Meat colour, quality defects

Question 1

Meat pigments (3)

Answer 1

Myoglobin (Mb) 80-95% of pigment
Hemoglobin (Hb) 5-20% of pigment
Cytochrome C small amounts

Question 2

2 major (myoglobin) reactions affecting colour

Answer 2

1. Reaction with oxygen (binding)
2. Oxidation; reduction of the heme iron FE(II)<=>FE(III)

Question 3

Purple colour in meat

Answer 3

Deoxymyoglobin

Question 4

Red colour in meat

Answer 4

Oxymyoglobin

Question 5

Brown colour in meat

Answer 5

Metmyoglobin

Question 6

Factors affecting meat color (8)

Answer 6

Fibre type distribution/pigment content
pH
Water-holding capacity
Denaturation of myoglobin
Method of packaging
Meat age, microbial stability
Heating
Additives, other ingredients

Question 7

What’s used for curing?

Answer 7

Nitrite

Question 8

Effects of Nitrite

Answer 8

Red/pink cured colour
Cured flavour
Antioxidant (forms complex with Fe in myoglobin)
Bacteriostatic effect

Question 9

Vacuum packaging

Answer 9

Oxygen impermeable film
Stable purple colour (deoxymb)

Question 10

Modified atmosphere packaging

Answer 10

Oxygen impermeable film
Large headspace
Bright red colour

Question 11

DFD

Answer 11

Dark colour, firm texture, dry

> short shelf life, spoils quickly
high ultimate pH
high water-holding capacity

Question 12

PSE

Answer 12

Pale and soft (pigs)

> low initial pH
low water-holding capacity, bound water lost

Question 13

WB

Answer 13

Wooden breast (poultry)

Question 14

WS

Answer 14

White striping (poultry)

Question 15

What causes DFD?

Answer 15

Dark colour, firm textrue, dry

Chronic sress - low glycogen level before slaughter

Question 16

What causes PSE?

Answer 16

Pale and soft

Acute stress