used to color water-based products. Blue corn
chips, brightly colored soft drinks, and jelly
are often dyed with anthocyanins.
More than 500 different anthocyanins have
been isolated from plants. They are all based
on a single basic core structure, the flavylium
ion (Fig. 2). This ion contains three six-carbon
rings, as well as many hydroxyl (–OH) groups
that make the molecule polar (it has partially
negative and partially positive charges) and
The next time you enjoy strawberry-flavored yogurt or cranberry juice, you may
be eating bugs! But don’t worry. These
insects did not contaminate your food by
accident. An extract from a type of insect,
known as the cochineal, was deliberately
added by the food manufacturer.
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, called carminic
acid (C22H20O13) (Fig. 3). This dye is safe
to ingest, so it found its way into a variety of
food and cosmetic products that required a
red color. However, the thought of eating bugs
is unappealing to some people. Starbucks
formerly used cochineal dye in its strawberry-
flavored products, but it has since removed
this dye in response to customer complaints.
To find out if your food contains bugs, look for
carmine, carminic acid, cochineal, or Natural
Red 4 on the ingredient label. While these
substances are typically considered safe, in
rare instances, people can have a severe allergic reaction to them, leading to a life-threaten-ing condition called anaphylactic shock.
Why go artificial?
Why bother with artificial, or synthetic, food
colorings? Aren’t there enough natural colors
to go around? A big reason to go artificial is
cost. Synthetic dyes can be mass-produced
at a fraction of the cost of gathering and processing the materials used to make natural
Another reason is shelf life. Artificial food
dyes might be longer-lasting than natural
ones of the same color. Also, although nature
produces an impressive hue of colors, those
suitable for use as a food dye are limited. But
there is no limit to the variety of colors that
can be artificially produced in a lab. Considering
the thousands of different substances that
color our food, it may come as a surprise
to discover that the U.S. Food and Drug
Administration granted approval to just seven
synthetic food colorings for widespread use
in food. These food colorings are summarized
in Table 1.
Artificial food colorings were originally
manufactured from coal tar, which comes
from coal. Early critics of artificial food colorings were quick to point this out. Today, most
synthetic food dyes are derived from petroleum, or crude oil. Some critics may argue
that eating oil is no better than eating coal.
But the final products are rigorously tested to
make sure they contain no traces of the original petroleum. One dye that does not have a
petroleum base is Blue No. 2, or indigotine,
which is a synthetic version of the plant-based
indigo dye, used to color blue jeans.
How to color food
What makes a good food coloring? First,
when added to water, it must dissolve. If the dye
is not soluble in water, it does not mix evenly.
When a typical solute, such as salt or sugar,
is added to water, it dissolves, meaning it is
broken down into individual ions or molecules.
For instance, individual molecules of sugar
(C12H22O11) are held together by relatively weak
intermolecular forces. So when sugar dissolves
in water, the attractive forces between the
individual molecules are overcome, and these
molecules are released into solution.
Food-coloring molecules are usually ionic
solids, that is, they contain positive and negative
ions, which are held together by ionic bonds.
When one of these solids dissolves in water,
the ions that form the solid are released into the
solution, where they become associated with
the polar water molecules, which have partially
negative and partially positive charges.
Another important property of food coloring is that when it is dissolved in water, the
Figure 2. Chemical structure of an anthocyanin.
R1 and R2 are functional groups, and R3 is a sugar
Another natural food additive you have probably consumed is turmeric, which is added
to mustard to impart a deep yellow color.
Turmeric is obtained from the underground stem of a plant that grows in
India, and it is commonly used as
a spice in Indian food. Many U.S.
food companies are using tumeric
and other natural spices to color their
products. Turmeric is also a great acid/
base indicator. If you add a basic sub-
stance to mustard, it will turn red.
6 ChemMatters | OCTOBER/NOVEMBER 2015 www.acs.org/chemmatters
FD&C Designation Name Color Molecular Formula
Blue No. 1 Brilliant Blue FCF Blue C37H34N2Na2O9S3
Blue No. 2 Indigotine Indigo C16H8N2Na2O8S2
Green No. 3 Fast Green FCF Turquoise C37H34N2Na2O10S3
Red No. 3 Erythrosine Pink C20H6I4Na2O5
Red No. 40 Allura Red AC Red C18H14N2Na2O8S2
Yellow No. 5 Tartrazine Yellow C16H9N4Na3O9S2
Yellow No. 6 Sunset Yellow FCF Orange C16H10N2Na2O7S2
Figure 3. Chemical structure of carminic acid
Table 1. Food colorings approved by the U.S. Food and Drug Administration. FD&C stands for
laws passed by the U.S. Congress in 1938, called the Federal Food, Drug, and Cosmetic Act.