Dietary Functional Ingredients: Performance of Animals and Quality
and Storage Stability of Irradiated Raw Turkey Breast
H. J. Yan, E. J. Lee, K. C. Nam, B. R. Min, and D. U. Ahn1
Department of Animal Science, Iowa State University, Ames 50011
ABSTRACT The objective of this study was to evaluate
the effect of dietary functional ingredients vitamin E (VE),
Se, and conjugated linoleic acid (CLA), alone or in combination, on the quality of irradiated turkey breast meat. A
total of 480 male turkeys (11-wk-old, raised on a cornsoybean basal diet) were randomly allotted to 32 pens
and fed 1 of 8 experimental diets (4 pens/treatment) supplemented with none (control), 200 IU/kg of VE (VE),
0.3 ppm Se (Se), 2.5% CLA (CLA), 200 IU/kg of VE + 0.3
ppm Se (VE + Se), 200 IU/kg of VE + 2.5% CLA (VE +
CLA), 2.5% CLA + 0.3 ppm Se (CLA + Se), 200 IU/kg of
VE + 0.3 ppm Se + 2.5% CLA (VE + Se + CLA) for 4 wk.
At 15 wk of age, all birds were slaughtered, and breast
muscles of 8 birds from each pen were separated, pooled,
and ground. Patties were prepared using the ground
meat, aerobically packaged, and irradiated at 0 or 1.5 kGy
absorbed dose. Lipid oxidation, color, and volatiles of the
patties were measured after 0, 7, and 12 d of storage at
4°C. The content of VE and Se and fatty acid composition
of lipids were also determined. Dietary supplementation
of VE and CLA increased their concentrations in turkey
breast. Dietary CLA decreased monounsaturated and
non-CLA polyunsaturated fatty acids content in meat.
Irradiation increased (P < 0.05) Hunter color redness value
of turkey breast and accelerated lipid oxidation, regardless of dietary treatments. However, dietary VE, Se, and
CLA, alone and in combinations, decreased (P < 0.05)
lipid oxidation in meat caused by both irradiation and
storage. It was concluded that dietary supplementation
of VE, Se, and CLA, alone and in combination, improved
the storage stability of irradiated turkey breast meat.
Key words: dietary functional ingredient, irradiation, turkey breast, color, lipid oxidation
2006 Poultry Science 85:1829–1837
INTRODUCTION
Irradiation, up to 3 kGy, is permitted for use in poultry
meat to control pathogenic microorganisms such as Salmonella, Escherichia coli, and Listeria. A major concern of
irradiating poultry meat, however, is its negative effects
on meat quality, such as generation of pink color, irradiation off-odor, and acceleration of lipid oxidation (Ahn
et al., 1998). Functional ingredients are defined as the
components in food or animal feed that can prevent or
treat certain disorders and diseases in addition to their
nutritional values (Jiménez-Colmenero et al., 2001).
There are 2 advantages of using functional ingredients
in animal feed: They can directly improve the health of
farm animals and the quality of animal-derived foods
and indirectly promote human health by providing
foods containing functional ingredients. The production
of value-added, safe, and healthful meat products, thus,
is the primary objective of adding functional ingredients
in animal feed.
2006 Poultry Science Association Inc.
Received December 21, 2005.
Accepted June 17, 2006.
1
Corresponding author: duahn@iastate.edu
The role of vitamin E (VE) as a protective antioxidant
is well documented, and supranutritional levels of dietary VE have been found to improve the quality of
poultry products by reducing the rates of both lipid and
heme oxidations (Ahn et al., 1997; Nam et al., 2003b).
As a unique mineral, Se has a number of important
biological functions that are closely related to the activities of Se-containing proteins. The first identified functional selenoprotein was glutathione peroxidase, which
is the major cellular antioxidant defense system in animals (Stadtman, 2002). The function of these enzymes
is maintaining low levels of H2O2 within cells, thus decreasing potential free-radical damage. They also provide a second line of defense against hydroperoxides
that can damage membranes and other cell structures
(Rotruck et al., 1973). In addition, Se and VE have significant interactions: The antioxidant properties of Se
and VE differ but are complementary. Within cell membranes, VE scavenges free radicals before they initiate
lipid peroxidation. On the other hand, glutathione peroxidase reduces preformed hydroperoxides to alcohols.
Thus, VE and Se can work together to prevent cellular
and tissue damages caused by oxidation (Combs and
Regenstein, 1980).
Supplementation of conjugated linoleic acid (CLA) in
bird feed is primarily based on their biological functions
1829
1830
YAN ET AL.
and consumers’ preference of value-added and healthful foods. Conjugated linoleic acids can be incorporated
into bird tissues via dietary supplementation (Du et al.,
2001; Huang et al., 2001; Thiel-Cooper et al., 2001) and
can alter the quality of meat. Du et al. (2000) reported
that dietary CLA increased total saturated fatty acids
and decreased total monounsaturated fatty acids
(MUFA) and polyunsaturated fatty acids (PUFA) in
breast fillets, which enhanced storage stability of turkey
products (Du et al., 2002).
Oxidation of unsaturated fatty acids in biomembranes
leads to the disruption of normal membrane structure
and functions, in addition to cell injury in living systems,
and is a major cause of quality deterioration in muscle
foods. Asghar et al. (1990) reported that the rate of
NADPH-induced peroxidation in microsomes and mitochondria depended primarily upon fatty acid composition of membrane lipids rather than tocopherol content.
If antioxidants such as VE and Se are combined with
CLA, they can modify fatty acid composition of cell
membranes and improve the antioxidant potential of
meat, which may reduce lipid oxidation and abnormal
color changes and off-odor production caused by irradiation and storage.
