Effects of aging on the fundamental color chemistry of dark-cutting beef


English, A.R.; Wills, K.M.; Harsh, B.N.; Mafi, G.G.; VanOverbeke, D.L.; Ramanathan, R.

Journal of Animal Science 94(9): 4040-4048

2016


NlmCategory="UNASSIGNED">The objective of the current study was to evaluate the effects of aging on myoglobin chemistry of dark-cutting beef. Ten USDA Choice (mean pH = 5.6; normal pH beef) and 10 no-roll dark cutter (mean pH = 6.4) strip loins were obtained from a commercial packing plant within 3 d of harvest. Loins were cut into 4 sections, vacuum packaged, randomly assigned to 0-, 21-, 42-, and 62-d aging at 2°C in the dark. Following aging, loin sections were cut into 2.5-cm-thick steaks and were used to determine bloom development, oxygen consumption (OC), metmyoglobin reducing activity (MRA), and lipid oxidation. Surface color readings were measured using a HunterLab Miniscan XE Plus spectrophotometer. A significant muscle type × aging time interaction resulted for OC ( < 0.001). Normal pH steaks declined more ( < 0.001) in OC during aging than dark-cutting beef. On d 0, dark-cutting beef had a greater OC ( < 0.001) than normal pH beef. There was a significant muscle type × oxygenation time × aging period interaction for L* values, deoxymyoglobin (DeoxyMb), and oxymyoglobin (OxyMb). When dark-cutting sections were aged for 62 d, both 0 and 60 min bloom development L* values were greater ( < 0.0001) than 0 min dark-cutting sections aged for 21 or 42 d. At all aging periods, normal pH beef had greater OxyMb content and lower DeoxyMb ( < 0.0001) during bloom development than dark-cutting beef. An aging period × muscle type interaction was significant for % overall reflectance ( = 0.0017) and absorbance ( = 0.0038). Dark cutting and normal pH beef loin sections aged for 62 d had greater reflectance ( < 0.0001) than 21 d. On d 0, dark-cutting beef had greater ( < 0.0001) MRA than normal pH beef. There were no significant ( = 0.14) differences in MRA between 42 and 62 d between dark-cutting and normal pH beef. Dark cutting steaks had lower thiobarbituric acid reactive substances values ( < 0.0001) than normal pH steaks. The results indicate that characterizing the myoglobin chemistry during aging will help to design strategies to improve appearance of high pH beef.

Effects
of
aging
on
the
fundamental
color
chemistry
of
dark-cutting
beef
A.
R.
English,
K.
M.
Wills,
B.
N.
Harsh,
G.
G.
Mafi,
D.
L.
VanOverbeke,
and
R.
Ramanathan
l
Department
of
Animal
Science,
Oklahoma
State
University,
Stillwater
74078
ABSTRACT:
The
objective
of
the
current
study
was
to
evaluate
the
effects
of
aging
on
myoglobin
chemistry
of
dark-cutting
beef.
Ten
USDA
Choice
(mean
pH
=
5.6;
normal
pH
beef)
and
10
no-roll
dark
cutter
(mean
pH
=
6.4)
strip
loins
were
obtained
from
a
commercial
packing
plant
within
3
d
of
harvest.
Loins
were
cut
into
4
sections,
vacuum
packaged,
randomly
assigned
to
0-,
21-,
42-,
and
62-d
aging
at
2°C
in
the
dark.
Following
aging,
loin
sections
were
cut
into
2.5-cm-thick
steaks
and
were
used
to
determine
bloom
development,
oxygen
consumption
(OC),
metmyoglobin
reducing
activity
(MRA),
and
lipid
oxidation.
Surface
color
readings
were
measured
using
a
HunterLab
Miniscan
XE
Plus
spectrophotometer.
A
significant
muscle
type
x
aging
time
interaction
resulted
for
OC
(P
<
0.001).
Normal
pH
steaks
declined
more
(P
<
0.001)
in
OC
dur-
ing
aging
than
dark-cutting
beef.
On
d
0,
dark-cutting
beef
had
a
greater
OC
(P
<
0.001)
than
normal
pH
beef.
There
was
a
significant
muscle
type
x
oxygenation
time
x
aging
period
interaction
for
L*
values,
deoxymyoglo-
bin
(DeoxyMb),
and
oxymyoglobin
(OxyMb).
When
dark-cutting
sections
were
aged
for
62
d,
both
0
and
60
min
bloom
development
L*
values
were
greater
(P
<
0.0001)
than
0
min
dark-cutting
sections
aged
for
21
or
42
d.
At
all
aging
periods,
normal
pH
beef
had
great-
er
OxyMb
content
and
lower
DeoxyMb
(P
<
0.0001)
during
bloom
development
than
dark-cutting
beef.
An
aging
period
x
muscle
type
interaction
was
significant
for
%
overall
reflectance
(P
=
0.0017)
and
absorbance
(P
=
0.0038).
Dark
cutting
and
normal
pH
beef
loin
sec-
tions
aged
for
62
d
had
greater
reflectance
(P
<
0.0001)
than
21
d.
On
d
0,
dark-cutting
beef
had
greater
(P
<
0.0001)
MRA
than
normal
pH
beef.
There
were
no
sig-
nificant
(P
=
0.14)
differences
in
MRA
between
42
and
62
d
between
dark-cutting
and
normal
pH
beef.
Dark
cutting
steaks
had
lower
thiobarbituric
acid
reactive
substances
values
(P
<
0.0001)
than
normal
pH
steaks.
The
results
indicate
that
characterizing
the
myoglobin
chemistry
during
aging
will
help
to
design
strategies
to
improve
appearance
of
high
pH
beef.
Key
words:
aging,
beef
strip
loin,
dark
cutter,
high
pH
beef,
oxygen
consumption
rate
©
2016
American
Society
of
Animal
Science.
All
rights
reserved.
INTRODUCTION
At
the
point
of
sale,
consumers
often associate
bright
red
color
as
an
indicator
of
freshness
and
whole-
someness.
Any
deviation
from
the
bright
red
color
dur-
ing
beef
processing
leads
to
discounted
prices.
Dark
cutting
beef
is
a
condition
in
which
beef
fails
to
have
the
characteristic
bright
red
color.
Although
the
etiol-
ogy
of
dark-cutting
beef
is
not
clear,
it
is
widely
ac-
cepted
that
pre-harvest
stress
leads
to
depletion
of
glycogen
reserves
prior
to
slaughter
(Hendrick
et
al.,
1959;
Ashmore
et
al.,
1971).
