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Food Chemistry II > Natural Pigments > Flashcards

Natural Pigments Flashcards

1
Q

Food quality attributes of natural pigments

A
  • Flavor (taste/smell)
  • Texture
  • Nutritive value
  • Microbial load
  • Color / appearance
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2
Q

Natural Food Pigments (8)

A
  • Chlorophyll
  • Myoglobin & Hemoglobin
  • Carotenoids
  • Anthocyanins
  • Flavonoids
  • Tannins
  • Quinones & Xanthones
  • Melanins & Betalains
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3
Q

Chlorophyll

A 
• Plant pigment (main sources are green vegetables, root vegetables, fruits)
o	Mg in the center
o	Fat soluble
o	Can be destroyed by heat
o	Sensitive to acids and alkali
o	Green color
o	Plant sources, algae
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4
Q

Chlorophyll structure

A

tetrapyrrole

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5
Q

Major chlorophylls are ____

A

‘a’ & ‘b’ (3:1)

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6
Q

The proportion of a and b chlorophylls is

A

3:1

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7
Q

What colour is alpha chlorophyll

A

green-bluish colour

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8
Q

What colour is beta chlorophyll

A

dull green colour

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9
Q

Is chlorophyll water soluble or fat soluble?

A

fat soluble

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10
Q

Heme pigments are ____ and ____

A

hemoglobin and myoglobin

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11
Q

Heme pigments general features

A
  • Responsible for red color of muscle foods;
  • Complex molecule with a protein part (globin), and an essential non-protein part (heme);
  • Both Mb and Hb are tetrapyrrole compounds.
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12
Q

Mb and Hb structure

A

tetrapyrrole compounds.

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13
Q

Is heme fat or water soluble

A

water soluble

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14
Q

What are the major food sources that contain heme

A

meats (beef, pork, chicken, fish)

o The pigment in the muscle is due to myoglobin, and the intensity of the color depends on the myoglobin content

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15
Q

Myoglobin structure

A

• Single polypeptide chain
• 4 N’s in the 4 pyrole molecules , covalently linked
to central Fe atom
• Fe also covalently linked to N in a histidine residue in globin (protein);
• Fe can bind electron pair donors (e.g., O2, CO, CO2, CN, etc).

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16
Q

Oxymyoglobin

A
  • Bright red color of fresh meats
  • Fe present as ferrous (Fe2+) form
  • Mb + O2 <==> MbO2
  • Mb (purple color; Fe2+)
  • MbO2 (bright red; Fe2+)
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17
Q

What is the compound that gives the fresh color to meat?

A

oxymyoglobin

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18
Q

Metmyoglobin (Met-Mb)

A
  • Brownish color (Fe3+)
  • MbO2 <==> Mb ==> Met-Mb
  • MbO2 (bright red)
  • Mb (purple)
  • Met-Mb (brown)
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19
Q

What is the compound that gives the brown color to meat?

A

metmyoglobin

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20
Q

Chlorophyll a vs. Chlorophyll b

A

One of the pyrroles have a methyl group = chlorophyll A

Formyl group –CHO = Chlorophyll B

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21
Q

What makes chlorophyll fat soluble molecule?

A

Fat soluble bc of the presence of the C20 carbon molecule that is attached to the chlorophyll molecule. 20C unit known as PHYTOL (300g/mol)

Phytol side chain is a hydrocarbon and highly hydrophobic, and this accounts to its insolubility in H2O, but highly solubility in lipids. – wax

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22
Q

What happens when the phytol group is removed form chlorophyll?

A

If we remove the phytol group, the molecule left behind is water soluble

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23
Q

How can we obtain chlorophyllide from chlorophyll and how does the color change?

A

loss of phytol by chlorophyllase

very bright color

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24
Q

How can we obtain pheophytin from chlorophyll and how does the color change?

A

expose it to acid and heat
loss of Mg atom
blue color

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25
Q

How can we obtain pheophorbide from chlorophyllide how does the color change?

