Muscle to Meat Phys Flashcards
What are the six constituents of meat?
Water, protein, fat, carbs, vitamins and minerals.
What percentage of meat is water?
70-78%
In what form is the water in meat?
Free and attached to protein-this gives meat its juiciness
What three types of protein are present in meat?
Muscle proteins, like actin and myosin; CT proteins, like collagen; and O-carrying proteins, like myoglobin and haemoglobin.
What percentage of meat is fat?
1-13%- although this is highly variable and depends on BCS of animal
What percentage of meat is carbs?
1-2%
What is the main carb found in meat?
Glycogen
Carbs are very important for determining what characteristic of meat?
Eating characteristics- amount of carbs affects things like WHC and tenderness
Meat is a good source of vitamin —–
B12
Meat is a good source of iron. (T/F?)
TRUE
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?)
TRUE
What is gristle?
Elastin protein- a type of CT. Includes tendons, ligaments and sheets of CT that cover and separate muscles.
What is the implication for the meat product of shorter sarcomeres in a muscle?
Shorter sarcomeres mean more contraction which means tougher meat.
What percentage of meat is protein?
15-22%
What is the first thing that happens when the animal is killed?
The supply of O stops, so conversion to meat begins. No O supply initiates anaerobic metabolism.
Not outside energy supply from cells is possible. This means the meat quality is defined by:
The energy present in the glycogen molecules
When the animal is killed, contractile units stop working immediately. (T/F?)
FALSE- they remain functional, but everything is done anaerobically.
What produces the pH drop when muscle converts to meat?
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.
Fat becomes liquidated during the rigour mortis process. (T/F?)
FALSE- fat solidifies
After this has occurred, the muscle will stay in whatever state it’s in, whether that be contraction or relaxation. Why?
Because all the ATP has been used up
Why does rigour mortis occur?
The sarcomeres shorten and become fixed- no ATP is present to release the myosin head from the actin.
What is the biochemical definition of rigour mortis?
Concentration of ATP is not sufficient to energise a muscle contraction
What is the chemical definition of rigour mortis?
Post mortem muscle pH is lower than 6.0
What is the industry/practical definition of rigour mortis?
The muscle has “set”. It is stiff or firm to the touch. Can be assessed by moving the forelimb on a carcass.
How long does it take to finish the rigour mortis process?
About 24-36 hours
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?
Water is lost due to protein breakdown because water is present within the myofibril proteins which are denatured by these enzymes.
What happens to the Ca concentration during the rigour mortis process?
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.
What is the ultimate pH?
< 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.
What is shear force?
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.
What is cold shortening?
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.
Pale Exudative Soft meat is the result of cold shortening. (T/F?)
FALSE- PSE is a result of heat shortening
Dark Firm Dry meat is the result of heat shortening. (T/F?)
FALSE- DFD is the result of cold shortening
What is heat shortening?
When the pH of the meat declines too fast and the ultimate pH is reached while the temp is still too high.
Will an animal with more glycogen stores have a faster or slower pH drop compared to one with lower glycogen stores?
Faster- DFD is a risk!
The carcass pH must pass through 6 between what temps?
15 and 35 degrees C
CT proteins change with post mortem changes and acidic environments etc. (T/F?)
FALSE- CT proteins re only affected by things like age of the animal etc.
What are the effects of a full glycogen bucket on meat quality?
If glycogen bucket is full, meat will have good juiciness and tenderness etc.
What factors deplete the glycogen bucket?
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.
Why do we need the glycogen bucket?
The glycogen reserves are converted to lactic acid which decreases the pH of the muscle, turning it into meat.
What are the visual (raw) meat quality traits?
Colour, softness/texture, water-holding capacity
What are the sensory (cooked) meat quality traits?
Tenderness, juiciness, flavour.
What affects meat tenderness?
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).
