PROCESSING AND PRODUCTS
Effects of Dietary Vitamin E Supplementation on Lipid Oxidation
and Volatiles Content of Irradiated, Cooked Turkey Meat Patties
with Different Packaging1
D. U. AHN,2 J. L. SELL, C. JO, X. CHEN, C. WU, and J. I. LEE
Animal Science Department, Iowa State University, Ames, Iowa 50011
ABSTRACT A study was conducted to determine the
effects of dietary vitamin E supplementation on the
storage stability and volatiles production in irradiated
cooked turkey meat. Turkeys, raised with diets containing 25, 50, 75, or 100 IU of dl-a-tocopheryl acetate (TA)/
kg diet from 1 to 105 d of age, were fed with diets
containing 25, 200, 400, or 600 IU of TA/kg diet from
105 to 122 d of age. Breast and leg meat patties were
prepared, irradiated at 0 or 2.5 kGy dose, cooked to an
internal temperature of 78 C, and stored in either
vacuum or aerobic packaging.
Thiobarbituric acid reactive substance (TBARS) values
gradually decreased as the dietary TA increased and >
200 IU TA/kg diet treatments were helpful in maintaining low TBARS values in irradiated breast and leg meat
patties during the 7-d storage period. With vacuumpackaging, irradiated cooked breast patties developed
more oxidation than nonirradiated patties but the
prooxidant effect of irradiation in cooked leg meat
patties was not consistent. In aerobic-packaged cooked
meat, irradiated patties had lower TBARS than nonirradiated patties in both breast and leg meat stored in
oxygen permeable bags for 7 d.
Propanal, pentanal, hexanal, 1-pentanol, and total
volatiles were highly correlated with the TBARS values
of meat. However, hexanal represented the lipid oxidation status of cooked meat better than any other volatiles
component. The amount of hexanal and total volatiles in
cooked breast and leg meat shows decreasing trends as
dietary TA increased. In vacuum packaging, irradiated
breast and leg meat had higher hexanal and total
volatiles content than nonirradiated meat at both 0 and 7
d of storage. In aerobic packaging, the amount of
hexanal and total volatiles greatly increased in both
irradiated and nonirradiated meat patties during the
7-d storage periods.
The results illustrated that the antioxidant effect of
TA was not strong enough to control lipid oxidation and
off-odor generation in cooked meat stored under aerobic
conditions because the progress of lipid oxidation in
cooked meat under aerobic condition is very rapid.
However, the combination of dietary TA and vacuum
packaging of cooked meat immediately after cooking
could be a good strategy to minimize oxidation and
volatiles production in cooked meat.
(Key words: dietary vitamin E, turkey meat, irradiation, volatiles, lipid oxidation)
1998 Poultry Science 77:912–920
supplementation of tocopheryl acetate has been shown
to increase vitamin E in muscle tissues, and the
antioxidant effect of the increased vitamin E in raw meat
during storage is well documented (Wen et al., 1996;
Sheldon et al., 1997).
Irradiation is considered to be the most effective
technology that can eliminate pathogenic bacteria in raw
meat (Gants, 1996). Irradiation is allowed by Food and
Drug Administration at 1.5 to 3 kGy to control
pathogenic microorganisms such as Salmonella, Escherichia coli and Listeria in poultry meat and the
irradiated poultry meats are available in certain supermarkets. In a review article, Brynjolfsson (1985) con-
INTRODUCTION
Vitamin E is one of the major antioxidants present in
the cell membranes. Vitamin E protects membrane fatty
acids and cholesterol from peroxidative damages caused
by the reactive free radicals (Buckley et al., 1995; Liu et
al., 1995). Free radicals generated by irradiation can
destroy antioxidants in muscle, as well as reduce the
storage stability and increase off-flavor production in
meat (Thayer et al., 1993; Lakritz et al., 1995). Dietary
Received for publication May 27, 1997.
Accepted for publication January 12, 1998.
1Journal Paper Number J-17431 of the Iowa Agriculture and Home
Economics Experiment Station, Ames, Iowa, Project Number 2794, and
supported by Hoffmann-LaRoach, and the Hatch Act.
