Term
| What does glycogen phosphorylase do? |
|
Definition
| initiates the release of chemical energy by breaking down glycogen |
|
|
Term
| What are the chemical products we see produced in stress-susceptible pigs, and their effects? |
|
Definition
ATP & glucose-6-phosphate
-prevent phosphorylase from being activated in myofiber |
|
|
Term
| What is lost from the circulatory system after exsanguination? |
|
Definition
-nutrient transport to muscles
-removal of waste & metabolites
-oxygen delivery
-heat removal |
|
|
Term
| After death, is the nervous system still functional in regards to muscle contraction? |
|
Definition
-if an electrical impulse is provided the muscle fiber can still be stimulated
-NS is not truly working but the infrastructure is still present |
|
|
Term
| What is the primary goal of stunning? |
|
Definition
| to render an animal unconscious so that death can occur by exsanguination |
|
|
Term
| As long as O2 is available, how is ATP generated? |
|
Definition
-metabolism of CHO, lipids, proteins
-ADP + phosphocreatine -> ATP & creatine |
|
|
Term
| What is the source of energy for converting creatine back to phosphocreatine? |
|
Definition
| using ATP produced in the Krebs Cycle |
|
|
Term
| When is the homeostatic mechanism of ATP production active? |
|
Definition
| when there is a high demand for ATP but oxygen is limited |
|
|
Term
| What is the product of anaerobic metabolism in the live animal? |
|
Definition
|
|
Term
| What is the fate of lactic acid in a live animal vs post mortem? |
|
Definition
live: goes to heart (energy) or liver (glucose)
post mortem: stuck in myofibers |
|
|
Term
| True or False Anaerobic metabolism can continue post mortem |
|
Definition
| True, as long as glycogen is available and the cell environment is not too acidic |
|
|
Term
| What are the implications of lactic acid remaining in muscle cells post mortem? What effect does this have on the eating quality of meat? |
|
Definition
-pH will decrease until glycolytic enzymes denature, & ATP production stops
-protein denature = less water holding ability = drier meat |
|
|
Term
| What is glycogen converted to so that anaerobic metabolism can take place post-mortem? |
|
Definition
| glycogen -> glucose 1 phosphate |
|
|
Term
| Why do we see an increase in body temperature after exsanguination? |
|
Definition
-metabolic heat production
-slaughter process (scalding, singeing, hot water wash) |
|
|
Term
| What factors affect rise in temperature after exsanguination? |
|
Definition
-rate of glycolysis
-size & location of muscles
-fat insulation
-fiber type |
|
|
Term
| What muscle fiber type will produce more heat and why? |
|
Definition
| white fiber because there is more anaerobic activity in these glycolytic fibers |
|
|
Term
| What is the result of not producing enough lactate in the conversion of muscle to meat? |
|
Definition
|
|
Term
| What is the result of producing too much lactate in the conversion of muscle to meat? |
|
Definition
| PSE meat (pale soft exudative) |
|
|
Term
|
Definition
| rapid rates of glycolysis decreasing pH too quickly & producing excess heat |
|
|
Term
| What causes protein denaturation in PSE? |
|
Definition
| increased carcass temperature & rapid rate of lactic acid production |
|
|
Term
Sort the following species in decreasing order of the time required to complete the acidification process
Pigs
Turkey
Sheep
Cattle |
|
Definition
|
|
Term
| Will animals who had large stores of glycogen in their muscles prior to slaughter have a higher or lower ultimate pH after acidification has completed? Why? |
|
Definition
| lower pH because more glycogen = more substrates for lactic acid production = lower pH |
|
|
Term
| When is the conversion of muscle to meat complete? |
|
Definition
-when the muscles' energy reserves are depleted
or
-when the muscles are unable to use remaining energy reserves |
|
|
Term
| What is required for the cycle of muscle contraction to repeat itself? What happens if this is not available |
|
Definition
ATP & Ca2+
-myosin heads will remain locked to actin if ATP not available (X bridges are permanent) |
|
|
Term
True or False
Passive filament sliding can still occur even if no ATP is available for muscle contraction |
|
Definition
|
|
Term
| What is the role of ATP in resting muscle? |
|
Definition
| forms a complex with Mg2+ and binds to the myosin head, preventing the formation of actomyosin |
|
|
Term
| How can muscle be stretched immediately after exsanguination? |
|
Definition
| adding a load/applying force to the muscle |
|
|
Term
| What happens if a load or force applied to a muscle immediately after exsanguination is removed? |
|
Definition
| natural elasticity returns the muscle to its resting length |
|
|
Term
| How many actomyosin bridges are present in a resting muscle that is being stretched? |
|
Definition
| very few, if any, because this muscle is resting |
|
|
Term
| What is the delay phase of rigor mortis? |
|
Definition
| the period after death when muscle is readily extensible & elastic |
|
|
Term
| How can ATP by synthesized after exsanguination? |
|
Definition
| using creatine phosphate + ADP, and then using glycogen stores to phosphorylate ADP |
|
|
Term
| What might affect the glycogen stores in a muscle? |
|
Definition
| how much stress or exercise the animal experienced prior to slaughter |
|
|
Term
| In the transition to rigor, what happens once actomyosin bridges form? |
|
Definition
| the muscle becomes less extensible if a load or force is applied |
|
|
Term
| What is the onset phase of rigor mortis? |
|
Definition
| when the muscle becomes less extensible |
|
|
Term
| As actomyosin bridges form, what is happening to the muscle? |
|
Definition
-sarcomere length decreases
-thick & thin filaments overlap more
-muscle tension increases
