1
The Color Phenomenon
• Color is a perception that is manifested in response to
a narrow span of the electromagnetic spectrum
emitted by light sources (e.g., sunlight).
• Light itself has no color and color does not exist by
itself; it only exists in the mind of the viewer
• What is light? A vibration in an electromagnetic
field through which energy is transported. Since it is
an electromagnetic field, it does not require a
medium.
2
The Electromagnetic Spectrum
Most wavelengths of light can not be seen by the human eye.
The visible part of the electromagnetic spectrum lies between
ultraviolet and infrared light (between about 400 and 700 nm).
The higher the frequency (shorter the wavelength), the higher
the photon energy. Radio waves are at the long wavelength end of
the spectrum and gamma rays are at the short wavelength end of
the spectrum.
3
Natural Pigments
4

Pigments are compounds that absorb light in the
wavelength range of the visible region. This
absorption is due to a molecule-specific structure
(chromophore) that captures the energy from a
radiant source.

Some energy is not absorbed and is reflected
and/or refracted; this energy is captured by the
eye and generates neural impulses, which are
transmitted to the brain, where they could be
interpreted as a color.
5
The Dry Color Manufacturers Association makes a clear
distinction between pigment and dyes:
1. Pigment is a colored, black, white, or fluorescent
particulate organic or inorganic solid, which is usually
insoluble and, essentially, physically and chemically
unaffected by the vehicle or substrate into which it is
incorporated. Thus, the pigmentation effect is by
selective absorption and/or by scattering of light; a
pigment will retain its crystalline or particulate structure.
2. Dyes are soluble in the carrying medium and therefore
crystalline/particulate features are lost in solution when
a dyestuff is used to impart color to a material.
6
In the latter definition, the difference between pigment
and dye is emphasized.
However, other authors prefer to use the more generic
term colorant
Colorants are defined as substances that modify the
perceived color of objects, or impart color to otherwise
colorless objects.


With this definition, pigments and dyes are grouped
within the term colorants. It is reasoned that if only
solubility is considered, the same substance could be a
dye or a pigment depending on how it is used.
It is important to be aware of such differences, but in our
discussions we will use the terms colorants and pigments
as synonymous.
7

Chlorophylls and carotenoids are the most abundant
pigments in nature. They are involved in fundamental
processes, and life on Earth depends on them.

Chlorophyll is not found in animals but carotenoids
accumulate in some organs (e.g., eyes) and tissues (e.g.,
skin of fish, bird plumage).

In general, animal carotenoids are obtained from the
common diet. Other pigments are also found in animals,
some have important functions (e.g.,heme proteins,
riboflavin), whereas the function of others is not yet
completely clear (e.g., melanins, flavonoids).
8
1. Tetrapyrroles: Chlorophylls (Green), Bilins
2. Isoprenoid derivatives:
 Carotenes (e.g., β-carotene, lycopene) Yellow-red
 Xanthophylls (e.g., lutein, zeaxanthin) Yellow
3. N-Heterocyclic compounds
 Betalains Yellow-red
4. Benzopyran derivatives:
 Flavonoids (e.g., anthocyanins, flavonols,flavones,
anthochlors), Blue-red, yellow-white, white, cream,
yellow
5. Quinones:Anthraquinone (e.g., carminic acid) Red-purple 9

Tetrapyrroles are very important in living organisms
and probably every organism has the ability to
synthesize them.

These pigments can be either linear or cyclic
structures, but the pyrrole ring is common in both
kinds of molecules

In the tetrapyrrole group, the chlorophyll subgroup is
the most important; this subgroup is mainly present in
the chloroplasts of higher plants and most algae
10

Chlorophylls - usually most abundant and most
important pigments in light harvesting
 located in protein complexes in internal membranes of
chloroplasts

