MEAT
SCIENCE
Meat Science 75 (2007) 61–70
www.elsevier.com/locate/meatsci
Effects of oleoresin–tocopherol combinations on lipid oxidation,
off-odor, and color of irradiated raw and cooked pork patties
K.C. Nam 1, K.Y. Ko, B.R. Min, H. Ismail, E.J. Lee, J. Cordray, D.U. Ahn
*
Department of Animal Science, Iowa State University, Ames, IA 50011-3150, United States
Received 28 February 2006; received in revised form 26 June 2006; accepted 26 June 2006
Abstract
Lipid oxidation, color, and volatiles of double-packaged pork loins with various oleoresin or oleoresin–tocopherol combinations were
determined to establish the best oleoresin–tocopherol conditions that can improve the quality of irradiated raw and cooked pork loins.
Rosemary and a-tocopherol combination at 0.05% and 0.02% of meat weight, respectively, showed the most potent antioxidant effects in
reducing both TBARS values and the amounts of volatile aldehydes in irradiated raw and cooked pork loins. The antioxidant combination, however, did not affect the production of sulfur volatiles responsible for irradiation off-odor and showed little effects on color
changes in irradiated raw and cooked pork loins. Exposing double-packaged irradiated pork to aerobic conditions for 3 days during
the 10-day storage was effective in controlling both lipid oxidation and irradiation off-odor, regardless of packaging sequences.
2006 Published by Elsevier Ltd.
Keywords: Oleoresin; Double packaging; Irradiation; Lipid oxidation; Off-odor; Pork loin
1. Introduction
Food irradiation is proven to be the best technology in
eliminating disease-causing pathogens from raw meat and
poultry (Murano, 1995; Thayer, 1993). The chemical
changes of meat and poultry by irradiation, however, are
concern to consumers, and the meat industry is having difficulties in using the technology to achieve its food safety
benefits. The generations of pink color (Millar, Moss, MacDougall, & Stevenson, 1995; Nam & Ahn, 2002a) and offodor (Ahn, Nam, Du, & Jo, 2001; Patterson & Stevenson,
1995) are critical issues for irradiating pork because consumers associate the presence of pink color in cooked meat
with undercooking or contamination, and off-odor with
bacterial spoilage. The characteristic off-odor in irradiated
meats was caused by the production of sulfur volatiles from
*
Corresponding author. Tel.: +1 515 294 6595; fax: +1 515 294 9143.
E-mail address: duahn@iastate.edu (D.U. Ahn).
1
Present address: Exam. Div. of Food and Biological Resources,
Korean Intellectual Property Office, Daejeon 302-701, Republic of Korea.
0309-1740/$ - see front matter 2006 Published by Elsevier Ltd.
doi:10.1016/j.meatsci.2006.06.016
sulfur-containing amino acids such as methionine and cysteine (Ahn, 2002; Jo & Ahn, 2000). The mechanism of pink
color generation in irradiated pork or poultry was through
the production of carbon monoxide from meat components (Lee & Ahn, 2004; Nam & Ahn, 2002b).
The chemical changes in irradiated meats are initiated
by the free radicals produced by irradiation, and the production of sulfur volatiles or carbon monoxide was
caused by reactions between meat components and radiolytic free radicals (Ahn, 2002; Nam & Ahn, 2002b). Thus,
antioxidants with free radical scavenging activities may
help protect the irradiated pork from chemical changes.
Various individual phenolic compounds separated from
natural sources (e.g., gallate, sesamol) are proven to have
very strong free radical scavenging capabilities, but are
not permitted for use in foods as an antioxidant. Oleoresins extracted from various plants contain large amounts
of phenolic antioxidants, however, are commercially available for use in meat products. a-Tocopherol is permitted
to use in meat at 0.02% level as a vitamin supplement or
antioxidants. Thus, combination of oleoresins extracted
62
K.C. Nam et al. / Meat Science 75 (2007) 61–70
from various spices (dill, basil, garlic, onion, and rosemary) with a-tocopherol may increase the antioxidant
effect of oleoresins.
The color and odor changes in irradiated meats are
highly dependent upon packaging conditions. Under aerobic packaging conditions, most of the sulfur volatiles in
irradiated turkey breast disappeared and the pink color
returned to normal after a few days of aerobic storage
(Nam & Ahn, 2003b). On the other hand, irradiation generates hydroxyl radicals that can initiate lipid oxidation,
but lipid oxidation became a potential quality problem
only when the meats were exposed to aerobic conditions
(Ahn et al., 2001). Double-packaging, which exposes the
vacuum packaged meat to aerobic conditions for 2–3 days
during storage, was effective in minimizing lipid oxidation,
pink color defect and sulfur-volatile production in irradiated pork loin during storage (Nam, Min, Lee, Cordray,
& Ahn, 2004). Double-packaging was proven to be effective
in reducing both color and off-odor problems in turkey
breast without adding any additives, but combination of
double-packaging and antioxidants was more effective than
double-packaging alone in controlling lipid oxidation and
irradiation off-odor (Nam & Ahn, 2003a).
