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FOOD2000 > MEAT > Flashcards

MEAT Flashcards

1
Q

What are the concerns associated with eating meat?

A
  • nitrates (carcinogenic?)
  • saturated fats
  • food bourn diseases (salmonella)
  • campylobacter
  • e.coli
  • bacterial resistance
  • sustainability/environment
  • animal welfare
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2
Q

What is the chemical composition of meat?

A

55-60% inorganic sustances (water and minerals)

35-40% organic substances
carbon, hydrogen, oxygen, nitrogen etc

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3
Q

What does muscle tissue consist of?

A

~75% water
~20% proteins
~5% fat

small amounts of glycogen and free amino acids

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4
Q

What are the different types of proteins in muscle?

A

Structural (e.g. collagen)

Contractile (actin and myosin)

Enzymes

Hormones

Antibodies

Transporters (haemoglobin)

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5
Q

Where are the 3 locations of fat in meat?

A

Subcutaneous (under the skin)

Intermuscular (between muscles)

Intramuscular (marbling in muscles)

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6
Q

TRUE OR FASLE: some breeds of animals are more prone to stress and dying in transport?

A

True

Some genotypes in pigs make then more prone to stress

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7
Q

What are the possible damages to carcasses that can occur during transport?

A

Bruising

Haemorrhages

Skin blemishes

Broken bones

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8
Q

What is shrinkage?

A

Losses in live weight due to less gut fill and excretory losses

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9
Q

What are the two major quality problems in meat?

A

Pale, Soft, Exudative (PSE)

Dark, Firm, Dry (DFD)

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10
Q

Which muscle fibres are more likely to become DFD?

A

Red fibres (e.g. beef and lamb)

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11
Q

Which muscle fibres are more likely to become PSE?

A

White fibres (poultry, pork)

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12
Q

What causes green colouration in meat?

A

Sulfmyoglobin

When haem pigments in the myoglobin react with sulfide producing bacteria under anaerobic conditions

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13
Q

When and how does PSE occur?

A

When animal killed while stressed and has minimal glycogen stores. Anaerobic glycolysis causes lactic acid and thus a LOW pH

Paleness is not due to a loss of myoglobin, but due to light reflecting water on the surface of the meat

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14
Q

When and how does DFD occur?

A

When animal is killed while stressed and with no glycogen stores, so cannot produce lactic acid and so pH remains HIGH and binds water very tightly

When cut there is no moisture so light is absorbed so looks dark

It is firm because the fibres are very tightly packed and is dry because the water is bound so tightly

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15
Q

What effects does PSE have on meat taste/ quality?

A

Tends to have dry taste and poor texture when cooked

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16
Q

What effect does DFD have on meat taste/quality?

A

Poor processing characteristics and spoils easier so has shorter shelf life

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17
Q

What effect does chronic preslaughter stress have on meat?

A

DFD

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18
Q

What effect does acute preslaughter stress have on meat?

A

PSE

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19
Q

What is exsanguination?

A

cutting of major arteries to the brain = bleeding to death

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20
Q

What gives meat a metallic taste?

A

Too much blood in the meat

Blood is also a breeding ground for bacteria

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21
Q

What are the three instruments used in mechanical stunning of animals?

A

Captive bolt pistol

Percussion stunner

Free bullet

All traumatise the brain = instant unconsciousness

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22
Q

What are two ways to stun animals non-mechanically?

A

Electric current

Immersion in anaesthetic gas

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23
Q

What are the two phases in effective stunning of animals?

A

Tonic Phase

  • immediate collapsing
  • stopping of rhythmic breathing
  • eyeball is fixed

Clonic Phase

  • involuntary kicking
  • 15-45 seconds
  • can recover if not killed immediately
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24
Q

What factors effect the rate at which a carcass looses heat?

A

Size of the carcass

Level of subcutaneous fat

Air circulation

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25
Q

What does rate of cooling effect in the muscles?

A
  • rates of pH fall through the production of lactic acid
  • the disappearance of CP and ATP
  • speed of onset of RM

Rapid chilling can reduce PSE in pork

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26
Q

What is the ‘magic number’ for muscle temp?

A

8-10 degrees

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27
Q

What occurs when cooling is too rapid?

