Meat Science & Hygiene

Question 1

What countries are responsible for most of the meat production in the world?

Answer 1

USA - beef

CHINA - poultry and pork

Question 2

What are the 3 major components of protein in meat?

Answer 2

1. stromal - connective tissue support
2. sarcoplastic - aerobic and anaerobic metabolic enzymes, myoglobins
3. myofiber - contractile myosin and actin

Question 3

What role do stromal protein and myosin have in meat?

Answer 3

STROMAL = toughness vs. tenderness

MYOSIN = juiciness, flavor, water-holding capacity

Question 4

What beneficial roles do lipids have in meat? Harmful roles?

Answer 4

BENEFICIAL - tenderness, juiciness, flavor

HARMFUL - rancid taste, impaired water-holding capacity

Question 5

What results with low levels of intramuscular fat?

Answer 5

• dry meat with low taste
• marbled meat preferred

Question 6

What are the 3 major components of carbohydrates in meat?

Answer 6

1. ATP
2. creatinine phosphate
3. glycogen

Question 7

What does ash contribute to meat? What ions are involved in living and postmortem muscle contraction?

Answer 7

iron heme (readily absorbed, makes up 40-60% of total iron)

• LIVING = calcium, magnesium, sodium, potassium
• POSTMORTEM = calcium, magnesium

Question 8

What are the 2 major components of skeletal muscle?

Answer 8

10% connective/fat tissue; 90% muscle cells/fibers

Question 9

What are the 3 layers of connective tissue in skeletal muscle?

Answer 9

1. ENDOMYSIUM - surrounds each muscle fiber
2. PERIMYSIUM - surround bundles of muscle fibers
3. EPIMYSIUM - surrounds whole muscle and acts as an extension of tendon

Question 10

What makes up most of the intracellular volume of muscle cells/fibers? What is the contractile unit?

Answer 10

myofibrils

sarcomere

Question 11

What is the general structure of muscle cells?

Answer 11

• multinucleated
• spindle-shaped
• elongated cells from a few mm to several cm

Question 12

Muscle cell:

Answer 12

Question 13

How does muscle contract?

Answer 13

action potential from motor nerves cause contraction allowing actin to use ATP, calcium, and magnesium to slide over myosin filaments and then relax upon depletion of energy

• ATP is required for contracting and relaxation

Question 14

What organelle is responsible for the conversion of muscle to meat?

Answer 14

lysosome

Question 15

What is a high number of mitochondria in meet associated with?

Answer 15

higher concentration of myoglobin, making the meat dark red

Question 16

What serves as an indicator of quality meat for grading? Depletion of what polysaccharide is important to meat quality?

Answer 16

lipid droplets

glycogen

Question 17

What is the length of the sarcomeres and cytoskeletal framework associated with?

Answer 17

toughness of meat

Question 18

What 2 types of death occur at slaughter?

Answer 18

1. somatic death - immediate, cells are still alive due using glycolysis
2. cellular death - 3-4 hr later

Question 19

What 4 changes in the body occur during somatic death and cellular death?

Answer 19

SOMATIC:
1. brain stops regulating the body
2. heart stops circulating blood
3. lung stops pumping oxygen
4. immune system stops surveillance

CELLULAR:
1. lower body temperature
2. changes in eye
3. changes in skin
4. changes in muscles

Question 20

What cellular mechanism is stopped upon cell death?

Answer 20

lack of nutrient supply (glucose and oxygen) causes the stop of aerobic respiration and the buildup of metabolic waste in cells (lactic acid)

Question 21

What key change happens to postmortem muscle development? What causes this?

Answer 21

rigor mortis —> decline in ATP

Question 22

What 3 changes develop following the switch to postmortem anaerobic metabolism? What does this lead to?

Answer 22

1. ATP level declines
2. creatine phosphate level declines
3. glycogen breakdown - glycolysis

• increase in lactic acid levels
• decline in pH
• rigor mortis
• proteolysis of muscles by lysosomal enzymes
• color change

Question 23

What color change occurs to postmortem muscle?

Answer 23

purple —> bright red or pink

• meat ripening due to aging

Question 24

How is meat classified according to color?

Answer 24

RED - high levels of myoglobin; beef, veal, lamb, mutton

WHITE - lower levels of myoglobin; pork, poultry, game, fish, shellfish

(it is believed that white meat is healthier than red meat)

Question 25

What 3 changes occur within 24 hours of death?

Answer 25

1. glycogen reduced into lactic acid (glycogen < 10 mmol/kg and lactic acid > 100 mmol/kg in meat) 2. muscle pH decreases from 7 to 5.6 due to lactic acid accumulation 3. color change from purple to bright red/pink

Question 26

How does the pH and lactate production compare in normal meat, dark meat, and pale meat?

