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Meat Science > Conversion of Muscle to Meat (Exam 4) > Flashcards

Conversion of Muscle to Meat (Exam 4) Flashcards

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1
Q

What is homeostasis?

A

Maintenance of the physiological state

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2
Q

What lies under the narrow range of physiological conditions?

A

pH
Temperature
Oxygen concentration
Energy supply

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3
Q

What makes the beginning of postmortem changes?

A

Drop in blood pressure

Homeostatic control

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4
Q

What are some homeostatic control mechanisms? (4)

A

Protective/survival mechanism
Increase in heart rate
Peripheral vessels constrict
50% blood remaining in vital organs

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5
Q

When is muscle converted to meat?

A

When metabolism stops

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6
Q

What happens when the oxygen supply is depleted?

A

TCA cycle and electron transport start failing

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7
Q

What does homeostatic maintenance do when oxygen is depleted?

A

Shifts to anaerobic metabolism

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8
Q

What accumulates when there is a decline of muscle pH?

A

Lactic acid

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9
Q

What is the most significant postmortem change?

A

Accumulation of lactic acid

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10
Q

What is the normal decline pattern of postmortem pH?

A

Gradually from 7.0 to 5.7 within 6 to 8 hours postmortem

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11
Q

What is the ultimate pH postmortem?

A

5.5 within 24 hours

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12
Q

What are some factors to postmortem temperature change?

A 
Rate of metabolism (heat production)
Size and location of muscles
Predominate muscle fiber type
Duration of metabolism
Fat insulation
Slaughter: handling, stress, stun/stick
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13
Q

What are 2 sources of ATP postmortem?

A

Glycolytic/anaerobic metabolism

Creatine phosphate

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14
Q

What sets in when ATP depletes?

A

Rigor

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15
Q

What is rigor mortis?

A

Stiffness of death

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16
Q

What are the phases of rigor mortis?

A

Delay phase
Onset phase
Completion phase

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17
Q

When does the delay phase occur?

A

Immediately after exsanguination

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18
Q

How many actomyosin cross bridges are there during delay phase?

A

Few

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19
Q

When does the onset phase occur?

A

Within hours, species-dependent

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20
Q

What happens during onset phase? (4)

A

Less and less phosphorylation of ADP to ATP
Sources of ATP decreased
More actomyosin cross-bridges
Gradually less extensible

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21
Q

What is the ATP supply like in the completion phase?

A

Exhausted because glycolysis stops and creatine phosphate depletes

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22
Q

Describe the completion phase.

A 
Maximum actomyosin cross-bridges
All binding sites used
Sarcomeres shortened
Muscle tension to maximum
Actomyosin bonds cannot be broken
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23
Q

Look at postmortem graph

A

Look at postmortem graph

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24
Q

How many binding sites are used in rigor?

