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PSE & DFD
pse, dfd, beef
79
Anatomy
Undergraduate 2
04/17/2014

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Cards

Term
What factors affect the range of pH decline in pork muscle?
Definition
-genetics
-muscle glycogen levels at slaughter
-management from farm to packing plant
-stress
Term
What is ultimate pH?
Definition
the pH of meat after the acidification process is complete
Term
What is the typical pH of normal meat 1 hour post-mortem? 6-8 hours PM? 24h PM?
Definition
1h PM: >6.0
6-8h PM: 5.6-5.7
24hPM: 5.3-5.7
Term
What is typical pH pale PSE P1 meat, 1 hour post-mortem? 24h PM?
Definition
1h PM: <6.0, as low as 5.4-5.5
24h PM: 5.3-5.6
Term
What is typical pH pale PSE P2 meat, 1 hour post-mortem? 24h PM?
Definition
1h PM: >6.0
6-8h PM: <5.5
24h PM: 5.2-5.4
Term
What is stress? What are some of the physiological responses we observe?
Definition
physiological adjustments that an animal makes when exposed to adverse conditions
-heart rate
-respiration
-body temperature
-blood pressure
Term
What is the role of epinephrine in stress response?
Definition
-maintenance of circulation
-breakdown of glycogen & lipid stores
Term
What are some of the pre-slaughter management & handling factors that can affect stress in meat animals?
Definition
-herd environment & human exposure
-marketing direct to packer vs auction
-truck loading technique
-experience of shippers
-use of electric prod
-transportation time
-crowding & co-mingling
-temperature
-lairage period
-post slaughter handling of meat
Term
True or False

Cattle are usually shipped direct to packer rather than run through an auction
Definition
False

Pigs & poultry are often marketed direct to packer
Term
What is lairage?
Definition
holding of animals at plant before slaughter
Term
What is the trade-off to be considered concerning the lairage period?
Definition
longer rest period allows for more time to recuperate, but also more room & opportunity for fights between animals
Term
What is the term for DFD in beef?
Definition
dark cutting
Term
What are some causes of DFD in swine?
Definition
Porcine Stress Syndrome (PSS)
General stress due to transport, hunger, fear, aggression etc.
Term
What type of muscle fibers are associated with DFD?
Definition
fast twitch red fibers
Term
What causes DFD?
Definition
-depletion of glycogen stores before death means inadequate amounts of lactic acid are produced to lower pH
Term
What are some characteristics of DFD beef?
Definition
-dark colour
-firm consistency
-high water holding capacity
-sticky surface
-prone to bacterial spoilage
Term
What colour characteristics would be observed in meat at pH 5.8-6.0? 6.5?
Definition
5.8-6.0 abnormal colour
6.5 extremely dark colour
Term
Why does DFD meat appear dry?
Definition
because the water is tightly bound within muscle fibers
Term
Why is DFD beef prone to bacterial spoilage?
Definition
because the high pH is a good environment for bacterial growth
Term
True or False

DFD carcasses are discounted by 10 cents per pound
Definition
False

25 cents per pound on average
Term
True or False

DFD pork is tough and has a lesser quality flavour
Definition
False

DFD pork is tender & has good flavour
Term
True or False

DFD beef is juicy
Definition
True

due to its increased water holding capacity
Term
What gender has a higher incidence of DFD beef, steers or heifers?
Definition
heifers
Term
Why is there a higher incidence of DFD in heifers?
Definition
-mounting behaviour & physical stress during estrus
Term
What is MGA?
Definition
-feed additive for heifers in feedlots
-prevents heifers from going into heat, decreases mounting behaviour, maximizes nutrient use for weight gain
Term
True or False

