Meat Science Test 2

Muscle Contration steps

1. Signal from brain travels down nerve.

2. Nerve signal passed to myoneural juncture

3. Sarcolemma depolarizes by releasing sodium into the muscle.

ATP role

1. ATP binds to myodin head

2. ATP phosphorolozes into ADP and a phosphate allowing myson to grab onto actin

3. Release of the phosphate allows myson to pull actin closer

4. When actin moves ADP is relased and myson is ina  fixed position with actin

5. A new ATP is needed to release myosin and start again

Types of Troponin

TnT, TnI, TnC

Most significant event to occur postmortem is?

pH decline of muscle

Rigor Mortis phases

1. Onset

2. Delay

3. Completion

4. Resolution

Delay phase

ATP still present in muscle. Muscle is most extensible and no cross bridges have formed

Onset Phase

ATP begins to decrease. Cross bridges begin to form between actin and myosin making muscle less extensible

Completion Phase

ATP is depleted. Relaxation can’t occur and rigor is acheived. No extensibilityand 100% cross bridges are formed

Resolution Phase

Considered aging. Proteolytic enzymes begin to break down the muscle

DFD

Occurs due to long term stress. Glycogen depletion in muscle causes build up of lactic acid and creates a high pH.

PSE (only in swine)

Occurs from short term stress. Short term glycogen depletion in the muscle causes premature lactic acid build up resulting in a low pH.

Elecrical stimulation

Accelerates rigor and benefits meat quality and color.

Meat color factors

• Animal factors

• muscle chem and function

• post harvest temp

• physical attributes and managment

Animal factors

• species

• stress

• diet

• housing

Post Harvest temp

• processing temp

• muscle temp

• rate of pH decline

Physical attributes

• postmortem age

• ground vs whole muscle

• packaging

Muscle chem and function

• pH

• Fiber type

• Muscle function

Myoglobin

What meat color is dependant on. stores O2 in cells

Deoxymyoglobin

Purplish red. Attached to free binding sites and requires little or no oxygen

Oxymyoglobin

Bright cherry red. Attached to free binding site O2. Requires continuous oxygen. Not stable eventually promotes oxidation

Metmyoglobin

Brown or tan. Attahed to fre binding site H2O. loss of an electron. Rate of oxidation is variable due to O2 partial pressure, temp, pH etc.

Sarcolemma

membrane around a muscle fiber. Resides under the endomysium.

Sarcoplasmic reticulum

Surrounds each myofibril. Stores calcium needed for contraction.