The term "FD&C color", often seen on ingredients labels, refers to "Food, Drug, and Cosmetic" colors. These are organic compounds (as opposed to inorganic pigments such as titanium dioxide) that are so intense in color that very tiny amounts can be used to color something, and thus can be used in concentrations so minute that they are safe for consumption.
As further described in the section on ?-carotene, organic dyes owe their colors to "resonance structures" in the molecule, where charges are free to move in the molecule at frequencies that fall in the range of visible light.
There are only seven non-natural (artificial) colors certified for consumption in the United States:
The dye Orange B is allowed only in hotdog and sausage casings.
Other FD&C colors are used in drug coatings and cosmetics.
If one of the above colors is used in a food product, it must be explicitly labeled in the ingredients list, (e.g. "contains FD&C Blue #1"). If the label does not name the compound specifically, but simply says something like "contains artificial color", then you know it does not contain one of the colors listed above.
A pigment is a solid that has a color. A dye is a liquid that has a color. FD&C colors are all dyes. To make a solid color from a dye, the dye is used to color a solid substance. The result is called a "lake". One common substrate used is aluminum hydroxide (commonly used as an antacid). A color made this way might be labeled "Red 40 Aluminum Lake". Lakes are often used on the outside of candies and pills, so that the dye does not wash off, or rub off on fingers.
Besides artificial colors, many natural colors are used in foods. Some of these are:
One of the most widely used colors is caramel, the color of burnt sugar.
There are many different types of caramel color, each engineered to serve a particular purpose in food chemistry. They are all based on the cooking of sugars and starches. Sometimes acids such as acetic acid, citric acid, lactic acid, or phosphoric acid, are used to break the bonds between sugars to create invert sugars, or to make sugars from starches, before the sugars are raised to a higher temperature for carmelization.
The heat is carefully controlled during carmelization to get the right products from the reaction. Besides acids, alkalies and salts may be used to further control the process.
Caramel color is a colloid, a mixture in which solid particles are suspended in water. The particles in colloids have electric charges that keep the particles from clumping together and settling out of solution. The charges can be positive or negative. If a negative coloid is added to a product that has positive colloidal particles in it, the two will attract one another and clump up, making the product cloudy.
Caramel color can be made with either positively or negatively charged particles. This allows manufacturers to use negative colloidal caramel in acidic soft drinks, and positive in beers and soy sauces. Beer has positively charged proteins suspended in it, and soy sauce has a high salt content that requires the more salt-tolerant positive caramel color.
Caramel color is an emulsifying agent as well as a colorant. In soft drinks, it helps keep the flavor oils suspended in the solution.
In chocolate milk, the muddy color of caramel is darkened by the addition of FD&C Red #40 to give what the industry refers to as a "Dutch" chocolate shade. Blues and yellows are sometimes used to give a more brown color.
Caramel color is added to baked goods, to poultry, to milk to give an "eggnog" color, to malt vinegars, canned meats, syrups, and soups, stews, and gravies.
beta carotene: InChI=1/C40H56/c1-31(19-13-21-33(3)25-27-37-35(5)23-15-29-39(37,7)8)17-11-12-18-32(2)20-14-22-34(4)26-28-38-36(6)24-16-30-40(38,9)10/h11-14,17-22,25-28H,15-16,23-24,29-30H2,1-10H3/b12-11+,19-13+,20-14+,27-25+,28-26+,31-17+,32-18+,33-21+,34-22+