A

Cold shortening

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28
Q

What occurs if meat is frozen before rigor mortis?

A

When it defrosts it goes through RM but much stronger and is called ‘thaw rigor’

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29
Q

What occurs in cold shortening?

A

If meat is rapidly chilled before RM and before glycogen is converted to lactic acid there is a super contraction

The contraction is not followed by relaxation and so results in shorter sarcomeres and thus tougher meat

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30
Q

Which muscles are more predisposed to cold shortening?

A

Red muscles tend to be more predisposed because of the potential reduced ability to sequester calcium

31
Q

What effect does electric stimulation have on meat?

A

Electric stimulation causes all muscles to contract which sues up glycogen and so enhances aerobic glycolysis

This gives a rapid fall in pH = enzymes active = tender meat

32
Q

TRUE OR FALSE: stunning and electric stimulation are the same thing

A

FALSE

33
Q

What is heat shortening?

A

Occurs if pH decline is too fast and the ultimate level is reached while the temp is still high, heat shortening occurs

34
Q

What is the optimum window for pH and carcass temp?

A

pH should not fall below 6 when temperature is greater than 35°C

pH should be below 6 before the temperature falls to 12°C

35
Q

What occurs when there is a quick pH drop + high temp?

A

Heat shortening

36
Q

What occurs when there is a slow pH drop + fast temp drop?

A

Cold shortening

37
Q

What are the three main functions of packaging meat?

A
  • protection from contamination
  • inhibits microbial growth
  • reduces/eliminates evaporative loss and surface drying and gives enhances appearance
38
Q

What are the three most common pigments found in meat?

A

Myoglobin (Mb)

Oxymyoglobin (MbO)

Metmyoglobin (metMb)

and their haemoglobin equivalents

39
Q

What colour is myoglobin

A

Purple

40
Q

What colour is oxymyoglobin?

A

bright red

41
Q

what colour is metmyoglobin?

A

grey/brown

42
Q

What occurs to MbO when it is left for 2-3 days in air?

A

Surface MbO oxidises to metMb

43
Q

What changes occur in the muscle between slaughter and consumption?

A
  • acidification
  • development of rigor
  • tenderisation
44
Q

What is the relationship between ultimate pH and lactate?

A

Ultimate pH is inversely proportional to lactate

45
Q

What are the two main characteristics affected by acidification and why?

A

Colour: goes pale and opaque

Water holding capacity decreases: weeping/drip loss

Both are a result of protein denaturation and myofibrillar proteins reaching isoelectric point

46
Q

Where are the 3 compartments in which water is held in the muscle?

A

Extracellular space

Intracellular space (outside myofibrills)

Space within myofibrils (between actin and myosin) = 80%

47
Q

What is rigor mortis and when does it occur?

A

RM occurs when ATP levels fall so low that they cannot maintain relaxation of the muscles

Actin and myosin combine to form actomyosin

Permanent cross bridges are formed

48
Q

What is alkaline rigor?

A

When RM occurs in the muscle while pH is still high

RM is determined by ATP availability not muscle pH

49
Q

What is conditioning?

A

The natural process of tenderisation when meat is stored post-rigor

50
Q

What are the two phases of conditioning?

A 
Rapid Phase (most important)
- changes in myofibrillar component

Slow Phase
- structure weakening of intramuscular connective tissue

51
Q

What do calpains and cathepsins do?

A

In living animals they breakdown and recycle proteins

In meat they give tenderisation

52
Q

What are the two types of calpains and when are they active?

A

m-calpains are activated by high concentrations of calcium ions

u-calpains are activated when calcium concentrations are low

u-calpains are more important in PM tenderisation
Both are maximally active in neutral or alkaline conditions

After activation they undergo autolysis

53
Q

What are the three phases of development of agricultural systems?

A

1) Simplify procedure enough to meet requirements
2) production systems which are reliable and efficient
3) once production is efficient quality improves

54
Q

What are the two types of meat quality?

A

Functional Quality: desireable attributes of a product e.g tender flavour etc

Conformance Quality: meets consumer specifications

55
Q

What are the 5 major components of meat quality?

