JFS:
Food Chemistry and Toxicology
Addition of Antioxidant to Improve Quality and
Sensory Characteristics of Irradiated Pork Patties
ABSTRACT: The effects of added antioxidants on the oxidative quality changes of irradiated pork patties were
studied. Lipid oxidation (TBARS) was not a concern, even in aerobically packaged irradiated pork patties when
antioxidants were added. Irradiation produced sulfur compounds, such as dimethyl sulfide and dimethyl disulfide,
responsible for irradiation off-odor. The addition of gallate + tocopherol or sesamol + tocopherol was effective in
reducing the sulfur volatiles, but had no effect on the redness of irradiated raw pork patties. Aerobic packaging was
highly effective in reducing sulfur volatiles and off-odor from irradiated meat during storage. Antioxidants had
little effect on the sensory characteristics and consumer acceptance of irradiated pork, and consumers did not
consider the red color of irradiated raw pork as a quality defect.
Keywords: antioxidant, irradiation, color, pork patties, sensory characteristics, consumer acceptance
Introduction
A
LTHOUGH LOW-DOSE IRRADIATION (⬍ 10 KGY) IS THE BEST-KNOWN
method for controlling pathogenic and putrefying microorganisms in raw meat, the production of off-odor volatiles by irradiation
negatively impacts the acceptance of the meat in the marketplace
(Ahn and others 2000a). Irradiated pork, regardless of packaging
methods, produced more volatiles than non-irradiated patties and
developed a characteristic aroma after irradiation (Ahn and others
1998). Ahn and others (2000b) reported that panelists detected a
characteristic odor from irradiated pork and described it as a “barbecued corn-like”. Irradiation also accelerated lipid oxidation of raw
pork patties when stored in oxygen-permeable bags during and
after irradiation (Ahn and others 1998). The increase in lipid oxidation increased the amounts of volatiles, but had only a small impact
on the overall off-odor of irradiated raw meat. Ahn and others
(2001) indicated that the major contributor to off-odor in irradiated
pork was not lipid oxidation but radiolytic products of sulfur-containing amino acids, such as dimethyl sulfide, dimethyl disulfide,
and dimethyl trisulfide. Methanethiol, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, and a few other sulfur compounds
were formed from irradiated methionine- or cysteine-containing oil
emulsion and liposome model systems (Jo and Ahn 2000; Ahn and
others 2001). These results well indicated that radiolysis of amino
acids was an important mechanism involved in the production of
off-odor in irradiated meat, and these sulfur compounds had very
low thresholds compared with other volatile compounds.
Irradiation made the color of vacuum-packaged pork loin redder
than the aerobically packaged ones (Nanke and others 1998; Kim
and others 2001). The increase in redness can be critical for the
consumer acceptance of irradiated pork. Nam and Ahn (2002) attributed the increased redness to the formation of CO-heme complexes in irradiated turkey breast. Woods and Pikaev (1994) reported that radiolytic degradation of organic components produced
carbon monoxide in irradiated frozen meat and poultry. Therefore,
the quality changes of irradiated meat are closely correlated with
the production of radiolytic by-products.
Antioxidants were added to nonirradiated fresh and further processed meats to prevent oxidative rancidity, retard development of
off-flavors, and improve color stability (Shahidi and Rubin 1987;
© 2002 Institute of Food Technologists
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2625
Xiong and others 1993; Morrissey and others 1998). Vitamin E functions as a lipid-soluble antioxidant and is capable of quenching free
radicals in meat during irradiation and storage (Gray and others
1996). Some phenolic compounds, such as gallate and sesamol, can
interrupt the free radical chain reactions and are water-soluble.
Therefore, the combination of these phenolic antioxidants with
tocopherol can be effective in reducing the oxidative changes in
meat because the antioxidant combinations can work for both water and lipid systems. Because those antioxidant combinations
scavenge and quench free radicals, they can be effective in reducing lipid oxidation, radiolytic degradation of proteins and organic
compounds, and thus, influence irradiation off-odor and color
changes in irradiated meat. Radiolytic changes in meat are accelerated in the presence of oxygen and the activities and mechanisms
of selected antioxidants can vary depending upon the combination
of antioxidants and packaging method used.
