Indigotine E132
synthetic — Primarily synthetic.
Disodium 3,3'-dioxo-2,2'-bi-indolylidene-5,5'-disulfonate
CAS: 860-22-0
Factual Regulatory Reference
This database provides factual regulatory information compiled from official government sources. It does not constitute medical, nutritional, or safety advice. Regulatory status varies by country and is subject to change. Always refer to your local regulatory authority for the most current information.
What Is Indigotine?
Indigotine (E132), also known as Indigo Carmine or FD&C Blue No. 2, is a synthetic indigo dye that produces a deep blue to blue-purple color, and is one of the few approved blue food colorants available across multiple regulatory systems. It is manufactured through chemical synthesis rather than from the natural indigo plant, and is used in confectionery, baked goods, beverages, and dairy products. Indigotine is approved in both the EU as E132 and in the USA as FD&C Blue No. 2 (21 CFR 74.302), as well as in Japan, Canada, and Australia/NZ. EFSA re-evaluated indigotine in 2014 and confirmed an ADI of 5 mg/kg body weight per day; the dye has a shorter stability profile than some other food dyes and can fade in acidic or alkaline conditions.
? Did You Know?
Beyond food, Indigotine is also used in medicine, industrial applications. Its versatility makes it one of the most multi-purpose chemical compounds in everyday life.
To reach the Acceptable Daily Intake limit, a 60kg adult would need to consume approximately ~50 blue raspberry ice pops (60g each) in a single day. (This is a mathematical illustration, not a safety recommendation.)
Detailed Regulatory Assessment
European Union (EFSA)
Must carry warning: 'May have an adverse effect on activity and attention in children' (since 2010); must meet 93% purity standard
Official EFSA LinkUnited States (FDA)
Approved for food use; FDA approved for medical diagnostic use in July 2022
Japan (MHLW)
Approved as designated synthetic colour additive
Acceptable Daily Intake (ADI)
International Standard (JECFA)
mg/kg body weight per day
European Standard (EFSA)
Everyday Perspective
For a 60kg adult, this limit is roughly equivalent to consuming:
Natural Occurrence
This additive is not known to occur naturally in significant quantities.
Manufacturing
Traditional method: Indigo is manufactured by fusion of N-phenylglycine (prepared from aniline + formaldehyde) in molten mixture of sodamide, sodium hydroxide, and potassium hydroxide under ammonia pressure. Purified indigo undergoes aromatic sulfonation to introduce sulfonic acid groups at 5,5' positions, creating water solubility. Converted to disodium salt form. Modern method: Can be produced biotechnologically using genetically modified microorganisms.
Applications Beyond Food
Tablet/capsule coatings; medical diagnostic procedures (cystoscopy, brain surgery, urological surgery, sentinel lymph node biopsy)
Textile dyeing (limited); laboratory pH indicator and research stain