Understanding and Managing
Variation in Meat Tenderness
T. L. Wheeler, D. A. King, and S. D. Shackelford
U. S. Meat Animal Research Center,
Agricultural Research Service,
U. S. Department of Agriculture,
Clay Center, Nebraska, USA
Presentation Outline
• Factors affecting tenderness variation
• Genetic influences on tenderness
• Predicting tenderness for sorting
• Tenderization strategies
Why is tenderness so important?
Consumer Rankings of Sensory Traits
$/pound
Price,
$/lb
Tenderness vs Price
8
7
6
5
4
3
2
Tenderloin steak
Top loin steak
Top sirloin steak
Rump roast
1
2
3
4
5
6
Overall tenderness
7
8
Biological basis for variation
in meat tenderness
•
•
•
•
Contractile state
Enzymatic degradation of proteins
Connective tissue
Marbling
Contractile State
Extent of muscle shortening during
rigor mortis formation
Rigor mortis
Effect of Muscle and Treatment on
Sarcomere Length
Effect of Muscle and Treatment
on W-B Shear Force
Effect of muscle on sarcomere length in beef
Muscle
Gluteus medius
Longissumus
Biceps femoris
Semimembranosus
Adductor
Supraspinatus
Semitendinosus
Rectus femoris
Infraspinatus
Triceps brachii
Psoas major
SL, µm
1.7
1.8
1.8
1.8
1.9
1.9
2.1
2.2
2.3
2.4
2.9
Enzymatic breakdown of protein
(proteolysis)
• Responsible for tenderization during
“aging” of meat
• Caused by an enzyme that naturally
occurs in muscle
• Regulated by level of that enzyme,
it’s specific inhibitor, and calcium
The Calcium-dependent
(Calpain) Proteolytic System
• µ-calpain
• m-calpain
• calpastatin
Effect of muscle on desmin degradation in beef
Muscle
Biceps femoris
Longissimus
Semimembranosus
Gluteus medius
Semitendinosus
Triceps brachii
Adductor
Rectus femoris
Infraspinatus
Supraspinatus
Psoas major
Desmin, %
61
60
47
39
38
35
30
29
25
24
20
The Toughening and
Tenderization Processes of Meat
• The Toughening Phase
• The Tenderization Phase
Sarcomere length, µm
Warner-Bratzler shear force, kg
Changes in Meat Tenderness after Harvest
9
Shear Force, kg
8
7
6
5
4
3
2
0 12 24
48
72
336
Time Postmortem, h
Connective Tissue
• Measured as the amount of collagen
Effect of muscle on connective tissue in beef
Muscle
Psoas major
Gluteus medius
Longissimus
Adductor
Rectus femoris
Triceps brachii
Infraspinatus
Semimembranosus
Biceps femoris
Semitendinosus
Supraspinatus
Collagen, mg/g
2.7
4.3
4.5
4.9
5.9
6.3
7.6
7.7
8.7
8.8
9.0
Marbling/Intramuscular Fat
Select
3.1%
High
Choice
Slight00
Low
Choice
Small00
4.5%
Moderate00
Average
Choice
6.0%
Slightly
Abundant00
7.8%
Low
Prime
10.2%
Modest00
Moderately
Abundant00
Average
Prime 12.1%
Warner-Bratzler shear force
W-B Shear Force vs Marbling
9
R2 = 0.02
8
7
6
5
4
3
2
1
0
200
300
400
500
600
Marbling score
n = 1,083
700
800
900
The tenderness of a specific
muscle primarily depends on:
The combination of extent of muscle
shortening, collagen content, and the
extent of postmortem proteolysis.
Effect of Muscle on Tenderness Rating
Muscle
Tenderness
Psoas major
7.4
Infraspinatus
5.9
Longissimus
5.7
Triceps brachii
5.2
Rectus femoris
4.9
Gluteus medius
4.7
Adductor
4.3
Semimembranosus
4.2
Supraspinatus
4.1
Semitendinosus
4.1
Biceps femoris
3.7
5.9
5.7
Tend
Sarc.
Collagen
Prot.
2.25 µm
1.80 µm
Infraspinatus
Longissimus
7.6 mg/g
4.5 mg/g
22%
degraded
Relative merit
60%
degraded
Muscle specific strategies can be
developed to improve tenderness problems.
Management Factors
• Age at harvest < 30 months
• Castration by 7 months
• Growth enhancement technologies
• anabolic implants
• β-adrenergic agonists
• Time on high energy diet
• Health
• Stress before harvest
Anabolic Implants
• Majority of cattle in the U.S. receive
anabolic implants
– Classified by active ingredients and strength
• Many cattle receive multiple implants
• More potent “aggressive” implant protocols
– Greater growth
– Deleterious effects on carcass and meat quality
Management Factors
• Age at harvest < 30 months
• Castration by 7 months
• Growth enhancement technologies
• anabolic implants
• β-adrenergic agonists
• Time on high energy diet
• Health
• Stress before harvest
Genetics and Meat Tenderness
• Beef breed studies
• Genetic markers
Beef Germplasm Evaluation
(GPE) Project
SIRE BREEDS USED TO PRODUCE FI CROSSES IN THE GERMPLASM
EVALUATION PROGRAM AT MARCa
Cycle I Cycle II Cycle III Cycle IV
1970-72 1973-74 1975-76 1986-90
Cycle V
1992-94
Hereford
Angus
Jersey
S. Devon
Limousin
Simmental
Charolais
Hereford
Angus
Tuli
Boran
Belg. Blue
Brahman
Piedmontese
aWith
Hereford
Angus
Red Poll
Braunvieh
Gelbvieh
Maine Anj.