The objective of this study was to determine the effect of selected
antioxidant combinations on color, lipid oxidation, off-odor volatiles, sensory characteristics, and consumer acceptance of pork patties irradiated and stored under different packaging conditions.
Materials and Methods
Sample preparation
Pork loins from 12 animals were purchased from Swift & Co.
(Marshalltown, Iowa, U.S.A.) on the slaughtering d. Each of 3 loins
was separately ground through a 3-mm plate and treated as a replication. Four different treatments were prepared: (1) no antioxidant added and nonirradiated, (2) no antioxidant added and irradiated, (3) sesamol ⫹ tocopherol added and irradiated, and (4)
gallate ⫹ tocopherol added and irradiated. Sesamol (3,4–methylenedioxyphenol) and gallate (3,4,5–trihydroxybenzoic acid) were
purchased from Sigma Chemical Co. (St. Louis, Mo., U.S.A.), and ␣–
tocopherol (vitamin E) was obtained from Aldrich Chemical Co.
(Milwaukee, Wis., U.S.A.). Each antioxidant was added to ground
pork at 0.01% level (final, w/w) and mixed for 3 min in a bowl mixer (Model KSM 90; Kitchen Aid Inc., St. Joseph, Mich., U.S.A.). The
mixed meats were ground again through a 3-mm plate to ensure
uniform distribution of the added antioxidants and pork patties
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Food Chemistry and Toxicology
K.C. NAM, K.J. PRUSA, AND D.U. AHN
Antioxidant effects on irradiated pork quality . . .
(100 g) were prepared. Half of the patties from each treatment
were aerobically packaged by individually placing them in polyethylene oxygen-permeable bags (4 x 6”, 2 MIL-Associated Bag Co.,
Milwaukee, Wis., U.S.A.), and the other half were vacuum-packaged
in high-oxygen-barrier bags (nylon/polyethylene, 9.3 mL O2/m2/24
h at 0 °C; Koch, Kansas City, Mo., U.S.A.).
Ionizing radiation and storage
Food Chemistry and Toxicology
Antioxidant-treated pork patties were electron beam-irradiated
at 0 or 4.5 kGy using a linear accelerator (Circe IIIR; Thomson CSF
Linac, Saint-Aubin, France) with 10 MeV of energy, 10 kW of beam
power, and 26.4 m/min of conveyor speed. The average dose rate
was 98.3 kGy/min and max/min ratio was approximately 1.17 for 4.5
kGy. To confirm the target dose, 2 alanine dosimeters per cart were
attached to the top and bottom surfaces of a sample. The alanine
dosimeter was read using an 104 Electron Paramagnetic Resonance
instrument (EMS-104, Bruker Instruments Inc., Billerica, Mass.,
U.S.A.). After irradiation, all samples were stored at 4 °C for up to 5
d. The TBARS of samples were determined at 0 and 5 d of storage,
and volatiles were analyzed within 1 h after irradiation. Lipid oxidation, color, and volatiles of the samples were determined at 0 and 5
d, and sensory characteristics and consumer acceptance were performed using the samples stored for 5 d.
2–Thiobarbituric acid-reactive substances (TBARS)
value
Lipid oxidation was determined by the TBARS method (Ahn and
others 1998). Sample (5 g) was placed in a 50-mL test tube and homogenized with 15 mL of deionized distilled water (DDW) and 50
mL of butylated hydroxytoluene (7.2% in ethanol, v/v) using a
Brinkman Polytron (Type PT 10/35; Brinkman Instrument Inc.,
Westbury, N.Y., U.S.A.) for 10 s at full power. A meat homogenate (1
mL) was transferred to a disposable test tube (13 ⫻ 100 mm), and
2 mL of thiobarbituric acid/trichloroacetic acid solution (20 mM
TBA/15% TCA, w/v) was added. The mixture was vortexed and
then incubated in a 90 °C water bath for 15 min to develop red color.
