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

8 7 6 5 4 3 2 1

Tenderness vs Price

2 Tenderloin steak Top loin steak Top sirloin steak Rump roast 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

Changes in Meat Tenderness after Harvest 9 8 5 4 7 6 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% Slight 00 Low Choice 4.5% Small 00 Average Choice 6.0% Modest 00 High Choice 7.8% Moderate 00 Low Prime 10.2% Slightly Abundant 00 Moderately Abundant 00 Average Prime 12.1%

9 8 7 6 5 4 3 2 1 0 200 W-B Shear Force vs Marbling R 2 = 0.02

300 400 500 600 Marbling score 700 800 n = 1,083 900

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 Psoas major Infraspinatus Longissimus Triceps brachii Rectus femoris Gluteus medius Adductor Semimembranosus Supraspinatus Semitendinosus Biceps femoris Tenderness 7.4 5.9 5.7 5.2 4.9 4.7 4.3 4.2

4.1

4.1

3.7

Tend Sarc.

Collagen Prot.

1.80 µm 7.6 mg/g 22% degraded 5.9

5.7

2.25 µm 4.5 mg/g Infraspinatus Longissimus 60% degraded

Relative merit

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 F I CROSSES IN THE GERMPLASM EVALUATION PROGRAM AT MARC a Cycle I Cycle II Cycle III Cycle IV Cycle V Cycle VI Cycle VII Cycle VIII 1970-72 1973-74 1975-76 1986-90 1992-94 1997-98 1999-00 2001-02 Hereford Angus Jersey S. Devon Hereford Angus Hereford Angus Red Poll Brahman Braunvieh Sahiwal Hereford Angus Longhorn Salers Limousin Gelbvieh Pinzgauer Galloway Simmental Maine Anj. Tarentaise Nellore Charolais Chianina Shorthorn Piedmontese Charolais Gelbvieh Pinzgauer Hereford Angus Tuli Boran Belg. Blue Brahman Piedmontese Hereford Angus Wagyu Norweg. Red Hereford Angus Red Angus Beefmaster Limousin Sw. Red&Wh. Charolais Friesian Simmental Gelbvieh Hereford Angus Brangus Bonsmara Romosinuano a With 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 • Piedmontese • Jersey • South Devon • Red Poll • Brangus • Charolais • Gelbvieh • Sahiwal • Nellore • Brahman • Boran • Beefmaster

Genetic Variation in Shear Force Within and Among Sire Breeds of Purebred Progeny HA Nellore Pinzgauer -6 -4 -2 0 2 4 Genetic Standard Deviations 6 8

Percentage Piedmontese and Myostatin Genotype • Ribeye • Top sirloin • Top round • Bottom round

Percentage Retail Product Yield

Inactive Myostatin Alleles Percentage Piedmontese 0 25 50 75 Myostatin 0 64.1

c 64.1

c 65.7

c 64.4

z 1 70.4

b 71.2

b 72.6

b 71.5

y 2 85.1

a 84.9

a 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

• 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 CAPN4751 homozygous tender (n = 517) 9% 40 35 CAPN4751 homozygous tough (n = 602) 23% 10 5 0 30 25 20 15 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 14 12 10 20 18 16 Mild Aggressive 0 2

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

50 45 40 35 30 25 20 15 10 5 0 5 to 10 Validation of Beef Tenderness Prediction

Experiment 2

n = 4,204 Comparison of means; SEM = 0.13 kg; P < 10 -87 Comparison of % > 25 kg; P < 10 -58 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 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 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 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