The purposes of this study were to investigate the
influence of 3 dietary functional ingredients, VE, Se, and
CLA on the performance of finishing turkeys and the
quality of irradiated turkey breast meat.
MATERIALS AND METHODS
Dietary Treatments
A 23 factorial design was utilized for the bird experiment. The 3 factors involved were 3 functional ingredients: VE, Se, and CLA at 2 levels each. The 8 dietary
treatments included control, 200 IU/kg of DL-α-tocopherol acetate (VE), 0.3 mg/kg of Se (Se), 2.5% CLA (CLA),
200 IU/kg of DL-α-tocopherol acetate and 0.3 mg/kg of
Se (VE+Se), 200 IU/kg DL-α-tocopherol acetate + 2.5%
CLA (VE + CLA), 2.5% CLA + 0.3 mg/kg of Se (CLA +
Se), 200 IU/kg of DL-α-tocopherol acetate + 2.5% CLA
+ 0.3 mg/kg of Se (VE + CLA + Se). Each treatment
included 4 replications.
The bird experiments were performed in the Poultry
Research Center of Iowa State University. A total of
480 0-wk-old male Large White turkeys were randomly
assigned to 32 pens and raised on a corn–soybean-based
diet (Table 1) for 11 wk. At the beginning of wk 12, 4
pens of turkeys were randomly assigned to 1 of the 8
dietary treatments (Table 2) and fed until 15 wk of age.
Feed consumption, amount of live birds, and bird
weight were recorded; weight gain, feed conversion rate
(FCR), and mortality were calculated.
Sample Preparation
At the end of the feeding trial, all birds were slaughtered and inspected following the USDA guidelines
Table 1. Corn–soybean-based diets fed to male turkeys from 0 to 12 wk
Ingredients (%)
Corn
Soybean meal
Fish meal
Dicalcium phosphate
Limestone
Soy oil
Mineral premix1
Vitamin premix2
Salt
L-Lys
DL-Met
BMD3
Total amount (%)
0 to
3 wk
4 to
6 wk
7 to
9 wk
10 to
12 wk
43.67
47.71
3.00
1.92
1.28
1.46
0.30
0.30
0.11
0.01
0.21
0.025
100.00
48.39
45.24
0.00
2.13
1.32
1.83
0.30
0.30
0.14
0.14
0.20
0.025
100.00
52.72
40.15
0.00
2.01
1.29
2.68
0.30
0.30
0.14
0.14
0.20
0.025
100.00
53.3
37.06
0.00
1.93
1.22
5.41
0.30
0.30
0.15
0.11
0.19
0.025
100.00
1
Contains the following: Na, 33%; chloride, 58%; Zn, 13,300 mg/kg;
Mn, 2,300 mg/kg; Fe, 12,300 mg/kg; and Cu, 2,000 mg/kg.
2
Contains the following: vitamin A, 2,688,333 IU/kg; vitamin D3,
526,667 IU/kg; vitamin E, 5,000 IU/kg; vitamin K (menadione Na
bisulfite complex), 1,200 mg/kg; riboflavin, 2,600 mg/kg; pantothenic
acid, 4,267 mg/kg; niacin, 25,000 mg/kg; choline, 169,667 mg/kg; folic
acid, 540 mg/kg; biotin, 90 mg/kg; pyridoxine, 2,025 mg/kg; thiamine,
675 mg/kg; and vitamin B12, 5,333 mg/kg.
3
BMD = bacitracin methylene disalicylate.
(USDA, 1982). Carcasses of birds from the same pen
were pooled and chilled in ice water for 3 h and then
drained in a cooler (0°C) until the internal temperature
was 4°C for further processing. Breast muscles were
deboned, and skin and visible fat were removed. All
breast samples of birds from the same pen (4 pens per
treatment) were pooled, ground twice through a 3-mm
plate, and treated as a replication. Four replications of
patties were prepared for the meat quality, fatty acid
composition of meat, and concentrations of dietary functional ingredients used in this study.
Meat patties (about 100 g, 5 cm in diameter, 0.5 cm
in thickness) prepared from each replication were packaged in O-permeable bags (polyethylene, Associated
Bag Co., Milwaukee, WI). Packaged samples were irradiated using a linear accelerator (Circe IIIR, Thomson
CSF Linac, Saint-Aubin, France) at room temperature
to an average dose of 0 or 1.5 kGy. Ten million electron
volts of energy, 10 kW of power, and 88.1 kGy/min of
average dose rate were used. To confirm the target dose,
alanine dosimeters were attached to the top and bottom
of samples and were read using a 104 electron paramagnetic resonance unit (EMS-104, Bruker Instruments Inc.,
Billerica, MA). The maximum:minimum ratio was approximately 1.3. Both irradiated and nonirradiated raw
meat patties were kept at 4°C; color and lipid oxidation
were measured after 0, 7, and 12 d; and volatiles were
measured after 0 and 7 d of storage. Concentrations of
VE, Se, and fatty acid composition were determined
before and after irradiation.
Meat Quality Analyses
Vitamin E content in breast patties was analyzed using the gas chromatography method of Du and Ahn
(2002b). α-Tocopherol concentration was quantified us-
1831
IRRADIATED TURKEY BREAST MEAT
Table 2. Corn–soybean-based diets fed to male turkeys from 12 to 15 wk
Ingredients (%)
Corn
Soybean meal
Soy oil
CLA source1
VE premix2
Mineral premix 13
Mineral premix 24
Vitamin premix5
Dicalcium phosphate
Limestone
DL-Met
L-Lys
Salt
BMD6
Total
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
62.50
29.10
4.36
0.00
0.00
0.00
0.30
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.40
28.20
4.33
0.00
1.00
0.00
0.30
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.50
29.10
4.36
0.00
0.00
0.30
0.00
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.50
29.10
1.86
2.50
0.00
0.00
0.30
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.40
28.20
4.33
0.00
1.00
0.30
0.00
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.40
28.20
1.83
2.50
1.00
0.00
0.30
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.50
29.10
1.86
2.50
0.00
0.30
0.00
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
62.40
28.20
1.83
2.50
1.00
0.30
0.00
0.30
1.72
1.27
0.17
0.13
0.15
0.03
100
1
CLA = conjugated linoleic acid.
