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Nutrition > Meat Proteins > Flashcards

Meat Proteins Flashcards

1
Q

Where is bovine meat from?

A

Cattle

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2
Q

Where is ovine meat from?

A

Lamb and mutton

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3
Q

What is the nutritional value of meat?

A
  • High biological value (composition close to human proteins)
  • Source of essential amino acids
  • Sounds of vitamins
  • High in saturated fats
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4
Q

What are the health concerns surrounding eating meat?

A
  • 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
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5
Q

What are the environmental concerns surrounding eating meat?

A 
Agricultural sustainability (lots of energy is lost in the production of animals from plants = inefficient)
Environment protection and animal welfare (animal exploitation)
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6
Q

How does protein and fat content vary between animals?

A

With age, breed and the cut of meat

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7
Q

When is the slaughter point of an animal?

A

When there is optimum protein content and intermediate fat content

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8
Q

What are the three meat protein classifications?

A
  1. Stromal proteins (connective tissue)
  2. Myofibrillar proteins
  3. Sarcoplasmic proteins
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9
Q

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

A
  • Epimysium = covers the muscle
  • Perimysium = covers fascicles (bundles of muscle fibres)
  • Endomysium = covers muscle fibres
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10
Q

What three components make up connective tissue?

A

Collagen
Elastin
Reticulin

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11
Q

How does collagen appear is meat?

A

White / transparent

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12
Q

What property of meat does collagen affect?

A

Tenderness - the older the meat the less tender it is

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13
Q

Does collagen degrade to form gelatin?

A

Yes - between 65 and 80 degrees

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14
Q

What is the structure of collagen?

A

Triple helix

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15
Q

What is powdered collagen used for?

A

Useful gels

  • Sausage casing
  • Contact lenses
  • Pharmaceuticals
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16
Q

What is gelatin?

A

The end product of the thermal degradation of collagen

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17
Q

How does elastin appear in meat?

A

Yellow

18
Q

Is elastin degraded to form gelatin?

A

No

19
Q

What components make up myofibrillar proteins?

A 
Myosin
Actin 
Troponin 
Tropomyosin 
Desmin
20
Q

What are the properties of myosin?

A

Long
Filamentous
Charged = polar
High affinity for calcium and magnesium

21
Q

What is the structure of myosin?

A

2 subunits

  • Light meromyosin = LMM
  • Heavy meromyosin = HMM
22
Q

How is desmin affected with ageing?

A

Ageing increases water holding capacity

23
Q

What is the structure of actin?

A

Globular G actin molecules link to form filamentous F actin

24
Q

What molecule is troponin and tropomyosin associated with?

A

Filamentous F actin

25
Q

What are most sarcoplasmic proteins?

A

Enzymes and pigments

26
Q

What are the properties of sarcoplasmic proteins?

A

Small, water soluble proteins

27
Q

What are calpains?

A

Enzymes which contribute to tenderization and flavouring

28
Q

What is haemoglobin?

A

A pigment which is responsible for colour variations in meat

29
Q

What is myoglobin?

A

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

30
Q

What determines the colour of meat?

A

The oxidation state of iron within myoglobin and the attached ligands

31
Q

When is meat purple/blue?

A

When myoglobin is in the form deoxymyoglobin

  • Fe II
  • No ligands
32
Q

When is meat red?

A

When myoglobin is in the form oxymyoglobin

  • Fe II
  • Oxygen
33
Q

When is meat brown?

A

When myoglobin is in the form metmyoglobin

  • Fe III
  • No ligands
34
Q

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

A
  1. Animal slaughtered
  2. Acidification
  3. Onset of rigor mortis
  4. Resolution of rigor mortis
  5. Conditioning
35
Q

What happens when an animal is slaughtered?

A

O2 levels fall
Supply of O2 to muscles stop
Respiration stops

36
Q

What happens during acidification?

A
  • 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
37
Q

What occurs during onset rigor mortis?

A
  • 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
38
Q

What happens during the resolution of rigor mortis?

A
  • Tenderization starts

- Muscles soften as myofibrils become fragmented

39
Q

What does the rate of tenderization depend on?

A

Species
Temperature
Age

40
Q

What happens during conditioning?

A
  • Continuation of tenderization
  • Myofibrils weaken
  • Calpains provide flavouring
41
Q

What is PSE meat and when is it produced?

A

Pale soft exudative

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

42
Q

What is DFD meat and when is it produced?

A

Dark firm dry

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

Nutrition (27 decks)

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