Muscle to Meat

Muscle fibers are repetatitve functional units called

Sarcomeres

Sarcomeres are composed of many parallel and overlapping __ and __ fibers

Actin (thin), myosin (thick)

What molecule is required for cross bridge cycling/ continuing muscle contractions?

ATP

Why do bodies become rigid (rigor mortis) shortly after death?

No ATP available to release the muscle contractions

What can creatine phosphate do for muscle fibers?

Excess ATP can transfer energy to this molecule. When muscle contractions begin, this molecule can move the muscle fibers for about 15 seconds before another energy source is needed

What is the anaerobic method of ATP production?

Glycolysis

What is the general process of glycolysis?

Glucose → ATP + pyruvic acid (this can become lactic acid in low oxygen environments)

What is the aerobic method of ATP production?

__ Respiration

How does aerobic respiration work (generally)?

Glucose + O2 → CO2 + H20 + ATP

What is the most efficient method of ATP production in animals?

Aerobic respiration

What proportion of ATP is produced via aerobic respiration?

~95%

What physiological changes (that are kinda obvious) occur when an animal is slaughtered?

Circulation stops and oxygen intake stops

When an animal is slaughtered and circualtion stops, what are the first few physiological steps that happen next?

Aerobic respiration stops → anaerobic ATP production and ATP is consumed faster than produced.

Lactic acid builds up, acidifing muscles (~pH 5.5)

Enzymes activated by the acidic environment → changes in flavor

When proteolysis begins after an animal is slaughtered, what are the next physiological steps?

Myofibrillar proteins are broken down (Z plates) and release aminoa cids and peptids

Sugars are reduced and used in reactions; flavor changes again and resulting increased tenderness

What is the process called that meat goes through from the moment circualtion stops until the muscel/meat becomes tender again?

Conditioning

What are pre-mortem factors of meat quality?

Breed, genetics, energy level of diet, type of muscle, stress level

What qualities will the carcass have if energy level of diet is too low?

Dark, firm, and dry

What qualities will the carcass have if energy level of diet is too high?

Fat in muscles

What post-mortem factors imapct meat quality?

Storage conditions and processing conditions

What storage conditions can impact meat quality?

Temperature, humidity, airflow, length of time aging

What processing conditions can impact meat quality?

Tenderizing techniques and speed

How can dark, firm, dry meat (DFD) be caused pre-mortem?

Chronic stress (long-term condition)

Associated with long transport times, unloading/loading issues, and periods without food

What pH can our Dark firm dry (DFD) meat become within 12-24 hours?

pH >6

Describe how pre-mortem lactic acid build up leads to dark firm dry meat.

→ normal drop in pH prevented → proteins stay intact → water-holding capacity intact → intracellualr water reflects less light

How can pale, soft, exudative meat (PSE) be caused pre-mortem?

Acute stress (short term condition)

What species are more prone to PSE meat defects?

Poultry and pigs

How can pale, soft, exudative meat (PSE) be caused post-mortem?

pH 45 min post mortem as low as 4 (too fast of a pH drop)

What physiologically happens if glycogen stores are depleted faster after slaughter (while carcass is hot)?

Low pH and high temp denatures proteins quickly → decreased water holding capacity → increased exudate on cut surface → meat becomes pale

Why does it matter if meat is PSE?

Difficult to cook, potential condemnation due to lack of consumer interest

Consumers eat with their eyes! (Lost revenue)

Why does it matter if meat is DFD?

Reduced shelf life (more microbes grow more easily due to high water retention and less spoialge competing bacteria that rely on glycogen)

Not as good of flavor (Proteins can’t break down)

Consumers eat with their eyes!

What is the most important thing that can be done to limit/prevent DFD/PSE meat and improve tenderness and quality?

Gentle/quiet handling

How can we limit/prevent DFD/PSE meat and improve tenderness and quality?

Ramp usage, no electical goads at alirage/loading, access to food/water, breed stress resistance, reduce transport times where possible, do not mix animals, spray pigs with water to keep cool, gentle and quiet handling

What are the benefits of speeding up the chilling process?

reduces weight loss and reduces bacteria growth

What are the cons of speeding up the chilling process?

cold shortening (makes tough)

When is cold shortening more likely to occur?

When a carcass is dropped below 10C before rigor mortis sets in

How can we combat cold shortening in cattle and lamb carcasses?

Chill to 12 C for the first 10 hours after slaughtered, then drop temp to 7 C or less

What species are we less concerned with cold shortening in?

Poultry and pigs

What type of chilling is this?

hip suspension

What are the benefits of hip suspension chilling?

More stretching improves tenderness of some of the more expensive muscles around rump

What is a side effect of hanging a carcass from the Achilles tendon?

More stretching leads to increased tenderness of rump muscles, leading to potential deformation of prime cuts

Where is the suspension in hip suspension chilling?

through the obturator foramen

Where are carcasses typically suspended?

through the Achilles’ tendon

What are the advantages of Hot boning? (4)

more efficient and quicker refrigeration of meat, reduced evaporative weight loss (up to 1%), less dripping in vac pack and better color

What are the disadvantages of Hot boning? (4)

synchronize slaughter and boning, fat difficult to trim, high hygiene standards, electrical stimulation required

What does electrical stimulation do to the carcass?

used to speed rigor, meat ages faster, decreased pH

Why does electrical stimulation decrease the pH?

stimulates muscle to contract = glycogen/ATP used up

How do you perform electrical stimulation to a carcass?

electrode in neck - earthed(grounded) on overhead rail - also use higher voltage later in the process (can be more effective)