The
National
Beef
Quality
Audit
reported
that
the
US
beef
industry
lost
approxi-
1
Corresponding
author:
ranjithsamanathan@okstate.edu
Received
April
18,
2016.
Accepted
June
19,
2016.
J.
Anim
Sci.
2016.94:4040-4048
doi:10.2527/jas2016-0561
mately
$1654170
million
in
2000
due
to
dark-cutting
carcasses
(McKenna
et
al.,
2002).
More
specifically,
this
loss
results
from
discounted
value
in
beef
car-
casses.
Depletion
of
glycogen
reserves
before
slaugh-
ter
results
in
minimal
decline
in
pH,
thus
ultimate
pH
remains
greater
than
normal
pH.
An
increased
pH
can
promote
water
holding
capacity,
resulting
in
tightly
packed
muscle
fibers.
Consequently,
meat
will
have
a
darker
color
because
its
surface
does
not
reflect
light
to
the
same
extent
as
in
normal
pH
meat
(Seideman
et
al.,
1984).
Increased
pH
also
enhances
mitochondria
activ-
ity,
which
can
limit
myoglobin
oxygenation
(Lawrie,
1958;
Ashmore
et
al.,
1972).
Recently,
McKeith
et
al.
(2016)
reported
greater
mitochondrial
abundance
in
dark-cutting
beef.
Postmortem
aging
decreases
oxygen
consumption
and
improves
bloom
development
by
de-
creasing
competition
for
oxygen
between
myoglobin
4040
Extended
aging
and
dark
cutting
color
4041
and
mitochondria
(Mac
Dougall,
1982;
Mancini
and
Ramanathan,
2014).
Further,
extended
aging
also
can
af-
fect
proteolysis
of
cytoskeletal
proteins
such
as
desmin,
talin,
and
vinculin,
and
thus
limiting
the
ability
of
mus-
cle
to
hold
water
(Huff-Lonergan
and
Lonergan,
2005).
However, limited
knowledge
is
currently
available
on
the
influence
of
aging
on
biochemical
properties
of
dark-
cutting
beef.
Therefore,
the
objective
was
to
determine
the
effects
of
aging
on
biochemical
properties
of
dark-
cutting
longissimus
lumborum
muscle.
MATERIALS
AND
METHODS
Raw
Materials
and
Processing
Ten
USDA
Choice
beef
and
10
no-roll
dark-cutting
beef
carcasses
were
selected,
individually
identified,
and
tagged
prior
to
fabrication
from
the
Tyson
Fresh
Beef
Plant
at
Garden
City,
KS,
72
h
after
slaughter.
After
fabrication,
both
normal
pH
and
dark-cutting
strip
loins
(longissimus
lumborum,
n
=
10
loins
each,
IMPS
#180)
were
vacuum
packaged
and
transported
on
ice
to
the
Food
and
Agricultural
Products
Center
at
Oklahoma
State
University.
Each
loin
was
cut
into
4
sections,
vac-
uum
packaged
(oxygen
partial
pressure
within
vacuum
package
=
6
mm
Hg
or
0.78%
oxygen;
Prime
source
vacuum
pouches,
12
x
18
cm,
3
mil
high
bather),
and
randomly
assigned
to
0-,
21-,
42-,
or
62-d
aging
periods.
Loin
sections
were
stored
in
the
dark
at
2°C
for
aging.
Sample
Allocation
for
Biochemical
Studies
After
respective
aging
periods,
three
2.5-cm-thick
steaks
were
cut
from
the
anterior
end
using
a
meat
slicer
(Bizerba
USA
Inc.,
Piscataway,
NJ).
The
first
steak
was
assigned
for
oxygenation
studies,
the
second
for
oxygen
consumption
(OC)
and
metmyoglobin
reducing
activity
(MRA),
and
the
third
steak
was
used
for
lipid
oxidation,
pH,
myoglobin
concentration,
and
proximate
analysis.
Muscle
pH
Ten
gram
of
samples
from
steak
assigned
to
0-,
21-,
42-,
and
62-d
were
blended
with
100
mL
of
deionized
water
and
homogenized
for
30
s
in
a
Sorvall
Omni
tabletop
mixer
(Newton,
CT).
The
pH
of
the
muscle
homogenates
was
obtained
by
using
an
Accumet
com-
bination
glass
electrode
connected
to
an
Accumet
50
pH
meter
(Fisher
Scientific,
Fairlawn,
NJ).
Proximate
Analysis
Protein,
moisture,
and
fat
analysis
were
conduct-
ed
on
d
0
samples
using
an
AOAC-approved
(Official
Method
2007.04)
near-infrared
spectrophotom-
eter
(FOSS
Food
Scan
78800;
Dedicated
Analytical
Solutions,
Hillerod,
Denmark).
Compositional
values
were
reported
on
a
percent
(%)
basis.
Myoglobin
Quantification
On
d
0,
a
5-g
sample
from
steak
designated
as
#3
was
homogenized
for
45
s
at
low
speed
with
25
mL
of
ice-cold
40
mM
phosphate
buffer
at
pH
6.8.
Homogenized
samples
were
held
on
ice
for
1
h,
then
transferred
to
an
Eppendorf
tube
and
centrifuged
at
16,000
x
g
for
15
min.
Supernatant
was
filtered
through
a
0.45
j.tM
syringe
filter
(Phoenix
Research
Products,
Candler,
NC),
and
the
absorbance
was
mea-
sured
at
525
nm
to
calculate
total
myoglobin
concen-
tration
using
the
Isobestic
Point
Assay
(AMSA,
2012).
Surface
Color
Measurement
All
instrumental
color
measurements
were
per-
formed
using
a
HunterLab
MiniScan
XE
plus
spectro-
photometer
(Model
45/0
LAV,
2.5-cm
diameter
aperture,
illuminant
A,
10°
observer;
HunterLab,
Reston,
VA)
on
0-,
21-,
42-,
and
62-d.
Both
reflectance
spectra
from
400
to
700
nm
(10
nm
increments)
and
CIE
L*
values
were
measured
on
each
steak
at
3
random
locations,
and
the
subsamples
were
averaged
for
statistical
analyses.
Reflectance
properties
of
normal
and
high
pH
beef
are
different
due
to
changes
in
muscle
structure
and
water
holding
capacity
(Hunt
and
Hedrick,
1977;
Ramanathan
et
al.,
2010;
McKeith
et
al.,
2016).
Hence,
K/S
ratios
at
isobestic
points
were
used
to
estimate
oxymyoglobin
(OxyMb),
deoxymyoglobin
(DeoxyMb),
and
metmyo-
globin
(MetMb).
