Red food coloring?
Allura Red AC or FD&C Red #40
-2;4-Hydroxy-3-(2,4-dimethyl-5-sulfophenylazo)-1-naphthalenesulfonic acid disodium salt
FD&C Red Dye # 40, or Red # 40, is widely used to color food, drugs, and cosmetics, hence the label FD&C. It is the most used colorant according to a survey completed by the National Academy of Sciences, with the Average Daily Intake, for humans, being 100 mg.
Chemically speaking, Red # 40 is a member of the Azo Dyes. They are structured with double bonded Nitrogen atoms (-N=N-). There have been over 2 million of these dyes produced since the azo's were first discovered. Furthermore, they account for more than half of all commercially used dyes. The extra electrons on each of the nitrogens allow the azos to combine with other nitrogen pairs or aromatic groups. The differing combinations result in different colors and substances.
Red # 40 is among the nine colors approved by the Food and Drug Administration and is among the eight commercially available. Also known as allura red, it has an orange red hue and, like other dyes, has several properties that have led to its wide usage. It is soluble in water, propylene glycol, and glycerin. This solubility is vital to its coloring power, since the process of dissolving is the only method for producing the physical color. Although it is extremely dark in tone, its coloring strength is directly proportional to the actual quantity of dye in the product. It also has "good" stability when exposed to heat and/or light.
This Orange-Red dye is commonly used in gelatins, puddings, dairy products, confections, beverages, and condiments. Most Azo dyes cause allergy reactions in aspirin sensitive people. Allura Red may cause slightly less reaction than most of the azo dyes. It is presently banned in Austria, Japan, Norway, and Sweden.
Why Allura Red AC is Red:
Molecules are made up of atoms linked together by sharing electrons. Electrons in atoms and molecules are restricted to energy levels. This is somewhat like stairs in that you can occupy the level of a stair but not any level in between.
When electrons are spread out over many atoms, the energy levels become closer together. The electrons in atoms and molecules can jump up energy levels if exactly the right amount of energy is supplied. This amount of energy can be provided by electromagnetic radiation.
Visible light is one form of electromagnetic radiation. Small molecules, with little spreading out of electrons, have large energy steps and so require electromagnetic radiation of higher energy than visible light. Consequently, visible light passes through such molecules and they appear transparent. For larger molecules, if the electrons are spread out enough in the molecule, the energy levels for the electrons are close enough together that visible light has enough energy to make the electrons jump up a level.
When this happens, the particular energy of light, which corresponds to a particular wavelength or color, is absorbed and disappears. The remaining light, lacking this color, shows the remaining mixture of colors as non-white light.
For molecules to spread electrons out enough to absorb visible light, several double bonds (=) must be present alternating with single bonds (-). You can note this phenomenon in the structural diagram above. The wavelength of light absorbed in Allura Red AC corresponds to 507 nm.
Page by Sandra Allen