1
Q
Describe the conformation classification of lamb carcasses
A
- Visual appraisal of shape, taking into account carcass blockiness and fullness of legs
- No adjustment made for influence of fatness on overall shape
- 5 classes: EUROP
2
Q
Describe the fat cover classification of lamb carcasses
A
- Fat class determined by visual appraisal of external fat development
- 5 main classes from 1-5 as in beef, but classes 3 and 4 subdivided into L (leaner) and H (fatter)
3
Q
What are the requirements for pig carcass classification?
A
- Slaughterhouse slaughtering more than 200 clean pigs per week averaged over 12 month rolling period, must be registered with Pig Carcass Grading Scheme
- Regulations on carcass weighing, dressing and grading for lean meat content
- Grade marked on the carcass or documented
4
Q
What are the pig dressing requirements?
A
Dressed according to either EU or UK dressing specifications only
5
Q
Which parts must be removed from pig carcasses before weighing under EU specification?
A
- Tongue
- Bristles
- Hooves
- Genital organs
- Flare fat
- Kidney
- Diaphragm
6
Q
Which parts can be left in the pig carcass before weighing according to UK specification?
A
- Kidneys
- Flare fat
- Diaphragm
- Tongue may be left in or taken out
7
Q
What are the requirements regarding carcass weighing in pigs?
A
- Must be recorded as appear on actual scale display
- Dressed carcass weighed for its warm weight
- Ideal up to 45 mins after pig has been stuck
- Coefficients applied by FBO to account for different conditions of carcass (organs left in, time after sticking)
8
Q
Describe the grading of pig carcasses
A
- Assessment is estimate by measuring fat thickness over Longissimus dorsi, 6.5cm from dorsal midline at the last rib
- Measurement performed using optical probe
- Probe must be approved by legislation
- Result of probe assigned to grade on scale (SEUROP)
9
Q
Outline the recording of pig carcass grades
A
- Grade either marked directly on carcass or recorded at time of grading
- Carcasses destined for export uncut to EU member state marked with either appropriate letter from grading scale, or %age lean meat content
- For other cases, also need to keep record of letter or %age lean meat content
- Marking: use indelible, non-toxic, heat resistant ink
- Letters and numbers min 2cm high
10
Q
Outline the process of rigor in the conversion of muscle to meat
A
- Muscle contraction requires Ach, broken down by Achases to stop contraction
- Onset of rigor is variable
- May be less than 1 hour after death to several hours
- Marks the start of conversion from muscle to meat
- Depends on length of time ATP production can be sustained, ATP consumption rate
- Rigor occurs when ATP supply is exhausted and myosin heads remain irreversibly locked onto actin
11
Q
What leads to dark cutting beef?
A
- Condition associated with incomplete acidification
- Normally red meat has pH 5.5-5.6, DCB has pH >6.0 at 24 hours post slaughter
- Caused by depleted muscle glycogen in stressed animal, early onset of rigor mortis
12
Q
Describe the meat quality of dark cutting beef
A
- Darker than normal
- Able to retain structural water
- Prone to rapid spoilage
- Meat is tougher (actin-myosin complexes still present)
13
Q
What is Pale Soft Exudative meat?
A
- Primarily condition of pork
- Accelerated glycolysis after slaughter, rapid lactic acid build up
- pH lower than 6.0 less than 45 mins after slaughter
14
Q
Describe some characteristics of Pale Soft Exudative meat
A
- Rapid onset of rigor mortis
- Excessive drip loss from cut surface and cooking
- Paleness due to high reflectance from wet surface
15
Q
What condition is associated with Pale Soft Exudative meat?
A
- Mutation in ryanodine receptor (RYR1)
- Causes uncontrolled calcium release
- Leads to rapid glycolysis
16
Q
What is cold shortening of meat and how does it occur?
A
- Carcass shortening (can be as much as 1/3 of original length)
- Muscle cooled to below 10degreesC before rigor mortis
- Rapid chilling leads to accumulation of cytosolic Ca2+ causing muscle contraction and shortening
17
Q
How can cold shortening be prevented?