For
example,
reflectance
values
were
converted
to
K/S
ratios
using
the
following
equation:
K/S
=
(1-
R)
2
÷
2R,
where
R
represents
the
%
reflectance
expressed
as
a
decimal.
The
ratio
of
K/5474
÷
K/S525,
K/5572
÷
K/5525,
and
K/5610
÷
K/5525
was
used
to
estimate
DeoxyMb,
MetMb,
and
OxyMb,
respectively
(AMSA,
2012).
K/S
ratios
were
used
to
make
the
data
more
linear
and
to
account
for
absorptive
(absorbance
coefficient,
K)
and
scattering (scattering
coefficient,
S)
properties.
In
addition,
overall
surface
reflectance
values
were
calculated
from
the
average
of
all
30
wavelengths
taken
from
400-700
nm
at
10
nm
increments
(overall
reflectance
=
[ER400
to
R700
nm
÷
30].
Overall
reflec-
tance
values
represent
the
amount
of
light
reflected
from
steak
surfaces
in
the
visible
spectrum
(HunterLab,
2006;
Ramanathan
et
al.,
2010).
Overall
absorbance
was
cal-
culated
using
reflectance
values
from
400
to
700
nm
ac-
cording
to
Faustman
and
Phillips
(2001)
and
Millar
et
al.
(1996):
A
=
(2
-
log
R),
where
A
represents
absorbance
and
R
represents
percent
reflectance.
4042
English
et
al.
Oxygenation
Properties
(Bloom
Development)
Bloom
development
was
measured
on
21-,
42-,
and
62-d
aging
period.
From
each
loin,
a
2.5-cm-thick
steak
was
cut,
and
color
readings
were
recorded
im-
mediately
to
indicate
0
min.
Following
initial
color
reading,
steaks
were
wrapped
with
polyvinyl
chlo-
ride
film
(oxygen-permeable
polyvinyl
chloride
fresh
meat
film;
15,500
to
16,275
cm
3
0
2
/m
2
/
2
4
h
at
23°C,
E-Z
Wrap
Crystal
Clear
Polyvinyl
Chloride
Wrapping
Film;
Koch
Supplies,
Kansas
City,
MO)
and
stored
at
4°C.
Bloom
measurements
were
taken
using
a
Hunter
Lab
Miniscan
repeatedly
on
the
steak
at
0,
15,
30,
and
60
min.
Blooming
properties
were
reported
as
changes
in
K/5474
÷
K/5525
(indicates
DeoxyMb),
K/5610
÷
K/5525
(indicates
OxyMb),
%
overall
reflectance,
ab-
sorbance,
L*
values
(lightness),
and
reflectance
spec-
tra
from
400
to
700
nm
at
10
nm
increments.
Oxygen
Consumption
(OC)
A
modified
procedure
of
Madhavi
and
Carpenter
(1993)
was
utilized
to
estimate
OC
after
aging
for
0-,
21-,
42-,
and
62-d.
The
samples
(approximately
3
cm
x
3
cm
x
1.5
cm
section
with
minimal
visible
fat
or
con-
nective
tissue)
were
allowed
to
oxygenate
for
30
min
at
4°C,
vacuum
packaged,
and
immediately
scanned
twice
on
the
bloomed
surface
to
measure
DeoxyMb.
OC
was
measured
by
the
conversion
of
OxyMb
to
DeoxyMb
during
the
incubation
of
vacuum
packaged
samples
for
30
min
at
30°C
and
then
scanned
imme-
diately.
DeoxyMb
was
quantified
using
the
ratio
of
K/
S474
÷
K/5525
(AMSA,
2012).
The
conversion
of
OxyMb
to
DeoxyMb
depends
on
the
reducing
activ-
ity
of
meat.
Hence,
in
aged
beef,
OC
calculated
based
on
changes
in
OxyMb
level
pre-
and
postincubation
may
not
accurately
represent
OC
as
OxyMb
will
be
converted
to
MetMb
if
MRA
is
less.
Hence,
OC
was
calculated
as
changes
in
pre-
and
postincubation
DeoxyMb
values
(English
et
al.,
2016).
Metmyoglobin
Reducing
Activity
(MRA)
Various
studies
have
reported
that
resistance
to
myoglobin
oxidation
is
a
better
indicator
of
metmyo-
globin
reducing
property
than
postreduction
values
(O'Keeffe
and
Hood,
1982;
Mancini
et
al.,
2008).
Hence,
MRA
was
measured
as
resistance
to
myoglobin
oxidation.
The
methodology
described
by
Sammel
et
al.
(2002)
was
used
to
determine
MRA
on
steaks
aged
for
0-,
21-,
42-,
and
62-d.
Samples
from
the
interior
of
steak
halves
(approximately
3
cm
x
3
cm
x
1.5
cm
tis-
sue
with
no
visible
fat
or
connective
tissue)
were
sub-
merged
in
a
0.3%
w/v
solution
of
sodium
nitrite
(Sigma
Aldrich,
MO)
for
20
min
at
30°C
(Model
630F;
Fisher
Scientific,
New
York
City,
NY)
to
facilitate
MetMb
for-
mation.
The
sections
were
then
removed,
blotted
to
re-
move
visible
nitrite
solution.
The
level
of
MetMb
con-
tent
on
the
surface
was
determined
by
using
a
Hunter
Lab
Miniscan.
Resistance
to
myoglobin
oxidation
was
reported
as
K/5572
÷
K/5525.
A
lower
number
indi-
cates
greater
MetMb
formation
and
a
lower
MRA.
Lipid
Oxidation
Thiobarbituric
acid
reactive
substances
(TBARS)
values
were
measured
on
steaks
aged
for
21-,
42-,
and
62-d
according
to
the
procedure
of
Witte
et
al.
(1970).
From
each
steak,
5
g
of
sample
that
contained
both
inte-
rior
and
surface
(section
of
2
cm
x
2
cm
x
2.54
cm
thick)
was
blended
with
25
mL
trichloroacetic
acid
(TCA)
so-
lution
(20%)
and
20
mL
distilled
water.
Samples
were
homogenized
using
a
Sorvall
Omni
mixer
(Newton,
CT)
for
1
min
and
filtered
through
a
Whatman
(#1)
filter
paper.
One
mL
of
filtrate
was
mixed
with
1
mL
thiobarbituric
acid
(TBA)
solution
(20
mM)
and
incu-
bated
in
a
boiling
water
bath
for
10
min.
After
incuba-
tion,
samples
were
cooled,
and
absorbance
at
532
nm
was
measured
using
a
Shimadzu
UV-2600
PC
spectro-
photometer.
The
blank
consisted
of
2
mL
TCA/distilled
water
(1:1
v/v)
and
2
mL
TBA
solution.
