Introduction:

Substances
with intense colors are often called colorants. Colorants may be natural or synthetic. Colorants are any substances that are added to food or
cosmetics to change or enhance its color.  Colorants used for textile and foods
are often called dyes. Colorants used for inks, paints and cosmetics are often
called pigments.

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The
use of natural dyes began back in 2600BC in China and adding colorants to foods
and things used for appearance, but known today as cosmetics was in Europe
during the Bronze age. In 1856, Sir William Henry Perkin created the first
synthetic color. The production and recovery of synthetic colors came from the petroleum-derived
products like aniline. They were called “coal tar colors because the starting
substance were taken from coal (Lakshmi, 2014).

 

Sources
of natural colorants are plants, but also can be animals and minerals.  They are extracted from natural things like
fruits, vegetables, insects, leaves, algae, seeds and etc. In order for the use
of these colors, they must be certified through the Food & Drug
Administration (FDA). The FDA uses the U.S. Federal Food, Drug, and Cosmetic
Act(FD & C Act) to oversee the safety of food, drugs, and cosmetics.
Congress passed this set of laws in 1938. A dye that is labeled “FD &C” means
it can only be used in foods, drugs, and cosmetics. Labeled “D & C” means
it can only be used for drugs and cosmetics (Calvo, 2001).

 

There
are 26 colors that are permitted to be used in food and 28 to be used in
cosmetics and pharmaceuticals (drugs). Natural colorants are mainly used on
food and synthetic colorants are mainly used on cosmetics.  A few commonly used natural colors are Annatto
(seed), turmeric, beet juice (root), red Cabbage (vegetable), spinach (leaf),
anthocyanin, carotenoids, chlorophyll, and caramel. Easy availability of these food
dyes is also one of the reasons for their popularity. But the driving reason
behind the popularity of natural food colors is the concern that revolves
around the synthetic food colors like tartrazine.

 

Synthetic
colors have their drawbacks because of the chemicals used to create the
product. So the demand for natural colors in the international market
increased. For example Japan and European countries have banned trading
synthetic color made products. They encourage the use of natural colors in
crayons, organic textile printing, infant toys, etc., but natural colors
obtained from plants, animals, and minerals also known as bicolor had their
drawbacks. For instance, heat, pH and light stability, and oxidizing agents in
food (Lakshmi, 2014). This is what led to synthetic colors gaining awareness in
cosmetics and food industries.  In contrast,
synthetic colors are easier to produce, inexpensive and far much better in
coloring properties when needed to blend. Even though synthetic colors gained
popularity so did the safety concerns across the world and in the United States
of America (USA). That led to only seven synthetic colors to be authorized.

 

Natural
colorants are in demand today than synthetic colors. They are safer with in
food. Since they are obtained naturally they are free of harmful side effects.
They are only harmful to those who have certain allergies and intolerances.
Things like that are only individual problems and are not generalized.

 

 

But the driving reason behind the growing
demand of natural food colors is the concern that revolves around the synthetic
food colors like tartrazine

 

Dyes are certified, water soluble synthetic
food colorants. They are manufactured as powders, granules and liquids. The
synthetic dyes are of several types as per their basic compound and structure.

 

 

Chemistry of Natural Colorants

 

Turmeric:

Turmeric is a root that has been
used to add color to food and cosmetics for centuries. Grinding the rhizomes of
the perennial herb, Curcuma longa, which is native to India, South America,
China, and the East Indies, produces it. It also
has another name known as Indian Saffron. It has been used in Indian cooking
for centuries

 

            Curcuma
longa is one of the most essential spice used all over the world. It is called
the ” golden spice of life” (Lakshmi, 2014). The primary color is curcumin,
which is an orange- yellowish color. Curcumin is oil soluble and seems to fade
in light but has good heating stability. Many food industries uses it for
coloring. It is predominantly used in dairy products, beverages, cereal,
pickles, sausages, soups, ice cream, and bakery. It is also used for skin care
and hair care cosmetics products such as foundation, shampoos, face cream, face
soup and eye shadow because it is antibacterial in nature. It has typical turmeric like odor, which is very strong. 

Curcumin
are naturally insoluble in water but manufacturers have found a way to use it
in beverages by using particle size reduction and emulsifiers. This allows it
to be used in aqueous and lipid solutions or products

 

Figure 2: Structure of curcumin pigment.