After cooling for 10 min in cold water, the sample was vortexed and
centrifuged at 3000 x g for 15 min at 5 °C. The absorbance of the supernatant layer was read at 531 nm against a blank prepared with
1 mL DDW and 2 mL TBA/TCA solution. The amounts of TBARS
were expressed as mg of malondialdehyde (MDA) per kg meat using a standard curve.
Color measurement
Color was measured on the packaged surface of samples with a
Labscan spectrophotometer (Hunter Associated Labs Inc., Reston,
Va., U.S.A.) that had been calibrated against white and black reference tiles packaged in the same bags as those used for meat packaging. CIE L- (lightness), a- (redness), and b- (yellowness) values were
obtained using an illuminant A. An average value from 2 random
locations on each sample surface was used for statistical analysis.
tiles were trapped using a Tenax column (Tekmar-Dohrmann) and
desorbed for 2 min at 225 °C, focused in a cryo-focusing module (90 °C), and then thermally desorbed into a column for 30 s at
225 °C. An HP-624 column (7.5 m ⫻ 0.25 mm i.d., 1.4 mm nominal),
an HP–1 column (52.5 m ⫻ 0.25 mm i.d., 0.25_ mm nominal;
Hewlett-Packard Co.) and an HP-Wax column (7.5 m ⫻ 0.25 mm
i.d., 0.25 mm nominal) were connected using zero dead-volume column connectors (J &W Scientific, Folsom, Calif., U.S.A.). 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/min, increased to 45 °C at 5 °C/min, increased to 110 °C at 20 °C/min, increased to 210 °C at 10 °C/min, and then was held for 2.5 min at
210 °C. Constant column pressure at 20.5 psi was maintained. The
ionization potential of the mass-selective detector (Model 5973;
Hewlett-Packard Co.) was 70 eV, and the scan range was 18.1 to 300
m/z. Identification of volatiles was achieved by comparing mass
spectral data of samples with those of the Wiley Library (HewlettPackard Co.). Standards, when available, were used to confirm the
identification by the mass-selective detector. The area of each peak
was integrated using the ChemStationTM (Hewlett-Packard Co.),
and the peak area (total ion counts ⫻ 104) was reported as an indicator of volatiles generated from the sample.
Sensory evaluation
Fourteen trained sensory panelists were used to evaluate offodor in meat. Panelists were selected on the basis of ability to distinguish irradiation off-odor from other aroma using triangle tests.
Training sessions were conducted for panelists to familiarize them
with the irradiation off-odor, the scale to be used, and the range of
attribute intensities likely to be encountered during the study.
Panelists were trained with meat samples irradiated at different
irradiation doses and containing specific chemical compounds,
such as dimethyl sulfide and dimethyl disulfide, that have been
found in the volatile analysis of previous studies (Ahn and others
2000a,b). Samples (15 g) stored at 4 °C for 5 d were placed in coded
and capped glass scintillation vials and held 30 min at 22 °C before
testing. Four different samples with the same packaging method
were presented to each panelist in isolated booths at each separate
session. Panelists were instructed to smell the samples in random
order and record the intensity of irradiation off-odor on a 15-cm line
scale anchored from “not detectable” to “intense”.
Seventy-two participants (age of 20s to 40s) who regularly consume pork were chosen for the consumer acceptance test. Four coded
samples with the same packaging were presented to participants.
Panelists were asked to assign a numerical value between 1 (dislike
extremely) and 7 (like extremely), depending on their acceptance of
odor and color of the meat. Consumers were instructed to compare
the color of samples before and after opening the packaging bags,
and then asked to evaluate the aroma for odor acceptance.