The objective of this study was to select the best oleoresin–tocopherol combinations to control lipid oxidation,
off-odor, and color in irradiated pork loins.
2. Materials and methods
2.1. Sample preparation
Pork loin (Longissimus dorsi) muscles (3 days after
slaughter) from 8 different animals (Berkshire, female,
approximately 105 kg live weight) were purchased from
the Meat Laboratory at Iowa State University (Ames,
IA) and ground through a 5-mm plate. Loins from two animals were pooled, ground and used as a replication (4 replications). Oleoresin from dill, basil, garlic, onion, or
rosemary (0.05% of meat wt.) singly or in combination with
tocopherol (0.02%) was added to ground pork, mixed for
2 min in a kitchen mixer, and then patties were prepared.
The patties were individually packaged in oxygen-permeable plastic bags (polyethylene, 4 · 6, 2 mil; Associated
Bag Company, Milwaukee, WI), irradiated at 2.5 kGy
using a Linear Accelerator (Circe IIIR; Thomson CSF
Linac, Saint-Aubin, France) with 10 MeV of energy,
10.2 kW of power level, and 88.9 kGy/min of average dose
rate. Half of the aerobically packaged patties were stored at
4 C and lipid oxidation of the patties was determined at
Day 0 and Day 10 of storage. The other half of the patties
were cooked in a 176 C electric oven to an internal temperature of 75 C at Day 0, stored in oxygen-permeable
plastic bags at 4 C, and analyzed for lipid oxidation after
0 and 3 days of storage. Irradiated and nonirradiated
ground pork patties with none added were used as controls.
Two oleoresin or oleoresin–tocopherol combinations
that provide the best control for lipid oxidation in irradi-
ated raw and cooked meat were selected and used for the
next study, which determines the effect of antioxidant
(oleoresin–tocopherol)/double-packaging
combinations
on the quality changes in irradiated raw and cooked
ground pork loins during storage. Pork loins were ground
through a 5-mm plate, mixed with selected oleoresin–
tocopherol combinations, and then patties were prepared.
The patties were packaged, irradiated (2.5 kGy), and
stored at 4 C according to two double-packaging models:
for double-packaging model A3/V7, patties were individually packaged in oxygen-permeable bags (polyethylene,
4 · 6, 2 mil), irradiated at 2.5 kGy, and then stored at
4 C. After 3 days of storage, the aerobically packaged
patties were packaged again with oxygen impermeable
vacuum bags (nylon/polyethylene, 9.3 mL O2/m2/24 h at
0 C; Koch, Kansas City, MO), and then stored at 4 C
for another 7 days. For V7/A3 double-packaging model,
patties were individually packaged in oxygen-permeable
bags first, and then vacuum-packaged in oxygen-impermeable bags (nylon/polyethylene, 9.3 mL O2/m2/24 h at
0 C). The doubly packaged patties were irradiated and
then stored at 4 C. After 7 days of storage, the outer vacuum bags of the patties were removed and then patties
were exposed to aerobic conditions for 3 days. Nonirradiated and irradiated vacuum-packaged patties were used as
controls. The patties were cooked immediately after irradiation in a 176 C electric oven to an internal temperature of 75 C. Lipid oxidation, color, and volatiles of
the cooked patties were determined at 0 day and 10 days
of storage.
2.2. 2-Thiobarbituric acid reactive substances (TBARS)
Lipid oxidation was determined by a modified TBARS
method of Buege and Aust (1978). Minced sample (5 g)
was placed in a 50-mL test tube and homogenized with
15 mL deionized distilled water (DDW) using a Brinkman Polytron (Type PT 10/35; Brinkman Instrument,
Inc., Westbury, NY) for 15 s at high speed. The meat
homogenate (1 mL) was transferred to a disposable test
tube (13 · 100 mm), and 50 lL butylated hydroxytoluene
(7.2% in ethanol) and 2 mL of thiobarbituric acid/trichloroacetic acid (20 mM TBA and 15%, w/v, TCA) solution
were added. The mixture was vortex-mixed and then
incubated in a 90 C water bath for 15 min. After cooling, the samples were vortex-mixed and centrifuged at
3000g for 15 min. The absorbance of the resulting upper
layer was read at 532 nm against a blank (1 mL
DDW + 2 mL TBA/TCA). The amounts of TBARS were
expressed as mg of malondialdehyde (MDA) per kg of
meat.
2.3. Color values
CIE color values were measured on the sample surface
using a LabScan colorimeter (Hunter Associate Labs,
Inc., Reston, VA) that had been calibrated against black
K.C. Nam et al. / Meat Science 75 (2007) 61–70
and white reference tiles covered with the same packaging
materials as used for samples. The CIE L* (lightness), a*
(redness), and b* (yellowness) values were obtained by an
63
illuminant A (light source). Two random readings from
both top and bottom locations on a sample surface were
used for statistical analysis.