Contains 20,000 IU/kg of vitamin E (VE).
3
Contains 100 mg/kg of Se, plus the following: Na, 33%; chloride, 58%; Zn, 13,300 mg/kg; Mn, 2,300 mg/kg; Fe, 12,300 mg/kg; and Cu, 2,000
mg/kg.
4
Contains only the following: Na, 33%; chloride, 58%; Zn, 13,300 mg/kg; Mn, 2,300 mg/kg; Fe, 12,300 mg/kg; and Cu, 2,000 mg/kg, without
Se.
5
Contains the following: vitamin A, 2,688,333 IU/kg; vitamin D3, 526,667 IU/kg; vitamin K (menadione Na bisulfite complex), 1,200 mg/kg;
riboflavin, 2,600 mg/kg; pantothenic acid, 4,267 mg/kg; niacin, 25,000 mg/kg; choline, 169,667 mg/kg; folic acid, 540 mg/kg; biotin, 90 mg/
kg; pyridoxine, 2,025 mg/kg; thiamine, 675 mg/kg; and vitamin B12, 5,333 mg/kg.
6
BMD = bacitracin methylene disalicylate.
2
ing 5α-cholestane as an internal standard and expressed
as micrograms/kilogram of muscle. Selenium in breast
meat was analyzed according to the fluorometric
method of AOAC International (1995). Gas chromatography (HP6890, Hewlett-Packard Co., Wilmington, DE)
was used to determine fatty acid composition. Fatty
acids were identified by comparing the retention times
to standards and were expressed as peak area percentage of total fatty acids (Du and Ahn, 2002b).
A Labscan color meter (Hunter Associates Laboratory
Inc., Reston, VA) was used to measure color of raw meat
patties. Each patty sample in transparent packages was
put directly under the light source. Light source was
illuminant D 10°, port size was 1 cm, and viewing area
was 0.63 cm. Hunter lightness, redness, and yellowness
were read 3 times from 3 different areas around the
center of each patty sample and were averaged as the
measurement of this sample. Lipid oxidation was determined by measuring 2-TBA reactive substances
(TBARS) content, as described by Nam et al. (2003a).
Volatiles were determined using a dynamic headspacegas chromatography mass spectrometry method (Nam
and Ahn, 2003).
Raw turkey aroma and irradiation off-aroma of both
irradiated and nonirradiated samples from birds fed
different diets were assessed by 8 trained panelists. Panelists were recruited from faculty, staff, and students,
and a 1-h training session was performed before actual
samples were presented to panelists. Panelists assessed
the differences in aroma characteristics between irradiated and nonirradiated meat and made comments as to
the description of sensory terms. Testing was conducted
in partitioned booths and under red fluorescent lights.
A line scale (numerical value of 15 units) was used with
descriptive anchors (none and high) at each end of the
line. Data were collected by using a computerized sensory scoring system (Compusense 5, Version 4.4, Compusense Inc., Guelph, Ontario, Canada).
Statistical Analysis
Analyses of variance were conducted using the GLM
procedure appropriate for complete randomized block
designs (SAS Institute, 1995). Statements of probability
are based upon P ≤ 0.05. When significant differences
among or between treatment means were found, means
were compared using Tukey’s multiple tests mean
value, and SEM were reported. Data for each treatment
were combined and analyzed using the multivariate
(YX) PRINCOP program of SAS 8.2 (SAS Institute, 1995)
to determine principal components and correlations.
RESULTS AND DISCUSSION
Dietary VE, Se, and CLA
on Turkey Performance
Conjugated linoleic acid supplementation (treatment
CLA, VE + CLA, Se + CLA, VE + Se + CLA) lowered feed
consumption in general, but the decrease was significant
only for SE + CLA and VE + SE + CLA treatments (Table
3). Results from other studies on CLA supplementation
were mixed: Eggert et al. (2001) showed that dietary
CLA increased average daily gain of growing pigs,
whereas Cook et al. (1998) observed a decrease of average daily gain. Wiegand et al. (2002) reported no effect
of dietary CLA on weight gain. Du and Ahn (2002a)
1832
YAN ET AL.
Table 3. Effect of dietary functional ingredients on weight gain, feed
consumption, and feed conversion rate (FCR) of male turkeys during
the 12- to 15-wk feeding period
Diets
1
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
Weight gain
(kg)
ab
3.39
3.43a
3.41a
3.27b
3.46a
3.46a
3.29b
3.47a
0.13
Feed consumption
(kg)
a
10.65
10.69a
10.61a
10.21ab
10.63a
10.27ab
9.96b
10.02b
0.75
Table 4. Concentration of vitamin E (VE) and Se in turkey breast with
different diets
VE content
(␮g/g)
FCR
3.14a
3.12a
3.10a
3.12a
3.07ab
2.96b
3.02b
2.89b
0.18
a,b
Means within a column with no common superscript differ significantly (P < 0.05); n = 4.