Statistical analysis
Volatile compounds analysis
A purge-and-trap apparatus (Precept II and Purge & Trap Concentrator 3000; Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.) connected to a gas chromatograph/mass spectrometer (GC/MS;
Hewlett-Packard Co., Wilmington, Del., U.S.A.) was used to analyze
volatiles produced (Ahn and others 2001). Minced meat sample (3
g) was placed in a 40-mL sample vial, and the vial was flushed with
helium (40 psi) for 5 s. The maximum waiting time of a sample in a
refrigerated (4 °C) holding tray was less than 4 h to minimize oxidative changes before analysis (Ahn and others 1999). The meat sample was purged with helium (40 mL/min) for 12 min at 40 °C. Vola2626
Data were analyzed using analysis of variance and the generalized linear model procedure of the SAS software (SAS Institute
1995) was used with Student-Newman-Keul’s multiple range tests
to compare the mean values. Mean values and standard error of
the means (SEM) were reported (P ⬍ 0.05).
Results and Discussion
Lipid oxidation
Irradiation and antioxidants affected the TBARS of pork patties
during storage (Table 1). Without added antioxidants, irradiated
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Antioxidant effects on irradiated pork quality . . .
fluenced much by antioxidant treatments and the results of b–
values were inconsistent.
Color
Volatile compounds
Irradiation at 4.5 kGy made the color of pork patties redder (Table 2). Color a–values increased after irradiation regardless of packaging methods, and the increased redness was maintained or increased during the 5 d storage. The a–values of vacuum-packaged
nonirradiated control were lower than that of the aerobically packaged one, due to low oxygen partial pressure inside the meat bag.
Therefore, the visual effects between nonirradiated and irradiated pork patties were more distinct in vacuum than aerobically
packaged meats. The perception of red color in vacuum-packaged
irradiated pork patties was much more intense than in the nonirradiated control. Nam and Ahn (2002) reported that carbon monoxide
(CO) production by irradiation was related to the pink compound,
CO-heme pigment, formation in poultry. Nawar (1985) reported
that irradiation-induced free radicals stimulated CO production via
the radiolytic changes in lipids. Although the use of free radical
scavengers was expected to reduce color changes, antioxidants had
no effect on the color of the irradiated pork. L–values were not in-
Irradiation, antioxidant, and packaging affected the profiles and
amounts of volatiles in pork patties at d 0 (Table 3). Irradiation produced many new volatiles, such as hydrocarbons, sulfur compounds, benzene, and toluene. Among them, critically increased
volatiles were octane, toluene, and sulfur-containing compounds
(methanethiol, dimethyl sulfide, methanethiol ethane, dimethyl
disulfide, and dimethyl trisulfide). Under aerobic conditions, added antioxidant combinations reduced the amounts of some sulfur
volatiles as well as total volatiles, compared to the irradiated control. Huber and others (1953) reported that the use of antioxidants
such as ascorbate, citrate, tocopherol, gallate esters, and polyphenols was effective in reducing the odor of irradiated meat. Gallate
plus tocopherol lowered the amount of dimethyl sulfide by 80% of
the irradiated control, but the antioxidant combination was not
effective in reducing other sulfur volatiles. Ahn and others (2000a)
reported that dimethyl disulfide was a major sulfur compound responsible for the irradiation off-odor. Under vacuum packaging,
Aerobic packaging
Day 0
0.25by
Day 5
0.32bx
SEM
0.01
Vacuum packaging
Day 0
0.18by
Day 5
0.27cx
SEM
0.01
0.32ay
0.53ax
0.02
0.24by
0.36bx
0.02
0.26by
0.52ax
0.01
0.01
0.01
0.28ay
0.41ax
0.01
0.29a
0.32b
0.01
0.28a
0.32b
0.02
0.01
0.01
1 Sesamol
2Tocopherol
3 Gallate
a-c Different letters within a row are significantly different (P < 0.05).
x, y Different letters within a column with same packaging are significantly
different (P < 0.05).