A

expose it to acid and heat
loss of Mg atom
red color

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26
Q

How can we obtain pheophorbide from pheophytin how does the color change?

A

loss of phytol

chlorophyllase

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27
Q

What happens when chlorophyll is exposed to acid?

A
  • removal of the Mg atom from the centre
  • if the centre is removed then the molecule is not green anymore (brownish)
  • molecule is still water soluble
  • PHEOPHYTIN
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28
Q

Alkali/Acid conditions (chlorophyll) cause the removal of the phytol group.

A

Alkali

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29
Q

True/False

When the phytol group is cleaved, the molecule is still fat soluble.

A

False

When the phytol group is cleaved, it becomes water soluble.

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30
Q

Pheophytin can go under hydrolysis to remove the phytol group that forms a new molecule that is called __________. This molecule is also water soluble, but the magnesium is lost so this molecule has a brownish color as well.

A

PHEOPHORBIDE

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31
Q

Moist Cooking vs Dry Heat on chlorophyll

A

Processes such as moist cooking (blanching) can cause destruction of green color. (chlorophyll). Dry heat (microwave) on the other hand, inactivates enzymes but does not remove Mg so green color is retained

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32
Q

What other effects can cause color loss in chlorophyll

A

o Fermentation produces acids and can lead to color destruction
o Exposure to light and air can also cause oxidation and lead to color loss.

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33
Q

True/False

Chlorophylls are antioxidants

A

true

It is highly unsaturated, therefore it can function as antioxidant

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34
Q

Other uses of chlorophyll containing foods

A

food additives
mouthwash
toothpaste
The magnesium of chlorophyll helps boost the blood volume.

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35
Q

How does cooking affect chlorophyll?

A

Cooking –> pheophytins

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36
Q

How does dehydration affect chlorophyll?

A

Dehydration –> bleaching by photodegradation (lipoxidases)

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37
Q

How does exposure to light and 02 affect chlorophyll?

A

Exposure to O2&light –> bleaching

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38
Q

How does blanching affect chlorophyll?

A

Blanching –> pheophytins & phophobides

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39
Q

How does irradiation affect chlorophyll?

A

Irradiation –> degradation by peroxidation

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40
Q

Heme pigments are complex molecules with a protein part (______), and an essential non-protein part (______);

A

globin

heme

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41
Q

Structure of heme pigment

A

Both Mb and Hb are tetrapyrrole compounds.

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42
Q

Is Hb bigger than Mb?

A

o Mb < Hb
♣ 17 < 64 KDA
♣ muscle vs blood vessels

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43
Q

What is the central atom of heme pigments?

A

Both Mb and Hb are tetrapyrrole compounds. 4 pyrrole rings attached to a central atom Fe

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44
Q

What is the difference between a Mg central atom and a Fe central atom?

A

Fe, unlike Mg, can accept 6 lone pairs of electrons: 4 from N, 1 from histidine, and 1 donor (O2, CO2, CO, CN, OH)

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45
Q

Fe central atom can accept 6 lone pairs. What types of molecules does it accept?

A

can accept 6 lone pairs of electrons: 4 from N, 1 from histidine, and 1 donor (O2, CO2, CO, CN, OH)

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46
Q

What color is Mb?

A

(purple color; Fe2+)

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47
Q

What color is MbO2?

A

(bright red; Fe2+)

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48
Q

What color is Met-Mb

A

Met-Mb (brown) (Fe3+)

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49
Q

Phytol:
size
solubility
structure

A

296 kda, water insoluble, attached directly to tetrapyrrole

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50
Q

Globin:
size
solubility
structure

A

16.4 kda, water soluble, Fe

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51
Q

4Mb = ? Hb

A

1

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52
Q

1Hb = ? Mb

A

4

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53
Q

red meat/poultry/finish color intensity is due to the amount of Mb/Hb present

A

Mb

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54
Q

Storage of heme pigments

A

Storage => gradual oxidation, forming dark/brown color

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55
Q

Cooking of heme pigments

A
  • denatures protein;
  • oxidation of Fe2+ to Fe3+;
  • formation of dark color (as in barbecued meats - pigment formed known as hemichrome)
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56
Q

in barbecued meats - pigment formed known as _______

A

hemichrome

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57
Q

Curing of meats with nitrites => red colored _______;