-ATP levels decrease |
|
|
Term
| Why are xbridges permanent in rigor mortis? |
|
Definition
because there is no ATP available to enable myosin heads to detach themselves from the binding site
(phosphocreatine & glycogen have been used up) |
|
|
Term
| When is rigor mortis complete? |
|
Definition
| when all binding sites between actin & myosin have actomyosin bridges |
|
|
Term
| Why can the body not get ride of the Ca2+ in muscle cells to relax the muscle? |
|
Definition
| no ATP available to pump Ca from sarcoplasm into SR |
|
|
Term
| Compare the number of xbridges formed in muscle contraction vs in RM |
|
Definition
Muscle contraction: 20%
RM: 100% |
|
|
Term
| In the transition to rigor, ATP availability ______ and muscle extensibility _____ post-mortem |
|
Definition
|
|
Term
| What is the rapid phase of rigor mortis? |
|
Definition
| running out of ATP on an individual muscle fiber basis, resulting in rapid loss of extensibility |
|
|
Term
| Why might Ca2+ leak from the SR and what would be the effect of this? |
|
Definition
chilling effect on the muscle
-stimulates contraction |
|
|
Term
| If a small amount of glycogen is present, what effect will this have on the phases of rigor? |
|
Definition
speeds up the onset
-not much ATP able to be produced
short rapid phase
-run out of ATP quickly |
|
|
Term
| If lots of glycogen is present, what effect will this have on the phases of rigor? Why? |
|
Definition
delays the onset
-ATP is able to be produced
slow/drawn out rapid phase
-takes a while to run out of ATP |
|
|
Term
| Will a starved animal at slaughter have a long or short delay & rapid phase? |
|
Definition
| short delay, long rapid phase |
|
|
Term
| Will an exhausted animal at slaughter have a long or short delay & rapid phase? |
|
Definition
short/no delay
very short rapid phase |
|
|
Term
|
Definition
| lysosomal enzymes degrade the xbridges |
|
|
Term
| Why might you freeze meat prerigor? |
|
Definition
improve water binding properties
enhance flavour |
|
|
Term
|
Definition
| Sudden release of Ca2+ when thawed results in massive contraction, rapid breakdown of ATP & onset of rigor, extensive muscle shortening |
|
|
Term
Order the following meats in increasing order of delay time before onset of RM
Pork
Fish
Chicken
Lamb
Beef
Turkey |
|
Definition
Chicken
Turkey & Fish
Pork
Beef & lamb |
|
|
Term
| Are all muscles affected the same by thaw rigor? Why/why not? |
|
Definition
no
muscles attached to bone will show less shortening |
|
|
Term
| What is the effect of thaw rigor on meat quality? |
|
Definition
|
|
Term
|
Definition
| rapid depletion of ATP stores & severe muscle shortening caused by muscle temperature reaching 50C before rigor develops |
|
|
Term
| When does cold shortening occur? |
|
Definition
| If the onset of rigor doesn't happen until the carcass is less than 10C |
|
|
Term
| What causes cold shortening? |
|
Definition
| release of Ca / failure to pump Ca into SR at lower temperatures, activates ATPase, causes contraction & decrease in sarcomere length |
|
|
Term
| What is more severe, cold shortening or thaw rigor? |
|
Definition
|
|
Term
True or False
Chilling has no effect on function of the SR |
|
Definition
|
|
Term
Are the following species at high or low risk of cold shortening & why?
Pork
Poultry
Beef
Lamb |
|
Definition
P&P: low risk, go into RM quickly
Beef: high risk, cool slowly & enter RM slowly
Lamb: very high risk, cool quickly & enter RM slowly |
|
|
Term
| What muscles would be affected more by cold shortening, red or white? Why? |
|
Definition
|
|
Term
| What is the effect of cold shortening on meat tenderness? |
|
Definition
| 20-50% shortening will cause toughening of meat |
|
|
Term
|
Definition
| water that is not bound, will be easily lost during cooking |
|
|
Term
| How can you stop rigor contraction of unrestrained muscles? |
|
Definition
| -hanging the carcass by the aitch bone |
|
|
Term
| At what point during meat production would you use electrical stimulation to tenderize muscles? |
|
Definition
| before it enters the chill cooler |
|
|
Term
| Why is electrical stimulation not used on pork? |
|
Definition
| because it already goes into rigor quickly and has a fast rate of pH decline |
|
|
Term
| What is the effect of electrical stimulation on a carcass? |
|
Definition
-increase rate of pH decline via glycolysis
-increase rate of RM development
-tenderizes the muscle |
|
|
Term
| Why does electrical stimulation speed up the development of rigor mortis? |
|
Definition
| -causes violent muscle contractions which uses up ATP quickly, and subsequently uses up glycogen stores |
|
|
Term
| How does electrical stimulation tenderize the muscle? |
|
Definition
-prevents cold shortening
-disrupts myofiber structure
-increases release of Ca, calpain enzymes & lyososomal enzymes (proteolitic) |
|
|
Term
|
Definition
| Ca2+ enzymes responsible for increasing post-mortem tenderization |
|
|
Term
| What are some other benefits of electrical stimulation, aside from tenderizing the meat? |
|
Definition
-enhances colour & appearance (more red)
-increases firmness
-increases marbling visibility
-prevents formation of coarse bands
-increases flavour |
|
|
Term
| Is electrical stimulation effective on DFD beef? Why or why not |
|
Definition
no
-already has low glycogen stores so won't benefit from increasing the rate of lactic acid production |
|
|
Term
| What level of voltage should be used for electrical stimulation right after death? Why? |
|
Definition
low voltage
-direct stimulation of muscle contraction will increase the Ach being released, stimulating the sarcolemma |
|
|
Term
| What level of voltage should be used for electrical stimulation just prior to entering a chill cooler? |
|
Definition
high voltage
-less Ach will be released at this point |
|
|