Table 1
TBARS values of raw pork loin affected by irradiation, oleoresins, and tocopherol during refrigerated storage
Irradiation
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Oleoresina
Control
Control
Dill
Basil
Garlic
Onion
Rosemary
Dill
Basil
Garlic
Onion
Rosemary
a-Tocopherol
0 day
10 day
SEM
–
–
–
–
–
–
–
0.02%
0.02%
0.02%
0.02%
0.02%
(mg MDA/kg meat)
0.24bx
0.21bx
0.19bx
0.45ax
0.39ax
0.22bx
0.18bx
0.16bx
0.21bx
0.30bx
0.19bx
0.18bx
0.03
1.50cy
1.78cy
0.68dy
2.74by
4.19ay
1.32cy
0.29dy
0.36dy
0.71dy
2.50by
0.37dy
0.36dy
0.14
0.07
0.11
0.07
0.23
0.06
0.13
0.02
0.04
0.12
0.08
0.02
0.02
Mean values with different letters (a–d) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Added at 0.05%.
Table 2
TBARS values of cooked pork loin affected by irradiation, oleoresins, and tocopherol during refrigerated storage
Irradiation
Oleoresina
a-Tocopherol
0 day
3 day
SEM
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Dill
Basil
Garlic
Onion
Rosemary
Dill
Basil
Garlic
Onion
Rosemary
–
–
–
–
–
–
–
0.02%
0.02%
0.02%
0.02%
0.02%
(mg MDA/kg meat)
1.13ax
1.11ax
1.03ax
1.15ax
1.08ax
0.93abx
0.52dx
0.59dx
0.70cdx
0.79bcx
0.62cdx
0.56dx
0.05
3.19ay
3.19ay
2.72bcy
3.18ay
2.85aby
2.48cy
1.43dey
1.49dey
1.59dy
1.71dy
1.19efy
1.02fy
0.10
0.10
0.14
0.14
0.06
0.05
0.08
0.04
0.05
0.03
0.04
0.02
0.02
Mean values with different letters (a–f) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Added at 0.05%.
Table 3
TBARS values of irradiated raw pork patties affected by oleoresin + tocopherol and packaging during refrigerated storage
Irradiation
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Antioxidanta
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Packaging
0 day
10 day
SEM
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
(mg MDA/kg meat)
0.20
0.21
0.15
0.15
0.17
0.15
0.02
0.21a
0.22a
0.16b
0.16b
0.18b
0.16b
0.01
0.02
0.02
0.02
0.01
0.01
0.01
Mean values with different letters (a, b) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Oleoresin–tocopherol combination added at 0.05–0.02% of meat wt.
b
Aerobically packaged for 3 days first and then vacuum-packaged for 7 days.
c
Vacuum-packaged for 7 days first and then aerobically packaged for 3 days.
64
K.C. Nam et al. / Meat Science 75 (2007) 61–70
2.4. Volatile compounds (volatiles)
A dynamic headspace analysis was performed using a
Solartek 72 Multimatrix-Vial Autosampler/Sample Concentrator 3100 (Tekmar-Dohrmann, Cincinnati, OH) connected to a GC/MS (HP 6890/HP 5973, Hewlett-Packard
Co.) according to the method of Ahn et al. (2001). Minced
sample (3 g) was placed in a 40-mL vial, He (40 psi) was
flushed for 3 s, and a Teflon fluorocarbon resin/silicone
septum (I-Chem Co.) was capped airtight. The maximum
waiting time in a loading tray (4 C) was less than 2 h to
minimize oxidative changes before analysis. The meat sample was purged with He (40 mL/min) for 14 min at 40 C.
Volatiles were trapped using a Tenax/charcoal/silica column (Tekmar-Dohrmann) and desorbed for 2 min at
225 C, focused in a cryofocusing module ( 80 C), and
then thermally desorbed into a column for 60 s at 225 C.
An HP-624 column (7.5 m, 0.25 mm i.d., 1.4 lm nominal),
Table 4
TBARS values of irradiated cooked pork patties affected by oleoresin + tocopherol and packaging during refrigerated storage
Irradiation
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Antioxidanta
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Packaging
0 day
10 day
SEM
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
(mg MDA/kg meat)
1.60ay
1.57ay
0.57cy
0.41cy
0.36by
0.30cy
0.04
2.26ax
2.33ax
1.96bx
1.78bx
1.18cx
0.99cx
0.08
0.05
0.12
0.03
0.04
0.04
0.02
10 day
SEM
57.2
57.5x
58.4
59.8x
58.8
59.1x
0.7
0.9
0.8
0.8
0.8
0.9
0.9
12.9abx
14.4ax
10.3c
13.4ax
11.9by
14.4a
0.4
0.3
0.2
0.4
0.5
0.4
0.5
15.1d
16.4dx
16.5d
20.1bx
18.5c
21.9ax
0.5
0.4
0.3
0.4
0.5
0.5
0.3
Mean values with different letters (a–c) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Oleoresin–tocopherol combination added at 0.05–0.02% of meat wt.
b
Aerobically packaged for 3 days first and then vacuum-packaged for 7 days.
c
Vacuum-packaged for 7 days first and then aerobically packaged for 3 days.
