Food Pigments thru Heme

Question 1

quality attributes imparted by food pigments: (5)

Answer 1

• flavor (taste/smell)
• texture
• nutritive value
• microbial load
• color/appearance

Question 2

what are sources of chlorophyll?

Answer 2

fruits, vegetables, microorganisms

Question 3

muscle foods are good source of what pigments?

Answer 3

heme

Question 4

what are sources of carotenoids?

Answer 4

eggs, fish, crustaceans, dairy products fruits and veggies

Question 5

what are sources of anthocyanins?

Answer 5

fruits, veg, microorgs

Question 6

what are sources of flavonoids?

Answer 6

fruits, veg, microorgs

Question 7

what are sources of melanins?

Answer 7

shellfish, dried fruits, veg, mircoorgs

Question 8

what is the name of the structure of the molecule comprising chlorophylls?

Answer 8

pyrrole; four of them = tetrapyrrole linked by methylene bridges; 4 nitrogens are linked to a central magnesium;

20C hydrocarbon tail = phytol

methanol is esterified

Question 9

describe a pyrrole

Answer 9

4 Cs, NH. pentagon shaped with 2 double bonds on the walls of the house.

Question 10

chlorophylls (are/aren’t) water soluble

Answer 10

aren’t

Question 11

how do you turn chlorophyll into pheophytin?

Answer 11

presence of acid and heat, loss of Mg

Question 12

how do you turn chlorophyll into chlorphyllide?

Answer 12

loss of phytol; catalyzed by chlorphyllase

Question 13

how do you turn chlorophyllide to pheophorbide?

Answer 13

presence of acid and heat, loss of Mg

Question 14

how do you turn pheophytin to pheophorbide?

Answer 14

loss of phytol; catalyzed by chlorophyllase

Question 15

____ is dark green

Answer 15

chlorophyll

Question 16

____ is bright green

Answer 16

chlorphyllide

Question 17

____ is a dull brown color

Answer 17

pheophytin

Question 18

____ is a brownish color

Answer 18

pheophorbide

Question 19

what 2 pigments are water soluble?

Answer 19

chlorophyllide, pheophorbide

Question 20

what 2 pigments are water insoluble

Answer 20

chlorophyll, pheophytin

Question 21

what happens when you cook chlorophylls?

Answer 21

• converts them to pheophytins (water soluble –> leaks into cooking water)

Question 22

what happens when you dehydrate chlorophylls?

Answer 22

bleaching by photodegradation (lipoxidase destroys double bonds)

Question 23

what happens when you expose chlorophylls to O2?

Answer 23

bleaching (oxidation)

Question 24

what happens when you blanch chlorophylls?

Answer 24

converts to chlorophyll to pheophytin or chlorophyllide to pheophorbide

Question 25

what happens when you increase exposure to irradiation in chlorphylls?

Answer 25

degradation by peroxidation

Question 26

what are the 2 predominant enzymes that degrade chlorophylls?

Answer 26

chlorophyllase, lipoxidase

Question 27

2 types of heme pigments

Answer 27

myoglobin, hemoglobin

Question 28

what colors are heme pigments responsible for in muscle?

Answer 28

red

Question 29

describe the structure of myoglobin

Answer 29

single polypeptide chain; molecular weight of 16.4 kdaltons; contains a protein part (globin) and an essential non-protein part (heme)

Question 30

describe the structure of hemoglobin

Answer 30

comprised of 4 myoglobins

Question 31

a tetrapyrrole structure with a central atom being iron and a side chain of globin describes what kind of pigment?

Answer 31

myoglobin

Question 32

heme pigments (are/aren't) water soluble

Answer 32

are

Question 33

major food sources of heme pigments?

Answer 33

meats (beef, pork, chicken) and fish

Question 34

describe what's happening around the central iron atom of myoglobin

Answer 34

- Fe has 6 coordination points - 4 of these are occupied by nitrogens of pyrroles - hisitidine binds to the 5th coordination point - 6th coordination point can accept any other molecule with a lone pair, like oxygen or CO2

Question 35

what heme pigment is found in animal muscle?

Answer 35

myoglobin

Question 36

what heme pigment is found in animal blood vessels?

Answer 36

hemoglobin

Question 37

which heme pigment is of greater interest to food scientists?

Answer 37

myoglobin

Question 38

what color is myoglobin with and without oxygen?

Answer 38

without O2: purplish | with O2: red

Question 39

when oxygen is bound to myoglobin, this is called the ______ ______

Answer 39

oxymyoglobin complex (MbO2)

Question 40

iron is predominantly present in the ______ state

Answer 40

2+

Question 41

what's metmyoglobin?

Answer 41

- oxidized form of iron 2+ to iron 3+ | - brownish in color

Question 42

the oxidation of myoglobin to metmyoglobin (is/is not) reversible

Answer 42

not!

Question 43

what happens to heme pigments when an animal dies?

Answer 43

myoglobin is oxidized (iron 2+ to 3+) to metmyoglobin, making the meat turn brownish

Question 44

how can you tell if a meat has been treated to look prettier after metmyoglobin has done its thing?

Answer 44

look at edges of plastric wrap - if it's green, the sulfur groups in plastics had interacted with the pigments to make sulfur myoglobin

Question 45

what conditions enable the oxidation of ferrin 2+ to ferrin 3+?

Answer 45

cooking

Question 46

what steak is characterized by the presence of Fe2+ and globin not denatured?

Answer 46

rare

Question 47

what steak is characterized by the presence of Fe 3+ and denatured globin?

Answer 47

well-done

Question 48

Which is more readily absorbed? Fe2+ or Fe3+?

Answer 48

Fe2+

Question 49

what's the deal with cunner fish?

Answer 49

don't know, ask steven what he wrote lol

Question 50

water only binds when iron is in the _____ state

Answer 50

Fe3+

Question 51

what is the effect of storage on heme pigments?

Answer 51

gradual oxidation, formation of dark/brown color

Question 52

what is the effect of cooking on heme pigments?

Answer 52

denaturation of protein, oxidation to Fe3+, formation of dark color

Question 53

what is the effect of curing meats?

Answer 53

- red colored nitrosomyoglobin - killing of clostridium botulinum - development of different flavors

Question 54

what is the effect of cooking cured meats?

Answer 54

- oxidation to Fe3+ | - brown product formation: nitrosohemichrome

Question 55

______ can be used to reverse oxidation in meats. it also happens to be unacceptable

Answer 55

reducing agents.

Question 56

what unacceptable product do -SH containing reducing agents produce?

Answer 56

sulfur myoglobin