Contain tetrapyrrole ring (chlorin) similar to heme, but
contains Mg2+

Chlorophylls a (Chl a) and b (Chl b) in plants
11
Chlorophyll is found and Photosynthesis
takes place in the chloroplasts of plant cells
Leaf cross-section
Cells containing
chloroplasts
Leaves contain millions of chloroplasts
12
chlorophyll a – primary pigment in plants and
cyanobacteria
-absorbs violet-blue and red light
chlorophyll b – secondary pigment absorbing light
wavelengths that chlorophyll a does not absorb
13
14
Chlorophyll
H2 C
H3 C
H
CH
R
C H2 C H3
N
N
Mg
H
N
H
N
C H3
H3 C
O
C O 2 C H3
C H2
C O2
C H3
C H3
C H3
C H3
15
16
17
Photosynthesis
• Light Dependent Reaction
– Energy from the high energy electron of chlorophyll is
used to make ATP and NADPH
• Light Independent Reaction (Calvin Cycle)
– ATP and NADPH is used to make glucose from CO2
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19
20
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1. Tetrapyrroles: Chlorophylls (Green), Bilins
2. Isoprenoid derivatives:
 Carotenes (e.g., β-carotene, lycopene) Yellow-red
 Xanthophylls (e.g., lutein, zeaxanthin) Yellow
3. N-Heterocyclic compounds
 Betalains Yellow-red
4. Benzopyran derivatives:
 Flavonoids (e.g., anthocyanins, flavonols,flavones,
anthochlors), Blue-red, yellow-white, white, cream,
yellow
5. Quinones:Anthraquinone (e.g., carminic acid) Red-purple2222
2. Isoprenoid derivetives

Isoprenoids are also known as terpenoids and are
widely distributed in nature. They are found in all
the kingdoms where they develop multiple
functions (hormones, pigments, phytoalexins).

The isoprenoid group has three main subgroups:
quinones, carotenoids, and iridoids are the most
important pigments in the isoprenoid group
23
Carotenoids

Carotenoids are compounds constituted by eight
isoprenoid units (ip). The ip units are joined in a headto-tail pattern, but the order is inverted at the molecule
center

Lycopene is considered the first colored carotenoid in
the biosynthesis of many other natural carotenoids and
it is linear.
24

Carotenoids are pigments (C40) that naturally occur in
chloroplasts and other photosynthetic organisms and absorb light
for photosynthesis.

There are over 600 carotenoids including beta-carotene.

Carotenoids have been found to have antioxidative properties,
reducing the risk of mortality from chronic illnesses.

Animals are incapable of producing carotenoids and must obtain
them from their diet. E.g the pink in flamingos & red in lobsters
are from carotenoids in their diets.

