork sausage when purged at 40⬚C. Although the flavor dilution
factors of sulfur-containing compounds, pyrazines, and furans were
very high (Specht and Baltes, 1994; Patterson and Stevenson, 1995),
their contributions to flavor of cooked sausages at 40°C should be
negligible. As shown by Ramarathnam et al. (1993), hexanal was the
major lipid oxidation-related volatile in cooked meat. However, the
Volume 64, No. 2, 1999—JOURNAL OF FOOD SCIENCE 227
Volatiles of Cooked Irradiated Sausages . . .
Table 1—Relative production of volatiles in vacuum-packaged cooked irradiated pork sausages as affected by irradiation dose and storage
time (4°C)d
Day 0
Volatile compound
1-Pentene, hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Trimethylhexane
Hexanal
3-Heptanone
1-Pentanol
Nonanal
1-Heptanol
Total volatiles
0 kGy
84.78
6.35c
2.26
18.93c
12.93c
20.75
104.80
12.85
70.70
57.43a
2.30
13.35a
2.80
3.55a
420.55b
2.5 kGy
99.33
38.03b
3.19
22.80b
30.43b
26.13
133.15
16.95
90.90
48.65ab
1.95
11.40b
2.70
2.98ab
534.60a
4.5 kGy
93.88
73.38a
2.65
25.60a
44.38a
25.45
134.23
19.05
92.75
37.30b
1.90
9.23c
2.65
2.35b
571.33a
Day 4
SEM
6.02
4.27
0.24
0.66
0.61
3.35
23.76
2.45
16.49
5.00
0.13
0.56
0.08
0.21
20.79
0 kGy
2.5 kGy
4.5 kGy
45.28c
8.25c
3.81
20.55c
11.55c
21.53
99.00
13.10
62.15
66.83a
2.23
14.35a
2.35b
3.55a
381.35b
Peak area (pA*sec)
67.35b
89.20a
36.50b
73.05a
3.18
3.80
24.28b
28.75a
b
28.78
41.88a
24.23
21.15
115.53
98.00
12.30
10.63
71.55
59.83
ab
55.25
47.58b
2.30
1.90
11.23b
10.40b
ab
2.65
2.93a
2.88b
2.60b
465.03a
499.23a
Day 8
SEM
0 kGy
2.5 kGy
4.5 kGy
SEM
4.93
5.92
0.33
0.65
0.66
1.62
11.73
1.30
8.75
4.62
0.15
0.50
0.12
0.20
25.07
118.13
10.90c
8.58b
19.45c
11.75c
26.15ab
155.20
20.10
97.63
48.80a
2.20
12.33a
tr
3.48a
540.38b
132.63
40.80b
9.55a
22.78b
30.05b
28.58a
163.70
20.00
103.40
48.58a
2.03
13.55a
tr
3.20a
624.98a
120.73
8.73
60.73a 1.47
b
8.75
0.19
26.35a 0.42
a
41.33
0.47
24.38b 0.95
143.85
5.52
20.13
0.80
90.65
4.02
b
34.75
3.54
2.00
0.08
8.83b
0.83
tr
—
2.18b
0.19
ab
590.33 16.34
a-cDifferent letters within a row of the same storage time are different (P < 0.05).
dSamples (2g) were purged at 32°C. n = 4. SEM = standard error of mean.
