2- Muscle to meat

Question 1

Name the 3 sources of ATP production

Answer 1

Oxidative phosphorylation of ADP in mitochondria (Immediate source)

Direct phosphorylation of ADP to ATP by creating phosphate (Intermediate source)

Anaerobic glycolysis (Ultimate source)

Question 2

How many ATP molecules are produced per glucose molecule in oxidative phosphorylation?

Answer 2

36

Question 3

What products are made from anaerobic glycolysis?

Answer 3

2 ATP per glucose & Lactic acid

Question 4

How many ATP molecules are produced in direct phosphorylation

Answer 4

1 ATP per CP molecule

Question 5

What is exsanguination?

Answer 5

bleeding out

Question 6

After circulatory failure what happens prior to rigorous mortis?

Answer 6

PM glycolysis
- remaining energy is used to allow muscle extensibility - acts like live muscle

Once ATP is depleted = Onsent of rigor mortis

Question 7

Define rigor mortis

Answer 7

Muscle stiffening & loss of extensibility after death

Question 8

Name the 4 stages of rigor mortis

Answer 8

Delay, Onsent, Completion and resolution

Question 9

Why does rigor result in a rigid muscle structure?

Answer 9

Supply of ATP is exhausted, myosin heads remain irreversibly locked onto the actin = rigid structure

Question 10

List pre-slaughter factors that affect rigor mortis and they do affect it

Answer 10

Physical stress or disease- depletes muscle glycogen store –> depletes muscle glycogen store
Limited glycolysis–> early RM and high muscle pH

Question 11

T/F Ca-ATPase pump is inactivated rapidly at low temperature causing increase of calcium ions

Answer 11

True

Question 12

What are the 2 endogenous proteases which play an important role in resolution of rigor ? & What inhibits them?

Answer 12

Calpains = inhibited by calpastatin

Cathepsins = Inhibited by cystatin

These soften the meat
breeds which have more calpastain (like Brahman cattle) have tougher meat- as inhibits the enzymes that cause muscle tension to decrease

Question 13

Certain breads have more calpastatin than other what does this mean in regards to the meat tenderness?

Answer 13

Tough as it is inhibiting proteases (calpains)

Question 14

What contributes to the meaty flavour of meats?

Answer 14

During ageing proteins/fats are broken down

Glutamic acid
Inosinic acid

Question 15

What is cold shortening?

Answer 15

Rapid chilling of meat

Reduces microbial growth, evaporation, drip loss but risks shortening of muscle

Occurs when below 10 degrees

Tough on cooking

Question 16

What process prevents cold shortening?

Answer 16

Electrical stimulation = within 1hr of slaughter

Causes muscle contraction, accelerates pH fall, depletes ATP & induces early rigor

Question 17

What causes acidification of meat after death

Answer 17

Lactic acid accumulates after death causing acidification
The speed of acidification affects quality of meat

Question 18

T/F If acidification is very slow gives pale, soft & exudative meat (PSE)

Answer 18

False = this would be rapid acidification

Question 19

Which meat mentioned below is caused by chronic stress > high ultimate pH leading to proteins not denaturing & after being held by proteins?

Pale soft exudative (PSE) meat
or
Dark Firm dry (DFD) meat

Answer 19

Dark Firm Dry Meat

Question 20

pH of 5.2 is called a what in meat?

Answer 20

Isoelectric point pH when +Ve and -ve chargers are always equal and net charge is zero

Question 21

What is boar taint?

Answer 21

Unpleasant urine like odour of entire boars

Cause by sex steroids deposited in intramuscular fat

Question 22

In pig carcass classification, Price depends on what 3 things?

Answer 22

Weight, Age & P2 backfat

Question 23

Name the main steps of conversion of muscle to meat

Answer 23

Muscle
Slaughter
blood supply ceases
Remaining energy used to allow muscle extensibility
When energy is depleted–> rigor mortis
Without oxygen, glucose–> lactic acid
pH 5.4-5.7
Meat

Question 24

Name the post-slaughter factors which affect rigor mortis and how they affect it

Answer 24

excessive rate of chilling –> cold shortening –> tough meat

Question 25

What type of muscle is most prone to pale soft exudate and which animals do NOT have these

Answer 25

Fast glycolytic muscles
Cattle and horses- not prone to PSE

Question 26

What is a risk of prolonged ageing of meat

Answer 26

Can cause fat oxidation –> rancid odour

Question 27

Name the 3 different ways tenderness can be expressed

Answer 27

Shear force
Myofibrillar fragmentation index (MFI)
Taste or eating quality assessment

Question 28

What conditions are required for cold shortening to take place

Answer 28

Cooling below 10 degrees C before rigor mortis sets in

Question 29

What can electrical stimulation induce in pork

Answer 29

pale soft exudate

Question 30

Apart from electrical stimulation name other methods to improve tenderness

Answer 30

stretching the muscles- hip suspension
needle/ blade tenderisation
Marination
papain, bromelin, ficin

Question 31

Name some properties of meat quality

Answer 31

Dark cutting beef/ Dark firm dry pork = not good
Pale soft exudate = bad
Water holding capacity
Succulence
Colour and paleness - paleness = bad
Boar taint = bad

Question 32

What affects the water holding capacity of meat

Answer 32

pH of meat

Question 33

How able is dark, firm, dry meat able to hold onto water vs pale soft exudate

Answer 33

DFD meat has higher water holding capcity
PSE- has higher drip loss so reduced water holding capacity

Question 34

What gives meat its colour

Answer 34

myoglobin

Question 35

T/F The paleness of meat is inversely proportional to pH

Answer 35

True

Question 36

T/F DFD pork and DCB dont “bloom” in presence of oxygen

Answer 36

True - because they have a high water holding capacity which makes the meat turgid and reduces oxygen penetration, so no blooming - so the meat becomes dark

Question 37

List 4 ways that boar taint is managed/ prevented

Answer 37

castration
avoiding overcrowding
slatted floors to reduce faecal contamination
early slaughter of males