Carotenoids:

Carotenoids are yellow, red or orange pigments that are
spread in both plant and animal world. They occur in annatto, carrots,
oranges, prawns, red peppers, saffron, tomatoes, and palm fruits. Carotenoids can occur in nature
in four states; crystals, esters of fatty acids, combinations with sugar, and
others with protein (Butnariu,
2016).

Carotenoids were
identified in a free form in natural products. Carotenoids are divided into: carotenoid
hydrocarbons and oxygenated derivatives of hydrocarbon carotenoids. Hydrocarbon
carotenoids are carotenoids with 40 carbon atoms, formula C40H56. In figure 3 the
most important of these are shown: lycopene (red carotenoid pigment),
?–carotene (alpha-carotene is a precursor to retinoic acid, or a provitamin A
compound), ?–carotene (Butnariu, 2016).

 

 

Figure 3: This figure demonstrates the structures of the most
important carotenoids (Butnariu
M, 2016).

Lycopene
are acyclic carotenoid formed from the sequential desaturation. It is a
crystalline material. It has a red–purple color. It is insoluble in water and soluble
in organic solvents. The color of fruits and tomatoes are obtained from
lycopene.

 

?–carotene
has a form of carotene with a ?-ionone ring at one end and a ?-ionone ring at
the opposite end. It is a copper–colored crystalline substance soluble in
organic solvents. Alpha-carotenes are antioxidant. They
give the color orange and red fruits and vegetables.

 

?–carotene
is composed of two retinyl groups. By heating ?–carotene it can be converted into
?–carotene.  It is found in plants in
smaller quantities than ?–carotene. ?–carotene has a red orange colored fats soluble
terpenoid with antioxidant properties It is soluble in organic solvents.

Figure 4: This chart is representations of the kinds of plants the
most important carotenoids are found in. The data was taken from the database
for flavonoid content of selected foods.

Table 1: Carotenoids
Structures

Structures

Examples of
Carotenoids

Hydrocarbons

Hexahydrolycopene, Lycopersene, Phytofluene, Torulene, and
?–zeacarotene

Acids and Acid Esters

Torularhodin, and Torularhodin methyl
ester

Esters of Alcohols

Astacein, Fucoxanthin, Isofucoxanthin,
Physalien, Siphonein, and Zeaxanthin

Glycosides

Oscillaxanthin,
and Phleixanthophyll

Nor– and Seco–carotenoids

?–carotenone, Actinioerythrin, Peridinin,
Triphasiaxanthin, and Pyrrhoxanthinino

 

There
are many representatives of these derivatives such as: xanthophylls,
carotenoids ketones, and carotenoid acids. Xanthophylls are hydroxyl
derivatives of carotenoid hydrocarbons, which comprise a diverse group of
oxygenated carotenoids with varied structures and complexes functions. Responsible
for yellow colorants less hydrophobic

 

 

 

 

Figure 5: Chemical structure of Xanthophylls

 

 

Carmine/Cochineal:

            Cochineal is a native insect of South America and Mexico.
It is a parasite that lives on cacti of genus Opuntia. It feeds on the moisture
and nutrients of the cactus. These female insects are used to produce a deep
red color. The dye extracted from the insects comes from their eggs. It is
called carminic acid (C22H20O13) also
known as Carmine. For centuries, the Aztecs used these insects to dye
fabrics a deep-red color. If you crush
up 70,000 of these bugs, you can extract a pound of a deep-red dye (Lakshmi,
2014). This dye is safe to ingest, so it found its way into a variety of
food and cosmetic products that required a red color. It is found in food such
as juices, ice cream, yogurt, and candy and in cosmetic products such as eye
shadow and lipstick.

Carminic acid’s main color that
is produced is red but it also can be pink purple, or even orange coloring
depending on the extraction method being used, such as using water or
alcohol.  When the carminic acid is
extracted in low pH it is orange but in high pH it is purple. The color change
is due to phenolic groups on the carminic acid molecule being affect by he pH
levels of solvents (“Carmine/
Cochineal | DDW The Colour House”, 2017).

