Muscle to Meat quality Flashcards
(119 cards)
1
Q
Talk through the 8 steps leading to a muscle contraction:
A
- There is initiation, either as a voluntary activity from the brain or reflex from the spinal cord.
- A motor neuron in the ventral horn of the spinal cord is activated, and an action potential passes out in a ventral root of the spinal cord.
- The axon branches to supply a number of muscle fibres called a motor unit, and the action potential is conveyed to a motor end plate on each muscle fibre.
- at the motor end plate, the action potential causes the release of Ach into the synaptic cleft on the surface of the muscle fibre.
- Ach causes the electrical resting potential under the motor end plate to change, and this then initiates an action potential which passes in both directions along the surface of the muscle fibre.
- at the opening of each transverse tubule onto the muscle fibre surface, the action potential spreads inside the muscle fibre.
- at each point, where a transverse tubule touches part of the sarcoplasmic reticulum, it causes the sarcoplasmic reticulum to release calcium ions.
- the calcium ions result in movement of troponin and tropomyosin on their thin filaments, and this enables the myosin molecule heads to ‘grab and swivel’ their way along the thin filament. this is the driving force of muscle contraction.
2
Q
Name the 4 events which turns of muscle contraction?
A
- Ach at neuromuscular junction is broken down by acetylcholinesterase, and this terminates the stream of action potentials along the muscle fibre surface.
- The SR stops releasing calcium ions and requesters calcium that has been released
- in the absence of calcium, a change in the configuration of troponin and tropomyosin occurs and blocks the action of myosin heads, and contraction ceases.
- In the living animal, an external stretching force e.g. gravity or an antagonistic muscle, pulls the muscle back to its original length.
3
Q
What is the sarcomere?
A
The contractile unit
4
Q
What is the M band?
A
It dissects the sarcomere
5
Q
What is the A band?
A
The thick band which contains thick and thin filaments.
6
Q
what is the H zone?
A
Only thick filaments (myosin)
7
Q
What is the I band?
A
Thin filaments only (actin)
8
Q
How does the cross-strike occur?
A
Calcium binds to tropomyosin C and myosin releases phsophate causing the cross strike.
ATP binds to the myosin head to release the head.
9
Q
What returns the myosin heads to the normal relaxed state?
A
Magnesium complex and ATP
10
Q
When does rigor mortis set in?
A
Variable - can be 1hr to several hours after death?
11
Q
What can rigor mortis be used to determine?
A
Whether death occurred at PM or in the abattoir
12
Q
What does the onset of rigor mortis mark?
A
The conversion of muscle to meat
13
Q
What 2 things determine the onset of rigor mortis?
A
- How long the ATP production can be sustained
2. The consumption rate of ATP
14
Q
What causes the rigor mortis?
A
There is a lack of ATP from exhaustion, therefore myosin heads remain irreversibly locked onto actin, leading to a rigid structure.
15
Q
What are the three phases of rigor mortis?
A
- delay phase (6-12 hours PM)
- Onset phase
- Resolution phase
16
Q
What is the delay phase?
A
- 6-12hr PM
- not enough phosphate to re-phosphorylase ADP to ATP therefore halting muscle ability to breakdown cross bridges.
17
Q
What is the onset phase?
A
Muscle inextensible - maximum tension. all cross bridges form during rigor, not 20% as with normal muscle function. cross bridge affinity and tension at maximum.
18
Q
What is the resolution phase?
A
Muscle tension decreases, proteolytic degradation, not the breakdown of actin myosin cross bridges.
19
Q
Name 3 factors used to assess meat quality?
A
- water holding capacity
- colour and paleness
- succulence/ juciness (subjective trait)
20
Q
What controls the water holding capacity of meat?
A
The pH of the meat influences muscle protein charge which is needed to attract and hold the dissociated form of water. Most proteins in meat lose their charge around pH 5.1-5.5 which is the ultimate pH of meat. In this range, proteins lose water.
21
Q
What is the colour of meat influenced by?
A
Myglobin.
22
Q
What does bright red meat indicate?
A
Oxygen (blooming) is synonymous with freshness.
23
Q
Why do different muscles have different colours?
A
Because there is more myoglobin in slow muscle than fast muscle.
24
Q
What kind of carcass confers less juicy meat?
A
A lean carcass.
25
What needs to be increased to improve succulence and juciness?
Fat.
26
name two conditions which can affect meat quality?
Dark cutting meat and Pale Soft Exudative.
27
What is dark cutting meat?
Meat that is subdued to stress before slaughter
28
What causes pale soft exudative?
Stress in the animal.
29
How can tenderness be measured objectively?
Shear force and the myofibrillar fragmentation index (MFI).
30
Name 4 features that affect tenderness of meat?
1. age of the animal (collagenous tissues increase with age and more intermolecular collagen bonds).
2. Kind of muscle - white muscle like longissimus forsi, less tender than red muscle.
3. Amount of sarcomeric shortening during rigor mortis - the faster the rate of glycolysis, the greater the likelihood of sarcomere shortening.