A

nitrosomyoglobin

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58
Q

cooking of cured meats denatures the protein, also Fe2+ is oxidized to Fe3+ - & brown product – ______;

A

nitrosohemichrome

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59
Q

nitrosomyoglobin

A

Curing of meats with nitrites => red colored

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60
Q

nitrosohemichrome

A

cooking of cured meats denatures the protein, also Fe2+ is oxidized to Fe3+ - & brown product

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61
Q

Give an example of a reducing agent that can prevent sulfmyoglobin formation

A

with –SH containing reducing agent

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62
Q

what do you prevent oxidation by adding reducing agents to meat?

A

o By adding reducing agents, it is possible to reverse the oxidation.
♣ Fe2+ Fe3+ +e- (by using cysteine cystine / glutamine (GSH) GSSG)
♣ This reverses the brownish color of Met-Mb. However, a yellowish/greenish tinge forms along edges of meat which would indicate that reducing agents have been applied to “old meat” to make it look fresh
♣ The yellowish/greenish tinge is dues to a product known as sulfmyoglobin

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63
Q

what color is sulfmyoglobin

A

The yellowish/greenish tinge is dues to a product

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64
Q

what does yellowish/greenish tinge along edges of meat indicate?

A

indicate that reducing agents have been applied to “old meat” to make it look fresh

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65
Q

Fe 3+ on cooked meats______

A

not readily absorbed through the GIT although there is the advantage of extensive denaturation to facilitate the hydrolysis as well as the destruction of harmful pathogens that may be present in the meat.

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66
Q

Fe2+ on rare/medium cooked meats _______

A

Fe2+ is rare/medium cooked meats is much more readily absorbed through the intestinal membrane into the cytosol to make more RBCs.

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67
Q

Use of nitrates in foods can form nitroso-amines that are considered to be ______

A

carcinogenic

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68
Q

When meats are cured with nitroso-amines, what else should be added to decrease the carcinogenic effect?

A

ascorbic acid/vitamin C is added to the curing brine to reduce nitrosoamines formed back to nitrates to remove the potential harm.

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69
Q

EXAM QUESTION

Compare chlorophyll and myoglobin

A

o Different sources (plant vs animal)
o Both tetrapyrrole compounds but central atoms are different (Mg vs Fe)
o Different colors (green vs red)
o Relative solubility (fat soluble vs water soluble)
o side groups attached to molecule
o both are heat sensitive

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70
Q

Carotenoid pigments are present in

A
  • Present in plants, animals & microorganism

* Responsible for yellow, orange & red-orange colors in plants & animals

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71
Q

Animal sources of carotenoids

A

♣ egg yolk,
♣ milk/dairy products,
♣ shellfish
♣ salmons

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72
Q

Plant sources of carotenoids

A

♣ Fruit
♣ Vegetables
♣ Palm oil

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73
Q

Microbial sources of carotenoids

A

♣ Yeast

♣ Fungi

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74
Q

Structure of carotenoids

A

5C compounds – isoprene as repeating unit known as ISOPRENE

75
Q

Isoprene is cyclic/acyclic

A

both

76
Q

Isoprene can be composed of

A

May be hydrocarbon exclusively (hydrocarbon carotenoids or carotenes), or may contain oxygen (oxy-carotenoids)

77
Q

Hydrocarbon Carotenoids, a.k.a., Carotenes

A

β-carotenes,
α-carotene
lycopene

78
Q

Hydrocarbon carotenoids

A

carotenes

79
Q

β-carotenes

A

gives 2 molecules of vitamin A on hydrolysis - thus described as pro-vitamin A

80
Q

pro-vitamin A

A

β-carotenes

81
Q

the difference between β-carotenes and α-carotene

A

o α-carotene - same molecular formula as β- carotene, but the α-form is not symmetrical.
o on hydrolysis, the α-carotene yields only one molecule of vitamin A in the body

