Muscle to Meat Flashcards
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
Define rigor mortis
Muscle stiffening and loss of extensibility after death.
Name the 4 stages of Rigor Mortis
Delay - 6-12 hours post mortem
Onset - when ATP is exhausted
Completion
Resolution - proteolytic enzymes come into action
Name the pre-slaughter factors that can affect rigor mortis and how they affect it
Physical stress or disease
Depletes muscle glycogen store
Limited glycolysis => early RM and high muscle pH
Name the post-slaughter factors which affect rigor mortis and how they affect it
Excessive rate of chilling => cold shortening (severe 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
Name the endogenous proteases which play an important role in the resolution of rigor mortis, and what are they inhibited by
Calpains - inhibited by calpastatins
Cathepsins - inhibited by cystatin
What does increased calpastatin cause
Inhibition of calpains
Leads to tougher meat
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
Myofibrilar fragmentation index (MFI)
Taste or eating quality assessment
What are the positives and negatives of rapid chilling of meat
+ve = reduces microbial growth, evaporation and drip loss
-ve = risks cold shortening of the meat making it tough
What conditions are required for cold shortening to take place
Cooling below 10 degrees C before rigor mortis sets in
How to prevent cold shortening in beef/lamb and pork, and generally
Beef/lamb - not below 10 degrees in the first 10 hours
Pork - not below 10 degrees in the first 3 hours
Generally - electrical stimulation
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
Papain, bromelin, ficin
Marination
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
If acidification of meat is very rapid, what is the result
Pale soft exudate
If the acidification of meat is very slow, what is the result
Dark, firm, dry meat
What affects the water holding capacity of meat
pH - influences the extent that muscle proteins are charged, which is needed to hold onto water
How able is dark, firm, dry meat able to hold onto water vs pale soft exudate
DFD - Higher water holding capacity
PSE - lower, high drip loss of water
The paleness of meat is inversely proportional to pH - true or false
True
What gives meat its colour
Myoglobin
Bright red colour in presence of oxygen is synonymous with freshness
DFD pork and DCB dont “bloom” in presence of oxygen - true or false and why
True
High water holding capacity makes meat turgid and reduces oxygen penetration therefore no blooming
What is “blooming” when talking about meat colour
The bright red colour in presence of oxygen
What are the causes of boar taint
Sex steroids, like androsterone, deposited in intramuscular fat.
Give 4 ways that boar taint is managed/prevented
- Castration
- Avoiding overcrowding
- Slatted floors to reduce faecal contamination
- Early slaughter of males.