1
VE = vitamin E; CLA = conjugated linoleic acid.
found no difference in the live weight of chickens after
feeding 1% CLA for 3 wk. However, when dietary CLA
levels for chickens were increased to >2% and fed to 5
wk, feed consumption, BW, and daily gain tended to
decrease as dietary CLA level increased. Results from
the current study agreed with those of Du and Ahn
(2002a), confirming that a higher level of CLA decreased
live weight as a result of reduced feed consumption
(Table 3). Park et al. (1999) reported that the effect of
CLA on animal growth and feed efficiency was dependent on isomers: cis-9, trans11 CLA isomer was active
in enhancing BW gain and appeared also to enhance
feed efficiency in weanling mice, but they had no effect
on body fat change. However, trans10, cis-12 CLA isomers reduced body fat levels relative to control but did
not enhance either body growth or feed efficiency. So
the overall effects of CLA on growth, feed efficiency, and
body level appeared to be due to the different biological
activities of the 2 isomers.
Decrease in weight gain by CLA was reduced when
CLA was combined with VE (VE + CLA) or both VE
and Se (VE + Se + CLA; P < 0.05). When CLA was fed
along with VE, or VE + Se, the birds had a better growth
rate than CLA alone and control, even though feed consumption was not increased. As a result, feed efficiency
of treatments VE + CLA and VE + Se + CLA decreased
(P < 0.05) as compared with control and CLA alone.
Increasing dietary concentration of VE from 48 to 178
IU/kg resulted in improved performance and economic
returns from flocks inflicted with subclinical infectious
diseases (McIlroy et al., 1993). Guo et al. (2001) reported
that addition of VE at 100 mg/kg significantly (P < 0.05)
improved the growth and FCR of broilers fed the control
diet during 0 to 3 wk of age. In this study, 200 IU/kg
of added VE showed no influence on performance (total
weight gain, feed consumption, and feed efficiency) of
birds, but the reduced weight gain caused by dietary
CLA was improved by VE. Selenium was required for
maximum poultry performance (Scott et al., 1965). With
Se supplementation (0.3 mg/kg), however, there was no
significant performance improvement except that FCR
Diets1
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
Se content
(␮g/g)
No
irradiation
Irradiation
(1.5 kGy)
0.20b
0.19b
0.48a
0.22b
0.50a
0.22b
0.49a
0.52a
0.15
0.86b,x
3.93a,x
0.91b,x
0.90b
4.16a,x
3.86a
0.81b
4.05a,x
1.56
0.66b,y
2.53ab,y
0.70b,y
0.78b
3.26a,y
3.30a
0.71b
3.41a,y
1.25
a,b
Means within a column with no common superscript differ significantly (P < 0.05); n = 4.
x,y
Means within a row with no common superscript differ significantly (P < 0.05).
1
CLA = conjugated linoleic acid.
was decreased when Se was supplemented along with
VE (Table 3).
Meat Composition
Supplementation of tocopherol acetate in turkey diets
singly or in combination with other functional ingredients (Se and CLA) increased VE levels in breast muscles
(Table 4). The levels of VE in breast meat increased by
more than 4-fold over the control and the treatments
without VE. When VE was combined with Se (treatments VE + Se and VE + Se + CLA), muscle accumulations of VE were higher than that of single supplementation; when VE was combined with CLA, the average
accumulation was lower but was not statistically significant (P > 0.05). Dietary Se increased the tissue accumulations of Se, but VE or CLA had no effect on its
concentration (Table 4).
Dietary CLA changed the composition of other fatty
acids, both total MUFA and total non-CLA PUFA were
decreased (P < 0.05; Table 5). Among PUFA, all n3 fatty
acids, including C20:5 n3 and C22:6 n3, were increased.
Two long-chain n6 fatty acids (C20:4 n6 and C22:5 n6)
were decreased, but no consistent change in arachidonic
acid (C22:4 n6) was observed. There were no differences
in total saturated fatty acid between CLA-supplemented
groups and other groups, except a decrease in saturated
fatty acids, such as C14:0, C18:0, and C22:0 by CLA.
Du et al. (2000) reported similar changes in fatty acid
composition by dietary CLA. The decreases in C18:1 n9,
C18:1 n7, and C20:1 n9 and increases in C14:0 and C18:0
were very likely due to the inhibition of stearoyl-CoA
desaturase, a key enzyme involved in the synthesis of
MUFA by CLA (Lee et al., 1998), activity. The decreases
of long-chain n6 PUFA could be caused by the competitive inhibition of ∆6-desaturase by CLA (Liu and Belury, 1998). ∆6-Desaturase is required for long-chain
PUFA synthesis from either linoleic acid (n6 precursor)
or α-linolenic acids (n3 precursor). If ∆6-desaturase was
1833
IRRADIATED TURKEY BREAST MEAT
Table 5. Fatty acid composition of turkey breast as affected by dietary vitamin E (VE), Se, and conjugated linoleic acid (CLA)
Fatty acids1
Control
VE
Se
CLA
VE + Se
C14:0
C16:0
C16:1, n7
C17:0
C17:1, n10
C18:0
C18:1, n9
C18:1, n7
C18:2, n6
C18:3, n6
