Muscle to meat Flashcards
What theory is used to describe muscle contraction and relaxation
sliding filament theory
what is the sliding filament theory supported by
molecular structure and interactions
myofribillar proteins
describe myosin structure
large elongated
two regions
describe the head region of myosin
globular
-pear shaped
-functional: actin binding site
describe the tail region of myosin
rod
responsible for filament
name of complex that resembles a string or pearls
actin-troponin-tropomyosin complex
what is the Tn-C of the complex
caclium binding site
what is the Tn-T
binding site with tropomysin
what is the Tn-I of the complex
Inhibits ATP-ase
what does the binding of calcium do to the complex
reveals a binding site for myosin
describe the process of the complex
-Calcium ion binds to tropomyosin which exposes the myosin binding site on actin
-ATP binds to the myosin head
-mysoin detaches from actin
-ATP hydrolysis occurs which activate myosin head
-tropoyosin bind to site on actin and phophate disociates strengthening the bond between actin and myosin
-ADP disociates and myosin contracts pulling actin
first step of muscle contraction/relaxtion event
nerve impulse transmitted via T-Tubules
what are T-tubules
blanket that surrounds the myofibrils
describe calcium’s role in contraction (steps 2 and 3 of the sequence)
sarcoplasmic reticulum releases Ca2+
Ca2+ binds to Tn-C
What happens to the troponin complex after calcium is bound
changes position to reveal myosin binding site
what is required for actin-myosin interaction
ATP
why can muscle contract after death
ATP is still present in the muscle which can cause contraction
Which respiratory cycles are not supported after slaughter
oxidative phosphorylation
After death what does the muscle use for energy
glycogen and creatine phosphate stored in the muscle
what does glycolysis without oxygen generate
lactic acid
what does the production of lactic acid do to the meat
drop pH
what happens once all the energy stores have been used
muscles stay contracted = maximum toughness
process of glycogen to lactate
glycogen -> glucose-> pyruvate-> lactate
what is the ultimate pH
final pH the tissue will reach
at what pH is muscle near at death
7
what is the rejection of the ultimate pH of lamb
<5.5
what is the rejection of the ultimate pH of beef
> 5.8
characteristics of meat at a high pH
DFD
dark firm dry
characteristics of meat at low pH
PSE
pale soft exudative
what can cause a dark color in meat
stress before death
rate and extent of pH fall is affect by what
intial glycogen in muscle
pre-slaughter stress
muscle fibre type
temperture
what is rigor mortis
stiffness of death
when does rigor mortis occur
when all ATP is depleted
what happens during rigor mortis
irreversible cross-bridges form between actin and myosin
another name for pre-rigor meat
hot boned
what is hot boned beef
when carcass is boned while warm and in pre-rigor state
why is hot boned beef used for production of burgers and sausages
-it is often dark in color becuase endogenous enzymes have not been able to relax the meat
-it has high WHC
-lower eating quality
how can toughness of rigor be resolved
aging
how does aging resolve rigor
proteolytic enzymes hydrolyse myofilaments which caused release between actin and myosin= relaxtion
types of proteolytic enzymes that resolve rigor
calpains
cathepsins
describe calpains
require Ca2+ and high pH
-disrupts Z lines
what pH are cathepsins active at
lower pH
what is cold shortenign
excess contraction/shortening
when does cold shortening occur
when pre-rigor meat is chilled too quickly (between 10 and 0C)
effect on mea tof cold shrotenign
excess drip
low WHC
extremely tough
mechanism of cold shortening
at low temp muscle is still alive with plenty of ATP and ph>6
-sarcoplasmic reticulum becomes leaky and Ca2+ leaks out to trigger contraction
-calcium pump can no longer remove Ca2+ and muscle remains contracted
why does DFD meat appear darker
light does not reflect off dry meat as well
why does PSE meat have a light appearance
more light reflects or watery surfaces
what causes the sfotness of PSE meat
protein denaturation at the low pH
what is accelerated aging and conditioning of meat
treatment that allows for control over time and temp to reach rigor
advantages to accelerated aging and conditioning
more consistent and tender meat
avoids cold shortening
what does accerlerated aging and condiitoning involve
the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime
what does accelerated aging and conditioning involve
the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime
what does accelerated aging and conditioning involve
the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime
what does accelerated aging and conditioning induce
induces rapid ATP hydrolysis
-muscle enter rigor sooner so it can be chilled without shortening
what does accelerated aging and conditioning involve?
the electrical stimulus of the carcass
-controlling the cooling rate through strict temp and time regime
what does accelerated aging and conditioning induce
induces rapid ATP hydrolysis
-muscle enters rigor sooner so it can be chilled without shortening