2To whom correspondence should be addressed:
duahn@iastate.edu
Abbreviation Key: MDA = malonaldehyde; TA = dl-a-tocopheryl
acetate; TBARS = thiobarbituric acid reactive substance.
912
DIETARY VITAMIN E ON OXIDATION AND VOLATILES OF COOKED TURKEY
cluded that irradiating foods with doses up to the
sterilizing doses of 56 kGy does not introduce harmful
effects. One of the major concerns in irradiating meat,
however, is its effect on meat quality, mainly related to
the free radicals reaction and off-odor generated by
irradiation. Irradiation could produce a large amount of
hydroxyl radical in meat because over 75% of muscle
cells are composed of water (Thakur and Singh, 1994).
Lipid radicals will be formed via the free radical
reactions, and lipid hydroperoxides will be formed
when oxygen is available. Reineccius (1979) suggested
that carbonyl compounds are important for irradiation
odor and the intensity of irradiation odor is dependent
upon oxygen content during irradiation. Al-Kahtani et
al. (1996) and Hampson et al. (1996) reported that
gamma irradiation at 1.5 to 10 kGy dosages increased
thiobarbituric acid values in turkey breast and fish
muscles. Irradiation-induced oxidative chemical changes
are dose dependent, and the presence of oxygen has a
significant effect on the rate of oxidation (KatusinRazem et al., 1992; Thayer et al., 1993).
Lynch et al. (1991) reported that irradiated turkey
breast fillet produced a set of unpleasant odor notes
when stored in oxygen-impermeable film and were
different from those developed from corresponding
nonirradiated samples. Heath et al. (1990) and Hashim et
al. (1995) also showed that irradiating uncooked chicken
meat produced a characteristic bloody and sweet aroma
that remained after the meat was cooked. Merritt (1966)
suggested that the volatile compounds responsible for
the off-odor in irradiated meat are produced by the
radiation impact on the protein and lipid molecules and
are different from those of lipid oxidation. Patterson and
Stevenson (1995) showed that dimethyltrisulfide is the
most potent off-odor compound in irradiated raw
chicken meat. However, Shahidi et al. (1991) reported
that irradiation had no detrimental effect on the flavor
of vacuum-packaged raw meat and cured meat, and
Shamsuzzaman et al. (1992) showed that electron beam
treatment had little effect on the odor and flavor of the
reheated meat with sous-vide treatment. At present,
however, little information is available on the nature
and off-odor generation mechanisms in irradiated meat,
especially at low-dose irradiation (< 10 kGy).
The antioxidant effect of tocopherol is not strong
enough to control lipid oxidation in cooked meat during
storage (Ajuyah et al., 1993; Ahn et al., 1995; Winne and
Dirinck, 1996); however, it may play an important role
in the final quality of cooked meat products. The initial
oxidation status of cooked meat is determined by the
degree of lipid oxidation in raw meat before cooking.
Also, the progress of lipid oxidation in cooked meat
during storage would also be highly dependent on the
3Thomson CSF Linac, Cedex, Saint-Aubin, France.
4Burker Instruments, Inc., EPR division, Bellerica, MA 01821.
5Burker Analytische Messtechnik, Silberstreifen, Germany.
6Koch, Kansas City, MO 64108.
913
amount of primary lipid oxidation products in raw
meat. Therefore, increased vitamin E in tissues by the
dietary supplementation may protect raw meat from
oxidation during and after irradiation, and the low lipid
oxidation conditions can be maintained when combined
with proper packaging methods after cooking. The
objective of this study was to determine the effects of
dietary vitamin E supplementation on 1) the storage
stability of irradiated cooked turkey meat with different
packaging, and 2) volatiles development in irradiated
cooked turkey meat during storage.
MATERIALS AND METHODS
Dietary Treatments and
Sample Preparations
Male Large White turkeys were fed diets containing 25,
50, 75, or 100 IU of dl-a-tocopheryl acetate (TA)/kg from 1
to 105 d of age. At 105 d, two pens of turkeys previously
fed 25, 50, 75, or 100 IU of TA were randomly assigned
diets containing 200, 400, or 600 IU of TA/kg diet to
increase tissue vitamin E content in the short term. Each of
the 200, 400, and 600 IU TA treatments was fed to eight
pens of poults, eight poults per pen, from 105 to 122 d of
age. Turkeys fed 25 IU of TA/kg diet from 1 to 122 d were
used as a control.