 

 

Figure 7: Chemical Structure of Carminic Acid

 

Chlorophyll:

Chlorophyll is a green pigment found
in most plants, algae, and cyanobacteria. The name was derived from the Greek
words “chloros” meaning green and “phyllon” meaning leaf(Lakshmi, 2014).
Chlorophyll is the most widely distributed natural plant pigment, present in
all green leafy vegetable. Chlorophyll is a green, oil soluble color.
Chlorophyllins are water-soluble and when exposed to heat and light it is
somewhat stable. Uses include sugar confectionery, dairy products such as ice
cream, and dry beverage mixes. They naturally occur in alfalfa grass, nettles,
parsley, and spinach (“Chlorophyll/ Chlorophyllins | DDW The Colour
House”, 2017).

 

Structure of Chlorophyll:

Chlorophyll is a green pigment that is similar to other porphyrin
pigments, such as heme. In Figure 5 at the center of the chlorophyll structure
there is a magnesium ion.  The chlorin
ring is connected to different side chains. The most widely distributed form is
chlorophyll a. Hans Fischer interpreted the structure of chlorophyll in 1940 (Lakshmi,
2014). The pigments chlorophyll a produces are blue-green and chlorophyll b
produces yellow-green pigments. As shown in Figure 9 the figure differ at one
of the carbons on the top. Chlorophyll a has a methyl (-CH3) while chlorophyll
b has an aldehyde( -OCH). This contributes to their varying in light absorption
physical properties. Chlorophyll
a absorbs blue, red and violet wavelengths in the visible spectrum. It
participates mainly in oxygenic photosynthesis in which oxygen is the main
by-product of the process. Chlorophyll b primarily absorbs blue light and is
used to complement the absorption spectrum of chlorophyll a by extending the
range of light wavelengths a photosynthetic organism is able to absorb (Perdue,
2017).

 

Chlorophyll a                        Chlorophyll b

Figure 8:Shows
chlorophyll in the form of a and b. The difference between them is that
chlorophyll a has a –CH3 at the top of the structure, while chlorophyll b has a
–OCH. (Lakshmi, 2014)

 

Anthocyanin:

Anthocyanin is the pigment compound
responsible for red, purple and blue colors in many fruits and vegetables (Lakshmi, 2014).
Within each plant source, these pigment compounds vary in concentration,
proportions, and chemical structure, all of which influence use for color in a
food or beverage. The pH causes a shift from red to purple to blue, from low to
high pH respectively, while heat and light degrade the pigments. The effects of
the pH change the structure of the anthocyanin present.

 

Anthocyanin is synthesized within
the plants from flavanol-derived structures called anthocyanidins (“Anthocyanin
| DDW The Colour House”, 2017). Examples of anthocyanidins include: delphinine,
pelargonidin, and cyaniding. Delphinine varies from blue to purple while
cyanidin is from red to purple. Pelargonidin is from orange to red color (Blackburn
& Trejo, 2016).

 

These anthocyanidins are the
building blocks that are further reduced, dehydroxylated and glycosylated
within the plant to produce anthocyanins. Anthocyanins further vary in
substitution patterns and glycosyl groups, both of which affect their color and
stability. Additionally, these pigments exhibit a reversible change in
molecular structure as the pH of solutions change from acidic to basic. This
change in structure is characterized by a shift in hue from red to purple to
blue as the pH changes from acidic to basic. At low pH (around 3), the anthocyanins are most
strongly colored, exhibiting their well-known purple–red color. Around pH 5,
anthocyanins turn almost colorless, and at neutral and alkaline pH the color
goes from blue to green (Mortensen, 2006).

 

Anthocyanins can be blended together
to enhance the visual appearance of the food or beverage product. 

 

Figure 9: This is a representation of anthocyanidin
with a R1 and R2 group. The R1 and R2 group can be replaced by –OH, -H, and
-OCH3. Combinations of these groups represent certain anthocyanidin colors (Lakshmi, 2014).

