Growth_ Composition and Meat Quality by pptfiles


									Growth, Composition
and Meat Quality

n   Quality versus Yield
n   Definition(s)- provide uniform standards
    ¨ Table 12.1
    ¨ Factors Affecting Quality Grades
       n   Kind, Class and Grade
       n   Maturity (Figure 12.2)
       n   Marbling relationship to palatability
    ¨ Poultry(Table 12.2)
    ¨ Yield/Cutability (Table 12.3)
Yield Grade Relationships
n   Fat, muscle and bone relationships
    ¨ Figure   12.14
n Regression models versus short-cut
n Anatomical measurements for
  compositional traits
n Ex. Pork percent muscle, Beef yield grade
Conversion of Muscle to Meat
n Ante-mortem versus post-mortem
  conditions of the animal
n Steps:
    ¨ Stunning
    ¨ Exsanguination
    ¨ Aerobicto anaerobic condition
    ¨ Glycogenolysis
Conversion of Muscle to Meat
n ATP to ADP , thus energy expended
n Pyruvate converted to Lactate and
  ultimately lactic acid
n Progressive reduction in pH
n Deviations of normal post-mortem
    ¨ Dark   cutters, PSE, etc.
Meat Tenderness
n Little can be gained by improvement of
  animal growth if the resulting quality of the
  endproduct is undesirable to the consumer
n Connective Tissue- collagen
    ¨ As animals mature crosslinkages increase
     resulting in more stability, yet tougher and
     stronger collagen bonds thus decreases
     solubility and reduces gelatinization
Meat Tenderness
n   Myofibrillar Protein Interactions
    ¨ Degree  of overlapping structures within
      actinomyosin formation resulting in varying
      sarcomere length
    ¨ Proteolytic activity
       n   Calpain enzyme system are responsible for
           destruction of myofibrils
Quality versus Quantity
n   Figure 12.23
n   Sex/gender variations within growth and
    development-biological maturity
    ¨ Intact   males have:
       n   Less fat as well as less firmness of fat
       n   Increased protein, myoglobin, red color, yields
       n   Increased off-odors due to increased steroid metabolism
           synthesized by the gonads, stored in the salivary glands,
           released by the saliva ingested and deposited in the fatty
       n   Skatole is a fat-soluble cmpd from tryptophan metabolism in
           the hind gut esp. in swine and is correlated to the off-odor
Absence of Fat
n Cold shortening possibility
n Age
    ¨ Negative relationship with increased age
    ¨ Except with feedlot cattle
PSS in pork
n   Rendement Napole Gene
    ¨ Acid   meat
    ¨ Responsible for glycolytic potential index
    ¨ AMPK- adenosine monophosphate-activated protein
      kinase which is responsible for synthesizing glycogen
    ¨ If this ability is lost and glycogen is accumulated at a
      higher rate this produces more lactate and ultimately
      results in more acid meat upon rigor mortis
PSS pork
n   Halothane Gene
    ¨ Extremely   lean pigs
    ¨ Incapable of handling stress
    ¨ Malignant hypothermia along with cyanotic (blue),
      lethargic, increased respiration, and increased core
      body temp
    ¨ Characterized by a severe reaction when exposed to
      halothane gas
    ¨ Positive pigs possess a mutated calcium release
      channel located in the SR. This is known as
      ryanodine receptor
PSS pork
n   Halothane cont.
    ¨ Increased  metabolism is a result of increased
      ctyoplasmic calcium in early postmortem. This
      stimulates increases in glycogen phosphorylase
      which speeds up glycogen breakdown.
    ¨ This increased rate of metabolism then increases the
      rate of pH decline when carcass temps are elevated
    ¨ This ultimately reduces the water holding capacity
Double Muscling
n Muscular hypertrophy- increase fiber size
n Increase yield and gains
n Decreased quality and reprod effic.
n Less connective tissue
n Increased cold shortening effect
n   Delayed feedlot gains will decrease tenderness
n   Shorter periods of feeding high energy will
    results in lower quality aspects
n   Connective Tissue concentration remains
    constant with increased growth rates
    ¨ Due to increased proteases
    ¨ Lacks excessive cross-linking
    ¨ More soluble collagen matrices
    ¨ Do not remove high energy too long before slaughter
       n   this may result in Dark Cutters
Repartitioning Agents and
Hormone Implants
n   Table 12.7 and 12.8
n   Somatotropin
n   Beta-agonists
n   Hormones- estrogen, progesterone, testosterone
n   Effects on tenderness Table 12.9
n   Effects on sensory perceptions Table 12.10

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