At the end of the trial, 2 birds per pen and the 8t turkeys
on the 25 IU diet (a total of 56 birds) were selected and
slaughtered following USDA guidelines (USDA, 1982).
Carcasses were chilled in ice water for 3 h and then
drained in a cold room. Breast and leg muscles were
deboned from the carcasses 24 h after slaughter. Skin and
visible fat were removed from the breast and leg meat, and
the meat was ground twice through a 3-mm plate. Breast
and leg meats from two birds from the same pen were
pooled and used as a replication. Twelve breast and 12 leg
meat patties (approximately 100 g each) were prepared
from each of the pooled ground breast and pooled leg
meats representing each pen. The breast and leg meat
patties were put on laminated foam trays and wrapped
with oxygen permeable plastic film and irradiated with
accelerated electrons to a average dose of 0- or
2.5-kGy (127 kGy/min) by using a Linear Accelerator3
(Model Circe IIIR). Dosimeters4 (Alanine) were placed on
surface and base of patties being irradiated, and the
dosimeters were read using an Electroparamagnetic
Resonance5 (EMS-104). The temperatures of the meat
were kept at 2-4 C during irradiation and after irradiation.
Twenty-four hours after irradiation, the patties were
cooked in an electric oven (300 C) to an internal
temperature of 78 C, chilled for 3 h at 4 C, and then
packaged. Half of the cooked meats was vacuumpackaged in oxygen-impermeable nylon/polyethylene
bags6 (O2 permeability, 9.3 mL O2/m2/24 h at 0 C), and
the other half was aerobic-packaged in oxygen-permeable
bags. The patties were stored in a refrigerator for 7 d. The
thiobarbituric acid reactive substances (TBARS) values of
914
AHN ET AL.
cooked meat were measured at 0, 3, and 7 d, and volatiles
were measured at 0 and 7 d of storage at 4 C. Zero-day
samples were analyzed 3 h after cooking.
Lipid Oxidation
Lipid peroxidation of cooked turkey meat was determined by the modified method of Buege and Aust (1978).
A 5-g meat sample was placed in a 50-mL test tube and
homogenized with 15 mL of deionized distilled water by
using a Brinkman Polytron (Type PT 10/35)7 for 15 s at
speed 7 to 8. Meat homogenate (1 mL) was transferred to a
disposable test tube (13 × 100 mm) and butylated
hydroxyanisole (50 mL, 7.2%) and 2 mL of a solution of 20
mM thiobarbituric acid/15% trichloroacetic acid were
added. The mixture was vortexed and then incubated in a
boiling water bath for 15 min to develop color. After color
development, the samples were cooled in cold water for 10
min and then centrifuged for 15 min at 2,000 × g. The
absorbance of the resulting supernatant solution was
determined at 531 nm against a blank containing 1 mL
double distilled water and 2 mL thiobarbituric acid/
trichloroacetic acid solution. The TBARS numbers were
expressed as milligrams malonaldehyde (MDA) per
kilogram of meat.
Volatiles Analysis
A purge-and-trap apparatus connected to a gas
chromatograph was used to quantify and characterize the
volatiles potentially responsible for the off-odor in
irradiated meat. Tekmar Precept II and Purge-and-Trap
Concentrator 30008 were used to purge and trap volatiles
from the samples. A Hewlett Packard gas chromatograph
(Model 6890)9 equipped with flame ionization detector
was used to analyze volatiles. In preparation for volatiles
analysis, minced cooked meat (2 g) was weighed into a
sample vial (40 mL), an oxygen absorber (Ageless type
ZPT-30)10 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 a 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,8 and desorbed for 2 min at 220 C.
A split inlet (split ratio, 29:1) was used to inject volatiles
into a gas chromatograph column (DB-Wax capillary
column,11 0.53 mm i.d., 30 m, and 1 mm film thickness),
and ramped oven temperature conditions (32 C for 0.5
min, increased to 40 C at 40 C/min, increased to 100 C at
7Brinkman Instruments Inc., Westbury, NY 11590-0207.
8Tekmar-Dohrmann, Cincinnati, OH 45249.