A

100%

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25
How many ending sites are used in normal contraction?
20%
26
What is the resolution of rigor mortis?
Decrease in tension with time postmortem
27
What happens in resolution of rigor? (4)
Proteolytic degradation Z disk dissolution Loss of ultrastructural integrity Actomyosin bonds still not broken
28
When does the most notable change occur?
48-72 hours postmortem
29
What does the most notable change cause?
Increased tenderness and aging effects
30
What is involved in the degradation of z disks?
Desmin
31
What is involved in the decrease in passive elasticity of muscle?
Titin
32
What is rigor tension?
Rupturing Z line/ I band junction
33
What happens during Z disk degradation?
Rigor tension | Decreases elasticity of myofibrils
34
What enzymatic activities cause resolution of rigor?
Postmortem proteolytic degradation of myofibril proteins | Calpain system
35
What is the calpain system?
2 calcium dependent enzymes and a specific inhibitor
36
What makes up the calpaan system?
m-calpain μ-calpain Calpastatin
37
What is the calpaan system activated by?
Ca released from mitochondria and SR during storage
38
What is looked at for meat sensory quality?
Color Tenderness Juiciness Flavor
39
What is looked at for meat technological quality?
``` Emulsifying capacity Binding properties Cooking loss Cooked color Cooked texture ```
40
What may happen when in animal is stressed?
They become excited, fatigued, overheated, or chilled
41
What can cause the animals to be stressed?
Unfamiliar environment Being alone Air movement, sound, space, temperature, humidity, light Fasting
42
What is stress?
A general expression referring to the physiological adjustments that occur during the exposure of the animal to adverse conditions
43
What are the physiological adjustments that occur during stress?
Heart rate Respiration rate Body temperature Blood pressure
44
What are adverse conditions known as?
Stressors
45
What are consequences of stress in muscle?
Increase demand of muscle contraction | Stress hormones help meet muscle demand
46
What happens when there is an increase demand of muscle contraction?
Increased rate of blood flow to muscle | Impossible for the circulatory system to maintain temperature and oxygen
47
What happens when stress hormones help meet muscle demand?
Anaerobic metabolism is favored | Accumulation of lactic acid
48
What happens when there is a rapid pH decline? (6)
``` Rapid conversion of muscle to meat Low ultimate pH of less than 5.5 Loss of protein solubility Loss of WHC (water holding capacity) Increased drip loss, cooked loss Loss of color intensity ```
49
What is PSE? DFD?
Pale, soft, exudative | Dark, firm, dry
50
What kind of stress is there in rapid pH decline? Species?
Short-term stress, few minutes before slaughter | Pig
51
What kind of stress is there in slow pH decline? Species?
Long-term stress, at expense of glycogen storage | Ruminants
52
What happens when there is a slow pH decline?
High ultimate pH greater than 6 Great WHC Dry surface, sticky Increased color intensity, dark cuts
53
What is slow pH decline great for?
Processed meats
54
what meat quality factors are looked at for pH?
Color WHC Protein functionality
55
What is WHC?
The ability of meat to retain naturally occurring or added water during application of external forces
56
What help water holding capacity?
Cutting Heating Grinding Pressing
57
What physical properties depend on WHC?
``` Color Texture Firmness Binding pH ```
58
What effects on processing does WHC have?
Technological quality (binding, emulsifying, curing, slicibility, texture) Shrinkage Yield
59
How much of water is bound water? Immobilized water? Free water?
4-5% Variable Surface water
60
What net charge do most proteins have?
Negative
61
Wat happens with WHC as pH declines?
Decreasing reactive groups on proteins are available for water binding
62
What happens with WHC as pH approaches isoelectric point?
Positive charge is similar to negative charge
63
What is the isoelectric point?
5.0 to 5.2
64
What is pH influence?
Net charge influence
65
What does a greater pH mean for net charge and WHC?
More negative net charge and greater WHC
66
What are 3 methods of immobilization?
Carbon dioxide Electric shock Captive bolt
67
What happens to blood pressure after stunning?
Increases dramatically
68
Why is rapid bleeding the goal?
To avoid blood splash
69
What is the most affected place for blood splash?
Hind quarter
70
What does lowering the carcass temperature prevent?
Protein degradation Enzymatic activities Microbial growth
71
What is thaw rigor?
Severe rigor mortis caused by freezing muscle pre-rigor
72
What is cold shortening?
Sudden shortening pre-rigor caused by nervous stimulation from muscle being too cold
73
What is heat ring?
Lean carcasses not chilled properly
74
How much backfat is there with heat ring in beef? Lamb?
Less than 0.25 in | Less tha 0.1 in
75
What must the temperature of a carcass be during tiger onset?
15-16ºC
76
What is pre-rigor deboning?
Cutting, deboning, and grinding immediately after slaughter
77
What happens with pre-rigor deboning?
Glycolysis is less extensive Greater ultimate pH of 6 to 6.7 Better WHC
78
What are the key processing steps in pre-rigor deboning?
Salting within 2-3 hours postmortem (no rigor or protein degradation) Rapid chilling to 2-3ºC
79
What does salting within 2-3 hours do?
Inhibits glycolysis, preventing pH decline | Increases protein solubility and WHC
80
What does electrical stimulation do?
Improves tenderness and meat quality
81
What happens with pH and contraction with electrical stimulation?
Accelerated pH decline | Violent contraction
82
What happens with violent contractions?
Rapid depletion of ATP reserves | Rapidly developed rigor mortis
83
What happens in cold shortening prevention?
Extremely rapid glycolysis and rigor onset
84
What happens in accelerated proteolysis?
Ca release
85
What happens in physical disruption of muscle structure?
Extreme contractions

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