 

 

 

Table
2: Anthocyanidin Colors

Anthocyanidin

Color

R1

R2

Cyanidin

Red-purple

OH

H

Delphinidin

Blue-purple

OH

OH

Pelargonidin

Orange-red

H

H

Malydin

Deep
purple

OCH3

OCH3

Peonidin

Red

OCH3

H

Petunidin

Purple

OH

OCH3

 

Synthetic Colors:

 

Synthetic colors are manufactured
chemically and are the most commonly used dyes in the food, pharmaceutical and
cosmetic industries. They are also known as Artificial Colors. Seven dyes were initially approved under the Pure Food and Drug Act of 1906, but several have been delisted and replacements have
been found. There are two types of synthetic colors, primary and blended
colors. Primary colors are that when mixed they produce other colors. For
example, Tartrazine, which is shown in figure 11.  It is a synthetic lemon yellow azo dye and is
water soluble, maximum absorbance at 427 nm. Blended colors are
prepared from mixing of previously certified batches of primary colors. Blended
food colors are the mixture of two or more water-soluble food coloring agents
that are combined in numerous ways to produce a vast array of shades.

 

 

 

Many synthetic food colors cause cancer, asthma, and
hyperactivity (but specifically in children). Tartrazine is known to cause
asthma and allergic reactions because of its nitrous derivatives. In the United
Kingdom Food Standards Agency, they found in the 2007 landmark Southampton,
that the food
dyes have a negative affect on children. A dye used in snack food is called
allura red, can cause lymphomas and tumors in children. Brilliant blue dye is
used in jellies, dairy products, syrups, and candy. It is derived from
petroleum distillates. It has caused death of some elderly patients because of
enteral feeding, which is done through a tube (Blackburn & Trejo, 2016). 

 

         

 

 

 

 

 

 

 

 

 

 

Figure 11: Shows
the seven FDA authorized synthetic colors’ structures: a) Tartrazine, b) Allura
Red c) Brilliant blue d) Sunset Yellow FCF e)Fast Green FCF f) Erythrosine g)
Indigotine.

 

Methods of Extraction of
Pigments:

 

Solvent
extraction is the widely used method that is usually followed to extract colors
from natural products such as plants. Anthocyanin and curcumin pigments are water-soluble
so they are extracted from the raw material with water and sometimes with
aqueous methanol (Lakshmi, 2014).  Carotenoids extraction use hexane as the
solvent of choice but acetone is better for initial extraction of pigment from
a plant (Butnariu, 2016). Carminic
acid extraction uses acidic, aqueous, alcoholic solution. It is then
precipitated as carmine (“Carmine/ Cochineal | DDW The
Colour House”, 2017).

 After extraction of the plant material the
substance is concentrated and put through purification steps using column
chromatography. Spectrophotometry or high-pressure liquid chromatography (HPLC)
is use for identification and quantification of the pigments.

 

Advancements in
extraction have been helpful in the industry because the uses of organic
solvents are harmful for health and the environment. The advancements in color
extraction are:

 

-High Hydrostatic Pressure (HHP)

-Pulsed Electric Field (PEF)

-Sonication-assisted Extraction

-Gamma Irradiation

-Enzymatic Extraction

-Membrane Technology

 

 

High Hydrostatic Pressure (HHP) and
Pulsed Electric Field (PEF)
are environment friendly. They enhance mass transfer processes within plant or
animal cellular tissues, since the content of cytoplasmic membranes can be
increased which results the enhancement extraction of good cell components. PEF
is reported to be an ideal method to enhance juice production and increase the
extraction of components better than the enzymatic maceration yields (Lakshmi, 2014).  

 

Sonication-assisted Extraction is the most used methods to enhance mass
transfer phenomena by cavitation forces, so bubbles in the liquid or solid
phase can collapse and generate pressure (Lakshmi,
2014).  This improves the release of intracellular
substances into the solvent being used. This is well used for the extraction of
metabolites such as tea, ginseng, and chamile.

 

Gamma irradiation increases cell wall permeabilization, which
results in the enhancement of cell constituents in higher yield.

 

Enzyme extraction is another new technology for extraction
of pigments antioxidants, and flavors from plant material. Enzymes cannot be a
complete replacement for solvent extraction but can result in yield being
increased of cell components and reduced time of extraction. Enzymes are seen
to enhance the extraction of carotenoids in marigold flowers. (Lakshmi, 2014)  

 

Conclusion:

 