9Hewlett Packard Co., Wilmington, DE 19808-1610.
10Mitsubishi Gas Chemical America, Inc., New York, NY
11J & W Scientific, Folsom, CA 95630-4714.
12Chromatography Research Supplies, Inc., Addison, IL
10022.
60101.
30 C/min, increased to 180 C at 20 C/min, and held for 1
min) were used. Inlet temperature was 180 C, and detector
temperature was 220 C. Helium was used as a carrier gas
and column flow was 5.8 mL/min. Detector air, hydrogen,
and make-up gas (helium) flows were set at 30, 30, and 28
mL/min, respectively. Individual peaks were identified
by the retention time of volatile standards. Standard kits
(aldehyde-ketones, alcohols, hydrocarbons, and alkenes
C6–C10) were purchased from Chromatography Research
Supplies,12 and a total of 44 standards (9 aldehydes, 11
alcohols, 8 ketones, and 16 hydrocarbons) were used to
identify peaks in meat volatiles. The area of each peak was
integrated by using ChemStation software,9 and the total
peak area (pA*sec) was reported as an indicator of
volatiles generated from the meat samples.
Statistical Analysis
The experiment was designed primarily to determine
the effect of high level dietary vitamin E (> 200 IU TA/kg
of diet) on the lipid peroxidation and off-odor production
of irradiated cooked turkey breast and leg meat stored in
packaging film with different oxygen permeability
(oxygen-permeable or oxygen-impermeable wrap). Breast
and leg meat data were analyzed independently by SAS
software (SAS Institute, 1989). Analyses of variance were
conducted to test dietary TA effect within irradiation and
storage time, irradiation effect within storage time and
dietary TA, and storage effect within dietary TA and
irradiation. The Student-Newman-Keuls multiple range
test was used to compare differences among mean values.
Mean values and SEM were reported.
RESULTS AND DISCUSSION
TBARS Values of Cooked Meat
In nonirradiated breast, TBARS values of vacuumpackaged cooked breast meat patties gradually decreased
as the dietary TA increased at all storage times (Table 1).
High level dietary TA (> 200 IU TA/kg of diet) treatments
were also effective in maintaining low TBARS in irradiated breast during storage. However, the difference
between the TBARS of irradiated breast meat from toms
fed 200 or 400 IU dietary TA/ kg was not consistent.
Irradiated meat developed more lipid oxidation than
nonirradiated. The TBARS values of vacuum-packaged
cooked breast remained relatively low throughout the
7-d storage period.
The TBARS values of leg meat were much higher than
those of the breast (Tables 1 and 2) because leg meat
patties had higher fat content than breast meat (1.74% for
breast and 6.45% for leg meat patties) as reported by Ahn
et al. (1995). High level dietary TA (> 200 IU TA/kg of diet)
treatments were helpful in maintaining low TBARS values
in cooked leg meat for 3 d but the prooxidant effect of
irradiation in cooked leg meat patties was not consistent
(Table 2). Unlike in cooked breast meat patties, the TBARS
DIETARY VITAMIN E ON OXIDATION AND VOLATILES OF COOKED TURKEY
915
TABLE 1. Effect of dietary vitamin E, irradiation, and storage time (4 C) on the thiobarbituric
acid reactive substances (TBARS) values of vacuum-packaged cooked turkey breast meat patties
Day 01
Day 3
Day 7
Dietary
vitamin E
Control
IR2
SEM
Control
(IU/kg)
25
200
400
600
SEM
1.23x
0.64y
0.52b,yz
0.44b,z
0.05
1.19x
0.88x
1.04a,x
0.61a,y
0.09
0.05
0.08
0.10
0.05
(mg MDA3/kg meat)
1.16x
1.23x
0.10
0.71y
0.76y
0.06
0.35b,z
0.82a,y
0.05
0.31b,z
0.44a,z
0.02
0.05
0.07
IR
SEM
Control
IR
SEM
1.18b,x
0.84y
0.64z
0.58z
0.05
1.63a,x
1.02y
0.74z
0.59z
0.09
0.08
0.10
0.07
0.04
a,bValues
within a row of same storage period with no common superscript differ significantly (P < 0.05).
within a column with no common superscript differ significantly (P < 0.05).