Answer 26

NORMAL (bright red/pink) - 5.6, high DARK - 6.0-6.5, abnormally low PALE - 5.2, abnormally high

Question 27

In what animals is it common to have dark, firm, and dry meat? How does this affect pH?

Answer 27

cattle pH remains 6.0 (abnormally high) due to limited lactic acid production - good environment for microbial growth

Question 28

What are 2 causes of dark, firm, and dry meat? How can this problem be solved?

Answer 28

1. starvation - extended transport without feed depletes muscle glycogen 2. beef stress syndrome - alarm reaction to general adaptation syndrome (fight or flight) feed and rest for 24-48 hours prior to slaughter

Question 29

In what animals is it common to have pale, soft, and exudative meat? What are 2 causes? What does this lead to?

Answer 29

pigs (hereditary) 1. rapid glycolysis due to excitement antemortem or holding on kill floor before chilling 2. huge lactic acid production while temperature is wark rapid pH decline (5.2) causing loss of color, firmness, and water-holding capacity

Question 30

What are the 4 stages of rigor mortis?

Answer 30

1. pre-rigor (0-8 hr) - absent/delay stage where muscle is still relaxed and flexible due to ATP and creatine phosphate storage 2. onset (8-12 hr) - present stage where the stored ATP is used up and muscle loses its flexibility 3. rigor mortis (12-24 hr) - complete stage where all muscle energy is depleted and there is no way to regenerate it, making it completely stiff 4. resolution (24-72 hr) - final stage where stiffness dissipates and muscle loses its stiffness and is ready for fabrication

Question 31

Where is meat kept while it is aged? What is the onset of rigor mortis linked to? When does it occur more rapidly?

Answer 31

chilling room around 3 C rate of ATP depletion very young and older animals due to their lower muscle mass

Question 32

What is essential for the ripening and tenderization of connective and contractile proteins in muscle? What are the 2 types?

Answer 32

enzymatic degradation 1. ENDOGENOUS ENZYMES - cathepsins, calpains 2. EXOGENOUS ENZYMES - proteinases, cysteine endopeptidases derived from papain, bromelain, and ficin

Question 33

What would be the ideal meat tenderizer?

Answer 33

proteolytic enzyme with specificity for collagen and elastin in connective tissue at the low pH of meat and low/high temperatures

Question 34

What is dry-aging? Wet-aging? How care they commonly combined?

Answer 34

DRY - carcasses stored in cooler without protective packaging at 0-3 C for 10-28 days with critical humidity and air velocity control WET - carcasses packaged in vacuum bags at 0-3 C until frozen or consumed without the humidity and air velocity control required; tight vacuum sealing essential DRY-THEN-WET - initial carcass holding in a cooler for early postmortem periods and fabricated into primals and further aged under vacuum packaging

Question 35

Why are meats graded? What 4 criteria is it based on?

Answer 35

helps setting price value 1. marbling - fat distribution in ribeye (number and texture of fat distribution) 2. texture - fine vs. coarse depending on size of fibers or bundles visible on transversely cut surface 3. color 4. maturity - A = young; E = old (based on cartilage ossification at the tips of the dorsal spine of sacral, lumbar, and thoracic vertebrae

Question 36

What are the 3 top ranks of marbling? What other qualities affect meat grading?

Answer 36

1. prime 2. choice 3. select - fine is preferred (not so much medium or coarse) juiciness, tenderness, flavor, texture

Question 37

What is considered the most luxurious, indulgent steak?

Answer 37

Wagyu ribeye

Question 38

What are the 8 US beef grades? What are the last 3 levels commonly used for?

Answer 38

1. prime 2. choice 3. select 4. standard 5. commercial 6. utility 7. cutter 8. canner ingredients/industrial food processing (hotdogs, dog food) - too much signs of age, too little intramuscular fat, too low quality for cooking on its own

Question 39

Grading score, age vs. marbling:

Answer 39

- age: A (young) to E (old) - commercial grade: older, usually over 2 years old, meaning the meat is less tender and more chewy

Question 40

What concentration of fat is most acceptable? What happens if the percentage goes above?

Answer 40

3-7.5% health issues

Question 41

Meat grades vs. palatability:

Answer 41

high marbling = higher quality = higher palatability

Question 42

What 4 terms generally describe meat quality?

Answer 42

1. satisfaction by consumers - color, texture, juiciness, tenderdenss, flavor 2. nutritional qualities - fats, carbohydrates, proteins 3. hygiene qualities - product's capacity to be safely consumed without exposing the consumer to biological, chemical, and physical hazards 4. servicability - ease of use, ability to be processed, prices