C18:3, n3
Cis-9, trans11 CLA
trans10, cis-12 CLA
C20:0
C20:1, n9
C20:4, n6
C20:5, n3
C22:0
C22:4, n6
C22:5, n6
C22:6, n3
Total MUFA
Total PUFA
Total n3 PUFA
Total n6 PUFA
Total non-CLA PUFA
Total saturated fatty acids
0.22b
9.06
8.62
0.48a
0.20
16.62
12.69ab
2.28a
24.81
0.09b
0.77b
0.00c
0.00c
0.89a
0.71a
11.87a
0.06c
0.38c
0.32a
1.92a
0.69b
34.50ab
37.69ab
3.43a
36.09
37.68a
27.65a
0.28ab
8.26
19.46
0.41ab
0.19
16.24
14.08a
2.24a
24.91
0.09b
1.09a
0.00c
0.00c
0.65b
0.63ab
10.24ab
0.13bc
0.36c
0.12c
1.69ab
0.61b
36.59a
38.88a
3.52a
35.36
38.88a
26.20b
0.29ab
9.03
19.79
0.42ab
0.18
16.74
13.97a
2.31a
24.34
0.07b
0.85b
0.00c
0.00c
0.75ab
0.61ab
9.53ab
0.13bc
0.33c
0.12c
1.60ab
0.61b
36.85a
37.26ab
3.20ab
34.06
37.26a
27.56a
0.33a
8.25
20.09
0.36b
0.18
17.26
11.46b
1.82b
23.87
0.14a
0.87b
2.20a
1.33ab
0.72ab
0.59ab
7.68b
0.32a
0.81a
0.35a
1.56b
0.95a
33.96b
39.04a
3.81a
35.18
34.47b
27.91a
0.28ab
8.33
19.46
0.41ab
0.18
16.57
13.14ab
2.21a
23.97
0.09c
0.85b
0.09c
0.00c
0.64b
0.76a
9.62ab
0.10b
0.60b
0.26ab
1.68ab
0.65b
35.49ab
37.05ab
3.31ab
33.74
37.03a
27.46a
VE + CLA
Se + CLA
VE + Se + CLA
SEM
0.30a
8.66
19.92
0.42ab
0.18
17.15
11.59b
1.95ab
23.16
0.13a
0.71ab
1.95ab
1.15ab
0.61b
0.57ab
8.17b
0.17b
0.69ab
0.38a
1.44b
0.88a
33.59b
38.64a
3.25ab
35.39
35.03b
27.77a
0.34a
8.90
20.22
0.38b
0.18
16.81
11.19b
1.70c
23.03
0.16a
0.62b
2.68a
1.80a
0.75ab
0.42b
7.62b
0.24ab
0.70ab
0.31a
1.34b
0.72ab
33.71b
38.41a
2.81b
35.60
33.93b
27.88a
0.32a
9.18
19.60
0.35b
0.18
17.10
10.47c
1.80b
23.59
0.20a
0.62b
2.68a
1.59a
0.44c
0.40b
8.24b
0.17b
0.71ab
0.23ab
1.48b
0.85a
32.45b
39.35a
2.82b
36.53
35.08b
28.20a
0.04
0.39
0.50
0.04
0.01
0.34
1.34
0.25
0.71
0.01
0.16
1.28
0.81
0.13
0.14
1.46
0.05
0.16
0.08
0.19
0.10
1.52
0.90
0.28
1.02
0.87
0.66
(%)
Means within a row with no common superscript differ significantly (P < 0.05); n = 4.
MUFA = monounsaturated fatty acid; PUFA = polyunsaturated fatty acid.
a–c
1
inhibited by CLA, n3 long-chain fatty acids would also
be decreased. But results from this study, as well as
others, showed that n3 fatty acids were increased. So
not only is inhibition of ∆6-desaturase involved in CLA
modulated fatty acids metabolism, but also other mechanisms that cause eicosapentaenoic acid and docosahexaenoic acid accumulations are involved. These fatty acid
composition changes are also important to improve storage stability of meat by minimizing lipid oxidation.
Lipid Oxidation
The TBARS values of raw meat increased by storage
in both irradiated and nonirradiated raw meat, but not
all of the increases were significant. Irradiated meat produced greater amounts of TBARS than nonirradiated
ones, and the TBARS increase over storage was also
greater in irradiated than nonirradiated meat. In nonirradiated meat, treatments containing VE (VE, VE + Se,
VE + CLA, and VE + Se + CLA) prevented oxidative
changes during storage. In irradiated meat, combinations of VE with Se, CLA, or both (VE + Se, VE + CLA,
and VE + Se + CLA) also minimized oxidative changes
during the 12-d storage (Table 6). Dietary functional
ingredients, singly or in combination, improved storage
stability of both irradiated and nonirradiated meat after
storage, but some of them (Se, CLA, and Se + CLA for
nonirradiated meat) were not significant.
Ahn et al. (1997) reported that dietary VE at >200 IU/
kg decreased lipid oxidation and total volatiles of raw
turkey patties after 7 d of storage. Nam et al. (2003b)
indicated that dietary VE at 100 IU/kg significantly improved the storage stability of turkey breast, which was
more distinct in irradiated than nonirradiated meats.
Du et al. (2000) observed decreased lipid oxidation by
dietary CLA in chicken meat during storage and attributed it to the reduced PUFA in the meat. Supplementation of feed with Se was found to decrease lipid oxidation in chicken meat (Combs and Regenstein, 1980).
However, our results indicated that only dietary VE
provided significant antioxidant property to raw meat.
However, combinations of VE and Se; VE and CLA; and
VE, Se, and CLA provided better protection from lipid
oxidation than their single supplementations.
Meat Color
Regardless of dietary treatments, irradiation improved Hunter color redness value of raw meat, and
the color changes remained over the 12-d storage period
(Table 7). Dietary supplementation of functional ingredients also had some effects on the redness value of
meat, but their effects were marginal compared with
irradiation. However, Nam et al. (2003b) reported that
dietary VE at >100 IU/kg was effective in stabilizing
turkey breast meat color with aerobic packaging. Dietary CLA in general reduced (P < 0.05) both lightness
value and redness value of nonirradiated raw meat, but
the changes were significant only in stored meats.
Volatile Profiles
Compared with nonirradiated meat, irradiation of
raw turkey breast created new S-containing compounds
1834
YAN ET AL.