4. meat maturation - longer the time left in chilling room, more tender the meat (proteolysis).
31
What is the meat maturation process called?
Meat ageing or conditioning.
32
Name two technical methods which can increase the tenderisation of meat.
1. Hanging methods
| 2. electrical stimulation
33
What can the storage conditions following slaughter influence?
meat tenderness and the flavours and aromas.
34
Name 4 problems that can be associated with storage of meat?
1. excessive dehydration of the carcass.
2. Overgrowing of moulds
3. development of rancid aromas
4. overgrowing of pathogenic organisms
35
Name 3 advantages of drying meat on the bone?
1. specific flavour development (not with vacuum)as a result of oxidation
2. desired by some customers
3. enables presentation of traditional product
36
Name 2 disadvantages of drying on the bone?
1. high weight loss (evaporation and trimming)
| 2. comparatively high demand for chiller space and hence increased energy loss.
37
Name 2 advantages of vacuum packaging meat on the bone?
1. enables traditional presentation of product
| 2. lower weight loss than dry-ageing loss
38
Name 1 disadvantage of vacuum drying on the bone?
May need to use bone-guard to prevent puncturing, particularly with lamb
39
Name 3 advantages of drying boneless?
1. specific flavour development
2. desired by some customers
3. lean can be trimmed from fresh bones
40
Name 2 diasadvantages of drying boneless?
High evaporative weight loss
high demand for chiller space (meat needs to be on racks).
41
Name 3 advantages of boneless vacuum drying meat?
1. lean can be trimmed from fresh bones
2. minimised weight loss
3. less space requirements
42
What is a major intervention used in meat industry to improve meat quality traits?
ES - electrical stimulation
43
Name 2 advantages of chilling carcasses quickly?
Less weight loss and microbial growth.
44
What does ES do?
It fast tracks post mortem glycolysis therefore fastens the onset of rigor mortis, reducing processing time and labour. improves meat tenderness.
45
Name 2 disadvantages of ES in some meats?
Affects colour stability and water holding capacity in some animals.
46
When is ES applied?
After exsanguination, within 1 hour of slaughter.
47
What are the low and high currents?
Low = 100V
| High current= 100-500V
48
What muscle does hip suspension use to hang?
Gastrocnemius
49
what will hanging the carcass from the obturator foramen prevent?
the muscles in the gluteal area suffering from cold shortening because the gluteal muscles will be stretched.
50
Why is tenderness in the hind end important?
Because the back quarter has the most expensive cuts.
51
Name another suspension method?
Achiles tendon
52
Name 3 other methods of tenderness improving?
1. mechanical methods - mincing
2. use of proteases - papain (papya), bromelin (pineapple skins) and ficin (fig tree)
3. marination - use of NaCl, phosphorylate, CaCl2 and bicarbonate.
53
What is meat quality?
About compositional quality e.g. lean to non-lean, such as fat ration, physical properties and eating qualities
54
What is carcass quality?
Conformation, fatness and weight
55
Name 4 conditions which can affect meat quality?
1. Dark cutting beef (DCB)/ Dark Firm and Dry meant (DFD)
2. Pale soft exudative (PSE)
3. Cold shortening
4. Boar taint
56
What causes DCB?
Incomplete acidification. Red meat reaches 5.5-5.6 normally, DCB will reach 6.0 at 24 hours post slaughter
57
What is the reason for DCB?
Depleted muscle glycogen in stressed animals, with early onset of rigor mortis.
58
What is the feature of dark cutting beef?
It is darker in colour and retains water therefore is prone to spoilage. The meat is also tougher as actin-myosin complex is still present.
59
Which meat experiences PSE?
Pork
60
What causes PSE and why does it happen?
Rapid glycolysis after slaughter with rapid lactic acid build-up. If the pH is less than 6 in 45 mins, the carcass will be affected with PSE.
61
Name 3 characteristic conditions of PSE?
1. rapid onset of rigor mortis
2. excessive drip loss from cut surface and cooking
3. paleness due to high reflectance from wet surface.
62
What mutation is PSE associated with and why?
Mutation of the ryanodine receptor (RYR1) leading to uncontrolled calcium release, leading to rapid glycolysis (glucose--> pyruvate)
63
Where do you look on carcass for PSE?
Look at 10th/11th rib
| - look at colour, firmness and wateriness.
64
When does Cold shortening occur?
when the carcass is cooled to <10 C before rigor mortis to reduce water loss and microbial developmemt
65
What happens with CS?
Accumulation of cytosolic calcium meaning carcass shortens as much as 1/3 original length
66
How to prevent CS?
Beef and lamb should not be chilled below 10c for the first 10 hours. Pork should not be chilled <10C in the first 3 hours.
67
What is boar-taint?
An unpleasant urine-like odour in entire boars.
68
What causes boar taint?
Sex steroids, andosterone depositied in IM fat.
Microbial breakdown of tryptophan in gut to skatole and indole which is absorbed and if not broken down effectively (as in boars), deposited in adipose tissues.
69
Name 4 methods to reduce boar taint?