Statistical
Analysis
A
split-plot
design
was
used
to
evaluate
the
effects
of
aging
time
and
muscle
type
(normal
pH
and
dark-
cutting)
on
biochemical
properties.
Within
the
whole
plot,
10
longissimus
lumborum
and
10
no-roll
longis-
simus
lumborum
muscles
were
considered
as
experi-
mental
units
(N
=
10
for
each
muscle
and
N
=
20
to-
tal
subprimals).
Within
the
subplot,
each
longissimus
was
divided
into
4
sections,
resulting
in
4
experimental
units
per
subprimal.
One
of
the
4
experimental
units
within
each
subprimal
was
randomly
assigned
to
1
of
4
aging
periods
(0-,
21-,
42-,
and
62-d).
The
analysis
of
variance
was
generated
using
the
mixed
models proce-
dure
of
SAS
(SAS
Inst.
Inc.,
Cary,
NC).
Fixed
effects
included
muscle
type,
aging
time,
bloom
time,
and
their
interactions.
For
the
split
plot,
random
effects
included
loin,
loin
x
whole
plot
treatments
(Error
A),
and
resid-
ual
error
(Error
B).
For
oxygenation
data,
the
random
term
included
loin,
and
the
repeated
option
was
used
to
assess
covariance—variance
structure
among
the
re-
peated
measures.
The
most
appropriate
structure
was
determined
using
AIC
and
BIC
output.
Least
squares
means
were
generated,
and,
when
significant
(P
<
0.05)
F-values
were
observed,
least
squares
means
were
sep-
arated
using
a
pairwise
t
test
(PDIFF
option).
Extended
aging
and
dark
cutting
color
4043
Table
1.
Effects
of
aging
time
and
muscle
type
on
pH,
myoglobin
concentration,
and
proximate
composition
Parameters
Normal
pH
Dark
cutter
SE
1
P-value
2
pH
Aged
0
d
5.66a
643a
0.03
<
0.0001
Aged
21
d
5.60a
1
'
645a
0.04
<
0.0001
Aged
42
d
5.55
1'c
6.42a
0.02
<
0.0001
Aged
62
d
5.52c
644a
0.04
<
0.0001
Myoglobin
concentration
(mg/g)
5.7
7.9
0.02
<
0.0001
Moisture
(%)
65.6
70.4
0.73
0.0013
Protein
(%)
23.3
22.5
0.39
0.08
Fat
(%)
9.8
7.6
1.52
0.03
ISE
=
standard
error.
2
P-values
represents
difference
between
normal
and
dark-cutting
beef
(P
<
0.05).
a
-
cWithin
a
row
least
squares
means
with
different
superscript
letter
dif-
fer
(P
<
0.05).
RESULTS
pH,
Proximate
Analysis,
and
Myoglobin
Concentration
Muscle
type
and
aging
time
had
an
effect
(P
<
0.0001;
Table
1)
on
pH.
At
all
aging
periods,
dark-
cutting
beef
had
a
greater
pH
(P
<
0.0001)
than
nor-
mal
pH.
Normal
pH
beef
aged
for
62
d
had
a
lower
pH
(P
<
0.0001)
than
d
0
samples.
However,
there
was
no
significant
effect
of
aging
on
dark-cutting
muscle
pH.
Dark
cutting
beef
had
greater
myo-
globin
concentration
(P
<
0.0001)
than
normal
pH
beef.
Proximate
analysis
indicated
no
differences
(P
=
0.08)
in
protein
content
between
normal
pH
and
dark-cutting
beef.
However,
dark
cutters
had
greater
moisture
(P
=
0.0013)
and
lower
fat
(P
=
0.03)
con-
tent
than normal
pH
samples.
Oxygen
Consumption
A
significant
muscle
type
x
aging
time
interaction
resulted
for
OC
(Fig.
1;
P
<
0.001).
On
d
0,
dark-cut-
ting
beef
had
a
greater
(P
<
0.001)
OC
than
normal
pH.
As
aging
time
increased,
OC
decreased
(P
<
0.001)
for
normal
pH
beef.
The
changes
in
OC
between
d
0
and
62
was
greater
(P
<
0.001)
for
normal
pH
beef
than
dark-cutting
beef.
There
were
no
differences
(P
=
0.18)
in
OC
between
42
and
62
d
for
dark-cutting
beef.
Oxygenation
Properties
The
oxygenation
properties
were
measured
by
L*
values,
K/S474
K1S525
(indicates
DeoxyMb
level),
K/
S610
÷
K/S525
(indicates
OxyMb
content),
%
overall
reflectance,
absorbance,
and
reflectance
spectra.
There
was
a
significant
muscle
type
x
oxygenation
time
x
ag-
110
Normal
I
ark
carer
21
10
21
Agin
nem
Figure
1.
Effects
of
aging
and
muscle
type
on
oxygen
consumption
of
beef
longissimus
steak.
a
-
eLeast
squares
means
with
different
letters
are
different
(P
<
0.05).
ing
period
interaction
for
L*
values
(P
<
0.0001;
Table
2),
K/S474
K/S525
(P
=
0.017),
and
K/S610
K/S525
(P
<
0.001).
At
all
aging
periods,
dark-cutting
beef
had
lower
(P
<
0.0001)
L*
values
than
normal
pH
beef.
Dark
cutting
and
normal
pH
loin
sections
aged
for
62
d
had
greater
L*
values
(P
<
0.0001)
by
60
min
than
other
ag-
ing
periods
at
60
min
When
dark-cutting
sections
were
aged
for
62
d,
0
min
L*
values
were
greater
(P
<
0.0001)
than
0
min
dark-cutting sections
aged
for
21
or
42
d.
For
both
dark-cutting
beef
and
normal
pH
beef,
K/S474
K1S525
increased
with
incubation
time.
A
lower
value
indicates
a
greater
DeoxyMb
content.
By
60
min
of
incubation,
dark-cutting
beef
had
greater
(P
<
0.0001)
DeoxyMb
content
than
normal
pH
beef.
However,
when
dark-cutting
sections
were
aged
for
62
d
and
incubated
for
60
min,
they
had
lower
(P
<
0.0001)
DeoxyMb
than
dark-cutting
sections
aged
for
21
d
and
incubated
for
60
min.
There
were
no
differ-
ences
(P
=
0.52)
in
DeoxyMb
level
by
the
end
of
60
min
at
all
aging
periods
for
normal
pH
beef.
A
lower
value
for
K/S610
K/S525
indicates
a
greater
OxyMb
content.
For
both
dark-cutting
beef
and
normal
pH
beef,
K/S610
K/S525
decreased
with
in-
cubation
time,
indicating
more
OxyMb
formation.