Table 6. Effect of functional ingredients on lipid oxidation of aerobically packaged raw turkey breast
Nonirradiated (d)
Diets1
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
0
7
1.5 kGy irradiated (d)
12
0
7
12
TBARS2 (mg of malondialdehyde/kg of meat)
0.41a,xy
0.60a,y
0.24a,x
0.75a,y
0.20b,xy
0.27b,y
0.18abc,x
0.30bc,xy
0.23b,x
0.48ab,y
0.21ab,x
0.40b,xy
0.24b,xy
0.49ab,y
0.19abc,x
0.35bc,xy
0.16bc,x
0.20b,x
0.17bc,x
0.20c,x
0.12c,x
0.18b,x
0.15c,x
0.17c,x
0.21bc,xy
0.46ab,y
0.18abc,x
0.40b,xy
0.12c,x
0.16b,x
0.14c,x
0.16c,x
0.03
0.08
0.02
0.06
0.18a,x
0.13b,x
0.15ab,x
0.14ab,x
0.12b,x
0.10b,x
0.12b,x
0.10b,x
0.02
1.05a,z
0.68bc,y
0.56bc,y
0.72bc,y
0.34cd,y
0.23d,y
0.80b,y
0.22d,x
0.08
Means within a column with no common superscript differ significantly (P < 0.05); n = 4.
Means within a row within the same irradiation dose with no common superscript differ significantly (P
< 0.05).
1
VE = vitamin E; CLA = conjugated linoleic acid.
2
TBARS = 2-TBA reactive substances.
a–d
x,y
such as dimethyl disulfide. The amount of S compounds
from control, VE, and Se diets increased after 7 d of
storage (Table 8). No S compounds were detected in
treatments VE + Se, VE + CLA, and VE + Se + CLA after
7 d of storage, and the levels in treatments CLA and Se
+ CLA were lower than that at d 0. Ahn et al. (2000)
reported that S-containing volatile compounds that
were responsible for irradiated meat off-odor were
highly volatile and easily evaporated under aerobic conditions.
Irradiation also increased the amounts of total hydrocarbons, aldehydes, alcohols, and ketones (P < 0.05; Ta-
Table 7. CIE color values of raw turkey breast patties during storage
Lightness
Diets1
0d
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
7d
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
12 d
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
Redness
Nonirradiated
1.5 kGy
rradiated
Nonirradiated
46.49
45.81x
45.07
44.16
44.52
44.46
44.13
44.94
0.45
46.16a
44.53ab,y
44.5ab
43.89b
44.38ab
44.41ab
43.75b
44.01b
0.41
1.18ab,x
1.32a,x
1.13ab,x
0.93b,x
1.35a,x
0.99b,x
0.90b,x
1.28a,x
0.08
46.99a
46.29a
46.57a
45.25a
46.38a
45.72a
45.32b
45.72b
0.47
47.07a
46.78a
46.30a
45.15b
46.11a
45.46b
46.17ab
46.15ab
0.47
48.08a
48.49a
48.05a
46.99b
47.43ab
46.07c
46.63bc
46.53bc
0.46
48.21a
47.33ab
47.60ab
45.53c
47.66abc
45.36c
45.15abc
46.19abc
0.17
Yellowness
1.5 kGy
irradiated
Nonirradiated
1.5 kGy
irradiated
3.72y
3.64y
3.62y
3.54y
3.45y
3.49y
3.77y
3.92y
0.11
8.79a,x
8.27ab,x
8.08ab
7.77b
7.67b
7.79b,x
7.92b
7.77b,x
0.18
8.79a,x
8.27ab,x
8.08ab
7.77b
7.67b
7.79b,x
7.92b
7.77b,x
0.18
1.05b,x
1.29ab,x
1.15b,x
0.93c,x
1.62a,x
0.98c,x
1.10x
1.65a,x
0.11
4.51a,y
3.94b,y
3.98ab,y
4.12ab,y
4.14ab,y
3.94b,y
4.20ab,y
4.07ab,y
0.12
7.95a
8.02a
7.76ab
7.02b
7.89a
7.62ab,x
7.39ab
7.52ab
0.2
7.82a
7.40abc
7.78ab
7.01bc
7.20abc
6.88c,y
7.54ab,y
7.25abc
0.17
1.18c,x
1.23ab,x
1.17c,x
1.02c,x
1.39a,x
1.21ab,x
1.05c,x
1.43a,x
0.12
4.27a,y
3.64bc,y
3.89abc,y
3.66bc,y
3.68bc,y
3.56bc,y
4.2ab,y
3.67abc,y
0.13
8.02x
8.1
7.83
7.38
7.51
8.17
7.72x
7.68
0.19
8.38y
8.34
8.29
7.68
7.9
7.91
8.23y
7.815
0.22
a–c
Means within a column with no common superscript within the same storage day differ significantly (P
< 0.05); n = 4.
x,y
Means within a row with no common superscript within the same color parameter differ significantly (P
< 0.05).
1
VE = vitamin E; CLA = conjugated linoleic acid.
1835
IRRADIATED TURKEY BREAST MEAT
Table 8. Volatiles of raw turkey breast patties as affected by different diet treatments, irradiation, and storage time.