10 d samples were analyzed 3 h after cooking (n = 4).
2Patties were irradiated (IR) at 0 or 2.5 kGy (avg.) and then cooked.
3MDA = malonaldehyde.
x–zValues
values of cooked leg meat patties increased significantly
during the 7-d storage period. The baseline TBARS values
(0 d) of cooked breast and leg meat patties in this study are
relatively high and the high baseline TBARS values in this
study were caused by the relatively long chilling time
before analysis. The baseline TBARS values of cooked
turkey breast and leg meat patties in our previous studies
(Ahn et al., 1992, 1993) were 0.7 to 0.8 and increased to
about 1.4 to 1.6 during 2-h chilling period. Most of the
oxidation products in cooked meat were produced by
oxygen contact with the cooked meat during the
3-h chilling period after cooking.
In aerobic-packaged conditions, both cooked breast
and leg meat patties developed lipid oxidation rapidly
(Tables 3 and 4). After 3 d of storage, the TBARS values of
irradiated and nonirradiated breast meat reached 3.7 to
5.0 range depending on dietary TA and irradiation
conditions. High level dietary TA treatments (> 200 IU
TA/kg of diet) significantly slowed the development of
lipid oxidation in irradiated and nonirradiated cooked
turkey breast meat during the 3-d storage, but the
antioxidant effect of dietary TA was not strong enough.
The TBARS values of cooked breast meat patties increased
to a range of 4.7 to 6.0 after 7 d of storage, but the
antioxidant effect of dietary TA was no longer observed.
Although the TBARS values of nonirradiated cooked
breast meat patties at 0 d were lower than or not different
from those of irradiated, they were higher than those of
irradiated after 7 d of storage (Table 3). The TBARS values
of aerobic-packaged leg meat increased very rapidly
during the first 3-d storage but decreased after that (Table
4). As in breast meat, irradiated leg meat patties had lower
TBARS than nonirradiated patties stored in oxygenpermeable bags.
The data presented in Tables 1 to 4 indicate that
irradiation had no direct effect on the TBARS values of
cooked meat during storage. Dietary TA at 600 IU
significantly reduced the TBARS values of irradiated
cooked leg meat after 7-d storage. However, all the
aerobic-packaged cooked leg meat patties had very high
TBARS values after 7 d of storage, and the differences in
TBARS values related to the dietary TA may not have
much meaning in terms of meat quality.
Tissue vitamin E is not significant enough to prevent
lipid oxidation in cooked meat during storage (Ajuyah et
al., 1993). However, vitamin E can play an important role
TABLE 2. Effect of dietary vitamin E, irradiation, and storage time (4 C) on the thiobarbituric
acid reactive substances (TBARS) values of vacuum-packaged cooked turkey leg meat patties
Dietary
vitamin E
(IU/kg)
25
200
400
600
SEM
a,bValues
Day 01
Control
2.85x
2.02y
2.02a,y
1.68y
0.15
IR2
3.18x
1.25y
1.73b,z
1.55z
0.11
Day 3
SEM
0.15
0.15
0.08
0.09
Control
(mg
3.24x
1.83y
1.54yz
1.23b,z
0.15
IR
MDA3/kg
3.41x
1.90y
1.53y
1.43a,y
0.16
Day 7
SEM
meat)
0.26
0.12
0.09
0.04
Control
IR
SEM
3.99x
3.43a,y
2.96z
2.77a,z
0.14
4.55x
2.60b,y
2.25y
2.34b,y
0.20
0.25
0.16
0.27
0.12
within a row of same storage period with no common superscript differ significantly (P < 0.05).
within a column with no common superscript differ significantly (P < 0.05).
10 d samples were analyzed 3 h after cooking (n = 4).
2Patties were irradiated (IR) at 0 or 2.5 kGy (avg.) and then cooked.
3MDA = malonaldehyde.
x–zValues
916
AHN ET AL.