Coloring
is very important. The choice of coloring can be very challenging. If the wrong
color were chosen for food or cosmetic product it would lead to many problems. The
main factors to evaluate food quality are color, flavor, and texture, but color
can be considered the most important of them, because if it is not appealing
consumers will not enjoy the flavor and texture of any given food so demand
will decrease. Coloring for cosmetics industry is vital, when making make-up,
lipstick, skin and hair care products, hair dyes, and nail colorants because if
the wrong color is chosen for cosmetic product it would lead to lack of
consumer appeal and the failure of product. To conclude, there is a high demand
in natural pigments in the food and cosmetics industry because of their
nontoxic properties and less side effects. Even though, synthetic colors are
inexpensive there all many health affects, which why awareness among people
towards natural color have increased (Chengaiah, Mallikarjuna Rao, Mahesh
Kumar & Alagusundaram, 2010)

 

 

 

 

 

 

 

 

 

 

 

References

 

Blackburn, R., & Trejo,
N. (2016). Cosmetic Chemistry:
Novel Approaches using Natural and Renewable Ingredients. ACS Chemistry for Life. Retrieved
from http://acs.org/acswebinars

Butnariu M (2016) Methods of
Analysis (Extraction, Separation, Identification and          Quantification) of Carotenoids from Natural Products. J
Ecosys Ecograph 6: 193.       doi:10.4172/2157-7625.1000193

 

Calvo, C. (2001). Book Reviews:
Coloring of Food, Drugs and Cosmetics. Food Science And Technology International, 7(1), 90-90.
http://dx.doi.org/10.1106/mngk-5awg-aym7-jpl4

Carmine
/ Cochineal | DDW The Colour House. (2014). DDW The
Colour House. Retrieved from http://www.ddwcolor.com/natural-colours/carminic-acid-carmine-cochineal/

Chengaiah, B., Mallikarjuna
Rao, K., Mahesh Kumar, K., & Alagusundaram, M. (2010). Medical Importance
of Natural Dyes-A Review. International
Journal Of Pharmtech Research, Vol.2(No.1), pg. 144-154. Retrieved from
http://sphinxsai.com/sphinxsaivol_2no.1/pharmtech_vol_2no.1/PharmTech_Vol_2No.1PDF/PT=24%20(144-154).pdf

Chlorophyll
/ Chlorophyllin | DDW The Colour House. (2017). DDW The
Colour House. Retrieved from

Chlorophyll / Chlorophyllin

DDW – Experts in Natural Food
Colouring. (2015). DDW
Colouring Foods. Retrieved from http://colouringfoods.ddwcolor.com

 

Food
Dyes, Natural Food Dyes, Food Dyes Suppliers, Natural Food Dyes Suppliers. (2017). Foodadditivesworld.com. Retrieved
from http://www.foodadditivesworld.com/food-dyes.html

Lakshmi, C. (2014). Natural
Food Coloring: The Natural Way. Research
Journal Of Chemical Sciences, 4(2), 87-96. http://dx.doi.org/2231-606X

Mortensen, A. (2006).
Carotenoids and other pigments as natural colorants. Pure Application Chemistry, 78(8), 1477-1491.
http://dx.doi.org/10.1351/pac200678081477

Natural
Food Colors….
(2017). Foodscintech.blogspot.com.
Retrieved from
http://foodscintech.blogspot.com/2014/10/natural-food-colors_29.html

Nontoxic,
Organic, (and Gorgeous) Pigments: What It Takes to Create Non-Toxic Makeup |
Goop.
(2017). Goop. Retrieved
from

Nontoxic, Organic, (and Gorgeous) Pigments: What It Takes to Create Non-Toxic Makeup

Perdue, M. (2017). What Are the Roles of Chlorophyll A & B?. Sciencing. Retrieved  from
https://sciencing.com/what-are-the-roles-of-chlorophyll-a-b-12526386.html

Rohrig, B. (2015). Eating
With Your Eyes: The Chemistry Behind Food Coloring.             American Chemical Society.

 

Synthetic
Food Colors, Synthetic Food Color Products, Synthetic Food Colors Suppliers. (2017). Foodadditivesworld.com. Retrieved
from http://www.foodadditivesworld.com/synthetic-food-colors.html

Ul-Islam, S. (2017). Plant-Based Natural Products: Derivatives
and Applications (pp. 66-67). John Wiley & Sons.

Vargas, E. (2016). 3 Reasons to switch to Natural Food Coloring. Blog.watson-inc.com. Retrieved from
http://blog.watson-inc.com/marketing/the-need-for-natural-food-color

 

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