82
Q

True/False

B-carotene, a-carotene and lycopene are examples of hydrocarbon carotenoids bc they are comprised of “H” and “C” atoms exclusively

A

true

83
Q

β-carotene and α-carotene vs. lycopene

A
  • lycopene is symmetrical, but unlike α- or β- carotenes, the ring structures in lycopene are open
  • lycopene has no vitamin A activity
84
Q

lycopene is cyclic/acyclic

A

acyclic

85
Q

hydrolysis of β-carotene gives

A

2 molecules of vitamin A

86
Q

α-carotene is symmetrical/nonsymmetrical

A

nonsymmetrical

87
Q

Hydrolysis of α-carotene yields to

A

only one molecule of vitamin A

88
Q

Lycopene is found in

A

tomatoes and apricots

89
Q

Oxy-carotenoids

A

common ones are: lutein, canthaxanthin, astaxanthin, cryptoxanthin & zeaxanthin

90
Q

Lutein

A

Oxy-carotenoid
• Sources:- green leaves and egg yolk
• molecule is similar to β-carotene - asymmetrical; but rings are hydroxylated; so has no vitamin A activity

91
Q

Sources of lutein

A

green leaves and egg yolk

92
Q

Does lutein have vitamin A

A

NO

93
Q

Canthaxanthin

A

Oxy-carotenoid
• present in microorganisms, plants & animals (e.g., mushroom, red pepper, brine shrimp & the flamingo)
• commercially produced by chemical synthesis
• used as feed supplement for cultured
salmonids & imitation seafood products
• has no vitamin A activity

94
Q

Canthaxanthin sources

A

• present in microorganisms, plants & animals (e.g., mushroom, red pepper, brine shrimp & the flamingo)

95
Q

Does Canthaxanthin have vitamin A activity

A

no

96
Q

Astaxanthin

A

Oxy-carotenoids
• major carotenoid pigment in salmonids & crustaceans; also redfish, ocean perch / red snapper
• produced on a commercial scale by chemical synthesis
• more stable than canthaxanthin for use as colorant for
fish flesh
• has no vitamin A activity

97
Q

Astaxanthin sources

A

• major carotenoid pigment in salmonids & crustaceans; also redfish, ocean perch / red snapper

98
Q

True/False

Canthaxanthin is more stable than Astaxanthin

A

false

Astaxanthin more stable than canthaxanthin for use as colorant for fish flesh

99
Q

Does Astaxanthin have vitamin A activity

A

no

100
Q

Cryptoxanthin

A

Oxy-carotenoids
• major carotenoid pigment in peaches, yellow corn and egg yolk.
• structure similar to β-carotene, except for presence of -OH group on one ring
• has vitamin A activity.

101
Q

sources of Cryptoxanthin

A

• major carotenoid pigment in peaches, yellow corn and egg yolk.

102
Q

Does Cryptoxanthin have vitamin A activity

A

yes

103
Q

Zeaxanthin

A

• widely distributed in nature
• major carotenoid in yellow corn & egg
yolk
• similar structure to β-carotene, but has an
-OH group substituted to each ring
• has no Vitamin A activity

104
Q

sources of Zeaxanthin

A

• major carotenoid in yellow corn & egg

yolk

105
Q

Does Zeaxanthin have vitamin A activity

A

no

106
Q

β-carotene vs Lutein

A

molecule is similar to β-carotene - asymmetrical; but rings are hydroxylated;

107
Q

β-carotene vs Cryptoxanthin

A

structure similar to β-carotene, except for presence of -OH group on one ring

108
Q

β-carotene vs Zeaxanthin

A

similar structure to β-carotene, but has an

-OH group substituted to each ring

109
Q

Effect of Handling & Processing of Carotenoids

A
  • O2 & light major cause of destruction
  • not lost to cooking water
  • destroyed by dehydration
110
Q

2 key uses of carotenoids are as

A
  1. antioxidants

2. colorants

111
Q

EXAM QUESTION

True/False

Anthocyanins are present in bacteria

A

False

they are present in plant sources

112
Q

EXAM QUESTION (Essay type)

Why is it important to study a particular pigment carotenoid?