Table 2—Relative production of volatiles in aerobic-packaged cooked irradiated pork sausages as affected by irradiation dose and storage
time (4°C)d
Day 0
Volatile compound
1-Pentene,hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Trimethyl hexane
Hexanal
3-Heptanone
1-Pentanol
Cyclohexanone
1-Hexanol
Nonanal
1-Heptanol
Total volatiles
0 kGy
41.63b
7.35c
3.10
21.73c
12.90c
15.13
57.13
8.15
44.80
44.18
2.15ab
11.78b
tr
tr
2.68
2.93b
281.90b
2.5 kGy
91.10a
48.13b
4.60
27.98b
30.78b
14.65
43.40
5.83
34.54
68.20
2.38a
16.08a
tr
tr
2.35
4.08a
397.86a
4.5 kGy
94.40a
86.18a
5.03
31.60a
40.40a
14.28
42.65
7.10
33.48
56.48
1.90b
12.13b
tr
tr
3.08
3.03b
435.50a
Day 4
SEM
4.20
5.35
0.41
0.68
0.82
1.72
7.65
1.63
5.72
6.11
0.08
0.78
—
—
0.25
0.20
19.34
0 kGy
2.5 kGy
4.5 kGy
131.28
16.18c
20.03
80.55a
15.30c
37.43
182.98
20.85
122.03
287.68
4.13
37.28a
3.68
2.80
4.43
10.00
981.50
Peak area (pA*sec)
137.78
154.05
48.03b
89.58a
23.25
23.52
61.40b
32.15c
30.28b
40.38a
40.53
42.40
168.58
166.98
19.03
21.75
112.05
110.78
283.18
270.90
4.00
3.70
a
34.18
30.08b
3.33
3.10
2.80
2.60
4.60
4.53
9.28
8.48
988.08
1010.53
Day 8
SEM
0 kGy
2.5 kGy
4.5 kGy
SEM
9.29
6.11
2.25
8.24
1.15
2.29
16.76
2.33
11.60
19.16
0.21
1.26
0.40
0.09
0.17
0.45
32.53
182.48
21.50a
24.92
55.20
14.85c
36.60
110.28
11.35
70.18
333.70
5.08
44.33a
3.85
3.43a
3.95
10.93a
941.03
183.18
64.10b
27.25
30.45
31.83b
38.80
114.30
11.50
73.45
338.30
4.63
38.25b
3.65
3.13a
4.33
10.18a
986.71
185.00 14.40
88.50c 3.34
24.25
1.80
33.78
9.82
a
40.60
1.30
37.43
1.50
115.58
8.25
11.58
1.09
74.35
6.26
291.25 16.84
3.83
0.15
31.70b 1.21
3.30
0.25
2.63b
0.11
4.30
0.15
b
8.05
0.44
964.23 32.67
a-cDifferent letters within a row of the same storage time are different (P < 0.05).
dSamples (2g) were purged at 32°C. SEM=standard error of mean.
contribution of other aldehydes such as heptanal, octanal, and nonanal to off-flavor of cooked meat would probably be considerably as
evidenced by their high flavor dilution factors (Specht and Baltes,
1994).
Table 3—Statistical significance of effects of irradiation dose, storage time, and packaging on volatiles production from cooked pork
sausagesa
Volatile compound
d.f.
Irradiation effect
2
TBARS
The changes of TBARS in irradiated cooked pork sausage with
different packaging conditions and storage time indicated that storage
time had no effect in vacuum-packaged sausage but had effects
(P⬍0.05) in aerobic-packaged sausage (Table 4). TBARS of sausage
in aerobic packaging increased two- to four-fold from Day 0 values.
Irradiating cooked pork sausage had some effect on TBARS of vacuum-packaged sausages at Day 0 and values of aerobic-packaged sausages at Day 0 and Day 4. Compared with storage time in aerobic
packaging, however, irradiation effects on the TBARS of cooked
meat were minor (Table 4). Ahn et al. (1998a,b) had reported that
preventing oxygen exposure after cooking had more important effects
on TBARS than antioxidant, irradiation, or storage conditions of raw
meat.
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JOURNAL OF FOOD SCIENCE—Volume 64, No. 2, 1999
1-Pentene, hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Trimethylhexane
Hexanal
3-Heptanone
1-Pentanol
Nonanal
1-Heptanol
Total volatiles
0.19
0.0001
0.95
0.48
0.0001
0.66
0.89
0.89
0.89
0.86
0.30
0.30
0.75
0.34
0.45
Storage effect
2
Packaging effect
1
Probabilities
0.0001
0.88
0.0001
0.007
0.98
0.0001
0.0001
0.01
0.002
0.0001
0.0001
0.0002
0.007
0.0003
0.0001
an = 24 for irradiation effect and storage effect; n = 36 for packaging effect.