Table 5
Color values of irradiated raw pork patties affected by oleoresin + tocopherol and packaging during refrigerated storage
Irradiation
Antioxidanta
Packaging
0 day
L*
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
value
58.1a
54.5aby
56.3ab
53.4by
57.5a
55.3aby
1.0
a* value
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
11.6by
13.4ay
11.4b
11.2by
13.3ax
12.8ab
0.4
b* value
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
Mean values with different letters (a–d) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Oleoresin–tocopherol combination added at 0.05–0.02% of meat wt.
b
Aerobically packaged for 3 days first and then vacuum-packaged for 7 days.
c
Vacuum-packaged for 7 days first and then aerobically packaged for 3 days.
16.1b
14.6cy
16.7b
13.9cy
19.0a
16.0by
0.3
K.C. Nam et al. / Meat Science 75 (2007) 61–70
an HP-1 column (52.5 m, 0.25 mm i.d., 0.25 lm nominal),
and an HP-Wax column (7.5 m, 0.250 mm i.d., 0.25 lm
nominal) were connected. Ramped oven temperature was
used to improve volatile separation. The initial oven temperature of 0 C was held for 1.5 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 170 C at 10 C per
min and held for 2.25 min at that temperature. Constant
column pressure at 20.5 psi was maintained. The ionization
potential of MS was 70 eV, and the scan range was 19.1–
350 m/z. Identification of volatiles was achieved by the
Wiley library (Hewlett-Packard Co.). The area of each
peak was integrated using ChemStation software (Hewlett-Packard Co.) and the total peak area (total ion
counts · 104) was reported as an indicator of volatiles generated from the samples.
2.5. Statistical analysis
The experiment was a completely randomized design
with four replications. Data were analyzed by the procedure of generalized linear model using SAS software
(SAS Institute, 1995): Student–Newman–Keuls’ multiple
range test was used to compare the mean values of treat-
65
ments. Mean values and standard error of the means
(SEM) were reported (P < 0.05).
3. Results and discussion
3.1. Screening of oleoresin or oleoresin–tocopherol
combinations
To screen two best oleoresins or oleoresin–tocopherol
combinations in preventing lipid oxidation of irradiated
ground pork, the TBARS values of irradiated pork patties
added with oleoresins or oleoresin + a-tocopherol combinations were determined during the 10 days of storage
under aerobic conditions. The TBARS values between
nonirradiated and irradiated raw ground pork were not different, but increased significantly during the 10-day storage
under aerobic conditions (Table 1). Rosemary, onion, and
dill oleoresins were effective in decreasing TBARS values in
irradiated ground raw pork, whereas basil and garlic oleoresins had no antioxidant effects. Rosemary oleoresin had
the most potent antioxidant effects among the oleoresins,
and all the oleoresins except for garlic oleoresin showed
strong antioxidant effects when they were combined with
a-tocopherol. Rosemary, rosemary–tocopherol, onion–
tocopherol, and dill–tocopherol reduced the TBARS values
Table 6
Color values of irradiated cooked pork patties affected by oleoresin + tocopherol and packaging during refrigerated storage
Irradiation
Antioxidanta
Packaging
0 day
L*
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
10 day
SEM
76.9a
76.9a
72.8by
77.9ax
73.0by
78.4ax
0.4
0.5
0.5
0.4
0.6
0.7
0.3
8.5a
8.6ay
7.4bc
8.0aby
7.0cy
8.1aby
0.2
0.2
0.3
0.2
0.3
0.3
0.2
23.1b
23.0b
22.8b
23.8abx
23.8abx
24.3ax
0.3
0.4
0.3
0.3
0.2
0.3
0.3
value
76.9ab
76.7ab
77.7ax
74.8by
77.5ax
74.5by
0.6
a* value
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
8.2b
10.9ax
7.9b
10.9ax
8.4bx
11.2ax
0.3
b* value
0 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
2.5 kGy
SEM
Control
Control
Onion + tocopherol
Onion + tocopherol
Rosemary + tocopherol
Rosemary + tocopherol
Vacuum
Vacuum
A3/V7b
V7/A3c
A3/V7
V7/A3
Mean values with different letters (a–c) within a column are significantly different (P < 0.05).
