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FOSC202 > Muscle to meat > Flashcards

Muscle to meat Flashcards

1
Q

What theory is used to describe muscle contraction and relaxation

A

sliding filament theory

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2
Q

what is the sliding filament theory supported by

A

molecular structure and interactions
myofribillar proteins

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3
Q

describe myosin structure

A

large elongated
two regions

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4
Q

describe the head region of myosin

A

globular
-pear shaped
-functional: actin binding site

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5
Q

describe the tail region of myosin

A

rod
responsible for filament

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6
Q

name of complex that resembles a string or pearls

A

actin-troponin-tropomyosin complex

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7
Q

what is the Tn-C of the complex

A

caclium binding site

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8
Q

what is the Tn-T

A

binding site with tropomysin

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9
Q

what is the Tn-I of the complex

A

Inhibits ATP-ase

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10
Q

what does the binding of calcium do to the complex

A

reveals a binding site for myosin

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11
Q

describe the process of the complex

A

-Calcium ion binds to tropomyosin which exposes the myosin binding site on actin
-ATP binds to the myosin head
-mysoin detaches from actin
-ATP hydrolysis occurs which activate myosin head
-tropoyosin bind to site on actin and phophate disociates strengthening the bond between actin and myosin
-ADP disociates and myosin contracts pulling actin

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12
Q

first step of muscle contraction/relaxtion event

A

nerve impulse transmitted via T-Tubules

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13
Q

what are T-tubules

A

blanket that surrounds the myofibrils

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14
Q

describe calcium’s role in contraction (steps 2 and 3 of the sequence)

A

sarcoplasmic reticulum releases Ca2+
Ca2+ binds to Tn-C

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15
Q

What happens to the troponin complex after calcium is bound

A

changes position to reveal myosin binding site

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16
Q

what is required for actin-myosin interaction

A

ATP

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17
Q

why can muscle contract after death

A

ATP is still present in the muscle which can cause contraction

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18
Q

Which respiratory cycles are not supported after slaughter

A

oxidative phosphorylation

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19
Q

After death what does the muscle use for energy

A

glycogen and creatine phosphate stored in the muscle

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20
Q

what does glycolysis without oxygen generate

A

lactic acid

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21
Q

what does the production of lactic acid do to the meat

A

drop pH

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22
Q

what happens once all the energy stores have been used

A

muscles stay contracted = maximum toughness

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23
Q

process of glycogen to lactate

A

glycogen -> glucose-> pyruvate-> lactate

24
Q

what is the ultimate pH

A

final pH the tissue will reach

25
Q

at what pH is muscle near at death

A

7

26
Q

what is the rejection of the ultimate pH of lamb

A

<5.5

27
Q

what is the rejection of the ultimate pH of beef

A

> 5.8

28
Q

characteristics of meat at a high pH

A

DFD
dark firm dry

29
Q

characteristics of meat at low pH

A

PSE
pale soft exudative

30
Q

what can cause a dark color in meat

A

stress before death

31
Q

rate and extent of pH fall is affect by what

A

intial glycogen in muscle
pre-slaughter stress
muscle fibre type
temperture

32
Q

what is rigor mortis

A

stiffness of death

33
Q

when does rigor mortis occur

A

when all ATP is depleted

34
Q

what happens during rigor mortis

A

irreversible cross-bridges form between actin and myosin

35
Q

another name for pre-rigor meat

A

hot boned

36
Q

what is hot boned beef

A

when carcass is boned while warm and in pre-rigor state

37
Q

why is hot boned beef used for production of burgers and sausages

A

-it is often dark in color becuase endogenous enzymes have not been able to relax the meat
-it has high WHC
-lower eating quality

38
Q

how can toughness of rigor be resolved

A

aging

39
Q

how does aging resolve rigor

A

proteolytic enzymes hydrolyse myofilaments which caused release between actin and myosin= relaxtion

40
Q

types of proteolytic enzymes that resolve rigor

A

calpains
cathepsins

41
Q

describe calpains

A

require Ca2+ and high pH
-disrupts Z lines

42
Q

what pH are cathepsins active at

A

lower pH

43
Q

what is cold shortenign

A

excess contraction/shortening

44
Q

when does cold shortening occur

A

when pre-rigor meat is chilled too quickly (between 10 and 0C)

45
Q

effect on mea tof cold shrotenign

A

excess drip
low WHC
extremely tough

46
Q

mechanism of cold shortening

A

at low temp muscle is still alive with plenty of ATP and ph>6
-sarcoplasmic reticulum becomes leaky and Ca2+ leaks out to trigger contraction
-calcium pump can no longer remove Ca2+ and muscle remains contracted

47
Q

why does DFD meat appear darker

A

light does not reflect off dry meat as well

48
Q

why does PSE meat have a light appearance

A

more light reflects or watery surfaces

49
Q

what causes the sfotness of PSE meat

A

protein denaturation at the low pH

50
Q

what is accelerated aging and conditioning of meat

A

treatment that allows for control over time and temp to reach rigor

51
Q

advantages to accelerated aging and conditioning

A

more consistent and tender meat
avoids cold shortening

52
Q

what does accerlerated aging and condiitoning involve

A

the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime

53
Q

what does accelerated aging and conditioning involve

A

the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime

53
Q

what does accelerated aging and conditioning involve

A

the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime

54
Q

what does accelerated aging and conditioning induce

A

induces rapid ATP hydrolysis
-muscle enter rigor sooner so it can be chilled without shortening

55
Q

what does accelerated aging and conditioning involve?

A

the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime

56
Q

what does accelerated aging and conditioning induce

A

induces rapid ATP hydrolysis
-muscle enters rigor sooner so it can be chilled without shortening

FOSC202 (28 decks)

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