Muscle to Meat Phys

Question 1

What are the six constituents of meat?

Answer 1

Water, protein, fat, carbs, vitamins and minerals.

Question 2

What percentage of meat is water?

Answer 2

70-78%

Question 3

In what form is the water in meat?

Answer 3

Free and attached to protein-this gives meat its juiciness

Question 4

What three types of protein are present in meat?

Answer 4

Muscle proteins, like actin and myosin; CT proteins, like collagen; and O-carrying proteins, like myoglobin and haemoglobin.

Question 5

What percentage of meat is fat?

Answer 5

1-13%- although this is highly variable and depends on BCS of animal

Question 6

What percentage of meat is carbs?

Answer 6

1-2%

Question 7

What is the main carb found in meat?

Answer 7

Glycogen

Question 8

Carbs are very important for determining what characteristic of meat?

Answer 8

Eating characteristics- amount of carbs affects things like WHC and tenderness

Question 9

Meat is a good source of vitamin —–

Answer 9

B12

Question 10

Meat is a good source of iron. (T/F?)

Answer 10

TRUE

Question 11

The properties of the muscle post-mortem, and therefore of the meat, depends on the structure, function and regulation of function in the living muscle. (T/F?)

Answer 11

TRUE

Question 12

What is gristle?

Answer 12

Elastin protein- a type of CT. Includes tendons, ligaments and sheets of CT that cover and separate muscles.

Question 13

What is the implication for the meat product of shorter sarcomeres in a muscle?

Answer 13

Shorter sarcomeres mean more contraction which means tougher meat.

Question 14

What percentage of meat is protein?

Answer 14

15-22%

Question 15

What is the first thing that happens when the animal is killed?

Answer 15

The supply of O stops, so conversion to meat begins. No O supply initiates anaerobic metabolism.

Question 16

Not outside energy supply from cells is possible. This means the meat quality is defined by:

Answer 16

The energy present in the glycogen molecules

Question 17

When the animal is killed, contractile units stop working immediately. (T/F?)

Answer 17

FALSE- they remain functional, but everything is done anaerobically.

Question 18

What produces the pH drop when muscle converts to meat?

Answer 18

The anaerobic functioning of the contractile units produces lactic acid which changes the pH, causing it to drop from approx 7.4 to approx 5.3-5.4. Because there is no blood supply to take the waste lactic acid away as it would in a live animal.

Question 19

Fat becomes liquidated during the rigour mortis process. (T/F?)

Answer 19

FALSE- fat solidifies

Question 20

After this has occurred, the muscle will stay in whatever state it’s in, whether that be contraction or relaxation. Why?

Answer 20

Because all the ATP has been used up

Question 21

Why does rigour mortis occur?

Answer 21

The sarcomeres shorten and become fixed- no ATP is present to release the myosin head from the actin.

Question 22

What is the biochemical definition of rigour mortis?

Answer 22

Concentration of ATP is not sufficient to energise a muscle contraction

Question 23

What is the chemical definition of rigour mortis?

Answer 23

Post mortem muscle pH is lower than 6.0

Question 24

What is the industry/practical definition of rigour mortis?

Answer 24

The muscle has “set”. It is stiff or firm to the touch. Can be assessed by moving the forelimb on a carcass.

Question 25

How long does it take to finish the rigour mortis process?

Answer 25

About 24-36 hours

Question 26

In early post mortem, proteins begin to denature under acidic conditions and action of enzymes which become very active under acidic conditions. What consequences does this have for the water in the carcass?

Answer 26

Water is lost due to protein breakdown because water is present within the myofibril proteins which are denatured by these enzymes.

Question 27

What happens to the Ca concentration during the rigour mortis process?

Answer 27

It increases due to failure of Ca pumps, which results in major contraction and consumption of ATP, the extent of which can have major effects on temp of muscle and meat tenderness.

Question 28

What is the ultimate pH?

Answer 28

< 6, when glycolysis stops because conditions are too acidic for enzymes to function. Also when glycogen is used up and there is no further ATP production and the actomyosin bridges are locked.

Question 29

What is shear force?

Answer 29

A measure of tenderness- the amount of force required to drive a steel blade through a 1/2 inch core of meat. This is measured in Newtons (N). A more tender piece of meat needs less force.

Question 30

What is cold shortening?

Answer 30

When the meat chills too rapidly, and the pH remains high. The muscles fall below 12 degrees C before pH falls below 6, or while ATP is present.

Question 31

Pale Exudative Soft meat is the result of cold shortening. (T/F?)

Answer 31

FALSE- PSE is a result of heat shortening

Question 32

Dark Firm Dry meat is the result of heat shortening. (T/F?)

Answer 32

FALSE- DFD is the result of cold shortening

Question 33

What is heat shortening?

Answer 33

When the pH of the meat declines too fast and the ultimate pH is reached while the temp is still too high.

Question 34

Will an animal with more glycogen stores have a faster or slower pH drop compared to one with lower glycogen stores?

Answer 34

Faster- DFD is a risk!

Question 35

The carcass pH must pass through 6 between what temps?

Answer 35

15 and 35 degrees C

Question 36

CT proteins change with post mortem changes and acidic environments etc. (T/F?)

Answer 36

FALSE- CT proteins re only affected by things like age of the animal etc.

Question 37

What are the effects of a full glycogen bucket on meat quality?

Answer 37

If glycogen bucket is full, meat will have good juiciness and tenderness etc.

Question 38

What factors deplete the glycogen bucket?

Answer 38

Stress! Including transport stress, high stress handling etc. We can avoid an empty glycogen bucket by providing good nutrition, low stock handling and reducing stress where possible. Genetics and breed also has an effect.

Question 39

Why do we need the glycogen bucket?

Answer 39

The glycogen reserves are converted to lactic acid which decreases the pH of the muscle, turning it into meat.

Question 40

What are the visual (raw) meat quality traits?

Answer 40

Colour, softness/texture, water-holding capacity

Question 41

What are the sensory (cooked) meat quality traits?

Answer 41

Tenderness, juiciness, flavour.

Question 42

What affects meat tenderness?

Answer 42

Breed, production (levels of CT and IM fat depend on nutrition and how the animal is raised etc.), processing including post-mortem proteolysis and sarcomere length, and value adding and cooking methods (cooking conditions and water loss affect tenderness- this is why there are cooking recommendations for different cuts of meat).