MGA can also be beneficial for steers
Definition
True

If heiffers are not in heat, the steers housed nearby will be less stressed as well
Term
How does nutritional status affect dark cutting meat?
Definition
different energy percentage in forage, less energy in forage than grain , affects glycogen stores
Term
What is a more important factor in regards to animal stress, cool seasonal temperatures or a sudden increase in temperature?
Definition
sudden increase is more likely to stress an animal than a constant cool temperature
Term
How does stress affect muscle contraction?
Definition
-increases muscle activity, which increases lactic acid production
Term
How does stress affect the circulatory system?
Definition
blood flow increases due to increased demands for nutrients & oxygen
Term
What happens when the demands of muscle are not met?
Definition
-shift from aerobic to anaerobic metabolism
-production of lactic acid
-increase in temperature
Term
What are the postmortem effects of stress on the conversion of muscle to meat?
Definition
-temperature
-glycolysis
-onset of rigor
-rate of pH decline
Term
What happens if lactic acid production overwhelms the ability of the body to use it?
Definition
systemic acidosis
Term
What are the effects of circulatory collapse?
Definition
-increased muscle temperature
-inability to remove lactic acid
-ATP production inhibited
Term
What is the 'expense' of stress handling in stress resistant animal?
Definition
handle stress at the expense of muscle glycogen, which affects lactic acid production & the conversion of muscle to meat
Term
What is PSS?
Definition
Porcine Stress Syndrome
-PSS is a genetic defect in pigs
-autosomal recessive gene, replacement of a single nucleotide in a Ca release channel protein of the SR
-excessive release of Ca2+
Term
What is the importance of ryanodine in PSS?
Definition
-plant alkaloid used to test for the genetic defect
Term
Does PSS cause PSE or DFD meat?
Definition
both
Term
What receptor releases Ca2+ into the sarcoplasm?
Definition
dyhydropyridine receptor
Term
Describe the steps of the contraction process which involve Ca2+ & ryanodine
Definition
1. dihydropyridine receptor releases Ca2+ into sarcoplasm
2. ryanodine receptor detects the release & allows additional Ca2+ from SR to be released
4. Troponin C binds Ca2+, myosin binding sites are exposed on actin to allow for contraction
Term
What is halothane sensitivity? What muscles are primarily affected?
Definition
halothane is an old anaesthetic
-rapid increase in body temperature
-large amounts of lactic acid production due to anaerobic glycolysis
-muscle rigidity due to overstimulation

-affects muscles of the ham/hindquarter & loin
Term
What are the 3 classes of genotypes in PSS?
Definition
NN: halothane resistant
Nn: carrier
nn: halothane sensitive
Term
How can halothane be used to detect PSS?
Definition
halothane-sensitive individuals will show muscle spasms/rigidity within 5 minutes of exposure
Term
True or False

Halothane can be used to detect individuals heterozygous for PSS
Definition
False

Need to do DNA testing
Term
How do PSS pigs react to stress?
Definition
-trembling muscles
-rigid/weak muscles, lethargy
-excessive lactic acid production
-vasoconstriction increases BP
-hypertension increases BP
-decreased cardiac output
-hyperthermia
-increased metabolic activity can kill the animal
-dyspnea
-hyperkalemia
Term
What is dyspnea?
Definition
rapid shallow breathing (PSS pigs)
Term
What is hyperkalemia?
Definition
elevated blood potassium, can stop the heart
Term
What breeds are primarily affected by PSS?
Definition
Pietrain
Poland
China
Landrace
Term
Will PSE pork have a higher or lower carcass temperature than normal post mortem?
Definition
higher
Term
What causes PSE pork?
Definition
rapid & extensive decline in pH
-if pH drops before heat dissipates, proteins are likely to denature
Term
How do we prevent denaturation of proteins PM?
Definition
chilling of meat so heat can dissipate before pH drops
-blast chilling can be used to control PSE in pork
Term
Is protein denaturation a guaranteed process with rapid pH decline?
Definition
no, not always
Term
When does visual appraisal for PSE pork take place?
Definition
in the cooler, 75 minutes after slaughter
Term
When is the carcass put into the cooler?
Definition
35-45 minutes after slaughter
Term
True or False