By
60
min
of
incubation,
normal
pH
beef
had
greater
(P
<
0.0001)
OxyMb
content
than
dark-cutting
beef.
Dark
cutting
sections
aged
for
42
d
and
incubated
for
60
min
had
greater
(P
<
0.0001)
OxyMb
than
dark-cutting
sec-
tions
aged
for
21
or
62
d
and
incubated
for
60
min
There
were
no
differences
(P
=
0.52)
in
OxyMb
level
by
the
end
of
60
min
at
all
aging
periods
for
normal
pH
beef.
A
significant
aging
period
x
muscle
type
interaction
occurred
for
%
overall
reflectance
(P
=
0.0017;
Table
3)
and
absorbance
(P
=
0.0038).
As
expected,
at
all
aging
periods,
dark-cutting
beef
had
lower
%
overall
reflec-
tance
and
greater
absorbance
than
normal
pH
beef.
Dark
cutting
loin
sections
aged
for
62
d
had
greater
overall
reflectance
and
lower
absorbance
than
21
d
dark-cutting
4044
English
et
al.
Table
2.
Effects
of
aging
time
and
muscle
type
on
oxygenation
properties
of
beef
longissimus
steaks
Parameters
Aging
time
(d)
Oxygenation
time
(min)
Muscle
type
0
15
30
60
a)
L*
value
(%)
21
Normal
pH
37.1a
,
w
40.9
13,
w
41.6kw
41.8
13,
w
Dark
cutter
28.1a
,
a
31.5
b,v
30.9
b,v
31.2
13,
u
SE
=1.2
1
42
Normal
pH
40.3a
,
x
43.2
13,
x
42.5
1
"
43.1
13,
x
Dark
cutter
26.2a
,
u
30.2
13,11
31.3
b,u
31.2
13,
u
62
Normal
pH
45.4a
,
Y
48.0
13,
Y
47.6
13,
x
47.4
13,
Y
Dark
cutter
33.7
a,v
36.4
13,
v
37.1
13,v
38.2
13,
v
b)
K/S474
K/S525
21
Normal
pH
0.62a
,
u
0.88b
,
v
0.91"
0.94c
1,
x
Dark
cutter
0.62a
,
u
0.84
13,11
0.82
1
x
,
"
0.80c
,
u
SE
=
0.01
42
Normal
pH
0.61a
,
u
0.88
13,11
0.91"
0.93"x
Dark
cutter
0.58a
,
v
0.84b
,
v
0.86
1
x
,
v
0.87c
,
v
62
Normal
pH
0.66"
0.90
13,11
0.93"
0.95c
,
x
Dark
cutter
0.68"
0.89
13,11
0.93" 0.91"
c)
K/S610
K/S525
21
Normal
pH
0.35a
,
u
0.27
13,11
0.26ku
0.22c
,
u
Dark
cutter
0.43a
,
v
0.43a
,
v
0.38
13,
v
0.35c
,
v
SE=
0.018
42
Normal
pH
0.31"
0.24
1
"
0.23b"
0.21c
,
u
Dark
cutter
0.31"
0.31a
,
x
0.29a
,
x
0.29"
62
Normal
pH
0.40a
,
x
0.31
13,
x
0.26c
,
u
0.22dx
Dark
cutter
0.44a
,
Y
0.42a
,
Y
0.43a
,
Y
0.33
b,v
ISE
=
standard
error.
a
dWithin
a
row
least
squares
means
with
different
superscript
letter
differ
(P
<
0.05).
a
zWithin
a
column
least
squares
means
with
different
superscript
letter
differ
(P
<
0.05).
beef.
However,
there
were
no
differences
(P
=
0.48)
in
overall
reflectance
of
normal
pH
beef
between
aged
21
and
42
d.
The
overall
shape
of
reflectance
spectra
from
400
to
700
nm
and
for
each
of
the
aging
periods
for
dark-cutting
and
normal
pH
beef
were
similar
(Fig.
2a
and
2b).
However,
when
loin
sections
were
aged
for
62
d
and
incubated
for
60
min,
reflectance
values
were
greater
than
21
and
42
d
steaks.
Metmyoglobin
Reducing
Activity
(MRA)
There
was
a
significant
muscle
type
x
aging
time
interaction
(P
<
0.0001)
for
initial
MetMb
forma-
tion
(indicates
MRA;
Fig.
3).
Dark
cutting
steaks
had
greater
MRA
(less
initial
MetMb
formation;
P
<
0.0001)
compared
with
normal
pH
steaks
across
all
aging
periods.
For
both
normal
pH
and
dark-cutting
beef,
d
0
aging
period
had
greater
MRA
than
other
ag-
ing
periods.
There
was
no
significant
(P
=
0.14)
dif-
ference
in
MRA
between
d
42
and
62
for
dark-cutting
and
normal
pH
beef.
Lipid
Oxidation
Only
main
effects
of
muscle
type
and
aging
peri-
ods
were
significant
for
lipid
oxidation
as
indicated
by
TBARS
values
(Fig.
4).
Dark
cutting
steaks
had
lower
TBARS
values
than
normal
pH
steaks
(P
<
0.0001).
Loin
sections
aged
for
21
d
had
lower
(P
<
0.0001)
TBARS
values
than
d
42
and
62.
However,
there
were
no
differences
(P
=
0.24)
in
TBARS
values
between
d
42
and
62
(aging
time
main
effect).
Table
3.
Effects
of
aging
time
and
muscle
type
on
oxygenation
properties
(absorbance
and
overall
reflec-
tance)
of
beef
longissimus
steaks
Aging
Normal
Dark
cutting
Parameters
time
(d)
pH
beef
a)
%
Overall
reflectance
21
15.2
13,
x
9.5
a,y
42
14.1
13,
x
7.9
a,x
P
=
0.0017
62
19.3b
,
Y
12.8ax
SE
1
0.51
b)
Overall
absorbance
21
0.82a
,
Y
,
1.03b
,
Y
42
0.85a
,
x
1.10
13,
z
P
=
0.0038
62
0.71a
,
x
0.91
13,
x
SE
0.01
1
SE
=
standard
error.
OWithin
a
row
least
squares
means
with
different
superscript
letter
dif-
fer
(P
<
0.05).
x
zWithin
a
column
least
squares
means
with
different
superscript
letter
differ
(P
<
0.05).
D
7:
3
E.
'
5 8
Lei
..,
.1.
43
Wavetength
(rim)
4"..1
-rr
Extended
aging
and
dark
cutting
color
4045
A.
