PH21: Muscle to Meat Flashcards
Define meat, carcass, offal, viscera,
Meat: edible parts of domestic bovine, porcine, ovine, caprine animals, domestic solipeds, poultry, rabbits, farmed game and wild game
Carcass: means a body of an animal after slaughter and dressing.
Offal:
fresh meat other than that of the carcass including viscera and blood.
Viscera: the organs of the thoracic, abdominal and pelvic cavities, as well as trachea and oesophagus. In birds, the crop.
What are the main ante-mortem and post-mortem changes that affect rigour mortis?
Ante-mortem
- Physical stress/fatigue and rest pre-slaughter (DFD, PSE meat)
- Health Status
- Genetics, exercise training
Post-mortem
- Time/temperature chilling
- Hot boning
- Carcass Suspension
- Use of Electrical stimulation
What is Dark Firm Dry Meat?
Due to chronic stress pre-slaughter (24-48 hours)
Stress → Activation of the Hypothalamic-Pituitary-Adrenal Axis (HPA) → release of glucocorticoids → depletion of glycogen storage → inadequate lactic acid production → high ultimate pH in meat.
Not suitable for vacuum packagining or long-distance due to high pH > advanced spoilage
What is Pale Soft Exudative Meat?
Acute Stress → Activation of the Sympathetic-Adrenal-Medulla Axis (SAM) → release of adrenaline → increased glycogenolysis → high rate of lactic acid production → rapid pH fall in meat.
What is cold shortening?
When temperature is reduced to 0 – 15°C before the onset of rigor mortis (pH of meat to be below 6.2 before chilling) the sarcoplasmic reticulum cannot function properly and is unable to bind calcium in the sarcoplasm (high concentration of Ca2+ ions in myofibrils). Because there is still ATP left in the muscle, the muscle contracts at the maximum extent causing the filaments of actin-myosin to slide over one another eliminating the I-band of the sarcomere.
Pigs and poultry not affected
How do you prevent cold shortening?
Electrical stimulation
Pre-chilling techniques: temp not to fall below 10C within 12 hours from slaughter
Describe the process of electrical stimulation.
- Electrical current pulsed through meat
- Electrode in neck-nose earthed on overhead rail
- Stimulates muscle to contract = glycogen/ATP used up = ph falls
- Speeds up rigor
- Meat ages faster
- Not to apply to pork
What are the benefits to electrical stimulation?
- Accelerates tenderness/reduces ageing times,
- Reduces storage times and weight loss,
- Avoids cold and thaw shortening
- Allows rapid chilling,
- Promotes better flavour and colour
- Allows hot boning = rapid chilling of cuts
What is hot boning?
The process of feeding carcases from slaughterhall directly to the cutting plant for de-boning without being chilled to at least 7C
What are the advantages to hot boning? Disadvantages?
Advantages
- more efficient and quicker refrigeration of due to carcases being cut to smaller sizes
- Reduced evaporative weight loss
- Less dripping in vac-pack
- Better colour
Disadvantages
- Synchronize slaughter and boning
- Fat difficult to trim
- High hygiene standards
- Electrical stimulation required
What is Tender Strech Hanging?
Carcases suspended from the hook in obturator foramen causing the limb to relax, muscles do not shorten > tenderising
Suspend within 90 minutes of slaughter
Minimum of 24 hours
What is the water holding capacity?
At low pH, proteins change their electrostatic charge and fail to attract water
- DFD meat with high pH can become turgid
- PSE meat with low pH are exudative
With falling pH the fibrillar structure shrinks and water moves to the sarcoplasm
What determines meat tenderness?
- Amount and chemical nature of connective tissue/fat in the muscle
- The amount of shortening during rigor mortis
- The extent of meat conditioning and ageing
- Water holding capacity of meat
- Use of AM or PM injection of enzymes
What impacts the colour of fat?
Species
- Sheep = white and hard
- Pig = white and soft
- Horse = yellow and oily
- Cattle = cream/yellow and firm
Age - older = yellower
Feeding