TABLE 3. Effect of dietary vitamin E, irradiation, and storage time (4 C) on the thiobarbituric
acid reactive substances (TBARS) values of aerobic-packaged cooked turkey breast meat patties
Day 01
Day 3
Day 7
Dietary
vitamin E
Control
IR2
SEM
Control
(IU/kg)
25
200
400
600
SEM
1.23x
0.64y
0.52b,yz
0.44b,z
0.05
1.19x
0.88x
1.04a,x
0.61a,y
0.09
0.05
0.08
0.10
0.05
(mg MDA3/kg meat)
5.00x
5.04x
0.18
4.19xy
4.48y
0.11
3.96y
3.86z
0.14
4.36xy
3.66z
0.26
0.22
0.13
IR
SEM
Control
IR
SEM
5.67a
5.58a
5.70a
6.00a
0.17
4.79b
4.82b
4.84b
4.69b
0.25
0.16
0.24
0.21
0.23
a,bValues
within a row of same storage period with no common superscript differ significantly (P < 0.05).
within a column with no common superscript differ significantly (P < 0.05).
10 d samples were analyzed 3 h after cooking (n = 4).
2Patties were irradiated (IR) at 0 or 2.5 kGy (avg.) and then cooked.
3MDA = malonaldehyde.
x–zValues
in the quality of cooked meat. Ahn et al. (1992, 1993)
showed that the storage stability of cooked meat can be
maintained if the meat is vacuum-packaged immediately
after cooking. Wen et al. (1996) reported that tissue
vitamin E is a highly efficient antioxidant and can
maintain low baseline lipid peroxidation levels in raw
meat. If dietary TA and vacuum packaging immediately
after cooking are combined, the oxidative quality of
cooked meat can be maintained throughout normal
storage periods.
Volatiles from Cooked Meat
Figure 1 shows typical chromatograms of volatiles in
cooked turkey meat with different degrees of lipid
oxidation. Aldehydes were the major components in
cooked oxidized meat, and the content of alcohols also
gradually increased as the lipid oxidation of meat
increased. As reported previously (Ahn et al., 1992, 1993),
the inclusion of oxygen was the most critical factor that
influenced the development of lipid oxidation in cooked
meat. Also, during volatiles analysis, presence of oxygen
in sample vials had a significant influence on lipid
oxidation and volatiles production while the samples
were waiting for volatiles analysis. Without eliminating
oxygen from the sample vial, it was impossible to evaluate
the amounts and profiles of volatiles in cooked meat
correctly. To resolve this dilemma, a bag of oxygen
absorber was added (Ageless 30 to 50) to each of the
sample vials along with cooked meat sample, resulting in
stabilization of samples from developing lipid oxidation
and volatiles production.
The correlation coefficients shown in Table 5 indicate
that propanal, pentanal, hexanal, 1-pentanol, and total
volatiles were highly correlated with lipid oxidation of
meat (TBARS values). Also, propanal, pentanal, hexanal,
1-pentanol, and total volatiles were highly correlated to
each other. This relationship indicated that any one or all
of these components could be used to accurately predict
the oxidation status of cooked meat accurately. However,
hexanal represented the lipid oxidation status of cooked
meat better than any other volatiles components in our
cooked meat study.
Figure 2 presents the summary of hexanal produced in
the cooked breast and leg meat patties with different
irradiation and packaging conditions. In vacuum-
TABLE 4. Effect of dietary vitamin E, irradiation, and storage time (4 C) on the thiobarbituric
acid reactive substances (TBARS) values of aerobic-packaged cooked turkey leg meat patties
Dietary
vitamin E
(IU/kg)
25
200
400
600
SEM
a,bValues
Day 01
Control
2.85x
2.02y
2.02a,y
1.68y
0.15
IR2
3.18x
1.25y
1.73b,z
1.55z
0.11
Day 3
SEM
0.15
0.15
0.08
0.09
Control
(mg
10.41a
9.97
10.05a
9.43
0.28
IR
MDA3/kg
9.29b
9.69
8.29b
8.46
0.37
Day 7
SEM
meat)
0.18
0.26
0.28
0.49
Control
IR
SEM
8.27
8.53a
8.91a
8.36a
0.23
9.11x
7.52b,y
6.98b,y
6.53b,y
0.33
0.40
0.21
0.20
0.28
within a row of same storage period with no common superscript differ significantly (P < 0.05).
within a column with no common superscript differ significantly (P < 0.05).
10 d samples were analyzed 3 h after cooking (n = 4).
