Molecular Fragments: Food Colours


Site and models created by Dr. Dave Woodcock, Associate Professor Emeritus, UBC (Kelowna).

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Copyright 1996, 1997, 2008 Dave Woodcock
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First: Where does the colour come from?

1. Molecules are made up of atoms linked together by sharing electrons.

2. Electrons in atoms and molecules are very restricted as to their energy, occupying only certain fixed (for any given atom or molecule) energy levels. This is somewhat like stairs in that you can occupy the level of a stair but not any level in between.

3. When electrons are spread out over many atoms, the energy levels (steps or stairs) become closer together.

4. 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.

5. 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.

6. 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 colour, is absorbed and disappears. The remaining light, lacking this colour, shows the remaining mixture of colours as non-white light.

7. For molecules to spread electrons out enough to absorb visible light, several double bonds (=) must be present alternating with single bonds (-). In all the following structures you will note this one phenomenon.

One note: a hexagon with a circle in it also represents a spreading out of electrons round the ring.


Compounds Certifiable for Consumption in the US.

Currently only seven non-natural compounds are certifiable for use in food in the US.
NameColourAbsorption
position
1. Allura Red ACRed #40Orange-red507 nm
2. Brilliant Blue FCFBlue #1Bright blue630 nm
3. ErythrosineRed #3Cherry red530 nm
4. Fast Green FCFGreen #3Sea green625 nm
5. IndigotineBlue #2Royal blue608 nm
6. Sunset YellowYellow #6Orange480 nm
7. TartrazineYellow #5Lemon yellow426 nm

Approximate wavelengths of coloured light (nm):
Violet: 400; blue: 450; green: 500; yellow: 580; orange: 620; red: 700.


1. Allura Red AC - Red #40.

Allura red AC is an orange-red azo dye.
It finds use in gelatins, puddings, dairy products, confections, beverages, and condiments.


2. Brilliant Blue FCF - Blue #1.

Brilliant Blue FCF is a bright blue dye
It finds use in beverages, dairy products, powders, jellies, confections, icings, syrops, extracts and condiments.


3. Erythrosine - Red #3.

Erythrosine is a cherry red dye
It finds use in cherries, confections, baked goods,dairy products, and snack foods.


4. Fast Green FCF - Green #3.

Fast Green FCF is a sea green dye related to Brilliant Blue FCF
It finds use in beverages, dairy products, puddings, cherries, confections, ice cream, sherbert, baked goods.


5. Indigotine - Blue #2.

Indigotine is a royal blue dye
It finds use in baked goods, cerials, snack foods, confections, ice cream, cherries.


6. Sunset Yellow - Yellow #6.

Sunset yellow is an orange azo dye
It finds use in beverages, confections, ice cream, dessert powders, cerials, baked goods, and snack foods.


7. Tartrazine - Yellow #5.

Tartrazine is a lemon yellow azo dye
It finds use in beverages, confections, ice cream, custards, preserves, and cerials.


Some References

National Foodsafety Database.

US Food and Drug Administration (1993)

Ditto: Background for Consumers

Overview and Analysis

Chronology of Food Additive Regulations

Red #3 and other Colorful Controversies


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