Conversion of Muscle to Meat (Exam 4) Flashcards
What is homeostasis?
Maintenance of the physiological state
What lies under the narrow range of physiological conditions?
pH
Temperature
Oxygen concentration
Energy supply
What makes the beginning of postmortem changes?
Drop in blood pressure
Homeostatic control
What are some homeostatic control mechanisms? (4)
Protective/survival mechanism
Increase in heart rate
Peripheral vessels constrict
50% blood remaining in vital organs
When is muscle converted to meat?
When metabolism stops
What happens when the oxygen supply is depleted?
TCA cycle and electron transport start failing
What does homeostatic maintenance do when oxygen is depleted?
Shifts to anaerobic metabolism
What accumulates when there is a decline of muscle pH?
Lactic acid
What is the most significant postmortem change?
Accumulation of lactic acid
What is the normal decline pattern of postmortem pH?
Gradually from 7.0 to 5.7 within 6 to 8 hours postmortem
What is the ultimate pH postmortem?
5.5 within 24 hours
What are some factors to postmortem temperature change?
Rate of metabolism (heat production) Size and location of muscles Predominate muscle fiber type Duration of metabolism Fat insulation Slaughter: handling, stress, stun/stick
What are 2 sources of ATP postmortem?
Glycolytic/anaerobic metabolism
Creatine phosphate
What sets in when ATP depletes?
Rigor
What is rigor mortis?
Stiffness of death
What are the phases of rigor mortis?
Delay phase
Onset phase
Completion phase
When does the delay phase occur?
Immediately after exsanguination
How many actomyosin cross bridges are there during delay phase?
Few
When does the onset phase occur?
Within hours, species-dependent
What happens during onset phase? (4)
Less and less phosphorylation of ADP to ATP
Sources of ATP decreased
More actomyosin cross-bridges
Gradually less extensible
What is the ATP supply like in the completion phase?
Exhausted because glycolysis stops and creatine phosphate depletes
Describe the completion phase.
Maximum actomyosin cross-bridges All binding sites used Sarcomeres shortened Muscle tension to maximum Actomyosin bonds cannot be broken
Look at postmortem graph
Look at postmortem graph
How many binding sites are used in rigor?
100%
How many ending sites are used in normal contraction?
20%
What is the resolution of rigor mortis?
Decrease in tension with time postmortem
What happens in resolution of rigor? (4)
Proteolytic degradation
Z disk dissolution
Loss of ultrastructural integrity
Actomyosin bonds still not broken
When does the most notable change occur?
48-72 hours postmortem
What does the most notable change cause?
Increased tenderness and aging effects
What is involved in the degradation of z disks?
Desmin
What is involved in the decrease in passive elasticity of muscle?
Titin
What is rigor tension?
Rupturing Z line/ I band junction
What happens during Z disk degradation?
Rigor tension
Decreases elasticity of myofibrils
What enzymatic activities cause resolution of rigor?
Postmortem proteolytic degradation of myofibril proteins
Calpain system
What is the calpain system?
2 calcium dependent enzymes and a specific inhibitor
What makes up the calpaan system?
m-calpain
μ-calpain
Calpastatin
What is the calpaan system activated by?
Ca released from mitochondria and SR during storage
What is looked at for meat sensory quality?
Color
Tenderness
Juiciness
Flavor
What is looked at for meat technological quality?
Emulsifying capacity Binding properties Cooking loss Cooked color Cooked texture
What may happen when in animal is stressed?
They become excited, fatigued, overheated, or chilled
What can cause the animals to be stressed?
Unfamiliar environment
Being alone
Air movement, sound, space, temperature, humidity, light
Fasting
What is stress?
A general expression referring to the physiological adjustments that occur during the exposure of the animal to adverse conditions
What are the physiological adjustments that occur during stress?
Heart rate
Respiration rate
Body temperature
Blood pressure
What are adverse conditions known as?
Stressors
What are consequences of stress in muscle?
Increase demand of muscle contraction
Stress hormones help meet muscle demand
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
What happens when stress hormones help meet muscle demand?
Anaerobic metabolism is favored
Accumulation of lactic acid
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
What is PSE? DFD?
Pale, soft, exudative
Dark, firm, dry
What kind of stress is there in rapid pH decline? Species?
Short-term stress, few minutes before slaughter
Pig
What kind of stress is there in slow pH decline? Species?
Long-term stress, at expense of glycogen storage
Ruminants
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
What is slow pH decline great for?
Processed meats
what meat quality factors are looked at for pH?
Color
WHC
Protein functionality
What is WHC?
The ability of meat to retain naturally occurring or added water during application of external forces
What help water holding capacity?
Cutting
Heating
Grinding
Pressing
What physical properties depend on WHC?
Color Texture Firmness Binding pH
What effects on processing does WHC have?
Technological quality (binding, emulsifying, curing, slicibility, texture)
Shrinkage
Yield
How much of water is bound water? Immobilized water? Free water?
4-5%
Variable
Surface water
What net charge do most proteins have?
Negative
Wat happens with WHC as pH declines?
Decreasing reactive groups on proteins are available for water binding
What happens with WHC as pH approaches isoelectric point?
Positive charge is similar to negative charge
What is the isoelectric point?
5.0 to 5.2
What is pH influence?
Net charge influence
What does a greater pH mean for net charge and WHC?
More negative net charge and greater WHC
What are 3 methods of immobilization?
Carbon dioxide
Electric shock
Captive bolt
What happens to blood pressure after stunning?
Increases dramatically
Why is rapid bleeding the goal?
To avoid blood splash
What is the most affected place for blood splash?
Hind quarter
What does lowering the carcass temperature prevent?
Protein degradation
Enzymatic activities
Microbial growth
What is thaw rigor?
Severe rigor mortis caused by freezing muscle pre-rigor
What is cold shortening?
Sudden shortening pre-rigor caused by nervous stimulation from muscle being too cold
What is heat ring?
Lean carcasses not chilled properly
How much backfat is there with heat ring in beef? Lamb?
Less than 0.25 in
Less tha 0.1 in
What must the temperature of a carcass be during tiger onset?
15-16ºC
What is pre-rigor deboning?
Cutting, deboning, and grinding immediately after slaughter
What happens with pre-rigor deboning?
Glycolysis is less extensive
Greater ultimate pH of 6 to 6.7
Better WHC
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
What does salting within 2-3 hours do?
Inhibits glycolysis, preventing pH decline
Increases protein solubility and WHC
What does electrical stimulation do?
Improves tenderness and meat quality
What happens with pH and contraction with electrical stimulation?
Accelerated pH decline
Violent contraction
What happens with violent contractions?
Rapid depletion of ATP reserves
Rapidly developed rigor mortis
What happens in cold shortening prevention?
Extremely rapid glycolysis and rigor onset
What happens in accelerated proteolysis?
Ca release
What happens in physical disruption of muscle structure?
Extreme contractions