40
Normal
pH
bet(
15
Asec121
d
•Ard
42d
•Azed452d
30
25
8
I
20
oC
15
10
Ip
=
oc
'42
4=
4
4-
4
.
oc
++1
+e)
Wavelength
(run)
Dark
cutting
beef
B.
40
Aged
21
J
Ajod
42
J
•Aged
62
d
35
'?C
C
30
25
1
20
A
15
10
17
I I I I I
I 1
Figure
2.
Effects
of
aging
on
reflectance
spectra
of
normal
pH
(A)
and
dark-cutting
(B)
beef
longissimus
steaks
oxygenated
for
60
min.
DISCUSSION
pH,
Proximate
Analysis,
and
Myoglobin
Concentration
Preslaughter
stress
depletes
muscle
glycogen;
hence,
less
lactic
acid
is
formed
postmortem
(Hendrick
et
al.,
1959).
Therefore,
meat
does
not
acidify
as
in
a
normal
postmortem
muscle,
thus
ultimate
pH
remains
high.
Dark
cutting
meat
has
a
pH
greater
than
5.8
(Viljoen
et
al.,
2002).
Previous research
also
reported
greater
pH
in
dark-cutting
loins
(Apple
et
al.,
2005).
More
specifically,
muscle
proteins
can
hold
more
wa-
ter
when
the
pH
moves
away
from
isoelectric
point
of
meat
(Gault,
1985).
In
support
of
this,
bound
water
was
greater
in
dark-cutting
beef
compared
with
normal
pH
(Sawyer
et
al.,
2009).
Hence,
moisture
content
was
greater
in
dark-cutting
muscle
than
normal
pH
steaks.
The
mechanistic
basis
of
greater
myoglobin
concen-
tration
in
dark-cutting
beef
compared
with
normal
pH
is
not
clear.
Previous
research
noted
a
greater
myoglobin
concentration
in
dark-cutting
beef
(Sawyer
et
al.,
2009).
4046
English
et
al.
11.1.
outirr
Novral
.44
Mork
culler
ti
1
ZI
42
62
Amin'
linx4dipl.
Minsk
(.pr
dim
hoinz
lim€ €Pirsi
Figure
3.
Effects
of
aging
and
muscle
type
on
metmyoglobin
reduc-
ing
activity
of
beef
longissimus
steaks.
a
-(
Least
squares
means
with
differ-
ent
letters
are
different
(P
<
0.05).
Figure
4.
Effects
of
aging
and
muscle
type
on
lipid
oxidation
of
beef
longissimus
steaks.
a
-
bLeast
squares
means
with
different
letters
are
dif-
ferent
(P
<
0.05).
Presence
of
more
oxidative
fibers
could
be
responsible
for
elevated
myoglobin
concentration
in
dark-cutting
beef
(Zerouala
and
Stickland,
1991; Hunt
and
Hedrick,
1977).
More
oxidative
muscle
fibers
suggest
greater
mi-
tochondria
and
myoglobin
concentration.
In
support
of
this,
McKeith
et
al.
(2016)
reported
greater
mitochon-
drial
abundance
in
dark-cutting
beef.
Hence,
increased
myoglobin
concentration
in
dark-cutting
steaks
might
be
attributed
to
differences
in
types
of
muscle
fibers.
Effects
ofAging
on
Meat
Color
Chemistry
of
Dark
Cutting
Beef
Aging
has
been
used
to
improve
organoleptic
qualities
and
tenderness
in
beef.
Specifically,
these
changes
are
mainly
attributed
to
proteolysis
by
en-
dogenous
enzymes
and
utilization
of
metabolites
for
biochemical
processes.
However,
no
reports
are
cur-
rently
available
on
the
effects
of
aging
on
myoglobin
chemistry
of
dark-cutting
beef.
In
normal
meat,
post-
mortem
glycolysis reduces
pH
to
5.8
or
lower
which
impairs
mitochondrial
oxygen
consumption
(Ashmore
et
al.,
1972)
and
allows
normal
bloom
on
meat
sur-
faces
when
exposed
to
air.
However,
in
dark-cutting
meat,
a
greater
muscle
pH
can
enhance
mitochondrial
oxygen
consumption,
resulting
in
less
oxygenation
of
the
surface
myoglobin,
leaving
a
darker
color
(Price
and
Schweigert,
1987;
Ledward
et
al.,
1992).
Extended
aging
improved
red
intensity
of
steaks
when
exposed
to
oxygen
(Mancini
and
Ramanathan,
2014).
Aging
can
deplete
the
substrates
available
for
mitochondrial
function
and
also
result
in
structur-
al
changes
(Tang
et
al.,
2005).
Hence,
there
will
be
less
competition
for
oxygen
between
mitochondria
and
myoglobin,
and
oxygen
can
penetrate
into
tissue.
Previous
research
also
reported
a
decline
in
OC
with
increased
storage
for
all
beef
muscles
(McKenna
et
al.,
2005).
In
the
present
study,
OC
of
dark-cutting
beef
was
lower
on
42
d
compared
with
21
d;
however,
there
was
no
difference
between
42
and
62
d.
Nevertheless,
OC
in
normal
pH
beef
decreased
with
each
aging
time.
Lawrie
(1958)
reported
that
mitochondrial
cyto-
chrome
C
oxidase
was
more
active
at
pH
values
above
6.0
and
concluded
that
increased
OC
of
dark-cutting
meat
could
increase
the
concentration
of
DeoxyMb.
In
the
current
study,
dark-cutting
beef
had
greater
DeoxyMb
(measured
as
K/S
474
÷
K/S
525)
and
lower
OxyMb
(measured
as
K/S
610
÷
K/S
525)
than
normal
pH
beef
during
oxygenation
period.
However,
extended
aging
decreased
DeoxyMb
level
in
dark-cutting
beef.
The
relative
proportion
of
myoglobin
forms
can
affect
the
reflectance
properties.
Predominant
OxyMb
form
will
impart
greater
reflectance
than
DeoxyMb.
In
sup-
port
of
this,
previous
research
reported
greater
reflec-
tance
for
OxyMb
and
carboxymyoglobin
forms
com-
pared
with
DeoxyMb
(Ramanathan
et
al.,
2010).
In
the
current
study,
aging
improved
L*
values
of
dark-cutting
beef.
Previous
research
reported
an
increase
in
L*
val-
ues
with
bloom
time
compared
with
0
h
(Wulf
and
Wise,
1999;
Lee
et
al.,
2008).
Hence,
a
greater
L*
value
will
result
in
brighter
red
color
for
dark-cutting
beef.
Aging
can
also
affect
the
proteolysis
of
muscle
fi-
bers.
More
specifically,
breakdown
of
cytoskeletal
pro-
tein
can
affect
the
ability
of
muscle
fibers
to
hold
water.