2Patties were irradiated (IR) at 0 or 2.5 kGy (avg.) and then cooked.
3MDA = malonaldehyde.
x–zValues
917
DIETARY VITAMIN E ON OXIDATION AND VOLATILES OF COOKED TURKEY
FIGURE 1. Gas chromatogram of volatiles from cooked turkey meat. A) Vacuum-packaged nonirradiated cooked breast meat at Day 0; B. Aerobicpackaged nonirradiated cooked breast meat after 7 d of storage.
TABLE 5. Correlation coefficient1 (r2) between thiobarbituric acid reactive substances (TBARS) value, major volatile components,
and total volatiles of cooked turkey meat2
Retention
1.54 min
TBARS
Retention 1.54
1-Heptene
Propanal
2-Methyl propanal
n-Butanone
Pentanal
Hexanal
1-Pentanol
1Correlation
0.25
1-Heptene
Propanal
0.11
0.01
0.70
0.29
0.26
2-Methyl
propanal
0.01
0.08
0.22
0.01
Butanone
Pentanal
Hexanal
1-Pentanol
0.01
–0.06
0.04
0.02
0.01
0.66
0.20
0.28
0.93
0.01
0.04
0.71
0.31
0.30
0.92
0.00
0.01
0.93
0.69
0.21
0.07
0.79
0.00
0.06
0.74
0.73
Total
volatiles
0.67
0.40
0.37
0.92
0.01
0.05
0.89
0.96
0.69
coefficient (r2) > ± 0.06 is significant at P < 0.05.
2Data obtained from both breast and leg meat patties of all packaging, irradiation, and storage conditions were pooled and used for the calculation of
correlation coefficients. (n = 320).
918
AHN ET AL.
FIGURE 2. The amount of hexanal produced in the cooked breast and leg meat patties with different irradiation and packaging conditions. ◊ =
nonirradiated, 0 d; ⁄ = irradiated, 0 d; o = nonirradiated, 7 d; ÿ = irradiated, 7 d. Different letters within a same dietary TA are significantly different (P <
0.05). Breast-vacuum packaging: 25 IU dietary TA, SEM = 10.20; 200 IU dietary TA, SEM = 6.53; 400 IU dietary TA, SEM = 3.54; 600 IU dietary TA, SEM =
4.10. Breast-aerobic packaging: 25 IU dietary TA, SEM = 14.30; 200 IU dietary TA, SEM = 17.70; 400 IU dietary TA, SEM = 11.87; 600 IU dietary TA, SEM =
13.14. Leg-vacuum packaging: 25 IU dietary TA, SEM = 12.23; 200 IU dietary TA, SEM = 11.81; 400 IU dietary TA, SEM = 13.64; 600 IU dietary TA, SEM =
9.09. Leg-aerobic packaging: 25 IU dietary TA, SEM = 16.66; 200 IU dietary TA, SEM = 19.47; 400 IU dietary TA, SEM = 20.44; 600 IU dietary TA, SEM =
24.76).
packaged cooked breast, irradiated meat had a higher
hexanal content than nonirradiated meat at both
0- and 7-d storage. The amount of hexanal was increased
in vacuum-packaged breast meat during the 7-d storage in
most dietary TA treatments. Except for an increase of
hexanal content in irradiated breast meat from toms on the
600 IU dietary TA, the amount of hexanal in cooked meat
tended to decrease as dietary TA increased (Figure 2A). In
aerobic-packaged cooked breast, the amount of hexanal
dramatically increased in both irradiated and nonirradiated meat patties during the 7-d storage periods. Irradiation produced higher hexanal in 0-d breast meat from
toms fed > 400 IU of dietary TA/kg but had no effect in
7-d samples. As in the vacuum-packaged breast meat, the
amount of hexanal gradually decreased as the level of
dietary TA increased (Figure 2B).