Table 2–Color values of irradiated pork patties treated with different antioxidants during storage at 4 °C
Aerobic packaging
Storage
L–value
Day 0
Day 5
SEM
a–value
Day 0
Day 5
SEM
b–value
Day 0
Day 5
SEM
NonIR
Control
Vacuum-packaging
Control
Irradiated
S1+E2
G3+E
SEM
50.1
53.5
0.8
51.5
53.5
1.0
50.1
52.6
1.0
53.1
52.5
0.9
6.6b
6.1b
0.4
8.5ay
9.2ax
0.2
8.7a
9.2a
0.6
15.6aby
17.1bx
0.2
14.5by
17.4abx
0.5
14.8by
17.6abx
0.3
NonIR
Control
Control
Irradiated
S+E
G+E
1.1
0.6
50.2
52.4
0.9
51.2
51.8
1.1
50.9
53.5
0.9
50.9
52.2
0.8
1.1
0.7
8.3ay
9.0ax
0.5
0.5
0.3
5.3bx
4.1by
0.4
9.7a
9.2a
0.5
8.8ay
10.2ax
0.5
9.1a
9.5a
0.3
0.5
0.4
16.1ay
18.1ax
0.3
0.4
0.2
14.8a
15.2
0.6
13.8by
15.3x
0.6
14.1ab
15.6
0.5
15.2b
15.2
0.7
0.3
0.3
SEM
1 Sesamol
2Tocopherol
3 Gallate
a, b Different letters within a row with same packaging are significantly different (P < 0.05).
x, y Different letters within a column with same color value are significantly different (P < 0.05).
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Food Chemistry and Toxicology
Table 1—TBARS values of irradiated pork patties treated
with different antioxidants during storage at 4 °C
Irradiated
NonIR
Storage
Control
Control
S1+E2
G3+E
SEM
pork patties produced higher TBARS than the nonirradiated patties. With aerobic packaging, addition of antioxidant combinations
- sesamol plus tocopherol and gallate plus tocopherols - were effective in controlling lipid oxidation of irradiated pork patties. The
TBARS of antioxidant-added irradiated patties were about the
same as that of the nonirradiated control. After 5 d of storage, the
TBARS of the samples treated with sesamol plus tocopherol or gallate plus tocopherol were much lower than that of the irradiated
control, whereas there was no difference between the 2 antioxidant
treatments. Overall TBARS data of pork patties during 5-d storage
indicated that lipid oxidation was not a great problem in irradiated
raw pork patties, but sesamol was superior to gallate in controlling
lipid oxidation under aerobic conditions. The combination of sesamol plus g–tocopherol was efficient in inhibiting hydroperoxide
formation in oils ( Yoshida and Takagi 1999). Chen and others
(1999) also reported that phenolic antioxidants were effective in
reducing lipid oxidation in aerobically packaged irradiated pork
patties. With vacuum packaging, however, antioxidant effect was
not found in irradiated pork patties at 0 and 5 d of storage because
of very small changes in TBARS under vacuum-packaging conditions.
Antioxidant effects on irradiated pork quality . . .