0.0001
0.06
0.0001
0.0001
0.88
0.004
0.115
0.03
0.33
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
Table 4—Changes of TBARS in cooked irradiated pork sausages as
related to packaging and storage conditions
Vacuum packaging
Storage
(day))
0
4
8
SEM
0 kGy 2.5 kGy 4.5 kGy
0.71by
0.89a
0.83a
0.03
1.08x
0.92
0.85
0.08
Aerobic packaging
SEM
0 kGy 2.5 kGy 4.5 kGy SEM
TBARS values (mg MDA/kg meat)
0.91xy 0.08
1.23cy
1.33cy
0.87
0.03
4.57bxy 3.97by
0.77
0.05
6.91a
5.94a
0.05
0.27
0.36
1.95bx 0.10
5.16ax 0.24
5.41a 0.44
0.25
x-zDifferent letters within a row of the same packaging are different (P<0.05). n=4.
a-cValues with different superscript letters within a column of the same irradiation dose are
different (P<0.05). SEM=standard error of mean.
Table 5—Correlation coefficients between specific volatile compounds and TBARS
Volatile compound
1-Pentene, hexane
1-Heptene
Propanal
2-Propanone
1-Nonene
Pentanal
2-Methylpentanal
2-Pentanone
Trimethylhexane
Hexanal
3-Heptanone
1-Pentanol
Cyclohexanone
1-Hexanol
Nonanal
1-Heptanol
Total volatiles
Vacuum
packaginga
0.02
0.02
0.04
0.04
0.03
0.19*
0.05
0.09
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.02
0.06
Aerobic
packaging
Vacuum+aerobic
packaging
0.77**
0.02
0.81**
0.11
0.00
0.65**
0.30*
0.16
0.23*
0.86**
0.83**
0.83**
0.69**
0.82**
0.60*
0.80**
0.75**
0.61**
0.06
0.84**
0.31**
0.00
0.54**
0.03
0.00
0.03
0.93**
0.88**
0.90**
0.79**
0.89**
0.74**
0.89**
0.74**
an=36 for vacuum-packaged and aerobic-packaged; n=72 for vacuum+aerobic packaged.
*P<0.01; **P<0.0001.
Relationships of volatile compounds with TBARS
There was little relationship between TBARS and volatiles produced in irradiated cooked pork sausage with vacuum packaging (Table 5). However, with aerobic packaging, TBARS of irradiated cooked
pork sausage highly correlated (P⬍0.0001) with production of 1pentene+hexane, propanal, pentanal, hexanal, 3-heptanone, 1-pentanol,
cyclohexanone, 1-hexanol, 1-heptanol, and total volatiles. Relationships were also found between TBARS and amounts of 2-methylpentanal, trimethylhexane, and nonanal (P⬍0.05). The production of pentanal was the only volatile compound correlated (P⬍0.01) with TBARS
in both vacuum and aerobic packaged cooked sausages. The production of 1-pentene⫹hexane, propanal, pentanal, hexanal, 3-heptanone,
1-pentanol, cyclohexanone, 1-hexanol, nonanal, 1-heptanol, and total
volatiles had a very high correlation (P⬍0.0001) with TBARS of
irradiated cooked pork sausage when vacuum- and aerobic-packaged
sausages were combined. 2-Propanone correlated (P⬍0.0001) with
TBARS when both aerobic and vacuum packaging were combined
but not when packaging type was analyzed separately. This indicated
that the amount of aldehydes, total volatiles, and ketones and alcohols
with longer retention times could be good indicators of oxidative
changes in cooked irradiated meat.
CONCLUSIONS
IRRADIATION AFFECTED LIPID OXIDATION OF COOKED PORK SAUsages, especially with aerobic packaging, but oxygen availability (packaging) to meat during storage had much stronger effects. The production of 1-heptene and 1-nonene in cooked sausages increased proportionally with the increase of irradiation dose but was not affected by
packaging or storage time. The low correlations of irradiation-dependent volatiles (e.g., 1-heptene and 1-nonene) with TBARS values
regardless of packaging and storage conditions indicated that volatile
compounds responsible for irradiation odor were different from those
of lipid oxidation odor in cooked pork sausages.
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Ms received 5/19/98; revised 9/12/98; accepted 10/3/98.
Volume 64, No. 2, 1999—JOURNAL OF FOOD SCIENCE 229