Mean values with different letters (x, y) within a row are significantly different (P < 0.05). n = 4.
a
Oleoresin–tocopherol combination added at 0.05–0.02% of meat wt.
b
Aerobically packaged for 3 days first and then vacuum-packaged for 7 days.
c
Vacuum-packaged for 7 days first and then aerobically packaged for 3 days.
22.6a
22.3a
22.5a
21.6aby
22.4ay
20.8by
0.3
66
K.C. Nam et al. / Meat Science 75 (2007) 61–70
method of choice because Nam et al. (2004) reported that
double-packaging was better than aerobic- or vacuumpackaging in controlling both lipid oxidation and off-odor
of irradiated meat.
Irradiated raw pork patties with oleoresin–tocopherol/
double-packaging combinations developed significantly
lower TBARS than those of irradiated and nonirradiated
controls with vacuum-packaging (Table 3). However, the
differences were very small and would not have any practical meanings. Nam and Ahn (2003b) reported that the
TBARS increase in turkey meat was proportional to the
exposure time to aerobic conditions: the TBARS of meat
was the highest with aerobic-packaging, lowest with vacuum-packaging, and in the middle with double-packaging.
However, the irradiated meat with antioxidants and double-packaging combinations had lower TBARS than nonirradiated vacuum-packaged meat after 10 days of storage.
The antioxidant effects of oleoresin–tocopherol combinations in irradiated cooked pork were distinct (Tables
2–4). The double-packaging conditions exposed patties to
aerobic conditions for 3 days during the 10-day storage
period, but the added oleoresin–tocopherol combinations
of irradiated raw ground pork by 80% after 10 days of aerobic storage.
The use of oleoresin alone was not much effective in preventing oxidative changes in cooked pork except for rosemary and onion. However, combinations of oleoresin and
tocopherol produced strong antioxidant effects in cooked
pork (Table 2). Among the oleoresin–tocopherol combinations, rosemary–tocopherol and onion–tocopherol produced the most potent antioxidant effects in irradiated
cooked pork loins.
3.2. Oleoresin–tocopherol/packaging combinations on lipid
oxidation of irradiated pork
From the previous screening result, two oleoresin–
tocopherol combinations (onion + tocopherol and rosemary + tocopherol) that provided the best control for lipid
oxidation in irradiated raw and cooked pork were selected,
and the effects of oleoresin–tocopherol combinations on
antioxidant and off-odor reducing effects of irradiated
raw and cooked pork with double-packaging were determined. Double-packaging was selected as a packaging
Table 7
Tentative identification of volatile compounds produced in irradiated raw pork patties treated by oleoresin–tocopherol combination and packaging at
0 day
Compound
NonIR
Irradiated (2.5 kGy)
Onion + tocopherol
Vacuum
Vacuum
a
Rosemary + tocopherol
b
A3/V7
V7/A3
A3/V7a
V7/A3b
SEMc
4
Acetaldehyde
Methanethiol
1-Pentene
Pentane
2-Propanone
Carbon disulfide
Ethanol
1-Hexene
2-Propanol
Hexane
2-Butanone
3-Methyl butanal
1-Propanol
1-Heptene
Heptane
2-Heptene
1-Methylthio propane
S-Methyl esterd
Dimethyl disulfide
Toluene
1-Octene
Octane
1-Butanal
Methyl propyl disulfide
(Total ion counts · 10 )
787
1364
0c
2136a
0b
220a
273c
1110a
4696
3664
0c
7177a
2981
4180
0b
285a
436
366
92b
550a
0b
0b
233
454
0c
197a
163
109
0
494
0b
788a
56
62
0c
117c
0b
81b
124
63
0b
3482a
121
791
490
93
0b
0b
1867
233b
179a
666b
3279
572c
2924
261a
445
489a
242a
393
47bc
171
306
627a
0
24 238b
210a
0
4158a
517
93
581ab
1540
2183a
207a
658b
4381
1947c
3702
266a
422
495a
86ab
457
82b
180
399
703a
0
28 320a
348a
0
5470a
577
247
1052a
345
307b
203a
719b
4069
1061c
3435
219a
501
472a
0b
422
41bc
405
377
695a
0
303c
85b
0
2277a
436
322
0b
236
1306ab
182a
633b
3309
4019b
3256
195a
293
427a
0b
340
68bc
140
329
560a
0
1305c
114ab
0
2471a
544
110
0b
540
132
22
65
660
619
889
37
87
51
55
41
19
98
47
52
15
1180
45
13
864
98
107
168
Total
10 519c
42769a
53 503a
16 763bc
19 970bc
3738
28 238b
Different letters (a–c) within a row are significantly different (p 6 0.05); n = 4.
a
Aerobically packaged for 3 days and then vacuum-packaged for 7 days.
b
Vacuum-packaged for 7 days and then aerobically packaged for 3 days.
c
Standard error of the means.
d
Sulfur–methyl ester ethanethioic acid.
