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Meat

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Meat. Justin Shimek and Jun Kim. FST 100A. Discussion Hour 6. Meat Lecture Outline ... Upton Sinclair, The Jungle (1906) Federal Meat Inspection Act of 1906 ... – PowerPoint PPT presentation

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Title: Meat


1
Meat
  • Justin Shimek and Jun Kim
  • FST 100A
  • Discussion Hour 6

2
Meat Lecture Outline
  • Today build on protein lecturesmeat as a
    complex structure and a commodity
  • Definition of meat
  • Regulation, Quality Grades, Safety
  • Microstructure protein fibers/molecular motors
  • Macrostructure the cuts
  • Structure related to key quality factors
    tenderness, color, and Water holding capacity

3
Meat Definition
  • General (historical)
  • solid food, i.e. that which is not drink
  • Intermediate (common)
  • animal tissues
  • may include game, poultry, fish
  • Specific (USDA)
  • the muscle of cattle, pigs, sheep, and goats

4
Meat Composition and Consumption
  • USDA estimates 99 eat meat, 94 eat red meat
  • American consumes average of 211.1 lbs/yr
  • 51.6 red meat, 41.7 poultry, 6.7 fish

5
Meat Inspection
  • Upton Sinclair, The Jungle (1906)
  • Federal Meat Inspection Act of 1906
  • Wholesome Meat Act of 1967
  • USDA Food Safety and Inspection Service charged
    with meat (poultry egg) inspection
  • purple stamp
  • Eight voluntary quality grades in beef
  • Prime, Choice, Select, Standard, Commercial,
    Utility, Cutter, Canner

6
  • Muscle
  • ends blend with tendon

Bundle of muscle cells
  • Muscle cell (or fiber)
  • surrounded by sarcolemma
  • surrounded by thin connective tissue layer

Muscle fibril
Sarcomere (myofilaments)
Actin and myosin
Size
7
Principle Myofibrillar Proteins
know
  • Actin
  • small spheres arranged like string of beads
  • two strings twisted together ? thin filaments
  • Myosin
  • shaped like golf clubs
  • cluster ? thick filaments

8
The Sarcomere
know
Thick filament
Z-line
Z-line
Thin filament
9
Muscle Contraction
Karlsson, 1977
3
4
  • 1) Rigor
  • myosin binds actin
  • 2) ATP association
  • pops off actin
  • 3) ATP hydrolyzed
  • weak actin/myosin assn
  • 4) Powerstroke
  • ADP Pi disassociate

ADP Pi
ADP Pi
ADP Pi
ATP
ATP
1
2
10
Primal Cuts
11
Connective Tissue
  • Amorphous substance with embedded fibers of
    collagen elastin
  • Collagen
  • white, doesnt stretch, 3 twisted ropes
  • hot water melts collagen to gelatin
  • Elastin
  • yellowish, stretches, in heavy use muscles
  • not greatly affected by cooking

12
Factors Affecting Tenderness
know
  • 1) Connective Tissue
  • More connective tissue, tougher
  • Collagen and solubility, elastin
  • Cooking decreases toughness
  • 2) Actin Myosin
  • In rigor, form stable cross-links
  • Aging increases tenderness due to enzymatic and
    chemical breakdown
  • Cooking proteins denature, microfibers
    coagulate, meat toughens

13
Postmortem Changes and Aging
  • Rigor mortis
  • Stiffening of carcass
  • Lactic acid accumulation?pH decrease
  • ATP gradually disappears
  • The muscle becomes contracted as a result of
    these changes
  • 2) Ripening or Aging
  • Breakdown of proteins in myofibrils by enzymes
  • Increase in tenderenss

14
Meat Color
know
N
N
  • Myoglobin
  • protein containing iron
  • purplish-red
  • Fe2
  • Oxymyoglobin
  • supermarket red
  • Fe2 O2
  • Metmyoglobin
  • brownish-red
  • Fe3 H2O

Fe2
N
N
Globin
O2
N
N
Fe2
N
N
Globin
H2O
N
N
Fe3
N
N
Globin
15
Water Holding Capacity(WHC)
  • The bound water to the proteins hydrophilic
    groups
  • The quantity of water immobilized within the
    network of actomyosin filaments
  • At pI of actomyosin(5.4) Most of the charged
    groups are involved in the formation of salt
    bridges or cross-linkage ? tighten the muscle
    structure ? WHC decreases
  • At above or below pI the cross-linkage are
    cleaved as result of charge repulsion
  • Bivalent cation (e.g. Ca2) forming cross
    linkage
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