Muscle Biology & Meat Science B. A. Reiling Know how. Know now. - - PowerPoint PPT Presentation

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Muscle Biology & Meat Science

• B. A. Reiling

University of Nebraska–Lincoln

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What is Meat?

 Animal tissue suitable for human consumption  Fresh Meats

• no mechanical treatments or added ingredients
• steaks, pork chops

University of Nebraska–Lincoln

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Conversion of Muscle into Meat

Series of postmortem chemical reactions & physical changes  Loss of blood  loss of O2  loss of ATP

• ATP = energy required for muscle movement

 With loss of ATP  Rigor mortis  Buildup of lactic acid

• pH  from ~ 7.0 to 5.4 in 24 h

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With Anaerobic Metabolism, carbohydrates (glycogen) stored in muscle are broken down for fuel, so muscle can still contract post-mortem for a limited time.  Also creates

• “lactic acid” which causes

the pH of muscle to drop from ~ 7.0 to 5.4

ATP Lactic Acid CHO ATP Lactic Acid CHO ATP Lactic Acid CHO

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Conversion of Muscle into Meat

 Muscles are designed for 1 of 2 purposes

• 1) locomotion
• 2) support

 The anatomy, physiology, and function of each muscle affects meat palatability.

• Locomotive muscles  more tough
• Support muscles  more tender

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Palatability vs. Cost

 Preferred retail cuts ...

• Originate from the Rib & Loin (middle meats)
• Muscles of support  TENDER; < connective tissue
• Cost: $8 to $20 / lb

 Less expensive cuts ...

• Originate from the Chuck & Round (end meats)
• Muscles of locomotion  TOUGH; > connective tissue
• Exception = Flat Iron
• Costs: $5 to $8 / lb

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Physical Composition of Meat

 Muscle  major component

• Muscle fibers composed of proteins

 Connective tissue

• surrounds each muscle

fiber and bundle

 Fat  Bone

Sarcomere

Smallest contractual unit of the muscle

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The Sarcomere

Comprised of overlapping protein filaments

 Thick filament = Myosin protein (80%)  Thin filament – Actin protein (20%)

Slide adapted from Ty Schmidt (UNL Meat Science)

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Sarcomere in state of rest (uncontracted)

Slide adapted from Ty Schmidt (UNL Meat Science)

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Sarcomere in contracted state

Slide adapted from Ty Schmidt (UNL Meat Science)

University of Nebraska–Lincoln

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Myosin Protein – Thick filament

ATP

Slide adapted from Ty Schmidt (UNL Meat Science)

University of Nebraska–Lincoln

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Actin Protein – Thin filament

Myosin Binding Site

Slide adapted from Ty Schmidt (UNL Meat Science)

University of Nebraska–Lincoln

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Sarcomere – Uncontracted

Myosin Binding Site ATP

Slide adapted from Ty Schmidt (UNL Meat Science)

University of Nebraska–Lincoln

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Sarcomere – Contracted

Myosin Binding Site

Slide adapted from Ty Schmidt (UNL Meat Science)

University of Nebraska–Lincoln

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Flank Steak Tenderization

 Muscle fibers run in one direction

• If cut “with the grain”
• Intact, long muscle fibers
• If cut “against the grain”
• Many small pieces of fibers

 Mechanical tenderization

• Physical breakdown of muscle fiber cell walls

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Flank Steak Tenderization

 Chemical tenderization

• Meat is acidic (pH = 5.4)
• Lactic acid production during rigor mortis
• Soy Sauce or Baking Soda is basic
• Chemical reaction  breakdown of proteins

 Enzymatic Breakdown – Papain

• Breaks down the myosin protein

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Effect of Cooking on Tenderness

 For a TOUGH piece of meat, what cookery method should result in the most tender, cooked product? Why?  Hey, this could be an experiment!

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Effect of Cooking on Tenderness

 Dry Heat -- Broiling & Grilling

• High temp, short time  tender cuts
• Sear outside to “lock in” juice
• Fiber & connective tissue breakdown
• not an issue; originated from muscles of support

 Moist Heat -- The “crock pot”

• Low temp, long time  tough cuts
• To an internal temp of ~180oF
• Heat & moisture break down connective tissue

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Key Points: Muscle Biology

 Muscle requires energy (ATP) to contract  During rigor mortis, muscle pH  to 5.4  Muscle = bundles of muscle fibers  Sarcomere is smallest contractile unit  Muscles of support vs. locomotion

University of Nebraska–Lincoln

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Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture. The Youth Development program abides with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department

• f Agriculture.