K.C. Nam et al. / Meat Science 75 (2007) 61–70
were effective in preventing oxidative changes in irradiated
cooked pork. Rosemary–tocopherol combination was
more effective than onion–tocopherol in reducing the
TBARS of irradiated cooked pork. However, the sequence
of double-packaging method (A3/V7 vs V3/A7) did not
affect the TBARS values of irradiated cooked pork significantly. Nam and Ahn (2003a) showed similar results with
turkey meat: the antioxidant effect was more distinct in
cooked meat than raw meat. Therefore, the problem of
lipid oxidation in double-packaged irradiated cooked pork
could be prevented by the addition of rosemary–tocopherol
combination.
3.3. Oleoresin–tocopherol/packaging combinations on color
of irradiated pork
Irradiation changed the color of raw pork patties redder, as indicated by the increased a* values in Table 5.
Nam and Ahn (2002a) reported that the color of irradiated
turkey breast became pinker due to carbon monoxide–
myoglobin complex formation, which was induced by the
production of carbon monoxide and reducing conditions
by irradiation. Lee and Ahn (2004) reported that asparagine, glyceraldehydes, and phospholipids were the major
sources of irradiation-dependent CO production from meat
67
components. The amounts of CO produced from these
sources were large enough to react with most of the heme
pigments present in light meats, and the production of
CO was via the radiolytic degradation and was closely
related to the chemical structure of molecules. The mechanism of color changes in irradiated turkey breast can be
similarly applied to that of irradiated pork loin because
the contents of heme pigments in those muscles are relatively low.
Onion–tocopherol combination was effective in reducing a*-values of irradiated raw pork patties but rosemary–tocopherol was not because of the characteristic
red color of rosemary oleoresin. The increased red color
in the control pork by irradiation was maintained during
the storage under vacuum conditions, but A3/V7 doublepackaging mode reduced a*-values after 10 days of storage. The color of cooked pork was also changed to red
by irradiation as in irradiated raw pork, but the red color
was not stable as in irradiated raw meat (Table 6). It can
be considered that the aerobic conditions during irradiation and early storage periods were helpful in minimizing
the formation of carbon monoxide-myoglobin complex.
Nam et al. (2004) reported that the packaging conditions
during irradiation process were important in determining
color changes in pork loin.
Table 8
Tentative identification of volatile compounds produced in irradiated raw pork patties treated by oleoresin–tocopherol combination and packaging at
10 days
Compound
NonIR
Irradiated (2.5 kGy)
Vacuum
Vacuum
Onion + tocopherol
Rosemary + tocopherol
A3/V7a
V7/A3b
A3/V7a
V7/A3b
SEMc
Acetaldehyde
Methanethiol
1-Pentene
Pentane
2-Propanone
Carbon disulfide
Ethanol
1-Hexene
2-Propanol
Hexane
2-Butanone
Benzene
1-Heptene
Heptane
Pentanal
1-Methylthio propane
Dimethyl disulfide
Toluene
1-Octene
Octane
1-butanal
Methyl propyl disulfide
(Total ion counts · 104)
1575c
2728b
0b
590a
0b
184a
306c
1122a
6778
5245
0c
9829a
1512
2206
0c
206a
343
261
80b
470a
356b
577a
0b
258a
0c
491a
0c
762a
113a
125a
0b
0b
0b
149a
0c
262a
0c
125a
155b
504a
477a
159ab
0b
0b
3734a
0b
198a
665b
4106
549c
1931
225a
393
444a
403b
21b
276b
683ab
0b
25 740a
0b
159b
114a
400a
138ab
356a
3081b
0b
174a
685b
5681
1930bc
2041
181ab
263
419a
463ab
51b
300b
679ab
0b
23 390a
0b
146b
81b
267b
132ab
183ab
691d
0b
141a
695b
4894
938c
1345
146ab
264
388a
367b
0b
263b
621ab
0b
150b
0b
146b
65b
242b
0b
0b
472d
0b
136a
592b
4659
2828b
861
120b
100
344a
336b
25b
228b
541b
0b
115b
0b
129b
55b
152b
0b
0b
202
19
16
84
278
484
343
19
50
65
37
17
25
41
7
1221
10
17
9
35
86
61
Total
11 698c
40 540a
40 155a
11 359c
11 699c
2014
26 396b
Different letters (a–c) within a row are significantly different (p 6 0.05); n = 4.
a
Aerobically packaged for 3 days and then vacuum-packaged for 7 days.
b
Vacuum-packaged for 7 days and then aerobically packaged for 3 days.
c
Standard error of the means.
