FD&C Blue No. 2 Indigo Dye (Indigotine, Indigo Carmine)
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Posted on 10 Aug 2015 22:22

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FD&C Blue No. 2 is a synthetic food colorant (aka artificial color) with a dark blue or "Royal blue" color and is used in baked goods, cereals, snacks, ice cream, and candy. It has a much darker color than FD&C No. 1, which is greenish-blue.

Also known as indigotine, or indigo carmine, FD&C Blue no. 2 is a derivative of indigo, and is made by the sulfonation of indigo dye. It is the only certified indigo type dye.

It comes as a blue, brown, to reddish powder which is not very soluble in water, but is soluble in ethanol. It has been permanently listed for use as a food colorant in the United States since 1987 and was one of the seven original dyes allowed for use by the Food and Drug Act of 1906.

FD&C Blue no.2 is manufactured by heating indigo or indigo paste in the presence of sulfuric acid, and then purified.

Other Names and Synonyms for FD&C Blue No. 2

  • Indigo carmine
  • indigocarmine
  • Indigotine
  • Indigotine disodium salt
  • Acid Blue 74
  • Food Blue No. 2
  • Indigocarmin
  • Indigotindisulfonate sodium

Safety of FD&C Blue No. 2

FD&C Blue No. 2 has not been shown to have any toxic or mutagenic effects even at very high feeing levels. Like other such dyes, it is poorly absorbed by the gut. There are reports of it causing tumors in lab rates but these tumors are injection site tumors and do not suggest any problems with ingesting the dye. The ADI is 2.5mg/kg, and daily intake is on the order of thousands of times less than this amount.

References
1. Smolinske, Susan C. Handbook of Food, Drug, and Cosmetic Excipients. Boca Raton, FL: CRC LLC, 1992.
2. Deshpande, S. S. Handbook of Food Toxicology. New York: Dekker, 2002.
3. Sabnis, R. W. Handbook of Biological Dyes and Stains: Synthesis and Industrial Applications. Hoboken, NJ: Wiley, 2010.
4. Maga, Joseph A., and Anthony T. Tu. Food Additive Toxicology. New York: M. Dekker, 1995.
5. Reineccius, Gary, and Henry B. Heath. Source Book of Flavors. New York: Chapman & Hall, 1994.
6. "Brilliant Blue - PubChem." The PubChem Project. Web. 17 April 2012. <http://pubchem.ncbi.nlm.nih.gov/compound/5284351>
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