A
- Beef and lamb not chilled below 10degreesC in first 10 hours
- Pork not chilled below 10degreesC in first 3 hours
18
Q
What is boar taint?
A
Unpleasant urine like odour of entire boards and a minority of pigs
19
Q
What is boar taint caused by?
A
- Sex steroids e.g. androstenon deposited in intramuscular fat
- Microbial breakdown of tryptophan in gut to skatole and indole
- Absorbed and if not broken down effectively is deposited in adipose tissues
20
Q
How can boar taint be prevented?
A
- Castration in male piglets
- Avoid overcrowding
- Use slatted floors to reduce faecal contamination
- Earlier slaughter of boars
21
Q
What properties of meat can be used to assess meat quality?
A
- Water holding capacity
- Colour and paleness
- Succulence/juiciness (subjective trait)
- Tenderness
22
Q
How can meat tenderness be improved?
A
- Conditioning/ageing
- Electrical stimulation
- Hip suspension
- Mincing
- Use of proteases
- Marination
23
Q
Explain the principle water holding capacity of meat
A
- pH of meat influences extent of muscle proteins that are charged
- Is necessary to attract and hold dissociated forms of water
- Most proteins in meat lose their charge between pH 5.1-5.5, close to ultimate pH of meat
- In this range, muscle releases water
24
Q
Explain the role of colour and paleness in the assessment of meat quality
A
- Colour influenced by presence of myoglobin
- Bright red colour in presence of oxygen (blooming) is synonymous with freshness
- Different muscles have different colour (higher proportion of myoglobin in slow vs fast muscle)
25
Explain the role of succulence/juiciness in the assessment of meat quality
- Succulence is an eating quality, often related to level of fat and moisture in cooked meat
- Excessively lean carcass confers less juicy meat
- tenderness and succulence can be improved by increasing the amount of fat present
26
How can tenderness of meat be assessed?
- Objective (laboratory based) methods e.g. measuring shear force and myofibrillar fragmentation index (MFI)
- Subjective methods e.g. taste or eating quality assessment
27
What is meat tenderness dependent on?
- Afe of animal (increased collagenous tissue with age, increased intermolecular collagen bonds)
- Type of muscle (white less vs red more tender)
- Amount of sarcomeric shortening during rigor mortis
- Meat maturation (longer = more tender)
28
Outline the process of meat conditioning/ageing
- Allows proteolysis to occur leading to more tender meat, more complex flavours and aromas
- Widely used
- Storage must be under right conditions
29
What are some problems that may occur during meat conditioning/ageing?
- Excessive dehydration of carcass
- Mould overgrowth
- Development of rancid aromas
- Potential overgrowth of pathogenic microorganisms
30
Outline the process of electrical stimulation
- Electric current transmitted through carcass of animal that has been freshly slaughtered and eviscerated (up to 1 hour after exsanguination)
- Can be low (up to 100volts) or high current (100-500volts)
- Fast-tracks post-mortem glycolysis, and so hastens onset and resolution of rigor mortis
31
What is the purpose of electrical stimulation in meat processing?
- Hastens onset and resolution of rigor mortis
- Shortens processing time and labour
- Improves meat tenderness and other meat quality traits
32
What are some potential disadvantages of electrical stimulation in meat processing?
- Rapid chilling required to minimise weight loss and microbial growth
- May have negative impact on some meat quality traits e.g. colour stability and water holding capacity in some animals
33
Outline the role of hip suspension in improving meat quality
- Traditionally hung by gastrocnemius
- But suspension from obturator foramen means gluteal muscles stretched-
- Reduces likelihood of problems such as cold shortening
- Back quarter of carcass has most expensive meat cuts
34
Give examples of proteases that can be used to improve meat quality
- Papain in papaya
- Bromelin in pineapple skins
- Ficin in fig trees
35
Give examples of marination ingredients that improve meat quality
- NaCl
- Polyphsophate
- CaCl2
- Bicarbonate
VPH
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