68
K.C. Nam et al. / Meat Science 75 (2007) 61–70
3.4. Oleoresin–tocopherol/packaging combinations on
volatiles of irradiated pork
Irradiation increased the amounts of many volatile compounds or newly generated a few volatiles not found in
nonirradiated raw pork: almost 3 times higher amounts
of volatiles were found in irradiated raw pork compared
with the nonirradiated meats (Table 7). Newly generated
compounds by irradiation were mainly sulfur-containing
compounds such as methanethiol, carbon disulfide, and
dimethyl disulfide. Ahn, Jo, and Olson (2000) reported that
sulfur volatiles 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.
Added oleoresin–tocopherol combinations for the purpose of preventing lipid oxidation had little effects on the
production of sulfur-volatiles by irradiation. The onion–
tocopherol combination added new sulfur volatile compounds such as sulfur methyl ester ethanethioic acid and
methyl propyl disulfide not found in other irradiated pork,
indicating that these compounds were derived from onion.
Sulfur compounds such as methanethiol, carbon disulfide,
dimethyl disulfide, and dimethyl trisulfide are responsible
for irradiation off-odor (Ahn et al., 2000; Patterson &
Stevenson, 1995), but some other sulfur compounds such
as 2-pentylthiophene are important for freshly cooked
meat flavor (Tang, Jin, Ho, & Chang, 1983). The contribution of sulfur compounds to irradiation off-odor, however,
has not been studied.
The amount of sulfur volatiles in irradiated pork loin
was highly dependent upon packaging conditions. More
amounts of methanethiol and carbon disulfide were found
in vacuum-packaged meat. The effects of packaging conditions on the sulfur volatiles were clearer after 10 days of
storage (Table 8). Double-packaged irradiated pork patties
(exposed to aerobic conditions for 3 days during the
10 days of storage) had no methanethiol and dimethyl
disulfide and lower amount of carbon disulfide than the
vacuum-packaged control. Both double-packaging modes
Table 9
Tentative identification of volatile compounds produced in irradiated cooked pork patties treated by oleoresin–tocopherol combination and packaging at
0 day
Compound
NonIR
Irradiated (2.5 kGy)
Vacuum
Vacuum
Onion + tocopherol
Rosemary + tocopherol
A3/V7a
V7/A3b
A3/V7a
V7/A3b
SEMc
Acetaldehyde
1-Pentene
Pentane
Propanal
2-Propanone
Carbon disulfide
2-Methyl propanal
Ethanol
1-Hexene
2-Propanol
Hexane
Butanal
2-Butanone
3-Methyl butanal
2-Methyl butanal
Benzene
1-Heptene
Heptane
Pentanal
1-Methylthio propane
Dimethyl disulfide
Toluene
1-Octene
Octane
1-Butanal
Hexanal
Heptanal
Methyl propyl disulfide
(Total ion counts · 104)
16 831
32 105
0b
559a
18 855b
26 869a
3144b
4571a
4018
5620
0
120
862
894
1103
5931
0b
590a
375b
752a
1578a
1516a
546b
1039a
609c
1122ab
1100a
1037ab
959a
648b
0b
212a
144b
1392a
1153b
3411a
9293b
13 879a
0b
0b
136
2974
0c
732b
0c
556a
1832b
2728a
250
277
57 081b
82 731a
228b
748a
0b
0b
34 234
440a
2846c
3196b
6707
122
1062
4157
615a
661a
1222ab
320c
1449a
1264a
902a
186a
1323a
2180b
1900c
13 449a
3374
918a
482a
1580bc
100
8607c
100b
396a
23 144
370a
2713c
2085c
4330
362
867
2575
572a
428b
1267ab
245c
1248a
1030ab
744ab
221a
1182a
1895b
1556c
12761a
3078
678b
396ab
1255bc
35
7047c
30b
295a
37 085
403a
4067c
1334d
5187
268
989
4995a
697a
920a
1352ab
390bc
1142ab
1121ab
733ab
200a
1392a
2209b
2739c
196b
3720
952a
557a
1875b
306
8712c
69b
0b
29 099
376a
3823c
903d
4834
258
736
5333
463a
912a
962b
270c
803bc
939b
629b
213a
842a
1292b
1589c
101b
2144
654b
324b
1073c
521
6588c
112b
0b
4846
51
1151
211
2821
47
80
644
49
66
110
51
91
68
45
19
124
253
611
337
1170
55
41
172
214
214
49
37
Total
120 043b
93 799bc
72 424c
83 642bc
65 799c
7528
193 002a
Different letters (a–c) within a row are significantly different (p 6 0.05); n = 4.
a
Aerobically packaged for 3 days and then vacuum-packaged for 7 days.
b
Vacuum-packaged for 7 days and then aerobically packaged for 3 days.
c
Standard error of the means.