24h pH is a good indicator for PSE
Definition
False

Only if the meat is severely PSE
Term
Is low pH necessarily bad for pork?
Definition
no, because it can prevent microbial growth
Term
What pH levels are good indicators for PSE & DFD?
Definition
PSE: <5.0
DFD: >6.0
Term
What is the importance of the 45-60 minute measurement for predicting PSE?
Definition
gives an indication of how fast acid production is occurring
Term
If pH is below 6.0 at the 45-60 minute measurement PM, what does this indicate?
Definition
PSE
Term
What is the RN gene?
Definition
-can carry a genetic defect which results in high levels of glycogen at slaughter
Term
What effect does RN have in regards to pH decline post mortem?
Definition
-slows the rate of glycolysis, will have a normal measurement at the 45-60 minute mark
-ultimate pH will be low
-causes PSE pork
Term
What are the effects of protein denaturation on meat quality?
Definition
-pale meat
-loss of water binding capacity (exudative)
-fluid may drip from surface of meat
-loss of protein solubility
Term
True or False

Consumers are good at judging whether a cut of meat is PSE
Definition
False

The low water holding capacity makes them think it's juicy
Term
Describe the steps in the development of PSE
Definition
1. Acidification
2. Protein denaturation
3. Proteins reach isoelectric point
4. increased light scattering & exudation of moisture
5. Opaque, pale appearance & drip loss
Term
How do we get DFD pork from a PSS animal?
Definition
-if the animal survives the stress of the transport/pre-slaughter process
-low/nonexistent glycogen stores at slaughter
-no lactate is produced, pH remains high (5.8-5.9)
Term
Describe the palatability of DFD pork from a PSS animal
Definition
-good aroma
-good flavour
-tender product
-moist/juicy
Term
If all pigs with PSS were eliminated, would the problem of PSE meat be eliminated as well?
Definition
no, the RN defect still exists

PSE can develop from any pigs genetics predisposed to rapid rates of glycolysis & pH decline, don't need to have the PSS defect
Term
True or False

PSS animals can produce normal pork
Definition
true
Term
PSS refers to ______ while PSE refers to _____
Definition
PSS: animal & its genetic defect
PSE: the meat that is produced
Term
What is the difference between water holding capacity & absorption?
Definition
Absorption: ability to bind water from the external environment

WHC: ability to bind or hold its own water
Term
What influences WHC?
Definition
pH

higher pH = higher WHC
if isoelectric point is reached there is no electrical charge, minimal water solubility
Term
Why is WHC important?
Definition
-water loss during chilling
-appearance of meat before cooking
-behaviour during cooking
-juicyness when chewing
-processing of meat
Term
What are some other terms for drip loss?
Definition
weep
shrink
Term
What causes a reduction in WHC as pH declines PM?
Definition
-thick & thin filaments move closer together
-water space between myofilaments decreases
-ATP is depleted, no energy for membranes to hold water
-fluid escapes between fasiculi
-denaturation of myosin
Term
What causes PSE pork to be soft?
Definition
-escaped water between fasiculi = easily separated muscle fiber bundles
-detachment of myosin heads
-tougher meat
Term
True or False

Paleness of PSE pork is directly proportional to pH
Definition
False

inversely proportional
Term
Why is pork more prone to paleness in PSE?
Definition
-little myoglobin to begin with -oxidation of myoglobin to metmyoglobin would turn it brown
Term
What is the major reason for DFD beef?
Definition
-mixing of unfamiliar cattle (co mingling) causes stress
-fighting, mounting, lots of physical activity depleting glycogen stores
Term
True or False

As lairage time increases, the incidence of DFD also increases
Definition
true (in general)

-short rest period is good, too long (e.g. overnight) might give more rest but is also very likely to result in more fights & stress between animals
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