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food commodities > Red Meat and Meat products > Flashcards

Red Meat and Meat products Flashcards

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1
Q

What is “red meat” and where is it sourced?

A

mammalian skeletal muscle to be consumed as food

from cows, pigs, mutton, rabbit, etc (usually young animals

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2
Q

Composition of meat will depend on what factors? (6)

A 
species
breed
age
sex
nutrition
muscle condition (activity)
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3
Q

Compare carcass and lean meat:

A

lean meat is carcass with fat removed

lean meat is higher in protein, lower fat

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4
Q

The major beef producing countries are;
the major pork producing countries are:
Overall, the most common meat is:

A

beef: USA, Brazil
pork: China, Europe
PORK

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5
Q

what gives meat its characteristic color?

A

high concentration of Mb in muscle

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6
Q

What is the FA profile of the triglycerides in meat?

A

SFA: 40-46%
MUFAs: 45-50% (especially OLEIC)
PUFAs: 5-12%

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7
Q

What are the 2 classes of lipids in mammals?

A

Structural (cholesterol + PL)

storage (TG)

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8
Q

What are the skeletal muscle proteins, and their proportions?

A

sarcoplasmic (soluble) - 25-30%
myofibrillar (salt soluble muscle proteins) - 50-60%
stromal (conn tissue): 10-20%

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9
Q

What is the content of the structural lipids in meat?

A

cholesterol: 0.7-0.9%
PL: 0.1-0.5%

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10
Q

Most of the sarcoplasmic proteins are ____, which are needed for what 2 metabolic processes? What are other enzymes/functions?

A

enzymes; glycolysis, glycogenlysis

creatine kinase, deaminases, proteinases, Mb

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11
Q

In comparison to fish lipids, meat has less ____, which makes it less prone to:

A

PUFAs; less prone to oxidative rancidity

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12
Q

In resting muscle, ___ and ____ act as a complex and prevent ___ binding to actin.

A

troponin; tropomyosin

myosin heads

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13
Q

The major myofibrillar proteins are:

A 
actin
myosin
troponin
tropomyosin
nebulin
titin
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14
Q

Are myofibrillar proteins solubilized in the body? What form do they take?

A

NO: muscle is only 0.15M NaCl (0.3 is needed to solubilize)

in complex filament structures

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15
Q

The most abundant SP is ____, (20%) which is required for _____ .

A

G3P dehydrogenase

glycolysis

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16
Q

What is the largest protein? Where is it found and what role does it play?

A

titin
connects z line to m line (attach thick filaments to z line)
gives “elasticity” - centers thick filaments, and lets muscle spring back after contraction

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17
Q

Which proteins are most affected in the conversion of muscle to meat?

A

myofibrillar

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18
Q

What are the units of muscle?

A

sarcomeres

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19
Q

What are the most abundant myofibrillar proteins?

A

actin/myosin (40%)

titin

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20
Q

What causes the light/dark regions in sarcomeres.?

A

ANISOTROPIC bands - thick filament (myosin) regions

ISOTROPIC bands - thin filament (actin) regions

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21
Q

What is the z line?

A

the end of a sarcomere unit, where actin is linked

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22
Q

What are the regions of the myosin chains? Which one overlaps and binds to actin?

A

head, neck , tail

head

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23
Q

What is the middle of the H zone called?

A

M line (middle of myosin)

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24
Q

muscle contraction depends on the presence of ____ in the ____.

A

Ca

sarcoplasm

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25
Q

____ is a large protein that plays a role during sarcomere formation. What is it associated to?

A

Nebulin

associated with actin to regulate length

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26
Q

Descibe the steps of muscle contraction (6)

A
  1. nervous signal
  2. Ca release from SR -> sarcoplasm
  3. Ca bind to troponin -> tropomyosin is moved
  4. myosin can now bind -> actomyosin
  5. using ATP -> power stroke (repeated)
  6. causes muscle to shorten (contraction
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27
Q

More stromal proteins are needed in mammals vs fish because:

A

need to support weight on land

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28
Q

How does muscle relaxation occur? )(5)

A
  1. nerve impulse ends
  2. Ca returned to SR by CaATPase
  3. troponin/tropomyosin returns to position
  4. myosin blocked, no more contraction
  5. titin helps muscle spring back
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29
Q

The roles of stromal proteins:

A

provide high tensile strength

attach muscle to bone to allow for movement

30
Q

The 3 main mammal stromal proteins:

A

collagen
elastin
desmosine

31
Q

What distinguished the types of collagens? What is the predominant type in meat?

A

polypeptide chain sequences in tropocollagen
Type 1 has 2 a1(I), and 1 a2(I); Type 3 has 3 a1(III)

Type 1 is most common

32
Q

What is the common sequence of AA in collagen? What AA is it especially high in?

A

Gly-Pro-X
Gly-X-HydroxyPro

high in glycine, hydroxyproline

33
Q

What is the main unit of collagen? Describe its structure

A 
tropocollagen
triple helix (3 polypeptide chains)
34
Q

What can be used as an estimate of collagen content?

A

hydroxyproline content: specific AA to collagen (makes up about 1/6 of it)

35
Q

____ is usually associated with collagen, and has higher ____, making is important for what body structures?

A

Elastin
elasticity
arteries, ligaments

36
Q

What causes the tougher meat as animals age?

A

collagen forms more cross-links

37
Q

True/False: meat contains beta-carotene

A

True. Also contains vitamin A

38
Q

Meat is not a good source of vitamins ___ and ____

A

vitamin C, vitamin K

39
Q

What makes the links between elastin and gives it the elasticity?

