Early Post-mortem Processes

Question 1

What happens during the delay phase?

Answer 1

• Calcium is still being maintained in the SR
• Normal supply of ATP
• Aerobic metabolism at beginning, but then switch to anaerobic as oxygen stores deplete

Question 2

What happens during onset?

Answer 2

• ATP depletion

- SR leaks calcium; begins contraction

Question 3

What are the ranges for time to complete for beef, pork, and chicken?

Answer 3

• Beef - 18-24 hrs
• Pork - 6-12 hrs
• Chicken - 0.5-1.5 hrs

Question 4

What causes chicken to reach completion faster than pork or beef?

Answer 4

Does not have a high oxygen holding capacity because of fast-twitch muscle composition

Question 5

Describe “thaw rigor”.

Answer 5

• Pre-rigor freezing

- Leads to very severe contraction

Question 6

Describe “cold-shortening” and what we do to prevent it.

Answer 6

• Result of rapid chilling
• Causes meat to be very tough
• To avoid be either use high-temperature conditioning or we freeze slowly
• Electrical stimulation as well

Question 7

What temperature range can lead to muscle shortening, proteolytic activities, and microbial growth?

Answer 7

77-98 oF

Question 8

What temperature does minimum shortening occur?

Answer 8

61 oF

Question 9

What does pre-rigor cooking lead to?

Answer 9

• Heat induced contraction
• Myofibrillar fracturing
• Lack of lactic acid

Question 10

What are the physical limits of contraction?

Answer 10

• Thick filament will run into z-line if skeleton is not resisting contraction
• Muscle attachments to bone

Question 11

How does pre-rigor grinding improve protein solubility and water binding ability?

Answer 11

• Incorporates oxygen into meat

- Terminates contractile processes of the meat pieces

Question 12

Describe “pelvic suspension”.

Answer 12

• Hang carcass from hip
• Shortens sirloin tip sarcomeres (less tender)
• NY strips become more tender

Question 13

Describe “tender stretch”.

Answer 13

• Sever connection between vertebra
• Improves tenderness of steaks
• Takes effort and has potential for microbial growth

Question 14

What are the downfalls of pre-rigor boning/hot stripping?

Answer 14

• Causes excessive shortening
• Reduces tenderness
• Reduces functional properties (water binding, solubilizes proteins, etc.)

Question 15

How does electrical stimulation improve tenderness and color development?

Answer 15

• Avoid cold shortening
• Rapid pH decline
• Accelerated rigor onset/shortened delay phase

Question 16

How does rigor affect meat functional properties?

Answer 16

• Less water binding from muscle shortening
• Rigor bridges of polyphospate
• pH decline (5.6)
• Proteolysis - severing of myosin head (needs to be intact for emulsification)