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food chem 2 > Food Pigments thru Heme > Flashcards

Food Pigments thru Heme Flashcards

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1
Q

quality attributes imparted by food pigments: (5)

A
  • flavor (taste/smell)
  • texture
  • nutritive value
  • microbial load
  • color/appearance
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2
Q

what are sources of chlorophyll?

A

fruits, vegetables, microorganisms

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3
Q

muscle foods are good source of what pigments?

A

heme

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4
Q

what are sources of carotenoids?

A

eggs, fish, crustaceans, dairy products fruits and veggies

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5
Q

what are sources of anthocyanins?

A

fruits, veg, microorgs

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6
Q

what are sources of flavonoids?

A

fruits, veg, microorgs

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7
Q

what are sources of melanins?

A

shellfish, dried fruits, veg, mircoorgs

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8
Q

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

A

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

20C hydrocarbon tail = phytol

methanol is esterified

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9
Q

describe a pyrrole

A

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

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10
Q

chlorophylls (are/aren’t) water soluble

A

aren’t

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11
Q

how do you turn chlorophyll into pheophytin?

A

presence of acid and heat, loss of Mg

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12
Q

how do you turn chlorophyll into chlorphyllide?

A

loss of phytol; catalyzed by chlorphyllase

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13
Q

how do you turn chlorophyllide to pheophorbide?

A

presence of acid and heat, loss of Mg

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14
Q

how do you turn pheophytin to pheophorbide?

A

loss of phytol; catalyzed by chlorophyllase

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15
Q

____ is dark green

A

chlorophyll

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16
Q

____ is bright green

A

chlorphyllide

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17
Q

____ is a dull brown color

A

pheophytin

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18
Q

____ is a brownish color

A

pheophorbide

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19
Q

what 2 pigments are water soluble?

A

chlorophyllide, pheophorbide

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20
Q

what 2 pigments are water insoluble

A

chlorophyll, pheophytin

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21
Q

what happens when you cook chlorophylls?

A
  • converts them to pheophytins (water soluble –> leaks into cooking water)
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22
Q

what happens when you dehydrate chlorophylls?

A

bleaching by photodegradation (lipoxidase destroys double bonds)

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23
Q

what happens when you expose chlorophylls to O2?

A

bleaching (oxidation)

24
Q

what happens when you blanch chlorophylls?

A

converts to chlorophyll to pheophytin or chlorophyllide to pheophorbide

25
Q

what happens when you increase exposure to irradiation in chlorphylls?

A

degradation by peroxidation

26
Q

what are the 2 predominant enzymes that degrade chlorophylls?

A

chlorophyllase, lipoxidase

27
Q

2 types of heme pigments

A

myoglobin, hemoglobin

28
Q

what colors are heme pigments responsible for in muscle?

A

red

29
Q

describe the structure of myoglobin

A

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

30
Q

describe the structure of hemoglobin

A

comprised of 4 myoglobins

31
Q

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

A

myoglobin

32
Q

heme pigments (are/aren’t) water soluble

A

are

33
Q

major food sources of heme pigments?

A

meats (beef, pork, chicken) and fish

34
Q

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

A
  • 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
35
Q

what heme pigment is found in animal muscle?

A

myoglobin

36
Q

what heme pigment is found in animal blood vessels?

A

hemoglobin

37
Q

which heme pigment is of greater interest to food scientists?

A

myoglobin

38
Q

what color is myoglobin with and without oxygen?

A

without O2: purplish

with O2: red

39
Q

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

A

oxymyoglobin complex (MbO2)

40
Q

iron is predominantly present in the ______ state

A

2+

41
Q

what’s metmyoglobin?

A
  • oxidized form of iron 2+ to iron 3+

- brownish in color

42
Q

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

A

not!

43
Q

what happens to heme pigments when an animal dies?

A

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

44
Q

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

A

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

45
Q

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

A

cooking

46
Q

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

A

rare

47
Q

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

A

well-done

48
Q

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

A

Fe2+

49
Q

what’s the deal with cunner fish?

A

don’t know, ask steven what he wrote lol

50
Q

water only binds when iron is in the _____ state

A

Fe3+

51
Q

what is the effect of storage on heme pigments?

A

gradual oxidation, formation of dark/brown color

52
Q

what is the effect of cooking on heme pigments?

A

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

53
Q

what is the effect of curing meats?

A
  • red colored nitrosomyoglobin
  • killing of clostridium botulinum
  • development of different flavors
54
Q

what is the effect of cooking cured meats?

A
  • oxidation to Fe3+

- brown product formation: nitrosohemichrome

55
Q

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

A

reducing agents.

56
Q

what unacceptable product do -SH containing reducing agents produce?

A

sulfur myoglobin

food chem 2 (5 decks)

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