A

o Preserve the color of the food
o Health benefits and they are active compounds
o The color changes

113
Q

EXAM QUESTION (Essay type)

Suggest 4 ways of controlling the chlorophyll

A

o Add salt while cooking
o Blanching
o Add sodium bicarbonate to neutralize the acids
—-

114
Q

Anthocyanins

A

• Water-soluble plant pigments;
• Impart red, blue and violet colors to
various fruits and vegetables;
• The basic structure is the flavilium ion (a.k.a. anthocyanidin or aglycone).

115
Q

structure of anthocyanins

A

flavilium ion (a.k.a. anthocyanidin or aglycone).

Two rings, and several hydroxyl groups attached – polyphenolic compound

They are glycosides or sugar esters of anthocyanidin

116
Q

Anthocyanins are glycosides or sugar esters of ______

A

anthocyanidin

117
Q

Monosides of anthocyanin

A

one sugar

always a monosaccharide

118
Q

Biosides of anthocyanin

A

two sugars

1 disaccharide or 2 monosaccharides

119
Q

Triosides of anthocyanin

A

three sugars

1 trisaccharide or 1 disaccharide and 1 monosaccharides

120
Q

True/False

Anthocyanins can accommodate more than 3 sugars in their structures

A

false

In nature they can take max 3 sugars

121
Q

Monosaccharides of anthocyanins can be

A 
D-glucose, 
D-galactose, 
L- arabinose, 
D-xylose 
L-rhamnose
122
Q

Disaccharides of anthocyanins can be

A

gentiobiose,
rutinose,
sophorose,
neohesperidose)*

123
Q

Trisaccharides of anthocyanins can be

A

gentiotriose*,
xylosylrutinose,
glucosylrutinose

124
Q

color and sources of Cynanidin

A

anthocyanin

(Cy:- orange-red color), in apples, cherries, oranges, plums, raspberries, & cabbage

125
Q

color and sources of Delphinidin

A

(Dp:- blue-red color), in grapes & oranges

126
Q

color and sources of Malvinidin

A

(Mv:- blue-red color); blue grapes

127
Q

color and sources of Pelargonidin

A

(Pg:- orange color) in strawberries

128
Q

color and sources of Peonidin

A

(Pn:- orange-red color), in cherries & plums

129
Q

color and sources of Petunidin

A

(Pt:- blue-red color) in blueberries

130
Q

Increasing hydroxy (-OH) content increases _____ color in anthocyanin

A

blue

131
Q

Increasing methoxy (-OCH3) content increases ____ color in anthocyanin

A

red

132
Q

the effect of ph on anthocyanin

A

acidic conditions change pigments to red color;

alkaline conditions change pigments to shades of blue or colorless

133
Q

the effect of cooking on anthocyanin

A

lost to cooking water

134
Q

some chemicals that decolorize anthocyanin

A

sulfites,
ascorbic acid,
H2O2

135
Q

effect of metals on anthocyanin

A

Form purple or gray colors with metals

136
Q

the effect of high temperatures on anthocyanin

A

High temperatures cause destruction of anthocyanin pigments (e.g., spray drying)

137
Q

the effect of high sugar content and the presence of oxygen on anthocyanin

A

High sugar content and the presence of O2 enhance destruction of anthocyanins

138
Q

Colorless forms of anthocyanins may undergo oxidation in presence of O2 to form colored products (e.g., “_____” of canned pears)

A

pinking

139
Q

Glucosidases and anthocyanases effects on anthocyanin

A

remove the sugars from anthocyanins, thus destabilizing the molecule and causing loss of color

Deleterious effects of these enzymes curtailed by microwave blanching - dry heat

140
Q

Complexion with metal ions ex. Fe, or Cu can result in _______ color formation which may be undesirable.