K.C. Nam et al. / Meat Science 75 (2007) 61–70
69
Table 10
Tentative identification of volatile compounds produced in irradiated cooked pork patties treated by oleoresin–tocopherol combination and packaging at
10 day
Compound
NonIR
Irradiated (2.5 kGy)
Onion + tocopherol
Vacuum
Vacuum
a
Rosemary + tocopherol
b
A3/V7
V7/A3
A3/V7a
V7/A3b
SEMc
4
Acetaldehyde
1-Pentene
Pentane
Propanal
2-Propanone
2-Methyl propanal
Ethanol
1-Hexene
2-Propanol
Hexane
Butanal
2-Butanone
3-Methyl butanal
2-Methyl butanal
Benzene
1-Heptene
Heptane
Pentanal
1-Methylthio propane
Dimethyl disulfide
Toluene
1-Octene
Octane
1-Butanal
Hexanal
Heptanal
Methyl propyl disulfide
(Total ion counts · 10 )
11 938b
15 455b
0b
385a
14 508
14 789
31 234a
32 816a
1125
4549
990
878
5085a
2138c
0b
545a
300
213
1386
1646
889b
752bc
844b
889b
1001b
1087b
999a
715b
0b
241a
101b
1310a
1107b
3465a
15 466a
14 982a
0b
0b
0b
919a
0b
574a
0c
399b
2408
2152
0c
0c
99 435a
102 857a
300
398
0c
0c
29 120ab
357a
6640
22 498b
7101
1097
3377bc
479a
515
1463
904b
1341a
1459a
956a
170a
1142a
3485a
10 315bc
8187a
0b
693a
522ab
2385
272b
70 892b
899
293b
27 829ab
332a
5143
18 418b
6861
889
5135ab
475a
720
1071
623c
1157ab
1164ab
759ab
170a
964a
2307ab
7314c
7724a
0b
601a
459ab
1688
375a
71 978b
750
316a
23 276a
357a
6237
8673c
6804
1100
5728a
408a
602
1309
1177a
1280ab
1337ab
789ab
180a
982a
2885a
10 426bc
0b
74b
732a
564ab
2599
0c
46 658c
791
0c
20 055ab
389a
4211
6492d
5924
953
4828ab
485a
753
1500
945b
1105ab
1013b
659b
202a
1206a
3488a
7895c
0b
0b
690a
597a
2940
0c
16 659d
972
0c
Total
200 767d
176 441bc
165 229bc
124 976a
83 972b
204 160c
3344
97
4317
480
495
68
557
49
156
190
64
97
86
54
16
125
412
918
295
102
52
43
309
31
7259
190
11
15 886
Different letters (a–d) within a row are significantly different (P 6 0.05); n = 4.
a
Aerobically packaged for 3 days and then vacuum-packaged for 7 days.
b
Vacuum-packaged for 7 days and then aerobically packaged for 3 days.
c
Standard error of the means.
were very effective in eliminating sulfur volatiles, but A3/
V7 double-packaging showed less carbon disulfide than
V7/A3 mode, indicating that considerable amounts of sulfur compounds were evaporated under aerobic conditions
during irradiation. Onion oleoresin-added pork patties
had still considerable amounts of 1-methylthio propane
after 10 days of storage.
The profile of volatile compounds in irradiated cooked
pork was more complex than that in irradiated raw meat
because more lipid oxidation products (hydrocarbons, aldheydes) were generated (Table 9). Hexanal was the most
predominant aldehyde in irradiated cooked pork but the
amount was reduced to about 10% of the control by the
oleoresin–tocopherol combinations after 10 days of storage. This indicated that oleoresin–tocopherol combinations
were effective in controlling hexanal content in cooked
pork (Table 10). Rosemary–tocopherol combination was
more effective than onion–tocopherol in reducing hexanal
production as in TBARS (Table 3).
Little dimethyl disulfide was detected in double-packaged irradiated pork patties at Day 10 (Table 10), indicat-
ing that regardless of double-packaging modes, exposing
meats for 3 days in aerobic conditions was effective in
removing sulfur volatiles responsible for irradiation offodor. The onion-added pork patties, however, still had
other sulfur volatiles (1-methylthio propane, methyl propyl
disulfide) derive from onion.
4. Conclusion
Rosemary and onion showed antioxidant effects in both
raw and cooked irradiated pork loins. When these oleoresins were used in combination with a-tocopherol, the antioxidant activity was more distinct in irradiated cooked
pork. Rosemary oleoresin–tocopherol (0.02–0.05% of meat
wt.) had stronger antioxidant effect than onion–tocopherol,
but none of the oleoresin–tocopherol combinations showed
any effects on the production of sulfur volatiles responsible
for the characteristic irradiation off-odor. Double-packaging methods, exposing the irradiated meats to aerobic conditions for 3 days and then keeping them under vacuum
conditions for the remaining 7 days of storage, effectively
70
K.C. Nam et al. / Meat Science 75 (2007) 61–70
reduced the sulfur volatiles in irradiated pork loins. Therefore, the combined use of rosemary oleoresin–tocopherol/
double packaging was an excellent strategy to prevent quality changes of irradiated raw and cooked pork loins.
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