In vacuum-packaged cooked leg meat (Figure 2C), the
amount of hexanal in nonirradiated meat, except for 600
ID dietary TA treatment, remained unchanged during the
7-d storage period. Hexanal content in irradiated leg meat,
however, was significantly increased during the 7 d of
storage. The amount of hexanal in irradiated meat at Day 7
was significantly higher than that of the nonirradiated
meat at Day 0 and Day 7. In aerobic-packaged cooked leg
meat (Figure 2D), the amount of hexanal in both control
and irradiated meat increased by about twofold during
the 7-d storage period. Irradiation had no effect on the
hexanal content of aerobic-packaged leg meat. High level
DIETARY VITAMIN E ON OXIDATION AND VOLATILES OF COOKED TURKEY
919
FIGURE 3. The amount of total volatiles produced in the cooked breast and leg meat patties with different irradiation and packaging conditions.◊ =
nonirradiated, 0 d; ⁄ = irradiated, 0 d; o = nonirradiated, 7 d; ÿ = irradiated, 7 d. Different letters within a same dietary TA are significantly different (P <
0.05). Breast-vacuum packaging: 25 IU dietary TA, SEM = 18.49; 200 IU dietary TA, SEM = 12.14; 400 IU dietary TA, SEM = 9.85; 600 IU dietary TA, SEM
= 11.00. Breast-aerobic packaging: 25 IU dietary TA, SEM = 21.43; 200 IU dietary TA, SEM = 25.11; 400 IU dietary TA, SEM = 19.67; 600 IU dietary TA,
SEM = 18.00. Leg-vacuum packaging: 25 IU dietary TA, SEM = 20.76; 200 IU dietary TA, SEM = 21.74; 400 IU dietary TA, SEM = 21.41; 600 IU dietary TA,
SEM = 15.16. Leg-aerobic packaging: 25 IU dietary TA, SEM = 24.75; 200 IU dietary TA, SEM = 26.85; 400 IU dietary TA, SEM = 27.80; 600 IU dietary TA,
SEM = 35.15.
dietary TA (> 200 IU TA/kg of diet) reduced hexanal
content in both vacuum and aerobic-packaged cooked leg
meat, but the decrease in hexanal content caused by
dietary TA may not have significant meaning for the
flavor of aerobic-packaged cooked meat after 7 d of
storage.
As expected from the correlation coefficient between
hexanal and total volatiles shown in Table 5, the changes
in total volatiles by the dietary TA, irradiation, and
storage were very similar to those observed with hexanal
(Figure 3). In vacuum-packaged cooked breast, irradiated
meat had higher total volatiles content than nonirradiated
except for the irradiated meat from toms fed 25 IU TA/kg
of diet at Day 0. The amount of total volatiles in meat
stored for 7 d was the same or higher than that of the
0-d samples in both irradiated and nonirradiated meat.
The changes of total volatiles by the dietary TA also
followed the same pattern as hexanal in vacuumpackaged breast meat. (Figure 3A). In aerobic-packaged
cooked breast, the amount of total volatiles increased twoto fourfold during the 7-d storage periods, but irradiation
had a negligible effect on the amount of total volatiles in
cooked breast meat after 7 d of storage (Figure 3B).
In vacuum-packaged cooked leg meat (Figure 3C), the
amount of total volatiles in irradiated meat increased
significantly, but small changes (significant only with 600
IU TA/kg of diet) were observed in nonirradiated meat
during the 7-d storage period. In aerobic-packaged
920
AHN ET AL.
cooked leg meat (Figure 3D), the amount of total volatiles
in leg meat increased significantly during the 7-d storage
period but was not as large as in aerobic-packaged breast
meat. Irradiation had no consistent effect on the total
volatiles content of aerobic-packaged leg meat, but a high
level dietary TA (> 200 IU TA/kg of diet) significantly
reduced the total volatiles content of aerobic-packaged
cooked leg meat after 7 d of storage.
Aldehydes are frequently used as a “warmed-over”
indicator for cooked meat, but hexanal was recommended
as the best single volatile component that can be used as an
indicator for warmed-over flavor in cooked meat (St.
Angelo et al., 1987; Konopka et al., 1995). Data on volatiles
indicated that hexanal constituted approximately 50 to
70% of total aldehydes in cooked meat. However, the
proportion of hexanal in 0-d samples with low TBARS
values was less than 5% of total volatiles and increased to
more than 50% of total volatiles in highly oxidized meat
(data not shown). Therefore, using total volatiles and
hexanal content together would be a better criterion for
determining lipid oxidation status and off-odor production in cooked meat than using hexanal or total volatiles
alone.
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