A

blue/green

141
Q

Uses of anthocyanins in food processing

A

♣ Antioxidants

♣ Color additive

142
Q

Flavonoids

A

• H2O-soluble pigments found in plants and microorganisms
• most abundant polyphenols in the diet
• a.k.a. anthoxanthins – they are glycosides
with a benzopyrone nucleus
• most common sugar – rutinose
• they give certain fruits, vegetables and herbs their dark red, blue and purple colors
• many are antioxidants

143
Q

what are the most abundant polyphenols in our diets?

A

flavonoids

144
Q

anthoxanthins

A

flavonoids

145
Q

structure of flavonoids

A

glycosides with a benzopyrone nucleus

146
Q

the most common sugar in flavonoids

A

rutinose

147
Q

the color of flavonoids

A

they give certain fruits, vegetables and herbs their dark red, blue and purple colors

148
Q

classification of flavonoids

A 
flavones
isoflavones
flavonols 
flavonones
flavononols
149
Q

True/False

flavonoids are antioxidants

A

true

150
Q

flavones

A

(double bond at 2:3 position)

apigenin

151
Q

Isoflavones

A

(benzene ring at 3 position)

Genistein

152
Q

Flavonols

A

(-OH group at 3 position)

Quercetin

153
Q

Flavonones

A

(no 2x bond at 2:3 position)

Naringenin

154
Q

Flavanonols

A

(-OH group at 3 position; no 2x bond at 2:3 position)

Xeractinol

155
Q

What are the basic differences between flavonoids and anthocyanins

A

they are both polyphenolic but the basic difference is their structure. They have different parent compounds

♣ anthocyanins with pyrene
♣ flavonoids with benzopyrene

also display a range of colors, but flavonoids tend to be less intensely colored than anthocyanins.

156
Q

True/False

Flavonoids are more intensely coloured than anthocyanins

A

false

flavonoids tend to be less intensely colored than anthocyanins.

157
Q

Polyphenolic nature of flavonoids

A

o flavonoids can act as substrates for enzymatic browning (and unlike anthocyanins, brown colors formed may manifest because of the low coloring power of flavonoids

158
Q

True/False

Flavonoids are not antioxidants

A

False

Also have antioxidant properties by virtue of metal chelation and radical scavenging
Flavonoids more potent antioxidants due to structural differences

159
Q

Flavonoids suggested to have provitamin ___ activity

A

C

i.e. enhance vitamin C. activity

160
Q

Oxidation and further oxidation of Vitamin C

A

Vitamin C –> dehydroascorbic acid –> (further oxidation) diketogluconic acid

161
Q

How can you stop and revert vitamin C oxidation?

A

If the oxidation keeps on going, we lose vitamin C activity but when we have flavonoids, they reduce the dehydroascorbic acid back to vitamin C

162
Q

How do flavonoids protect/preserve vitamin C?

A

Flavonoids protect/preserve vitamin C activity by reducing dehydroascorbic acid back to ascorbic acid and prevent further oxidation to the inactive diketogluconic acid form.

163
Q

Common properties of flavonoids

A
  • Polyphenolic structure, substrates in enzymatic browning reactions;
  • May be involved in other discoloration reactions in foods (e.g., may bind Fe in foodstuffs to form blue/green colors);
  • Chelating agent;
  • Antioxidant / free radical scavenger;
  • Pro-Vitamin C activity.
164
Q

Apigenin sources and common properties

A

found in fruits, vegetables and leaves.
Common sources are chamomile tea and celery
o Yellow in color with pleasant smell
o Has bitter and astringent taste (the dry sensation we feel in the cheeks-the proteins in saliva are precipitated out by the astringent molecules. Tea, lemon, cider, wine)
o Apart from its antioxidant effect, it is also said to elicit calming effect on consumers (i.e. relieves anxiety)

flavones

165
Q

Describe Astringent taste

A

the dry sensation we feel in the cheeks-the proteins in saliva are precipitated out by the astringent molecules. Tea, lemon, cider, wine

