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PHFS Exam 3 > Meat Science and Meat Hygiene > Flashcards

Meat Science and Meat Hygiene Flashcards

1
Q

who leads world in beef, poultry, pork

A
  • USA leads in beef
  • China leads in poultry and pork
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2
Q

composition of skeletal muscle tissue

A
  • 74% water
  • 19% protein
  • 5% lipid
  • 1% carbohydrates
  • 1% ash
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3
Q

composition of protein in muscle tissue

A
  • 2% stromal protein
  • 5.5% sarcoplasmic protein
  • 11.5% myofibrillar protein
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4
Q

what is stromal protein

A
  • connective tissue or support proteins (collagen, elastin)
  • has role in meat toughness vs tenderness
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5
Q

what is sarcoplasmic protein

A
  • aerobic and anaerobic metabolic enzymes, myoglobins
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6
Q

what is myofibrillar protein

A
  • contractile proteins
  • myosin (43%) - has role in juiciness, flavor, water holding capacity of meat
  • actin (22%)
  • other myofibrillar protein (35%)
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7
Q

beneficial roles of lipids in meat

A
  • tenderness
  • juiciness
  • flavor
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8
Q

bad roles of lipids in meat

A
  • rancid taste
  • impairment of water holding capacity of meat
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9
Q

low levels of intramuscular fat results in

A
  • dry meat with low taste
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10
Q

what is in the carbohydrate portion of skeletal muscle tissue

A
  • ATP
  • creatinine phosphate
  • glycogen
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11
Q

what type of iron is more readily absorbed in meat

A
  • the heme iron from meat is more readily absorbed as a nutrient, and heme iron accounts for 40-60% of total iron
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12
Q

what are directly involved in contraction in living muscle

A
  • calcium, magnesium, sodium, potassium
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13
Q

what contribute to muscle fiber contraction post mortem

A
  • magnesium and calcium
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14
Q

which species has lowest lipid %

A

cod

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15
Q

what does skeletal muscle consist of

A
  • 10% connective and fat tissues
  • 90% muscle cells and fibers
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16
Q

what are the 3 levels that connective tissues are distributed in muscles

A
  • endomysium - surrounds each muscle fiber
  • perimysium - surrounds each bundle of muscle fibers
  • epimysium - surrounds muscle as a whole and is an extension of the tendon
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17
Q

what part of the muscle cell occupies nearly the entire intracellular volume

A

myofibrils

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18
Q

what is the contractile unit of the muscle fiber

A

sarcomere

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19
Q

features of muscle cells

A
  • multinucleated
  • spindle shaped
  • 10-100 micrometers diameter
  • elongated (long cell) - few mm to several cm
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20
Q

muscle contraction mechanism

A
  • action potential from motor nerves
  • ATP, calcium, magnesium
  • actin slides over myosin filaments via climbing and falling onto myosin for contraction and relaxation respectively
  • ATP required during both climbing and falling
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21
Q

what is significant about lysosomes

A

may be significant in converting muscle to meat

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22
Q

what does high mitochondrial density indicate

A
  • aerobic metabolism
  • high mitochondrial density = dark and red meat
  • aerobic metabolism associated with red pigmented iron containing protein (myoglobin) in the sarcomere
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23
Q

what do lipid droplets serve as

A

indicators of quality meat during meat grading

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24
Q

what is important about glycogen

A

the preslaughter depletion of glycogen is important in meat quality

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25
Q

bands = protein in muscle or meat

A
  • A band - thick, myosin
  • I band - only thin filaments
  • Z disc - dark thin line in middle of I band, contains zig zag elements than anchor ends of thin filaments
  • M disc - darker line in middle of A band, contains protein myosin, connects centers of thick filaments
26
Q

what are sarcomere lengths related to

A

toughness of the meat

27
Q

what part of the cytoskeletal framework contributes to toughness of meat

A

T filaments (remain after thick and thin filaments stretched beyond their overlap)

28
Q

two types of death after slaughter

A
  • somatic death (immediate)
  • cellular death (3-4 hours later)
29
Q

biochemical changes during post mortem for conversion of muscle to meat

A
  • lack of nutrient supply –> aerobic metabolism stops
  • decline in body temp
  • buildup of metabolic waste in cells
  • anaerobic metabolism
  • increased lactic acid levels in muscle cells
  • decline in pH of muscle cells
  • rigor mortis
  • proteolysis of muscles by lysosomal enzymes (muscle aging = meat ripening)
  • color change in muscle from purple to bright red
30
Q

what biochemical processes do muscle undergo to become meat

A
  • rigor mortis
  • due to decline in ATP levels
31
Q

what determines the color of meat

A

concentration of myoglobin in the muscle fiber

32
Q

what happens within 24 hours after death to meat color, glycogen content, lactate production, pH