1. Castrate males
2. Less overcrowding
3. Not slatted floors to reduce faecal contamination
4. Kill boars at a young age.
70
Name 3 factors which could affect carcass quality?
Breed, age and sex.
71
What does MLCSL mean?
Meat and livestock Commercial Services Limited
72
Who tares the scales for weighing carcasses?
MLCSL
73
Who classifies pig carcasses?
Meat and Livestock Commercial Services Limited
74
Which plants need to classifiy pig carcasses?
Processing over 200 pigs a week.
75
How is back fat measured?
optical probe
76
What weight is recorded for cattle?
hot weight
77
Is optical probe used for cattle?
No because shape of carcass can vary greatly.
78
How is conformation and fatness assessed?
On a scale of 1-5
79
Do sheep need to be classified like pigs and cattle?
There is no mandatory requirement in the EU for sheep to be classified like pigs and cattle.
80
How are sheep assessed?
Visually
81
What happens to all of the information?
Passed back to the farmer to make sure he gets the best return possible.
82
What is the BCC?
Beef Carcass Classification Scheme
83
Who is required to register and classify carcasses under the BCC scheme?
Abattoirs which slaughter >75 cows a week.
84
What is the purpose of the BCC?
To make sure adult cow carcasses are uniformly classified and producers recieve fair payment based on Community EU grading.
85
How are cattle classified?
In accordance with the 'Community scale'
86
Who carries out classification?
People who are licensed.
87
Which three specifications must beef carcases be dressed in line with?
1. standard specification
2. EC reference specification
3. UK specification
88
What needs to be considered for BCC?
Conformation and fat cover.
89
What are the classes of shape and flesh coverage of the carcass?
E, U, R, O, P
```
E = excellent and no defects
U, O, P = 3 essential parts that are not of homogenous nature will be placed in the class that applied to two of the three parts.
```
90
What are the two further divided categories?
Upper and lower.
91
What must be given first when describing a carcass?
The conformation class must be given before the fat class.
92
How is fat measured on beef?
1-5 scale on visial appraisal.
5 = very fat.
4 and 5 subdivided into Leaner (L) and fatter (H) bands.
93
When was the EUROP scale introduced and why?
1970s, for uniform classification throughout Europe.
Producers appraised for supplying a carcass that is in high demand.
94
What 3 things are looked for in sheep on visual assessment?
Shape, blockiness and fullness of legs.
95
how is fat assessed?
Visual appearance on a scale of 1-5.
| £-4 subdivided into leaner (L) and fatter (F).
96
What does this information provide to farmers?
Spot ailments, monitor progress and adjust feed regimes.
97
What is the ideal weight and size that 85% market wants?
R3L
98
What is EBLEX?
English Beef and Lamb Executive.
99
Who must be registered with the Pig Carcass Grading System?
slaughterhouses that slaughter more than 200 clean pigs per week (over a 12 month period).
100
What are clean pigs?
Pigs which have not been used for breeding.
101
What 3 rules must registered slaughterhouses comply with/?
1. dressing carcasses
2. weighing carcasses
3. grading carcasses for lean meat - then marked on the carcass and documented.
102
According to EU specification, before weight the carcass, name 7 parts that have to be removed:
1. Tongue
2. Bristles
3. Hooves
4. Genital organs
5. Flare fat
6. Kidney
7. Diaphragm
103
According to UK specification, before weighing the carcass, which 3 parts can be left in the carcass?
1. kidney
2. flare fat
3. diaphragm
The tongue may be left in or taken out.
104
When must weighing take place with pigs?
Must be the warm weight of the carcass, not more than 45 minutes after the pig has been stuck.
105
What else does the Pig Carcass Grading Scheme enforce?
that the grading for lean meat content of the carcass is also assessed.
106
How is the lean meat content assessed?
Estimate the fat thickness over the longissimus dorsi, 6.5cm from dorsal mid-line of the last rib using an optical probe.
107
What is grade S?
>60%
108
What is grade E?
55-60%
109
What is grade U?
50-55%
110
What is R?
45-50%
111
What is O?
40-45%
112
What is P?
<40%
113
Where should carcass grades go?
either be recorded on the carcass or recorded.
114
What must carcasses destined to another EU member state, uncut, be marked with?
1. the letter from the grading scale
| 2. % lean content
115
What are the 2 requirements for other carcasses?
1. mark the carcass with the appropriate letter from the grading scale or with the % lean meat content
2. keep a record of the letter from the grading scale above or % lean meat content.
116
What are the requirements if the carcass is marked?
Indellible, non-toxic, heat-resistant ink.
| The letters and numbers must be at least 2cm high.
117
If carcass weighed with kidneys, flare and diaphragm, what adjustments must be made?
Carcass up to 56kg - reduce by 0.7kg
carcass 56.5 - 74.5kg - reduce by 1.1kg
Carcass of 74.6kg and over, reduce by 1.6kg
118
Weighed with tongue in?
Reduce by 0.3kg
119
Weighed more than 45 mins after being stuck?
Reduce by 0.1% for each additional 15 minutes that passes or part thereof.
