What Are the Compounds of Food Coloring?
The U.S. Food and Drug Administration lists seven approved artificial food dyes. Artificial dyes were originally manufactured from coal tar, a by-product of "coking" coal to obtain an enriched fuel for steel production. More recently, petroleum distillates are also source materials for dye manufacture.
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Molecular Structure
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The common molecular structures of the dye compounds are (1) at least one "azo" double bond joining two nitrogen atoms, (2) at least one aromatic hydrocarbon (six-carbon benzene ring) bonded to each of the nitrogens, and (3) a sulphonated bond site on one or more carbon ring.
Toxicity
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The seven dyes approved for products in the United States are the remaining few among more than one hundred being used prior to regulation. Sulphonated bond sites on one or more ring were engineered to reduce toxicity of the dyes by increasing elimination in urea after the azo bond is cleaved by bacteria in the gut. High doses of approved dyes can cause tumors in lab animals.
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Dyes versus Lakes
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Dye compounds are soluble in water, but not soluble in oils. Insoluble materials such as aluminum oxides are bonded to the dyes to form lake compounds, which also are not soluble in oils, but can be dispersed among oil molecules in suspension.
Commercial Labels
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The FDA requires labels to identify food dyes. Dye names begin with FD&C, for Food, Drug & Cosmetic. Listed dyes include Blue No. 1, Blue No. 2, Green No. 3, Red No. 40, Red No. 3, Yellow No. 5, and Yellow No. 6.
Public Concern
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Governments and public organizations began studying food additives just after 1900, and toxic colorings have been delisted. Food colorings are among food additives under scrutiny as contributing causes of ADHD, but no conclusive evidence supports an ADHD and food coloring link.
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