muscle biology & meat science...university of nebraska–lincoln know how. know now. conversion...
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Muscle Biology & Meat ScienceB. A. Reiling
University of Nebraska–Lincoln
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What is Meat?
Animal tissue suitable for human consumptionFresh Meatsno 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 ATPATP = energy required for muscle movement
With loss of ATP Rigor mortis
Buildup of lactic acidpH 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
ATPLacticAcid
CHO ATP LacticAcid
CHOATP
LacticAcid
CHO
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Conversion of Muscle into Meat
Muscles are designed for 1 of 2 purposes1) 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 componentMuscle fibers composed of proteins
Connective tissuesurrounds each muscle
fiber and bundle
Fat
Bone
SarcomereSmallest
contractual unit of the
muscle
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The SarcomereComprised of overlapping protein filaments Thick filament = Myosin protein (80%)
Thin filament – Actin protein (20%)
Slide adapted from Ty
Schmidt (UNL Meat Science)
University of Nebraska–Lincoln
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Sarcomere in state of rest(uncontracted)
Slide adapted from Ty
Schmidt (UNL Meat Science)
University of Nebraska–Lincoln
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Sarcomere in contracted stateSlide 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 directionIf cut “with the grain”
• Intact, long muscle fibers
If cut “against the grain”• Many small pieces of fibers
Mechanical tenderizationPhysical breakdown of muscle fiber cell walls
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Flank Steak Tenderization
Chemical tenderizationMeat 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 & GrillingHigh 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
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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 of Agriculture.