A
  • glycogen –> lactic acid
    • glycogen > 50 mmol/kg in live animals –> <10 mmol/kg in meat
    • lactic acid < 10 mmol/kg in live animals –> >100 mmol/kg in meat
  • muscle pH goes from 7.0 to 5.6 due to lactic acid
  • muscle color - purple to bright red (pH 7 –> 5.6)
33
Q

normal meat

A
  • high lactate production
  • pH 5.6
    • normal pH or ripened meat
34
Q

dark colored meat

A
  • abnormally low lactate production
  • pH 6-6.5
    • dark, firm, and dry (DFD) meat
35
Q

pale colored meat

A
  • abnormally very high lactate production
  • pH 5.2
    • pale, soft, and exudative (PSE) meat
36
Q

which species is DFD meat more common

A

cattle

37
Q

causes of DFD meat

A
  • starvation
  • beef stress syndrome, alarm reaction of general adaptation syndrome
  • limited lactic acid production postmortem
38
Q

to prevent DFD meat

A
  • feed and rest for 24-48 hours prior to slaughter
39
Q

which species is PSE meat more common

A

pigs (hereditary)

40
Q

causes of PSE meat

A
  • very rapid glycolysis due to antemortem excitement or long postmortem holding time before chilling
  • huge lactic acid production leading to rapid pH decline while carcass still warm
41
Q

abnormally low pH of PSE meat causes

A

loss of color, firmness, water holding capacity

42
Q

4 stages of rigor mortis

A
  • pre-rigor (0-8 hrs), absent stage, delay phase
  • onset (8-12 hrs), present stage, onset phase
  • rigor mortis (12-24 hrs), complete stage
  • resolution of rigor mortis (24-72 hrs), final, completion, passed, resolved stage
43
Q

what happens in pre rigor

A

muscle still relaxed and flexible due to storage of ATP and creatinine phosphate

44
Q

what happens in onset

A

stored ATP used up and muscle starts to lose flexibility

45
Q

what happens in rigor mortis

A

muscle energy depleted, no way to regenerate it, full rigor mortis sets in, muscles completely stiff

46
Q

what happens in resolution of rigor mortis

A

stiffness dissipates and muscles loose stiffness and is ready for fabrication

47
Q

what affects time for rigor mortis to activate or onset

A
  • linked to depletion of ATP in muscle
  • occurs more rapidly in the old and young due to lower muscle mass
48
Q

how is aging of meat done

A

keeping meat in chilling room at temperatures around 3 C

49
Q

endogenous enzymes for tenderization of meat

A
  • cathepsins
  • calpains
50
Q

exogenous enzymes for tenderization of meat

A
  • proteinases (cysteine endopeptidases)
  • derived from plants - papain (papaya), bromelain (pineapple), ficin (fig)
51
Q

how do catheptic enzymes cause tenderization of meat during aging

A
  • destroy collagenous connective tissue of the muscle
52
Q

ideal meat tenderizer

A

a proteolytic enzyme with specificity for collagen and elastin in the connective tissues at the low pH of meat which would act either at low refrigerator temps or high cooking temps

53
Q

three methods of storing meat for aging/ripening

A
  • dry aging - store in cooler without packaging
  • wet aging - packaging in vacuum bags
  • proposed stepwise aging - dry then wet aging
54
Q

4 criteria for meat quality grading

A
  • marbling - measure fat distribution in ribeye muscle
  • texture - determined by size of muscle fibers and bundles
  • color
  • maturity - A (young) to E (old), determined by degree of cartilage ossification at tips of dorsal spine of sacral/lumbar/thoracic vertebrae
55
Q

marbling - grade, eating experience, type

A
  • grade –> prime, choice, select
  • eating experience –> juiciness, tenderness, flavor, texture
  • types - fine, medium, coarse
56
Q

8 US beef grades

A
  1. prime
  2. choice
  3. select
  4. standard
  5. commercial
  6. utility
  7. cutter
  8. canner
57
Q

utility, cutter, canner grades of beef

A
  • too much signs of aging
  • too little intramuscular fat (too little marbling)
  • too low quality for cooking on own
  • usually sold to be used as an ingredient in industrial food processing -> hot dogs, dog food, etc
58
Q

acceptable levels of fat in meat

A

3% to 7.3%

59
Q

relationship between marbling, grade, meat palatability

A

greater marbling = higher quality grade = higher expected meat palatability

60
Q

meat quality is described by 4 terms

A
  • satisfaction by consumers
  • nutritional qualities
  • hygienic qualities (safety)
  • serviceability (ease of use, price, etc)
61
Q

one of primary casues of consumer failure to repurchase beef

A

variability in tenderness

PHFS Exam 3 (5 decks)

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