A

Yield and Gross Composition

Appearance and Technological Characteristics

Palatability

Wholesomeness

Ethical Quality

56
Q

What is yield and gross composition in regards to meat quality?

A

Determines how much there is to sell, the quantity of saleable products

Higher proportion of carcass to live weight = higher profits

57
Q

what is appearance and technological characteristics in regards to meat quality?

A

appearance of the lean mass and the tech characteristics are often linked, because factors effecting microstructure effect colour and WHC

58
Q

What is palatability in regards to meat quality?

A

Juiciness
Flavour/ aroma
Texture

Human perception of juiciness and tenderness are interrelated

59
Q

What is wholesomeness in regards to meat quality?

A

Wholesomeness has two components:

Safe to eat

  • free from parasites
  • free from hazardous chemicals
  • free from pathogens

Meat which is a benefit to health

  • high value protein
  • high EAAs
  • minerals
  • vitamins
60
Q

What is the ethical quality of meat refer to?

A

Belief that animals should have been born, bred and reared, handled and slaughtered in ways which are sympathetic to animals welfare in systems which are sustainable and environmentally friendly

61
Q

What are some conflicting problems with meat quality?

A
  • juiciness and intramuscular fat (unhealthy)
  • soft fat in very lean pigs
  • addition of nitrites to pork products
  • rapid carcass cooling for reducing of microorganisms
62
Q

What is the most essential aspect of quality assurance schemes?

A

Monitoring compliance with set standards and auditing them effectively

Also traceability

63
Q

What is involved in organically produced meat?

A

Animals are reared without the use of growth promotors

Limited use of antibiotics

Only organically grown feed is used, cannot be derived from GMOs

Also some regulations about good animal welfare

64
Q

What are the differences in fat and muscle between dairy and beef cows?

A

Beef cows tend to mature earlier and have more fat than late maturing breeds (e.g. angus and hereford)

At same slaughter weight, dairy breeds tend to store more fat internally as abdominal fat

65
Q

What is the halothane gene?

A

Also known as porcine stress syndrome

Double recessive halothane genotype in pigs causes a unique susceptibility to the common anaesthetic gas halothane

Halothane positive pigs get hyperthermia when exposed to gas. This causes rapid pH decrease in muscles and extreme PSE

66
Q

What can meat be marinated in to aid tenderisation?

A

Vinegar or wine, as these are both acidic they can help break down muscle structure possibly by encouraging the action of collagenases and cathepsins

Also makes myofibrils swell and hold water increasing juiciness and tenderness

67
Q

What is injected into meat to make it more tender?

What are potential problems with this?

A

CaCl2 solution is injected and helps tenderisation thought due to activation of proteolytic calpain system by calcium

However can have undesirable effects on flavour of beef

Can cause heme pigments to oxidise faster and give meat brown colour, shorter shelf life

68
Q

What is comminution?

A

Grinding and mincing of meat to be sold as mince, hamburgers or compressed into convenient shapes

Achieved by mincing, flaking or bowl chopping

69
Q

What are sausages?

A

Chopped/comminuted meat and fat mixed with salt, spices and flavourings filled into a casing

The casing is often made from cleaned intestines of cows sheep or pigs

Artificial casing is often used and is made from reconstituted collagen (from skin) to give more uniformity

70
Q

What are the 3 types of sausages?

A

Fresh

Cooked

Dry

71
Q

What are cooked sausages?

A

Cooked sausages such as frankfurter and bologna require no cooking and can be eaten directly

Can contain beef veal or pork which is cured by the addition of nitrate

May be smoked

72
Q

What are dry sausages?

A

Not normally cooked before eating but preserved by being cured with large amounts of salt and having very low water content

Usually held in production to age to enhance flavour, partly through growth of beneficial bacteria, especially LAB

e.g. salami and hot smoked chorizo

73
Q

What is tempering of meat?

A

When processed meat needs to be sliced

Often done when the meat is in a semi-frozen state as texture is firmer and cut is more precise

74
Q

What is mechanically recovered meat?

A

After normal deboning of meat small bits are still left on carcass

This meat can be recovered by grinding bones into a paste and forcing them through small holes, the meat will pass through but bone particles will remain

FOOD2000 (5 decks)

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