Chianina
Hereford
Angus
Brahman
Sahiwal
Pinzgauer
Tarentaise
Hereford
Angus
Longhorn
Salers
Galloway
Nellore
Shorthorn
Piedmontese
Charolais
Gelbvieh
Pinzgauer
Cycle VI
1997-98
Hereford
Angus
Wagyu
Norweg. Red
Sw. Red&Wh.
Friesian
Cycle VII Cycle VIII
1999-00 2001-02
Hereford
Angus
Red Angus
Limousin
Charolais
Simmental
Gelbvieh
Hereford
Angus
Beefmaster
Brangus
Bonsmara
Romosinuano
Angus and Hereford Dams.
Composite MARC III cows were also included in Cycles V, VI, VI, and VIII.
GPE Breed Summary
More Tender
Slightly less Tender
Less Tender
• Pinzgauer
• Brangus
• Sahiwal
• Piedmontese
• Charolais
• Nellore
• Jersey
• Gelbvieh
• Brahman
• South Devon
• Boran
• Red Poll
• Beefmaster
Genetic Variation in Shear Force
Within and Among Sire Breeds of Purebred Progeny
HA
Nellore
Pinzgauer
-6
-4
-2
0
2
4
6
Genetic Standard Deviations
8
Percentage Piedmontese and
Myostatin Genotype
• Ribeye
• Top sirloin
• Top round
• Bottom round
Percentage Retail Product Yield
Inactive Myostatin Alleles
Percentage
Piedmontese
0
0
64.1 c
1
-
2
-
25
64.1 c
70.4 b
-
50
65.7 c
71.2 b
85.1 a
75
-
72.6 b
84.9 a
Myostatin
64.4 z
71.5 y
85.0 x
1 allele
2 alleles
0 alleles
Effect of Muscle and Myostatin
on Tenderness Rating
Effect of Muscle and Myostatin
on Collagen Content
Myostatin Conclusions
Use of terminal homozygous Piedmontese sire
provides:
• A 7% increase in saleable product
• Improved tenderness in all four muscles
BREED SUMMARY
• Small improvements in tenderness can be
made by selection of breed
• But within breed variation is large
• Inactive myostatin or “double muscling”
has tenderness and muscling advantages
Genetic Markers for Meat
Tenderness
Heritability of meat tenderness
is estimated to be about 0.30
• Traditional genetic selection is a slow
process
• Greater progress in less time may be
possible with marker assisted selection
Two µ-calpain and calpastatin markers
that affect meat tenderness have been
commercialized
We have validated the tenderness
markers in commercial populations
Effect of µ-calpain (CAPN4751) genotype on beef
tenderness
50
45
40
Frequency, %
35
CAPN4751 homozygous tender (n = 517)
9%
CAPN4751 homozygous tough (n = 602)
23%
30
25
20
15
10
5
0
5 to 10 10 to 15 15 to 20 20 to 25 25 to 30 30 to 35 35 to 40 40 to 45 45 to 50
Slice shear force at 14 days postmortem, kg
Effects of CAPN1_316 in cattle treated with
differing implant protocols
20
Mild
Slice shear force, kg
18
16
14
12
10
0
1
Copies of favorable allele
2
Aggressive
Marker Conclusions
• So far we have found a small number
of markers that have small effects
• It is a time consuming process, but
technology is continually improving
GENETICS SUMMARY
Some of the variation in tenderness can
be controlled by manipulating genetics
Predicting and Enhancing
Tenderness
• It is not likely we will be able to
ensure 100% tender meat
• Thus, we need a technology to sort
the carcasses for tenderness
• Meat from “Tender” carcasses can
be marketed at a premium
• Meat from “Tough” carcasses can
be targeted for tenderizing
processes
The USMARC Beef Tenderness
System
Use of visible and near-infrared
reflectance to predict beef tenderness
Validation of Beef Tenderness Prediction
50
Experiment 2
n = 4,204
Comparison of means; SEM = 0.13 kg; P < 10-87
Comparison of % > 25 kg; P < 10-58
45
40
Frequency, %
35
VISNIR predicted tender
Mean SSF = 16.3 kg
SD = 4.5 kg
Range 7.6 - 37.5 kg
4.9% > 25 kg
n = 2,040
30
25
20
VISNIR not predicted tender
Mean SSF = 19.9 kg
SD = 6.9 kg
Range 7.2 - 65.0 kg
21.3% > 25 kg
n = 2,164
15
10
5
0
5
to
10
10
to
15
15
to
20
20
25
30
35
40
45
to
to
to
to
to
to
25
30
35
40
45
50
Slice shear force at 14 d postmortem, kg
50
to
55
55
to
60
60
to
65
Beef carcass grading
Tenderizing Technologies
Electrical Stimulation
Tenderstretch
Tendercut®
Postmortem aging 14 days or more
Marination
Blade/needle tenderization
Tenderizing Technologies
•
•
•
•
•
•
Carcass electrical stimulation
Postmortem aging
Tenderstretch
Tendercut®
Marination
Blade tenderization
Providing Consumers Lean, Tender Beef
•
•
•
•
Optimize genetics
Optimize management
Identify tender from tough
Tenderizing interventions