Ledward
et
al.
(1992)
reported
that
color
in
muscle
tissue
is
based
on
reflectance
and
myoglobin
oxygenation.
At
increased
muscle
pH,
proteins
are
able
to
bind
stronger
with
water,
allowing
less
free
water.
When
more
water
is
bound
to
proteins,
muscle
fibers
are
swollen,
leaving
less
space
between
the
muscle
fibers.
Hence,
meat
that
has
an
elevated
pH
will
be
darker
in
color
because
less
free
water
is
available
to
reflect
light
(Ledward
et
al.,
1992).
With
increased
aging
time,
ability
of
muscle
fibers
to
hold
water
will
decrease,
which
can
improve
reflec-
Extended
aging
and
dark
cutting
color
4047
tance
properties.
In
the
current
study,
dark-cutting
beef
aged
for
62
d
had
greater
reflectance
than
the
21-d
aging
period.
Changes
in
muscle
structure
during
aging
affect
the
entire
reflectance
spectra,
hence
no
specific
shirt
in
peaks
were
noticed
in
dark-cutting
beef.
Irrespective
of
the
aging
time,
normal
pH
steaks
had
greater
overall
re-
flectance
compared
with
dark-cutting
beef.
The
current
study
suggests
that
processes
that
can
affect
mitochon-
drial
activity
and
muscle
structure
have
the
potential
to
increase
reflectance
and/or
OxyMb
formation
in
dark-
cutting
steaks.
Previous
research
utilized
nontraditional
meat
conditions
such
as
use
of
rotenone
(complex
I
in-
hibitor
that
blocks
mitochondrial
activity)
to
improve
redness
of
dark-cutting
and
cardiac
muscle
homogenates
(Comforth
and
Egbert,
1985;
Ramanathan
et
al.,
2009).
A
greater
pH
will
increase
MRA
than
normal
pH.
Zhu
and
Brewer
(1998)
reported
greater
MRA
in
high-
pH
pork
compared
with
normal-pH
pork.
In
the
cur-
rent
study,
steaks
aged
for
62
d had
a
lower
MRA
than
21
d.
Decrease
in
mitochondrial
activity
and
depletion
of
substrates
might
be
responsible
for
decreased
MRA.
Lipid
oxidation
was
lower
in
dark-cutting
compared
with
normal
pH
steaks.
Previous research
also
noted
less
lipid
oxidation
in
dark-cutting
beef
than
normal
pH
beef
(Sawyer
et
al.,
2009).
A
greater
pH
favors
growth
of
spoilage
bacteria
(Gill
and Newton,
1979).
The
major
focus
was
to
de-
termine
the
effects
of
aging
on
biochemical
properties;
hence,
microbiological
quality
was
not
considered
in
the
current
study.
Future
research
will
determine
if
the
beneficial
effects
of
aging
on
color
will
have
an
im-
pact
on
premature
spoilage
of
high-pH
beef.
In
summary,
aging
influenced
OC,
oxygenation,
and
reflectance
properties
of
dark-cutting
beef.
Application
of
postharvest
strategies
such
as
enhancement,
packag-
ing,
or
processes
that
can
limit
mitochondrial
activity
have
the
potential
to
improve
surface
color
of
dark-
cutting
beef.
LITERATURE
CITED
American
Meat
Science
Association.
2012.
Meat
color
measurement
guidelines.
Am.
Meat
Sci.
Assoc.,
Chicago,
IL.
Ashmore,
C.
R.,
L.
Doerr,
G.
Foster,
and
F.
Canoll.
1971.
Respiration
of
mitochondria
isolated
from
dark-cutting
beef.
J.
Anim.
Sci.
33:574-577.
Ashmore,
C.
R.,
L.
Doerr,
and
W.
Parker.
1972.
Respiration
of
mito-
chondria
isolated
from
dark-cutting
beef-
postmortem
changes.
J.
Anim.
Sci.
34:46-48.
Apple,
J.
K.,
E.
B.
Kegley,
D.
L.
Galloway,
T.
J.
Wistuba,
and
L.
K.
Rakes.
2005.
Duration
of
restraint
and
isolation
stress
as
a
model
to
study
the
dark-cutting
condition
in
cattle.
J.
Anim.
Sci.
83:1202-1214.
Cornforth,
D.
P.,
and
W.
R.
Egbert.
1985.
Effect
of
rotenone
and
pH
on
the
color
of
pre-rigor
muscle.
J.
Food
Sci.
50:34-35.
English,
A.
R,
G. G.
Mafi,
D.
L.
VanOverbeke,
and
R.
Ramanathan.
2016.
Effects
of
extended
aging
and
modified
atmospheric
pack-
aging
on
beef
top
loin
steak
color.
J.
Anim.
Sci.
94:1727-1737.
Faustman,
C.
and
A.
Phillips.
2001.
Measurement
of
discoloration
in
fresh
meat.
Curr.
Protoc.
Food
Anal.
Chem.
3:3-13.
Gault,
N.
F.
S.
1985.
The
relationship
between
water-holding
capacity
and
cooked
meat
tenderness
in
some
beef
muscles
as
influenced
by
acidic
conditions
below
the
ultimate
pH.
Meat
Sci.
15:15-30.
Gill,
C.
0.,
and
K.
G.
Newton.
1979.
Spoilage
of
vacuum-pack-
aged
dark,
firm,
dry
meat
at
chill
temperatures.
Appl.
Environ.
Microbiol.
37:362-364.
Hendrick,
H.
B.,
J.
B.
Boillot,
D.
E.
Brady,
and
H. D.
Naumann.
1959.
Etiology
of
dark-cutting
beef.
Res.
Bull.
717
(Sun
Chiwawitthaya
Thang
Thale
Phuket).
University
MO
Agric.
Exp.
Stn.,
Columbia.
Huff-Lonergan,
E.,
and
S.
M.
Lonergan.
2005.
Mechanisms
of
water-
holding
capacity
of
meat:
The
role
of
postmortem
biochemical
and
structural
changes.
Meat
Sci.
71:194-204.
Hunt,
M.
C.,
and
H.
B.
Hedrick
1977.
Profile
of
fiber
types
and
re-
lated
properties
of
5
bovine
muscles.
J.
Food
Sci.
42:513-517.
HunterLab.
(2006).
Miniscan
XE
Plus
user's
guide.
Hunter
Assoc.
Lab.,
Reston,
VA.
Lawrie,
R.
A.
1958.
Physiological
stress
in
relation
to
dark-cutting
beef.
J.
Food
Agric.
9:721-727.
Ledward,
D.
A.,
D.