Carotenoids with only hydrogen and carbon in their molecules are
collectively called carotenes; oxygenated derivatives are called
xanthophylls.
25
IMPORTANT PHYSICAL AND CHEMICAL
PROPERTIES OF CAROTENOIDS
Quench singlet
oxygen
Absorb light
Easily isomerized
And oxidized
Scavenge or interact
with free radicals
CAROTENOIDS
Lipophilic
Bind to hydrophobic
surfaces
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PRINCIPAL CAROTENOIDS IN FOODS
b-Carotene
OH
b -Cryptoxanthin
Lycopene
HO
OH
Lutein
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HEALTH-PROMOTING FUNCTIONS AND
ACTIONS ATTRIBUTED TO CAROTENOIDS
Provitamin A
activity
Immunoenhancement
Reduction of the risk
of cancer
CAROTENOIDS
Reduction of the risk
of macular degeneration
Reduction of the risk of
cardiovascular
disease
Reduction of the risk of
cataract formation
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Beta-carotene & Lycopene
• Most commonly known as the pigment that makes carrots
orange, beta-carotene is a precursor of Vitamin A.
• Vitamin A, important for vision and as an antioxidant, is
made from beta-carotene via beta-carotene dioxygenase.
• Lycopene is an intermediate in the production of betacarotene, and is a bright red carotenoid.
• Lycopene is found in tomatoes, pink grapefruit, red bell
peppers, etc., and has been found to have antioxidant activity.
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1. Tetrapyrroles: Chlorophylls (Green), Bilins
2. Isoprenoid derivatives:
 Carotenes (e.g., β-carotene, lycopene) Yellow-red
 Xanthophylls (e.g., lutein, zeaxanthin) Yellow
3. N-Heterocyclic compounds
 Betalains Yellow-red
4. Benzopyran derivatives:
 Flavonoids (e.g., anthocyanins, flavonols,flavones,
anthochlors), Blue-red, yellow-white, white, cream,
yellow
5. Quinones:Anthraquinone (e.g., carminic acid) Red-purple3030
3. Benzopyran derivatives:
Flavonoids (e.g., anthocyanins,
flavonols, flavones, anthochlors),
Blue-red, yellow-white, white,
cream, yellow
31
Flavonoids and anthocyanins are conspicuous plant
pigments in nature that are responsible for the beauty
and splendor of flowers, fruits, fruit tree blossoms and
of the autumn leaves.
Flavones are responsible for the yellow and orange
colors; and the anthocyanins are the source of red,
violet and blue colors. These compounds occur mainly
in higher plants and are less common in the lower
orders. You don’t find them in algae, fungi or bacteria.
32
The flavonoids play a major role in attracting insects
to feed and pollinate these plants. Some of them also
have a bitter taste and repel harmful insects like
caterpillars.
Flavonoids are thought to be antioxidants, and play a
major role in our diet, preventing the ravages of aging
caused by free-radicals.
These compound have their biosynthetic origin in
both the skimic acid pathway and the acetogenin
pathway - they are of hybrid origin.
33
Anthocyanin
Flower Pigments
34
• Largest class of polyphenols: ~ 4,000 kinds
• Often responsible for yellow or red/blue/purple colors in
flowers, fruits, vegetables
• Serve as antioxidants for the plants during photosynthesis
• Includes antioxidant, anti-inflammatory, cancerpreventative, & cardioprotective compounds
35
36
I. Carotenoids as food colorants
Humans have utilized carotenoids as food colors for
centuries: saffron, pepper, leaves, and red palm oil are
some of the most used pigments.
 These products comprise mixtures of pigments and
other frequently unidentified substances; natural
sources of carotenoids have persisted through the years
and new ones have been introduced.
 As previously mentioned, carotenoids have very
important biological activities and their use as food
and feed is common today and recommended largely
due to their vitamin A and antioxidant activities, very
important for the maintenance of body health.

37
1. Carotenes

An oleoresin is obtained by solvent extraction of carrots or
alfalfa grass and vegetable oil with subsequent removal of
solvents.

The oleoresin contains oils, fats, and waxes of natural
occurrence in the source material.

The permitted solvents for the extraction process are
acetone, methanol, ethanol, propan-2-ol, hexane, and
dichloromethane; their use is allowed in different food
products.