Table 3—Volatile compounds of irradiated pork patties treated with different antioxidants at Day 0
Vacuum-packaging
Aerobic packaging
Storage
NonIR
Control
Control
Irradiated
S1+E2
G3+E
SEM
NonIR
Control
(Total ion counts ⫻
18
0d
13
160c
30
0c
39
36 c
5
0c
527
59 c
1
88a
21
0d
51
241c
12
0b
6
0c
14
0c
50
0c
12
99b
47
0b
–
63a
62
77 c
9
451b
52
1116b
7
271b
–
469b
52
0b
483
3136c
Control
Irradiated
S+E
G+E
SEM
104)
Food Chemistry and Toxicology
2–Methyl–1–propene
Methanethiol
1–Pentene
Pentane
2–Pentene
Dimethyl sulfide
Carbon disulfide
1–Hexene
Hexane
Methylthio ethane
Benzene
1–Heptene
Heptane
Trimethyl pentane
Dimethyl disulfide
3–Methyl heptane
Toluene
1–Octene
Octane
2–Octene
3–Methyl–2–heptene
Dimethyl trisulfide
Total
0c
0b
0c
42 c
0c
0d
54a
0c
196b
0c
0c
0c
0b
66b
0c
0
59 c
34 c
350b
66b
0
0b
869d
444a
83a
351a
532a
116a
12002 a
0b
371a
866a
236a
263a
388a
564a
171a
229b
0
1203a
195a
994a
161a
0
89b
19264 a
251b
47a
155b
177b
46b
4714b
0b
193b
362b
147b
179b
129b
160b
56b
175b
0
680b
102b
332b
77b
0
11b
8000b
249b
89a
220b
218b
48b
2335c
0b
183b
296b
149b
170b
162b
147b
53b
377a
0
722b
89b
39b
53b
0
393a
6353c
360a
1172a
387a
317a
77a
7135a
0b
390a
1017a
242a
301a
311a
411a
444a
5420a
0b
1250a
912a
2159a
535a
755a
2509a
26113 a
296b
1377b
269b
196b
44b
6037a
0b
290b
765ab
207a
229b
207b
286b
123b
2914a
0b
934b
620b
1855a
410ab
586ab
469b
18122 b
201c
20
1704b
195
184b
25
174b
17
43b
4
3967b
620
0b
2
126c
20
544b
87
246a
17
216b
12
182b
21
195b
33
152b
18
5052a
694
0b
1
1153a
49
351b
79
1072b
172
298b
57
402b
70
602b
489
16871 b 1391
1 Sesamol
2Tocopherol
3 Gallate
a–d Different letters within a row with same packaging are significantly different (P < 0.05).
greater amounts of total and sulfur volatiles were found compared
to aerobic packaging, because the volatiles generated by irradiation
could not be freed away from packaging bags. Dimethyl sulfide was
the major sulfur compound in aerobically packaged irradiated pork
patties, but large amounts of both dimethyl sulfide and dimethyl
disulfide were detected under vacuum packaging-conditions. The
ratios of dimethyl sulfide to dimethyl disulfide were about 60:1 and
1:1 in aerobic and vacuum-packaged irradiated pork patties, respectively. Gallate plus tocopherol reduced the amounts of total
volatiles, dimethyl sulfide, and dimethyl trisulfide compared to the
irradiated control.
After 5 d of storage, the profiles and amounts of volatiles of irradiated pork patties changed dramatically depending on packaging
and antioxidant treatments (Table 4). Most volatiles found in aerobically packaged irradiated pork patties at d 0 were volatilized and
only 18% of the volatiles detected in irradiated control remained at
d 5. Most sulfur volatiles, except for dimethyl sulfide, completely
disappeared at d 5. On the other hand, vacuum-packaged irradiated pork patties had increased total volatiles at d 5. Although Patterson and Stevenson (1995) reported that dimethyl trisulfide was the
most potent off-odor in irradiated chicken, dimethyl trisulfide was
almost gone at d 5 even in vacuum conditions. Nevertheless, aerobic conditions were still more beneficial than vacuum packaging
in terms of volatile composition if the lipid oxidation problem is not
serious during the storage of irradiated raw meat. No aldehydes
were detected in pork patties stored for 5 d, regardless of irradiation
doses.
Antioxidants had significant effects on the amounts of sulfur
volatiles in meat under both packaging conditions. In aerobically
packaged irradiated pork patties, both of the antioxidant treatments reduced the amounts of dimethyl disulfide in irradiated
2628
meat compared to that in control. In vacuum-packaged irradiated
pork patties, the combination of gallate plus tocopherol was highly
effective in reducing sulfur volatiles such as methanethiol, dimethyl disulfide, and dimethyl disulfide. The amounts of dimethyl
disulfide and dimethyl trisulfide were decreased by 55% and 91%
of the irradiated control, respectively. As a result, the ratio of dimethyl sulfide to dimethyl disulfide in gallate plus tocopherol treatment was different from that of control or sesamol plus tocopherol
treatment. The relative proportion of dimethyl sulfide in gallate
plus tocopherol treatment was much higher than in the others, and
this different ratio may affect not only irradiation off-odor intensities but also the odor characteristics, because the odor of dimethyl
sulfide is milder than that of dimethyl disulfide. In this respect, the
combination of gallate plus tocopherol was superior to that of sesamol plus tocopherol for vacuum-packaged irradiated raw pork
patties.