166
Q

Genistein sources and common properties

A

• is colorless pigment found in plant materials, fruits, vegetables, legumes.
o Ex. Soy, alpha alpha, pea
o Bitter, astringent taste
o Estrogenic effects
o Increase body fat and result in weight gain
o Loss of Zn but retention of Cu
o Utilization of Ca++, thus relieves osteoporosis
o Relieves menopausal symptoms (e.g. hot flashes)

Isoflavones

167
Q

Quercetin sources and common properties

A

• is ubiquitous in nature color ranges form shades of yellow to brown.
o Bitter, astringent taste
o Potent antioxidant

Flavonols

168
Q

Naringenin sources and common properties

A

o Found in plant material mostly in citrus fruits
o It is colorless and bitter and is what gives grapefruit the bitter taste

Flavonones

169
Q

Xeractinol sources and common properties

A

o Found in leaves and is colorless and bitter in taste
o Relatively newly discovered, so not well characterized.

Flavanonols

170
Q

Betalains

A
  • H2O-soluble plant pigments
  • Glycosides (glucose commonly present)
  • Two main colors - red & yellow
  • Red pigments => betacyanins (e.g., betanin)
  • Yellow pigments => betaxanthins (e.g., vulgaxanthin) • Found mostly in beet plants

o Used as food colorants because of color intensity
o Destruction by heating
o Ioss to cooking water
o Ex. Beets, Spanish chard, cactus fruit

171
Q

betacyanins color

A

red

e.g., betanin

172
Q

betaxanthins color

A

yellow

(e.g., vulgaxanthin) Found mostly in beet plants

173
Q

Tannins

A

o Complex plant pigments with a range of color (pale yellow to dark brown) and range of solubility
o The variations of solubility due to size differences
o Found a lot in tree barks and in leaves (tea)
o Cause astringency
o Because they can serve as substrates for enzymatic browning reactions by PPO, even the less intensely colored tannins may undergo enzymatic browning to cause dark discolorations in foods

174
Q

Quinones

A

o Are derived from aromatic compounds with even numbered –OH groups
o The –OH groups oxidize to form the corresponding quinone
o So if you were to start with benzene, you would require 2 hydroxylation steps to form dihyroxybenzene which can then oxidize to form a quinone.
o It is water soluble and has intense dark colors that enable it to be used as dyes.
o It is also used as a purgative because of its capacity to induce loose bowels.

175
Q

Melanins

A 
o	Quinone (polymerization) --> melanoidins or Melanins (depending on the sizes)
o	Depending on the size of Melanins will determine the degree of solubility as well as intensity of the color of the color of the product
176
Q

Xanthones

A
  • Plant pigments with structural resemblance to flavonoids & quinones, i.e., glycosides;
  • H2O-soluble and yellow in color;
  • Common e.g., mangiferin.
177
Q

Caramelization

A

o When sugars are heated at high temperatures, they oxidize to form various breakdown products that can aggregate to form the colored products caramelans, caramelens, and caramelins. (size increases respectively)

178
Q

MAILLARD BROWNING

A

o Non-enzymatic browning due to reaction between sugars and primary amino groups of proteins, peptides, amino acids, amine in foods when they are heated called MAILLARD BROWNING

179
Q

Gentiobiose

A

disaccharide
D-glucose
B 1–>6 linkage
It is a product of the caramelization of glucose

180
Q

Rutinose

A

disaccharide

is present in some flavonoid glycosides.

181
Q

Sophorose

A

disaccharide

It is a product of the caramelization of glucose

182
Q

Neohesperidose

A

is the disaccharide which is present in some flavonoids

183
Q

Rosinidin

A

red- anthocyanin (-OCH3)

Food Chemistry II (8 decks)

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