The FDA has permitted the use of these sources of carotenes
for coloring foods in general.
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2. Marigold
 Marigold (Tagetes erecta L.) is an annual herb and its petals have
a high content of carotenoids with values higher than 8 g of
carotenoids/kg of dried petals. It is also interesting that only one
carotenoid predominates in its composition — lutein — with more
than 80%.
 The main marigold products are flower meals and oleoresin, which
is obtained by hexane extraction.
 In the oleoresin, lutein is as ester with palmitate, myristate, and
stearate in all the possible combinations.
 It is used in feed pigmentation and in the European Union as a
food additive. Marigold pigment can be further purified and mixed
with a suitable vegetable oil, calcium silicate, and gelatin, among
others, to obtain a product of food grade. This product is suitable
for coloring pastas, vegetable oils, dairy and bakery products, as
well as juices and mustard, among others.
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3. Paprika
 Is obtained from the dried pods of sweet pepper (Capsicum
annum).
 To obtain paprika, pods are ground to produce a powder of
deep red color and pungent flavor.
 Paprika carotenoids are mainly capsanthin and capsorubin,
which occur primarily as lauric acid esters.
 The quality of paprika is commonly specified as color
strength by measuring the absorbance at 460 nm in an
acetone extract, as suggested by the American Spice Trade
Association (ASTA).
 Paprika oleoresin is an orangered oil-soluble extract that is
obtained by using hexane as solvent. The use of paprika, as
a spice, is limited to suitable savory products.The use of
paprika powder and oleoresin is permitted by the FDA for
coloring foods in general.
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4. Saffron
 (Crocus sativus L.) is the most expensive spice
used in the food industry and its consumption has
shown increments because of its health beneficial
properties.
 This plant is native to Greece and Asia, and today
is cultivated in various parts of the world. Iran and
India are the major world suppliers of saffron, but
its quality is not as high as that of Spain.
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 The coloring power is mainly attributed to water-
soluble carotenoids, the crocins, which are glycosyl
esters of 8,8′-diapocarotene-8,8′-dioic-acid (crocetin).
 The high solubility of saffron pigments in water is a
strong advantage, compared to other carotenoids that
require special formulations to be soluble or
dispersible in aqueous food systems, and is the reason
for their great application as a food colorant.
 Saffron is basically used to impart a pure yellow
color to rice and other foods; it is also employed as a
spice.
 Color is the major parameter for quality grading of
saffron Its use as a coloring agent for food in general
was established in 1966 by the FDA
42
Tomato (Lycopersicon esculentum) has a high
carotenoid content with lycopene the main compound
(80 to 90% of total carotenoids) followed by βcarotene. New tomato varieties with high and
improved content have been developed; efforts have
focused on developing tomatoes with higher βcarotene content, which are thus better sources of
vitamin A. Lycopene products have begun to be
commercialized.
However, it is clear that other modifications are
required to use tomato extract as colorant because of
its strong flavor.
43


In the United States, extracts of grape are the only
anthocyanin source approved by the FDA as a
food colorant.
The commercial preparations are enocyanin and
lees (sediment of grape juice tanks). The grape
color extract is approved to be used in
nonbeverage foods, whereas grape skin extract
(enocyanin) is permitted in beverages.
44



legislation, grape commercial extracts are used mainly
for beverages, soft drinks, as well as confectionery
products
In addition, the anthocyanins of red radish have good
stability; maraschino cherries colored with radish
anthocyanins have a shelf life of at least 6 months at
25°C, and their stability has been associated with the
presence of acylated pelargonidin derivatives.
The proposed method to produce radish
anthocyanins uses an abrasive peeler that is followed
by pressing of the epidermal pulp; this strategy
produces recoveries greater than 90%.
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Natural Colorants as
Nutraceuticals
46
I. Carotenoids
 Pathological processes, including cancer and strokes,
in living organisms are commonly associated with an
oxidative stress condition. Thus, antioxidant
compounds are usually considered beneficial agents
for prevention or treatment

As mentioned before, some carotenoids have a
considerable high antioxidant activity and
consequently a positive effect in human health

Carotenoids are membranal pigments: carotenes are
apolar and immersed in membranes, showing little
mobility, whereas xanthophylls are polar and have a
variable position and mobility in membranes.
47

As can be deduced, carotenes have good antioxidant
activity against radicals generated inside the
membrane.

On the other hand, the xanthophyll zeaxanthin has its
hydroxyl groups exposed to the aqueous cellular
media and it is able to react with radicals of that zone.
The relative mobility of carotenoids has been
associated with the fluidity of membranes;
particularly, carotenoids have shown an effect on
membrane permeability to oxygen and other
substrates
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Type of Carotenoid
Biological Function
1. All : Effect in the immune response and in the

intercellular communication, treatment of
photosensitivity diseases
The use of algae (especially Phaeophyta) carotenoids
diminishes the risks of being affected by certain types
of cancer
2. β-Carotene: Treatment of certain kinds of cancer (e.g.,
smoking-related cervical intraepithelial neoplasia and
cervical and stomach cancer), affects the immune
response in rats and by this mean tumor growth is
inhibited, inhibits lipid peroxidation, suppresses the
increase of hormones related to stress syndrome.
Suppresses the increase of hormones related to stress
syndrome
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3. lycopene:
 Has been evaluated in rats in relation to its role in
colon carcinogenesis using azoxymethane as a
chemical carcinogen.
 Lycopene has been provided in the form of a 6%
oleoresin, which is well absorbed and produces a
reduction in the serum of the thiobarbituric acid
reactive substances (TBARS), suggesting an important
role in the protection against oxidative stress.
 Moreover, the number and size of aberrant crypt foci
(ACF) is reduced; thus, it could have a positive role
against colon carcinogenesis.
50

Lycopene is accumulated in tissues such as
prostate, adrenals, and testes; consequently, a
selective uptake of the carotenoid may be
involved in a tissue-specific anticarcinogenic
mechanism.

