Slaughter 4 Flashcards
Describe the conformation classification of lamb carcasses
- 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
Describe the fat cover classification of lamb carcasses
- 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)
What are the requirements for pig carcass classification?
- 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
What are the pig dressing requirements?
Dressed according to either EU or UK dressing specifications only
Which parts must be removed from pig carcasses before weighing under EU specification?
- Tongue
- Bristles
- Hooves
- Genital organs
- Flare fat
- Kidney
- Diaphragm
Which parts can be left in the pig carcass before weighing according to UK specification?
- Kidneys
- Flare fat
- Diaphragm
- Tongue may be left in or taken out
What are the requirements regarding carcass weighing in pigs?
- 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)
Describe the grading of pig carcasses
- 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)
Outline the recording of pig carcass grades
- 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
Outline the process of rigor in the conversion of muscle to meat
- 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
What leads to dark cutting beef?
- 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
Describe the meat quality of dark cutting beef
- Darker than normal
- Able to retain structural water
- Prone to rapid spoilage
- Meat is tougher (actin-myosin complexes still present)
What is Pale Soft Exudative meat?
- Primarily condition of pork
- Accelerated glycolysis after slaughter, rapid lactic acid build up
- pH lower than 6.0 less than 45 mins after slaughter
Describe some characteristics of Pale Soft Exudative meat
- Rapid onset of rigor mortis
- Excessive drip loss from cut surface and cooking
- Paleness due to high reflectance from wet surface
What condition is associated with Pale Soft Exudative meat?
- Mutation in ryanodine receptor (RYR1)
- Causes uncontrolled calcium release
- Leads to rapid glycolysis
What is cold shortening of meat and how does it occur?
- 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
How can cold shortening be prevented?
- Beef and lamb not chilled below 10degreesC in first 10 hours
- Pork not chilled below 10degreesC in first 3 hours
What is boar taint?
Unpleasant urine like odour of entire boards and a minority of pigs
What is boar taint caused by?
- 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
How can boar taint be prevented?
- Castration in male piglets
- Avoid overcrowding
- Use slatted floors to reduce faecal contamination
- Earlier slaughter of boars
What properties of meat can be used to assess meat quality?
- Water holding capacity
- Colour and paleness
- Succulence/juiciness (subjective trait)
- Tenderness
How can meat tenderness be improved?
- Conditioning/ageing
- Electrical stimulation
- Hip suspension
- Mincing
- Use of proteases
- Marination
Explain the principle water holding capacity of meat
- 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
Explain the role of colour and paleness in the assessment of meat quality
- 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)
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
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
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)
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
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
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
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
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
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
Give examples of proteases that can be used to improve meat quality
- Papain in papaya
- Bromelin in pineapple skins
- Ficin in fig trees
Give examples of marination ingredients that improve meat quality
- NaCl
- Polyphsophate
- CaCl2
- Bicarbonate
