2- Muscle to meat Flashcards
Name the 3 sources of ATP production
Oxidative phosphorylation of ADP in mitochondria (Immediate source)
Direct phosphorylation of ADP to ATP by creating phosphate (Intermediate source)
Anaerobic glycolysis (Ultimate source)
How many ATP molecules are produced per glucose molecule in oxidative phosphorylation?
36
What products are made from anaerobic glycolysis?
2 ATP per glucose & Lactic acid
How many ATP molecules are produced in direct phosphorylation
1 ATP per CP molecule
What is exsanguination?
bleeding out
After circulatory failure what happens prior to rigorous mortis?
PM glycolysis
- remaining energy is used to allow muscle extensibility - acts like live muscle
Once ATP is depleted = Onsent of rigor mortis
Define rigor mortis
Muscle stiffening & loss of extensibility after death
Name the 4 stages of rigor mortis
Delay, Onsent, Completion and resolution
Why does rigor result in a rigid muscle structure?
Supply of ATP is exhausted, myosin heads remain irreversibly locked onto the actin = rigid structure
List pre-slaughter factors that affect rigor mortis and they do affect it
Physical stress or disease- depletes muscle glycogen store –> depletes muscle glycogen store
Limited glycolysis–> early RM and high muscle pH
T/F Ca-ATPase pump is inactivated rapidly at low temperature causing increase of calcium ions
True
What are the 2 endogenous proteases which play an important role in resolution of rigor ? & What inhibits them?
Calpains = inhibited by calpastatin
Cathepsins = Inhibited by cystatin
These soften the meat
breeds which have more calpastain (like Brahman cattle) have tougher meat- as inhibits the enzymes that cause muscle tension to decrease
Certain breads have more calpastatin than other what does this mean in regards to the meat tenderness?
Tough as it is inhibiting proteases (calpains)
What contributes to the meaty flavour of meats?
During ageing proteins/fats are broken down
Glutamic acid
Inosinic acid
What is cold shortening?
Rapid chilling of meat
Reduces microbial growth, evaporation, drip loss but risks shortening of muscle
Occurs when below 10 degrees
Tough on cooking
What process prevents cold shortening?
Electrical stimulation = within 1hr of slaughter
Causes muscle contraction, accelerates pH fall, depletes ATP & induces early rigor
What causes acidification of meat after death
Lactic acid accumulates after death causing acidification
The speed of acidification affects quality of meat
T/F If acidification is very slow gives pale, soft & exudative meat (PSE)
False = this would be rapid acidification
Which meat mentioned below is caused by chronic stress > high ultimate pH leading to proteins not denaturing & after being held by proteins?
Pale soft exudative (PSE) meat
or
Dark Firm dry (DFD) meat
Dark Firm Dry Meat
pH of 5.2 is called a what in meat?
Isoelectric point pH when +Ve and -ve chargers are always equal and net charge is zero
What is boar taint?
Unpleasant urine like odour of entire boars
Cause by sex steroids deposited in intramuscular fat
In pig carcass classification, Price depends on what 3 things?
Weight, Age & P2 backfat
Name the main steps of conversion of muscle to meat
Muscle
Slaughter
blood supply ceases
Remaining energy used to allow muscle extensibility
When energy is depleted–> rigor mortis
Without oxygen, glucose–> lactic acid
pH 5.4-5.7
Meat
Name the post-slaughter factors which affect rigor mortis and how they affect it
excessive rate of chilling –> cold shortening –> tough meat
What type of muscle is most prone to pale soft exudate and which animals do NOT have these
Fast glycolytic muscles
Cattle and horses- not prone to PSE
What is a risk of prolonged ageing of meat
Can cause fat oxidation –> rancid odour
Name the 3 different ways tenderness can be expressed
Shear force
Myofibrillar fragmentation index (MFI)
Taste or eating quality assessment
What conditions are required for cold shortening to take place
Cooling below 10 degrees C before rigor mortis sets in
What can electrical stimulation induce in pork
pale soft exudate
Apart from electrical stimulation name other methods to improve tenderness
stretching the muscles- hip suspension
needle/ blade tenderisation
Marination
papain, bromelin, ficin
Name some properties of meat quality
Dark cutting beef/ Dark firm dry pork = not good
Pale soft exudate = bad
Water holding capacity
Succulence
Colour and paleness - paleness = bad
Boar taint = bad
What affects the water holding capacity of meat
pH of meat
How able is dark, firm, dry meat able to hold onto water vs pale soft exudate
DFD meat has higher water holding capcity
PSE- has higher drip loss so reduced water holding capacity
What gives meat its colour
myoglobin
T/F The paleness of meat is inversely proportional to pH
True
T/F DFD pork and DCB dont “bloom” in presence of oxygen
True - because they have a high water holding capacity which makes the meat turgid and reduces oxygen penetration, so no blooming - so the meat becomes dark
List 4 ways that boar taint is managed/ prevented
castration
avoiding overcrowding
slatted floors to reduce faecal contamination
early slaughter of males