Hydrocarbons
Diets1
0 kGy
1.5 kGy
Aldehydes
0 kGy
1.5 kGy
Alcohols
0 kGy
1.5 kGy
Ketones
S compounds
0 kGy
1.5 kGy
0 kGy
1.5 kGy
(total ion count × 104)
0d
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
7d
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
459a,x
111c,x
360ab,x
359ab,x
129c
148c
243b,x
133c
58
1,867a,y
541bc,y
737b,y
868b,y
174c
89c
642bc,y
132c
126
654a,x
288b
589a,x
688a,x
197b,x
105c
485ab,x
0d
119
2,920a,y
538c
1,716b,y
1,630b,y
391cy
144d
1,529b,y
274c
136
474a,x
310ab
443a
313ab,x
226b
106c
250b,x
70c
169
1,317a,x
442b
537b,x
385b,x
193c
203c
309b,x
127c
134
1,070a,y
452b
483b
539b,y
219c
182c
455b,y
99c
117
7,006a,x
7,038a
5,762b,x
5,392b,x
6,087b,x
6,515ab,x
6,334ab,x
6,330ab,x
1,473
8,905y
7,564
8,314y
7,818y
7,450y
7,533y
8,008y
7,908y
1,719
5,911b
7,168ab,y
7,014ab,y
5,612b
8,648a
9,052a
6,480b
7,145ab
934
5,599c
6,213c,x
6,079c,x
5,903c
8,435a
8,433a
7,038b
6,331c
962
0x
0x
0x
0x
0x
0x
0x
0x
0
896a,y
323b,y
927a,y
394b,y
236bc
205c,y
294bc,y
179c,y
144
3,133a,y
563c
980b,y
1,365b,y
259d
282d
1,436b,y
186d
96
9,901a,x
5,988b,x
6,787b,x
7,729ab,x
5,975b,x
5,837b,x
4,965c,x
5,494b,x
1,473
11,804a,y
9,238b,y
10,450ab,y
9,680b,y
9,094b,y
7,602c,y
10,863ab,y
8,033c,y
2,141
4,452c,x
5,804c
7,620b
6,297bc
8,989a
7,421b
6,868bc
6,226bc
1,226
6,326bc,y
5,785c
6,105bc
5,980c
9,175a
7,172b
6,601bc
6,096bc
1,043
0x
0x
0x
0x
0
1,453a,y
628b,y
1,206a,y
203c,y
0d
0x
0
0
139c,y
0d
372
d
Means within a column within the same storage day with no common superscript differ significantly (P < 0.05); n = 4.
Means within a row within the same compound group with no common superscript differ significantly (P < 0.05).
1
VE = vitamin E; CLA = conjugated linoleic acid.
a–d
x,y
ble 8). Dietary supplementation of VE, VE + Se, VE +
CLA, and VE + Se + CLA reduced (P < 0.05) the production of hydrocarbons and aldehydes at d 0 and 7 (except
for dietary VE at d 0). However, there was no significant
pattern in the changes of alcohols and ketones by dietary
treatments. Hydrocarbons, aldehydes, alcohols, and ketones are volatiles that are derived from lipids. Autooxidation of unsaturated fatty acids is not only responsible
for rancid off-flavors during storage, known as
“warmed-over flavor,” but for characteristic meat flavor
due to complex volatile compounds produced by lipid
oxidation (Mottram and Edwards, 1983). Shahidi and
Pegg (1994) indicated that some aldehydes, like hexanal
and pentanal, were good indicators of lipid oxidation.
Our study showed that aldehydes and hydrocarbons
were generally increased by storage and irradiation.
Sensory Evaluation
Irradiation significantly (P < 0.05) reduced raw turkey
aroma and increased irradiation off-aroma of turkey
breast meat (Table 9). Dietary VE and VE + Se significantly reduced raw turkey aroma in nonirradiated meat,
but all dietary functional ingredients reduced raw turkey
aroma in irradiated meat. Sensory panels easily detected
irradiation off-aroma, but dietary VE + Se and VE + Se
+ CLA treatments significantly lowered irradiation offaroma in irradiated meat. Nonirradiated meat had little
irradiation off-aroma. During training sessions, sensory
panels described irradiation off-aroma of irradiated raw
meat as “sulfury,” “vegetable,” “hospital-like,” or “wetdog,” which was different from that of nonirradiated
meat. When the scores for irradiation off-aroma were
high, the scores for turkey aroma were low (Table 9).
Principal Component Analysis
The purposes of principal component analysis are as
follows:1) to derive a small number of independent linear combinations (principal components) that retain as
much of the information in the original variables as possible, and 2) to explore polynomial relationship. Thus,
principal component analysis, a multidimensional modeling method, provides an interpretable overview of the
key information through the loading plot. In the loading
plot, components (so-called principal components) that
are close together are positively correlated, whereas
those lying opposite to each other tend to have negative
correlation (Næs et al., 1996).
Table 9. Sensory scores of breast meats from turkeys supplemented
with different dietary functional ingredients
Treatments2
Control
VE
Se
CLA
VE + Se
VE + CLA
Se + CLA
VE + Se + CLA
SEM
Raw turkey
aroma1 (kGy)
Irradiation
off-aroma1 (kGy)
0
1.5
0
1.5
8.72ab
6.71b,x
8.73ab,x
8.82ab,x
6.63b,x
8.37ab,x
10.14a,x
10.05a,x
1.12
5.12a,y
3.68ab,y
3.72ab,y
2.84b,y
2.06b,y
2.42b,y
2.75b,y
2.60b,y
0.90
0.24x
0.22x
0.24x
0.13x
0.07x
0.19x
0.14x
0.16x
0.08
6.07ab,y
5.06ab,y
5.85ab,y
9.25y
4.59b,y
7.26ab,y
7.58ab,y
5.10b,y
1.16
a,b
Values with different superscripts within a column within the
same irradiation dose are significantly different (P < 0.05).
x,y
Values with different superscripts within each sensory attribute
are significantly different (P < 0.05); n = 4.
1
No aroma = 1; strong aroma = 15.
2
VE = vitamin E; CLA = conjugated linoleic acid.
1836
YAN ET AL.