A

Desmosine

40
Q

After the animal is killed, ____ process will exceed ___ processes, and ____ is no longer maintained.

A

catabolic; anabolic

homeostasis

41
Q

How are ATP levels maintained in the live animal muscle? What is it dependent on?

A

cellular respiration

requires blood flow to keep providing O2 and substrates, and remove CO2 and end products

42
Q

Meat is especially high in the minerals ___ and ____

A

K and P

43
Q

What are the further breakdown products of AMP and their relevance?

A

AMP -> adenosine and IMP -> inosine -> hypoxyxanthine -> xanthin -> uric acid

high IMP is good, meat still fresh
hypoxyxanthine and xanthine will taste bitter, poor quality meat

44
Q

True/False: ATP production ceases after blood flow stops.

A

False: will still continue for some time after death

45
Q

How will the muscle continue making ATP after death? (4)

A
  1. use some remaining O2 bound to Mb (only last 5 min)
  2. use Cr-P and creatine kinase -> regenerate ATP from ADP
  3. combine 2 ADPs using adenylate kinase -> ATP + AMP
  4. eventually, must use muscle glycogen for ANAEROBIC GLYCOLYSIS
46
Q

In the anaerobic glycolytic pathway, for every 2 mol ATP produced, 1 mol ____ will be made. What effect does this have?

A 
lactic acid
pH decline (eventually deactivates enzymes, no more glycolysis)
47
Q

The 3 phases of muscle conversion to meat:

A

delay -> rigor -> resolution

48
Q

Describe the delay phase. How long does it last?

A

ATP levels stay high (regenerated fast enough), cells still function adequately. No stiffening.
about 12 hrs

49
Q

Around what pH does glycolysis cease?

A

5.4-5.5

50
Q

The delay phase ends once: ____

What causes the next phase?

A

pH falls to 5.4-5.5, glycolysis ceases: no more ATP

No ATP -> Ca can’t be returned to SR, so muscle stays permanently contracted (rigor)

51
Q

Rigor mortis occurs because: (2)

A
  1. no ATP to pump Ca back to SR

2. no ATP to detach myosin heads

52
Q

True/False: in the resolution phase, the actomyosin will be dissociated, allowing muscles to relax again.

A

False; remains locked, but proteases break down muscle myofibril structures -> fragmented, so more tender

53
Q

How can rigor phase affect the texture of meat? Is this change permanent?

A

shortening of sarcomeres -> tougher

No, muscle will be softened again in resolution phase

54
Q

Are there major changes in connective tissue during the resolution tenderization?

A

Some, but much slower, less extensive. (mostly myofibril breakdown that has tenderizing effect)

55
Q

What are the proteases active during the resolution phase? (3) What proteins do each target?

A

Calpains - MOST active - myofibrillar proteins
Cathepsins - troponin/collagen, also some actomyosin
Proteosomes - conn tissue and myofibrillar, actomyosin

56
Q

The proteases largely target the _____ of the myofibrils.

A

z-line

57
Q

Tenderization time is different depending on the ____. It can be increase by:

A 
animal
increasing temperature (2x speed for every 10C increase)
58
Q

Why are calpains most active of the proteases?

A

Ca activated, and large amount of Ca in Sarcoplasm

59
Q

Which protease functions best at low pH?

A

cathepsins

60
Q

How do calpains and proteosomes function together?

A

proteosomes cannot break down intact myofibrils directly

calpains first start breakdown, and proteosomes can target the fragments

61
Q

ideally, the final pH decline of meat should reach:

What is too high, and too low?

A
  1. 6
  2. 2 too low
  3. 8 too high
62
Q

What are the steps to slaughter?

A

stunning (concussion, electric, CO2)
exsanguination (bleed out)
*except: halal and kosher, bleed out directly

63
Q

What happens if pH declines too much (final pH is very low)? What causes it?

A

PSE (pale, soft, exudative) meat
proteins rapidly denatured, lose water binding capacity -> dry texture, because water is exuded
denatured proteins appear pale

occurs if meat not chilled after slaughter, glycogen used very rapidly

64
Q

How would PSE and DFD meats be problematic?

A

PSE is mushy and dry texture, even after cooking (though pale color will be lost)
DFD has a dark color that consumers find unappealing

65
Q

How is the dead animal converted to a meat carcass?

A

remove head/feet/tail/skin/etc
eviscerate/gut
wash, weigh, chill

66
Q

What happens if the pH decline is not enough (final pH too high?) What could cause this?

A

DFD (dark firm dry) meat
myosin and other proteins not denatured, since pH is not low enough
myosin will retain water better, and proteins appear darker (dry surface, dark color)

caused by lack of GLYCOGEN - animal struggle during slaughter and used it up

67
Q

What happens if the meat is cut from the carcass immediately after slaughter and chilled?

A

ATP and muscle processes continue,
MgATPase is SLOWED due to cold temp, so Ca will build up in sarcoplasm

as Ca builds up the muscle will contract. No bone to hold it in place -> shortens and becomes tougher (COLD-SHORTENING)

will need longer resolution phase

68
Q

After death, what will happen to color of meat? What reverts it back to original, and what happens with prolonged time?

A

no oxygen -> deoxyMb (purple)
expose to O2 -> becomes MbO2 (red)
too long -> oxidized to MetMb (brown)

69
Q

What is thaw rigor? What are the effects?

A

meat is frozen before rigor-> form intracellular ice crystals -> disrupt SR -> Ca floods out, cause contraction of muscle
cause short, tough meat

70
Q

What are the water types in meat?

A

Bound - attached to proteins, innermost layer
Immobilized - less organized, may be expelled
Free - can participate in rxn, held very weakly

food commodities (5 decks)

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