Meat

Question 1

outline the nutritional values of meat

Answer 1

• high biological value
• contains essential amino acids
• source of vitamins and minerals
• high in saturated FAs

Question 2

what are the health related concerns of eating meat

Answer 2

• meat is energy dense and low in fibre
• may lead to chronic diseases e.g cancer, CV disease
• nitrites
• food safety e.g salmonella. ecoli
• antibiotic resistance

Question 3

what are the environmental concerns of eating meat

Answer 3

• agricultural sustainability

- animal welfare

Question 4

what are the three layers of connective tissue

Answer 4

There are three layers of connective tissue: epimysium, perimysium, and endomysium.

Question 5

what factors do protein and fat content vary with

Answer 5

age, breed, cut of meat

Question 6

what are the three classifications of meat proteins?

Answer 6

stromal
myofibrillar
sarcoplasmic

Question 7

what are the characteristics of stromal muscle cells

Answer 7

10-15% of the muscle

made up of collagen, elastin and reticulin

Question 8

what are the characteristics of myofibrillar muscle cells

Answer 8

55% of the muscle

made up of actin and myosin

Question 9

what are the characteristics of sarcoplasmic muscle cells

Answer 9

30% of the muscle

made up of haemoglobin and myoglobin

Question 10

what are the characteristics of collagen

Answer 10

white
thin
transparent
insoluble
triple helix structure

Question 11

what are the characteristics of elastin

Answer 11

yellow

does not degrade to geltin

Question 12

what are the characteristics of gelatin

Answer 12

product of the reversible thermal denaturation of collagen

used in jam, jelly, yoghurt, marshmallows

Question 13

what are the three myofibrillar proteins

Answer 13

myosin
actin
desmin

Question 14

what is myosin

Answer 14

long, filamentous, highly charged
have a strong affinity for calcium and magnesium
has two subunits

Question 15

what is actin

Answer 15

globular actin forms filamentous actin
involved in muscle contraction
associated with troponin and tropomyosin

Question 16

what is desmin

Answer 16

degrades during ageing

can increase water holding capacity

Question 17

what are the two subunits of myosin and what are their roles

Answer 17

light meromyosin- structural stability and muscle contraction

heavy meromyosin- ATP binding

Question 18

what are the sarcoplasmic proteins

Answer 18

enzymes
- e.g calpaan, for tenderisation and flavour contribution

pigments
- e.g myoglobin, haemoglobin, for colour intensity and variation

Question 19

what are the 3 types of myoglobin

Answer 19

deoxymyoglobin- Fe2+, no ligands, purple
oxymyglobin- Fe2+, oxygen, bright red
metmyoglobin- Fe3+, no ligands, brown

Question 20

what are the 4 stages of muscle to meat after death

Answer 20

acidification
onsent
resolution
conditioning

Question 21

what are the three stages of rigor mortis

Answer 21

pre-rigor
rigor
post-rigor

Question 22

outline the process of post-mortem acidification

Answer 22

animal dies and oxygen levels fall
respiration and oxygen supply to muscles stop
ATP is generated from glycogen by anaerobic glycolysis
lactic acid accumulates and the muscle acidifies
pH falls to 5.5

Question 23

what is pale soft exudative meat?

Answer 23

-short term stress on the animal, low pH at the time of slaughter

Question 24

what is dark firm and dry meat?

Answer 24

• long term stress on the animal, high pH at slaughter, produces better meat

Question 25

outline the onset stage during rigor mortis

Answer 25

glycolysis is inhibited by a lack of glycogen and pH
ATP falls
actin and myosin combine to form actomyosin
muscle extensibility is lost

Question 26

outline the conditioning stage during rigor mortis

Answer 26

continuation of tenderisation
myofibrils weaken
calpains are added for flavour

Question 27

outline the resolution stage during rigor mortis

Answer 27

tenderisation starts

muscles soften as myofibrils become fragmented