Meat Proteins

Question 1

Where is bovine meat from?

Answer 1

Cattle

Question 2

Where is ovine meat from?

Answer 2

Lamb and mutton

Question 3

What is the nutritional value of meat?

Answer 3

• High biological value (composition close to human proteins)
• Source of essential amino acids
• Sounds of vitamins
• High in saturated fats

Question 4

What are the health concerns surrounding eating meat?

Answer 4

• Cardiovascular disease
• Cancer (nitrites involved in producing cured meats may be carcinogenic)
• Food safety (salmonella)
• Spread of bacteria that are resistant to antibiotics from animal to human

Question 5

What are the environmental concerns surrounding eating meat?

Answer 5

Agricultural sustainability (lots of energy is lost in the production of animals from plants = inefficient)
Environment protection and animal welfare (animal exploitation)

Question 6

How does protein and fat content vary between animals?

Answer 6

With age, breed and the cut of meat

Question 7

When is the slaughter point of an animal?

Answer 7

When there is optimum protein content and intermediate fat content

Question 8

What are the three meat protein classifications?

Answer 8

1. Stromal proteins (connective tissue)
2. Myofibrillar proteins
3. Sarcoplasmic proteins

Question 9

What three layers are found in stromal proteins and what are they?

Answer 9

• Epimysium = covers the muscle
• Perimysium = covers fascicles (bundles of muscle fibres)
• Endomysium = covers muscle fibres

Question 10

What three components make up connective tissue?

Answer 10

Collagen
Elastin
Reticulin

Question 11

How does collagen appear is meat?

Answer 11

White / transparent

Question 12

What property of meat does collagen affect?

Answer 12

Tenderness - the older the meat the less tender it is

Question 13

Does collagen degrade to form gelatin?

Answer 13

Yes - between 65 and 80 degrees

Question 14

What is the structure of collagen?

Answer 14

Triple helix

Question 15

What is powdered collagen used for?

Answer 15

Useful gels

• Sausage casing
• Contact lenses
• Pharmaceuticals

Question 16

What is gelatin?

Answer 16

The end product of the thermal degradation of collagen

Question 17

How does elastin appear in meat?

Answer 17

Yellow

Question 18

Is elastin degraded to form gelatin?

Answer 18

No

Question 19

What components make up myofibrillar proteins?

Answer 19

Myosin
Actin 
Troponin 
Tropomyosin 
Desmin

Question 20

What are the properties of myosin?

Answer 20

Long
Filamentous
Charged = polar
High affinity for calcium and magnesium

Question 21

What is the structure of myosin?

Answer 21

2 subunits

• Light meromyosin = LMM
• Heavy meromyosin = HMM

Question 22

How is desmin affected with ageing?

Answer 22

Ageing increases water holding capacity

Question 23

What is the structure of actin?

Answer 23

Globular G actin molecules link to form filamentous F actin

Question 24

What molecule is troponin and tropomyosin associated with?

Answer 24

Filamentous F actin

Question 25

What are most sarcoplasmic proteins?

Answer 25

Enzymes and pigments

Question 26

What are the properties of sarcoplasmic proteins?

Answer 26

Small, water soluble proteins

Question 27

What are calpains?

Answer 27

Enzymes which contribute to tenderization and flavouring

Question 28

What is haemoglobin?

Answer 28

A pigment which is responsible for colour variations in meat

Question 29

What is myoglobin?

Answer 29

A conjugated protein which contains and heme group with an attached histidine-iron protein

Question 30

What determines the colour of meat?

Answer 30

The oxidation state of iron within myoglobin and the attached ligands

Question 31

When is meat purple/blue?

Answer 31

When myoglobin is in the form deoxymyoglobin - Fe II - No ligands

Question 32

When is meat red?

Answer 32

When myoglobin is in the form oxymyoglobin - Fe II - Oxygen

Question 33

When is meat brown?

Answer 33

When myoglobin is in the form metmyoglobin - Fe III - No ligands

Question 34

What are the main stages in the process of turning muscle to meat?

Answer 34

1. Animal slaughtered 2. Acidification 3. Onset of rigor mortis 4. Resolution of rigor mortis 5. Conditioning

Question 35

What happens when an animal is slaughtered?

Answer 35

O2 levels fall Supply of O2 to muscles stop Respiration stops

Question 36

What happens during acidification?

Answer 36

- ATP is generated from glycogen = anaerobic glycolysis - Lactic acid accumulates and the muscle acidifies (pH 7.2 to 5.5) = muscle proteins denature - Loss of biological activity = water holding capacity, solubility - Meat changes from dark to pale

Question 37

What occurs during onset rigor mortis?

Answer 37

- Glycolysis is inhibited and ATP levels fall - Actin and myosin form actomyosin (myosin cannot be released due to lack of ATP) - Muscle extensibility is lost

Question 38

What happens during the resolution of rigor mortis?

Answer 38

- Tenderization starts | - Muscles soften as myofibrils become fragmented

Question 39

What does the rate of tenderization depend on?

Answer 39

Species Temperature Age

Question 40

What happens during conditioning?

Answer 40

- Continuation of tenderization - Myofibrils weaken - Calpains provide flavouring

Question 41

What is PSE meat and when is it produced?

Answer 41

Pale soft exudative | Produced when the animal is under short term stress and there is a very low pH when the animal is slaughtered

Question 42

What is DFD meat and when is it produced?

Answer 42

Dark firm dry | Produced when the animal is under long term stress and there is a very high pH when the animal is slaughtered