Also, it has been reported that tissues high in
LDL receptors selectively accumulate lycopene,
and a protective effect of this carotenoid is
evident at a dose of 10 ppm, which is equivalent
to two servings of tomatoes or tomato products
per day.
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



The anthocyanins of Hibiscus sabdariffa L. (Malvaceae) have
been used effectively in folk medicines against hypertension,
pyrexia, and liver disorders.
tert- Butylhydroperoxide (t-BHP) can be metabolized into free
radical intermediates by cytochrome P-450 (in hepatocytes) or
hemoglobin (in erythrocytes), which can subsequently initiate
lipid peroxidation, affect cell integrity, and form covalent bonds
with cellular molecules resulting in cell injury.
t-BHP causes leakage of lactate dehydrogenase (LDH) and
alanine aminotransferase (ALT) and formation of
malondialdehyde
(MDA) in hepatocyte cultures. It also mediates DNA damage in
mammalian cells. These phenomena are similar to the oxidative
stress occurring in the cell or tissue
52

Oxidative stress is considered to play a prominent role in the
causation of many conditions, for example, inflammation, aging,
and cancer.

It is observed that Hibiscus anthocyanins inhibit lethal injury
induced by t-BHP in rat primary hepatocytes and rat livers that
might involve their ability to quench free radicals.

Hibiscus anthocyanins are able to quench the 1,1-diphenyl-2picryhydrazyl (DPPH) free radicals in a dose-dependent manner;
at 0.20 mg/ml they quench about 50% of the free radicals. It has
also been pointed out that up to 0.50 mg/ml concentration they
exhibit no toxic effect on the primary culture of hepatocytes.
53
.

Thus, Hibiscus pigments exhibit an antihepatoxicity
effect against t- BHP-induced cytotoxicity, probably
via their ability to quench free radicals and decrease
MDA formation. It is suggested that consuming soft
drinks containing Hibiscus pigments is sufficient to
reach the lowest dose (50 mg/kg) that showed some
antioxidant activity in this study.

Therefore, we suggest that daily consumption of
Hibiscus anthocyanins might be effective in
lowering oxidative damage in living systems.
54
Naturally occurring colorants
Substance
Anthocyanins
Caramel
Betacyanins
Colors
orangered
beige to
brown
red
Sources
berries,
grapes, apples,
roses, red
cabbage, sweet
potato
heated sugars
red beets,
cactus fruit
Used in
candy, fruit
beverages, ice cream,
yoghurt , jams
baked goods,
gravies, vinegars,
syrups, colas,
sauces
candy, yogurt, ice
cream, salad
dressing, cake mixes
Naturally occurring colorants
Substance
Colors
Sources
Carmine
red
cochineal
insects
Carotenoids
(precurser of
vit.A)
yellow to
orange to
red
Chlorophylls
green to
olive green
saffron,
tomatoes,
paprika, corn,
butter,red
salmon, marigolds,
marine algae,
carrots
green plant
leaves
cont.
Used in
candy, dairy
products, drinks,
fruit fillings
meat products,
cheese, butter, spice
mixes, salad
dressings
dehydrated spinach
Naturally occurring colorants
cont.
Substance
Colors
Sources
Riboflavin
(vit.B2)
yellow
vegetable
leaves, milk,
eggs, organ
meats, malt
flour, bread,
pastries, cereals,
dietary products
Curcuma longa
rhizome
pickles, mustard,
spices, margarines,
ice cream, cheese,
baked goods, soups,
cooking oil, salad
dressings
curcumin
yellow
Used in