Table 10. The variation sources of the first 2 principal components
(PC) for volatile analysis
Variables
Total hydrocarbons
Total aldehydes
Total alcohols
Total ketones
S compounds
Pentane
2-Propanone
Methanol
Ethanol
2-Propanol
2-Butanone
Dimethyl disulfide
Octane
Hexanal
1-Hexen-3-ol
Heptanal
1-Hexanol
1-Pentanol
1-Octen-3-ol
Nonanal
PC1
PC2
0.3209
0.3147
0.2051
−0.1555
0.1547
0.3263
−0.1608
0.0092
0.1709
−0.0787
0.1662
0.2564
0.1107
0.3195
0.2129
0.2102
0.2608
0.0697
0.2953
0.2882
−0.0363
−0.1148
0.0417
−0.0832
0.3893
−0.0334
−0.0858
−0.0853
0.2620
0.1905
0.0783
0.3869
−0.0452
−0.0504
−0.2393
−0.2522
−0.2582
−0.0993
−0.1129
−0.0820
Principal component analysis of volatiles showed that
94% (2 principal components: Pc1, 38% and Pc2, 56%)
of the total variability was derived from irradiation and
storage. The variation of Pc1 was mainly generated by
total hydrocarbons, total aldehydes, pentane, hexanal,
1-octen-3-ol, and nonanal. Hydrocarbons and aldehydes
weighed heavier than other compounds. The variation
of Pc2 was mainly attributed to dimethyl disulfide, and
S-containing compounds contrasted to other compounds
(Table 10).
Table 11 shows the correlation coefficients by principal
component analysis procedure among lipid oxidation,
2 sensory attributes (raw turkey aroma and irradiation
off-aroma), volatile components, and concentrations of
VE, Se, and CLA. Several significant correlations between the chemical and sensory parameters of turkey
patties with different treatments were detected. Lipid
oxidation (TBARS) was positively correlated (P < 0.05)
with total hydrocarbons, total aldehydes, total alcohols,
pentane, 2-butanone, octane, hexanal, 1-hexen-3-ol, 1hexanol, 1-octen-3-ol, and nonenal and was negatively
correlated (P < 0.05) with total ketones and 2-propanone.
Turkey meat aroma was negatively correlated (P < 0.05)
with irradiation aroma, total hydrocarbons, total S compounds, pentane, ethanol, 2-propanol, 2-butanone, and
dimethyl disulfide. Irradiation off-aroma was positively
correlated with dimethyl disulfide as well as total hydrocarbons, total aldehydes, total S compounds, pentane,
ethanol, 2-butanone, and hexanal (Table 11).
Vitamin E had negative relations (P < 0.05) with lipid
oxidation and production of total hydrocarbons, total
aldehydes, total alcohols, and total ketones. The individual representative compounds were pentane, hexanal,
1-octen-3-ol, and nonanal. 2-Propanone and 2-propanol
were positively related to VE concentration. Both Se and
CLA had negative correlations (P < 0.05) with the production of S-containing compounds.
In conclusion, dietary functional ingredients (VE, Se,
and CLA) improved the feed efficiency of turkeys during
the finishing period. Lipid oxidation and off-odor of
turkey breast meat caused by storage and ionizing irradiation were reduced by dietary functional ingredients,
especially when VE was combined with Se or with both
Se and CLA.
Table 11. Correlation coefficients among lipid oxidation, sensory attributes, volatile profiles, and concentrations
of vitamin E (VE), Se, and conjugated linoleic acid (CLA)
Item
Turkey aroma
Irradiation aroma
VE
Se
CLA
Total hydrocarbons
Total aldehydes
Total alcohols
Total ketones
S compounds
Pentane
2-Propanone
Methanol
Ethanol
2-Propanol
2-Butanone
Dimethyldisulfide
Octane
Hexanal
1-Hexen-3-ol
1-Pentanol
Heptanal
1-Hexanol
1-Octen-3-ol
Nonanal
TBARS1
Turkey aroma
Irradiation off-aroma
VE
Se
CLA
−0.11
0.13
−0.56*
−0.20
−0.30
0.78**
0.89**
0.42*
−0.39*
0.29 to 0.40*
0.78**
−0.43*
−0.01
0.21
−0.17
0.58* to 0.65**
0.29 to 0.40*
0.52* to 0.25
0.90** to 0.25
0.65** to 0.25
0.14 to 0.22
0.41
0.65* to 0.25
0.92** to 0.11
0.36* to 0.06
—
−0.96**
0.04
0.05
0.003
−0.43*
−0.28
−0.09
−0.04
0.54*
−0.44*
−0.006
−0.18
−0.40*
−0.30*
0.45*
0.64**
0.33*
0.30*
0.24 to 0.29
−0.18
−0.26
0.24 to 0.34
0.15 to 0.64**
0.04
—
—
—
—
—
—
—
−0.59*
−0.49*
−0.37*
0.39*
−0.31
−0.61**
0.40*
−0.16
−0.19
0.64**
0.05
−0.32*
0.05
−0.14
0.05
0.13
0.07
0.11
−0.26
−0.28*
—
—
—
—
—
−0.09
−0.14
0.05
0.26
−0.42*
−0.07
0.27
−0.25
0.04
0.06
−0.21
−0.42*
−0.21
−0.17
—
—
—
—
—
−0.13
−0.13
−0.46
0.18
—
−0.13
0.19
−0.09
−0.09
0.09
0.49*
0.31*
0.10
0.05
−0.20
0.49*
0.01
−0.25
0.42*
0.23
−0.14
−0.20
−0.14
−0.45*
0.13
−0.28
0.23 to 0.25
0.07
−0.15
−0.33*
*Significant correlation at P < 0.05; **Significant correlation at P < 0.01; n = 32.
1
TBARS = 2-TBA-reactive substances.
−0.22
0.25
—
—
−0.17
−0.28
−0.40*
—
—
—
—
—
—
—
—
—
—
IRRADIATED TURKEY BREAST MEAT
ACKNOWLEDGMENTS
This work was supported by the National Integrated
Food Safety Initiative (USDA grant 2002-5110-01957),
Washington, DC.
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