Sensory evaluation
The result of off-odor intensity in irradiated pork patties (Table
5) was consistent with that of volatile analysis at d 5 (Table 4). Panelists could easily distinguish odor differences between nonirradiated and irradiated pork patties at both packaging conditions.
During the training sessions, panelists came to a consensus to describe the irradiation off-odor as a “sulfury”, “boiled sweet corn”, or
“steamed or rotten vegetable”. Ahn and others (2000b) already
described the irradiation odor from irradiated pork as “barbecued
corn-like”. In aerobically packaged pork patties, sensory panelists
did not detect the antioxidant effects, because many volatiles responsible for the irradiation off-odor were volatilized at d 5 (Table
4), and the remaining amounts were under threshold levels. In
vacuum-packaged irradiated pork patties, however, the off-odor
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Antioxidant effects on irradiated pork quality . . .
Table 4—Volatile compounds of irradiated pork patties treated with different antioxidants at Day 0
Vacuum-packaging
Aerobic packaging
NonIR
Control
Storage
Control
Irradiated
S1+E2
G3+E
NonIR
Control
SEM
(Total ion counts ⫻
8
0c
8
0
–
0c
–
0c
21
0b
21
61 c
5
64
150
0c
3
94a
4
0
10
0b
17
165c
–
0c
10
0b
11
0b
23
0b
8
150
–
0b
–
29b
21
42 c
–
0c
22
748b
5
192b
–
315ab
–
0
149
1862c
Control
Irradiated
S+E
G+E
SEM
378b
0
61b
64b
356a
257b
67
23826 a
0b
0
376a
824b
276a
237a
205a
203a
187
2147a
78a
865a
441ab
1064b
297ab
330ab
199
32744 a
16
–
2
3
33
15
7
1425
2
–
26
83
15
11
18
30
14
251
10
27
45
87
29
41
52
1536
2–Methyl–1–propene
Butane
Methanethiol
1–Butene
1–Pentene
Pentane
2–Pentene
Dimethyl sulfide
Carbon disulfide
3–Methyl pentane
1–Hexene
Hexane
Methylthio ethane
Benzene
1–Heptene
Heptane
Trimethyl pentane
Dimethyl disulfide
3–Methyl heptane
Toluene
1–Octene
Octane
2–Octene
3–Methyl–2–heptene
Dimethyl trisulfide
Total
0b
0b
0
0
0c
0c
0b
0b
64
0b
0c
119
0
0c
0c
0c
39 c
0
0
51 c
0
85 c
0c
0
0
360c
76a
54a
0
0
184a
277a
27a
999a
70
54a
111b
381
0
63a
138b
256ab
81b
0
0
269a
0
352a
43b
0
0
3440a
47a
34a
0
0
73b
162b
0b
290b
69
0b
103b
362
0
16bc
131b
194b
80b
0
0
186b
0
257b
41b
0
0
2052b
60a
61a
0
0
160a
306a
0b
195b
64
0b
158a
570
0
44ab
200a
304a
138a
0
0
287a
0
416a
71a
0
0
3038a
488a
0
96a
80a
369a
341a
68
25520 a
0b
0
348a
1047ab
285a
223a
180a
219a
169
2274a
67a
816a
517a
1353a
357a
466a
189
35482 a
462a
0
0c
70ab
476a
358a
93
11285 b
0b
0
407a
1288a
210b
249a
188a
233a
202
197b
89a
724b
313b
818b
288ab
231b
59
18249 b
Food Chemistry and Toxicology
104)
1 Sesamol
2Tocopherol
3 Gallate
a–c Different letters within a row with same packaging are significantly different (P < 0.05).
