Muscle to Meat

Question 1

Post-mortem changes in meat

Answer 1

Exanguination leads to collapse of circulation
No oxygen is available
Energy comes from CP and anaerobic glycolysis - production of lactic acid

Question 2

What is rigor mortis

Answer 2

Muscle stiffening and loss of extensibility after ATP is exhausted

Question 3

What causes rigor mortis

Answer 3

ATP is depleted so myosin heads irreversibly bind to actin

Question 4

Phases of rigor mortis

Answer 4

Delay phase
Onset phase
Completion phase
Resolution phase

Question 5

Delay phase

Answer 5

Muscle gets energy from CP and anaerobic glycolysis
Causes lactic acid build up - lowers pH of meat

Question 6

Onset phase

Answer 6

ATP is exhausted and extensibility reduces

Question 7

Completion phase

Answer 7

Irreversible binding of actinomyosin bonds

Question 8

Resolution phase

Answer 8

Proteolytic enzyme action

Question 9

Pre-slaughter factors affecting rigor mortis

Answer 9

Stress depletes muscle glycogen stor
Leads to early rigor and high muscle pH

Question 10

Post-slaughter factors affecting rigor mortis

Answer 10

Excessive chilling causes severe shortening - tough meat
Electrical stimulation can accelerate rigor without excessive shortening

Question 11

Other factors affecting rigor

Answer 11

Fibre type composition - Determines ATP production/consumption
Fast muscle is prone to PSE - more glycogen

Question 12

When does resolution occur

Answer 12

After a variable period of time

Question 13

How does resolution occur

Answer 13

Two endogenous proteases:
Calpains
Cathepsins

Question 14

What inhibits calpains?

Answer 14

Calpastatins

Question 15

What inhibits cathepsins?

Answer 15

Cystastatin

Question 16

What happens during ageing?

Answer 16

Proteins are broken down into amino acids and fats then into aromatic fatty acids (glutamic acid, inosinic acid)

Question 17

Risks of prolonged ageing

Answer 17

Rancidity due to fat oxidation

Question 18

What is tenderness

Answer 18

Eating/physical quality
Expressed in terms of:
Shear force
Myofibrillar fragmentation index (MFI)
Taste/eating quality assessment

Question 19

What influences tenderness?

Answer 19

Age - older animals have more collagenous tissue
White meat is less tender than red
Amount of shortening during rigor

Question 20

What is cold shortening?

Answer 20

When muscle cools below 10 degrees BEFORE rigor mortis starts
Due to excessive release of Ca from SR in presence of ATP

Question 21

Prevention of cold shortening

Answer 21

Keep beef/lamb >10 degrees for first 10h
Keep pork >10 degrees for first 3h

Question 22

Electrical stimulation

Answer 22

Within 1 hr of slaughter
Causes muscle contraction
Accelerates pH fall
Depletes ATP
Induces early rigor
Prevents cold shortening
Improves meat tenderness
Fractures sarcomeres and activates proteases

Question 23

How do you suspend bovine carcasses?

Answer 23

By obturator foramen to stretch premium muscles (longissimus dorsi)
Makes meat more tender

Question 24

Methods of improving tenderness

Answer 24

suspend cattle from obturator foramen
Needle/blade tenderisation
Papain from papaya
Bromelin from pineapple
Ficin from pigs
Marination
Electrical stimulation

Question 25

How does pattern of acidification affect meat quality?

Answer 25

Rapid acidification = PSE Slow acidification = DFD Affected by pre-slaughter handling of animals

Question 26

What is PSE?

Answer 26

Pale Soft Exudative Meat Abnormally pale High drip loss Lower water holding capacity Tough Caused by rapid acidification

Question 27

What is DFD?

Answer 27

Dark Firm and Dry meat Abnormally dark Rapid spoilage Tender High water holding capacity Caused by slow acidification

Question 28

What is water holding capacity?

Answer 28

pH of meat influences extent muscle proteins are changed Most proteins lose change between pH 5.1-5.5 (In this range muscle release water) Isoelectric point is 5.2

Question 29

What causes the bright red colour

Answer 29

Oxidation of myoglobin to oxymyoglobin (Blooming)

Question 30

Why does DFD not turn bright red

Answer 30

High water holding capacity so reduced oxygen penetration No oxygenation of myoglobin

Question 31

What causes paleness in PSE?

Answer 31

Enhanced protein denaturation Increase in conversion to metmyoglobin

Question 32

How do you assess colour of meat?

Answer 32

Minolta colour meter

Question 33

Which is more succulent?

Answer 33

DFD

Question 34

How can you improve succulence

Answer 34

Increase fat content

Question 35

What is boar taint?

Answer 35

Unpleasant urine-like odour of uncastrated boars caused by sex steroids deposited in IM fat

Question 36

Prevention of boar taint

Answer 36

Castrate males Slaughter younger slatted floors to reduce faecal contamination Avoid overcrowding

Question 37

How is carcass quality assessed?

Answer 37

Weight Conformation Fatness