PSE and DFD Flashcards
what can cause different pH muscle pH?
- genetics
- muscle glycogen at slaughter
- management from farm to packing (stress)
what is normal pH in living muscle?
7.4
why does pH decline post mortem?
continues production of lactic acid from the anaerobic system
DFD pork pH
stays relatively high, around 6.7 ish
normal meat pH 1 and 24h post mortem
1 h - >6.0
24h - range of 5.3-5.7
rapid PSE pork pH 1h and 24h PM
1h- rapid decrease, <6.0, but can be 5.4ish too
24h - range of 5.3-5.6, similar to normal pork.
gradual PSE pork pH 1h and 24h PM
1h - >6.0
24h- very low pH, 5.0-5.4
what is stress
physiological adjustments made when exposed to adverse conditions.
occurs when envorionment has become uncomfortable or hazardous
what changes in an animal when stressed?
heart rate, respiration, body temp, blood pressure, etc
stockman ship in relation to factors affecting stress in meat animals
previous exposure to humans - may not see ppl day to day.
how animals are marketed in relation to factors affecting stress in meat animals
direct to packer vs auction - more stress when going to auction before slaughter
truck loading technique in relation to factors affecting stress in meat animals
experienced truckers = lower stress, reduced use of electric prod.
transportation in relation to factors affecting stress in meat animals
diff stage of life can be scarier for others, may be on trailer for a long time. they will be handled diff at end of a trip depending on age and destination
co-mingling in relation to factors affecting stress in meat animals
often leads to stress and fighting when unfamiliar animals are put together
temperature in relation to factors affecting stress in meat animals
hot out- heat stress
age impacts too
lairage in relation to factors affecting stress in meat animals
hours vs overnight- recommended for long haul, but not for mixed pens bc more time and room to fight
type of stunning in relation to factors affecting stress in meat animals
captive bolt makes them struggle more
things that impact glycogen from farm to slaughter/preslaughter stress
- fatigue
- fasting
- excitement
- exercise
- fighting
- restraint
- electrical shock
- leaving home pen
- truck ride
- meeting new pigs
- experiences at packing plant
stress impact on muscle contraction
increased
stress impact on circulatory system
increase nutrient and oxygen demands to meet requirements.
temp regulation - more activity, more glycogen (hot?)
what happens to oxygen supply, temp if muscle demands are not met
lower oxygen supply, greater demand
greater heat production
what happens if lactic acid production overwhelms ability of the body to use it?
systemic acidosis
what does exposure to stressors cause
shock and circulatory collapse (effects muscle temp, lactic acid production, ATP)
post mortem effect on the conversation of muscle to meat when animal is stressed at slaughter
temp increase, glycolysis increase, sped up rigor mortis, increased pH decline
stress resistant animals- how do they handle stress?
lowering muscle glycogen stores - good if it can rest and replete glycogen pre slaughter
porcine stress syndrome (PSS)
hereditary susceptibility to stress, genetic defect, alongside preslaughter stress.
what can happen when a PSS pig is stressed?
death during transport - can not cope due to acidosis or hypothermia
poor quality meat - PSE and DFD pork
halothane impact
high body temp, high lactate production
muscles get rigid, affects red and white muscles.
halothane sensitivity
rapid- will see effect w/in 5 min w muscle spasms
reliable and cheap
PSS pig rxn to stress
trembling muscles rigid muscles w lethargy excessive lactic acid production - acidosis which can be deadly circulatory failure- deadly hyperthermia - deadly
PSS breed effects
seen in some pigs more than others, usually lean breeds (pietrain, Poland, China, landrace)
how does PSS work
AA replaced in Ca release channel of SR, can’t stop excess release of Ca when they get stressed.
what does PSE stand for
pale, soft, exudative (wet, meat is losing fluid)
what happens if muscle pH drops before heat is dissipated?
protien is denatured, resulting in PSE pork
blast chilling can control
pse a bit.
when can PSE meat be detected by colour?
abt 90min PM
is 24h pH a good indicator for PSE?
no
where can you usually find PSE pork in the animal?
loin and ham muscles
RN gene
also called Hampshire effect bc common in that breed
- high glycogen at slaughter
- produces lots of lactic acid
- slowed rate of glycolysis
what happens when PSE meat protein gets denatured
loss of pigment (more pale)
loss of water and protien binding capacity - meat looks wet
fluid may drip from surface
what are the effects of protein denaturation
loss of protien solubility
affects the appearance and processing characteristics - can’t hold brine to process.
DFD pork - how do they get it?
animal survives stress, lots of lactate produced, makes muscles dark, firm to the touch, and dry bc increased water binding to protiens
is DF`D desirable?
trends to DFD for Japanese markets
what meat can you get from a PSS pig?
PSE, DFD, and normal. PSS is just a genetic condition, other genetics give PSE pork too
water absorption
ability to bind water from external environment - marinate
what is water holding capacity
- ability to bind/hold its water
- pH 10 - high WHC
- Ph 5 - low WHC
water associated with muscle fire escapes and leaves muscle
how does water holding capacity decrease? where does the water come from?
escapes between the fasciculi
what does WHC impact?
affects:
- processing yields (water loss during chilling)
- appearance of meat pre cooking
- behavoiur during cooking
- juiciness upon chewing
- processing of meat
what is water loss known as?
weep
drip/ drip loss
shrink
how does water holding capacity change with the pH declines postmortem
thick and thin filaments move together, decreases water space between myofilaments
myofibril shrinks
sarcoplasm volume increased
ATP depleted, no energy to hold water or maintain protein integrity
PSE pork drip loss
lower w greater water holding capacity
paleness of PSE pork relation to pH
inversely proportional
- lower pH, more paler meat
- caused by scattering light
effect of decrease in pH post mortem
protien denatured, myosin denatured, increased light scattering, increase paleness.
what is DFD in beef called?
dark cutting
what causes DFD in swine
PSS, stress, - transport exhaustion, hunger, fear, climatic stress, aggressive behaviour, any factor that depletes glycogen before killed.
what causes DFD in beef
glycogen depletion before death, inadequate lactic acid produced to lower the pH
how does glycogen get depleted?
more rapid in muscles w high ATPase, like fast twitch red
characteristics of DFD beef
dark colour. - muscle absorbs light, not reflect
dependent on pH
firm consistency.
high water holding capacity, very juicy.
sticky surface
prone to bacterial spoilage
DFD flavour in pork vs cows
good in pork, gross in cows
DFD carcasses discounted in beef. producers lose $200-250.
factors affecting dark cutting beef
- animal category
- nutritional status
- season of the year
- genetics
- temperament
- mixing of unfamiliar cattle
- large time
- fiber type
steer vs heifer vs bull DFD
lower incidence of DFD than heifers in steers bc of estrus cycles.
heifers in feedlots fed hormone regulators to stop cycling.
- bulls increased aggression