Table 5—Off-odor intensity of irradiated pork patties treated
with different antioxidants and stored for 5 d1
Packaging
Aerobic
Vacuum
NonIR
Control
Irradiated
S2+E3
G4+E
SEM
1.0b
5.9a
6.2a
6.1a
1.3c
9.9a
9.3a
7.6b
0.7
0.7
Control
1 Responses of 14 panelists with 2 replications. 0, not detectable; 15, very
strong.
2 Sesamol
3Tocopherol
4 Gallate
a, b Different letters within a row are significantly different (P < 0.05).
intensity of gallate plus tocopherol treatment was lower than that
of the control and the sesamol plus tocopherol. This result is in accordance with the lower total and sulfur compounds detected in
gallate plus tocopherols-treated pork patties.
The results of consumer acceptance for the irradiated pork odor
were different from those of sensory evaluation (Table 6). Consumers did not show any difference in odor acceptance between aerobically packaged nonirradiated and irradiated pork patties. In vacuum-packaged pork patties, consumer rated nonirradiated meat
more acceptable than irradiated and there was no difference within
irradiated samples. Thus, they did not detect the antioxidant effect
on the off-odor. These results indicated that there could be a few
sample-presenting errors. Irradiation was the most critical factor
influencing the aroma of pork patties, and, thus, the differences
between nonirradiated and irradiated pork patties were great, and
the differences among irradiated samples were relatively small.
Table 6—Consumer acceptance of irradiated pork patties
treated with different antioxidants and stored for 5 d1
Irradiated
NonIR
Attribute
Control Control S1+E2 G3+E SEM
Aerobic packaging
Color
Odor
Vacuum packaging
Color
Odor
4.7
4.5
5.0
4.3
4.6
4.1
4.5
4.0
0.2
0.4
3.0b
3.4a
4.8a
2.8b
4.9a
2.9b
4.5a
2.7b
0.2
0.1
1 Responses of 72 consumers. 1, dislike extremely, 7, like extremely
2 Sesamol
3Tocopherol
4 Gallate
a, b Different letters within a row are significantly different (P < 0.05).
Both contrast and convergence errors might be generated in presenting the samples to the consumers. One more interesting thing
was the color acceptance of vacuum-packaged pork patties. The
color acceptance of vacuum-packaged irradiated pork patties was
higher than the nonirradiated control regardless of antioxidant
treatments. This indicated that consumers did not consider the
increased red or pink color of irradiated raw pork patties as a quality
defect, but the red color of irradiated meat could be a serious quality defect if it remained after cooking.
Conclusion
A
LTHOUGH THE COMBINATION OF SESAMOL + TOCOPHEROL WAS
more effective in reducing TBARS, lipid oxidation itself was not
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Antioxidant effects on irradiated pork quality . . .
very problematic during the conventional storage of irradiated raw
pork patties. More attention should be focused on the sulfur-containing volatiles responsible for the irradiation off-odor, because a
large amount of sulfur-volatiles were found in irradiated pork patties, and their thresholds are very low, and the combination of
gallate + tocopherol (0.02%) was highly effective in reducing them.
The amounts of sulfur-volatiles in irradiated meat during storage
depended upon packaging conditions. When antioxidant is used,
aerobic packaging is recommended, because off-odor volatiles and
lipid oxidation in pork patties could be effectively controlled by
packaging and antioxidants, respectively.
Food Chemistry and Toxicology
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MS 20010709 Submitted 12/21/01, Accepted 3/14/02, Received 3/15/02
Journal Paper nr J - 19683 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. 50011. Project nr 3706, funded by National Pork Producers Council, on
behalf of the Iowa Pork Producers Association.
The authors are with the Dept. of Animal Science, Iowa State Univ., Ames,
Iowa 50011-3150. Direct inquiries to D.U. Ahn, e-mail: duahn@iastate.edu
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