E.
Johnston,
and
M.
K.
Knight
1992.
The
chem-
istry
of
muscle-based
foods.
R.
Soc.
Chem.,
Cambridge,
UK.
p.
128-139.
Lee,
M.
S.,
J.
K.
Apple,
J.
W.
Yancey,
J.
T.
Sawyer,
and
Z.
B.
Johnson.
2008.
Influence
of
vacuum-aging
period
on
bloom
develop-
ment
of
the
beef
gluteus
medics
from
top
sirloin
butts.
Meat
Sci.
80:592-598.
MacDougall,
D.
B.
1982.
Changes
in
the
color
and
opacity
of
meat.
Food
Chem.
9:75-88.
Madhavi,
D.
L.,
and
C.
E.
Carpenter.
1993.
Aging
and
processing
af-
fect
color,
metmyoglobin
reductase
and
oxygen-consumption
of
beef
muscles.
J.
Food
Sci.
58:939-942,947.
Mancini,
R.
A.,
M.
Seyfert,
and
M.
C.
Hunt
2008.
Effects
of
data
ex-
pression,
sample
location,
and
oxygen
partial
pressure
on
initial
nitric
oxide
metmyoglobin
formation
and
metmyoglobin-reduc-
ing-activity
measurement
in
beef
muscle.
Meat
Sci.
79:244-251.
Mancini,
R.
A.,
and
R.
Ramanathan.
2014.
Effects
of
postmortem
stor-
age
time
on
color
and
mitochondria
in
beef.
Meat
Sci.
98:65-70.
McKeith,
R.
0.,
D.
A.
King,
A.
L.
Grayson,
S.
D.
Shackelford,
K.
B.
Gehring,
J.
W.
Savell,
and
T.
L.
Wheeler.
2016.
Mitochondrial
abundance
and
efficiency
contribute
to
lean
color
of
dark-cut-
ting
beef.
Meat
Sci.
116:165-173.
McKenna,
D.
R,
D.
L.
Roebert,
P.
K.
Bates,
T.
B.
Schmidt,
D.
S.
Hale,
D.
B.
Griffin,
J.
W.
Savell,
J.
C.
Brooks,
J.
B.
Morgan,
T.
H.
Montgomery,
K.
E.
Belk,
and
G.
C.
Smith.
2002.
National
Beef
Quality
Audit-2000:
Survey
of
targeted
cattle
and
carcass
characteristics
related
to
quality,
quantity,
and
value
of
fed
steers
and
heifers.
J.
Anim.
Sci.
80:1212-1222.
McKenna,
D.
R,
P.
Mies,
B.
Baird,
K.
Pfeiffer,
J.
Ellebracht,
and
J.
Savell.
2005.
Biochemical
and
physical
factors
affecting
discolor-
ation
characteristics
of
19
bovine
muscles.
Meat
Sci.
70:665-682.
Millar,
S.
J.,
B.
W.
Moss,
and
M.
H.
Stevenson.
1996.
Some
observa-
tions
on
the
absorption
spectra
of
various
myoglobin
derivatives
found
in
meat.
Meat
Sci.
42:277-288.
O'Keeffe,
M.,
and
D.
E.
Hood.
1982.
Biochemical
factors
influenc-
ing
Metmyoglobin
formation
of
beef
from
muscles
of
differing
colour
stability.
Meat
Sci.
7:209-228.
Price,
J.
F.,
and
B.
S.
Schweigert.
1987.
The
science
of
meat
and
meat
products.
3rd
ed.
Food
and
Nutrition
Press,
Westport
CT.
4048
English
et
al.
Ramanathan,
R,
R.
A.
Mancini,
B.
M.
Naveena,
and
M.
K.
R.
Konda.
2009.
Effects
of
lactate
on
beef
heart
mitochondrial
oxygen
con-
sumption
and
muscle
darkening.
J.
Agric.
Food
Chem.
57:1550-
1555.
Ramanathan,
R,
R.
A.
Mancini,
B.
M.
Naveena,
and
M.
K.
R.
Konda.
2010.
Effects
of
lactate-enhancement
on
surface
reflectance
and
absorbance
properties
of
beef
longissimus
steaks.
Meat
Sci.
84:219-226.
Sammel,
L.
M.,
M.
C.
Hunt,
D.
H.
Kropf,
K.
A.
Hachmeister,
and
D.
E.
Johnson.
2002.
Comparison
assays
for
metmyoglobin
reduc-
ing
ability
in
beef
inside
and
outside
semimembranosus
muscle.
J.
Food
Sci.
67:978-984.
Sawyer,
J.
T.,
J.
K.
Apple,
Z.
B.
Johnson,
R.
T.
Baublits,
and
J.
W.
S.
Yancey.
2009.
Fresh
and
cooked
color
of
dark-cutting
beef
can
be
altered
by
post-rigor
enhancement
with
lactic
acid.
Meat
Sci.
83:263-270.
Seideman,
S.
C.,
H.
R.
Cross,
G.
C.
Smith,
and
P.
R.
Durland.
1984.
Review
Factors
affecting
fresh
meat
colour.
J.
Food
Qual.
6:211-237.
Tang,
J.,
C.
Faustman,
and
T.
A.
Hoagland.
2005.
Postmortem
oxygen
consumption
of
mitochondria
and
its
effects
on
myoglobin
form
and
stability.
J.
Agric.
Food
Chem.
53:1223-1230.
Viljoen,
H.
F.,
H.
L.
de
Kock,
and
E.
C.
Webb.
2002.
Consumer
ac-
ceptability
of
dark,
firm
and
dry
(DFD)
and
normal
pH
beef
steaks.
Meat
Sci.
61:181-185.
Witte,
V.
C.,
G.
F.
Krause,
and
M.
E.
Bailey.
1970.
A
new
extraction
method
for
determining
2-thiobarbituric
acid
values
of
pork
and
beef
during
storage.
J.
Food
Sci.
35:582-585.
Wulf,
D.
M.,
and
J.
W.
Wise.
1999.
Measuring
muscle
color
on
beef
car-
casses
using
the
L*a*b*
color
space.
J.
Anim.
Sci.
77:2418-2427.
Zerouala,
A.
C.,
and
N.
C.
Stickland.
1991.
Cattle
at
risk
for
dark-
cutting
beef
have
a
higher
proportion
of
oxidative
muscle
fibres.
Meat
Sci.
29:263-270.
Zhu,
L.
G.,
and
M.
S.
Brewer.
1998.
Metmyoglobin
reducing
capac-
ity
of
fresh
normal,
PSE
and
DFD
pork
during
retail
display.
J.
Food
Sci.
63:390-393.