Ammonia caramel
A brown food colouring made by heating sugar with ammonia compounds, used mainly in beer, soy sauce, gravies and dark soft drinks.
The manufacturing process produces two by-products with documented health signals: THI, which causes immune cell depletion in animal studies and prompted a lower regulatory limit for this class; and 4-methylimidazole (4-MEI), which caused lung tumours in mice and is classified by IARC as possibly carcinogenic to humans. EFSA found that toddlers and adults with high intake of E150c foods may still exceed the acceptable daily intake set for this class.
What is it?
Ammonia caramel (Class III caramel colour) is produced by controlled heating of carbohydrates, typically glucose or sucrose, in the presence of ammonium compounds such as ammonium hydroxide or ammonium carbonate. No sulphite compounds are used, which gives it a positive colloidal charge and distinguishes it from E150d. The result is a complex dark-brown mixture used purely for colour, not flavour.
What does it do?
It absorbs light across the visible spectrum to produce brown hues. Its positive colloidal charge makes it stable in the acidic, high-salt conditions found in beer and soy sauce, where negatively charged caramel colours would flocculate. At the permitted levels in food it adds no detectable flavour.
Where you will see it
Beer and dark ales (to standardise colour between batches), soy sauce and bouillon, gravies and gravy granules, some cola drinks, dark bread, vinegar, and certain sauces and dressings. On UK ingredient labels it appears as 'colour (ammonia caramel)', 'colour (E150c)', or simply 'caramel colour'.
What the science says
THI and immune system effects
When sugars are heated with ammonia compounds a trace by-product called 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole, or THI, forms. In animal studies THI causes a marked fall in circulating lymphocytes, the white blood cells central to immune defence, by sequestering them in non-lymphoid tissues. EFSA concluded that this effect was the main uncertainty driving a lower acceptable daily intake specifically for E150c compared with other caramel colour classes. EU specifications cap THI in E150c at 10 mg/kg of colour.
THI caused profound lymphopenia and suppression of cell-mediated immunity in rats, with reduced B and T lymphocytes in blood, spleen and lymph nodes.
EFSA set a lower individual ADI of 100 mg/kg bodyweight/day for E150c (versus 300 mg/kg bw/day for the group) specifically because of uncertainties about the immune effects of THI observed in animal studies.
4-methylimidazole (4-MEI) and cancer classification
The ammonia reaction during manufacture also produces traces of 4-methylimidazole (4-MEI). Two-year animal feeding studies by the US National Toxicology Program found clear evidence of lung tumour formation in male and female mice at high doses. Based on those animal studies, the International Agency for Research on Cancer classified 4-MEI as Group 2B, meaning possibly carcinogenic to humans, in 2013. No human epidemiological studies have confirmed a cancer link from food-level exposure, and the IARC classification relies solely on animal evidence.
Two-year NTP feed studies found clear evidence of lung carcinogenicity (alveolar/bronchiolar neoplasms) in male and female B6C3F1 mice exposed to 4-MEI; evidence in rats was equivocal.
IARC classified 4-methylimidazole as Group 2B, possibly carcinogenic to humans, based on sufficient animal evidence and limited human data.
A quantitative risk assessment found that routine consumption of certain caramel-coloured beverages in the US resulted in 4-MEI exposures exceeding California's Proposition 65 threshold of 29 micrograms/day, with estimated lifetime excess cancer risks ranging from approximately 1 in 500,000 (Coca-Cola) to 1 in 5,000 (Malta Goya).
Analytical studies found 4-MEI concentrations in Class III (ammonia) caramel of approximately 163-180 mg/kg of colour material; the EU cap for 4-MEI in E150c is 200 mg/kg.
Dietary exposure and ADI exceedance
EFSA's 2011 opinion found that anticipated dietary exposure for children and adults could exceed the ADI for E150c. A 2012 refined assessment using industry-provided use levels found lower estimates overall, but still concluded that toddlers and adults with high E150c food consumption could exceed the 100 mg/kg bodyweight/day ADI for this class. The combined exposure to all four caramel colour classes stayed within the 300 mg/kg bw/day group ADI.
Using refined industry-supplied use-level data, EFSA found that toddlers and adults remained capable of exceeding the individual ADI of 100 mg/kg bw/day for E150c, even after exposure estimates were substantially lowered compared to the 2011 assessment.
Where it stands with the regulators
Who should be careful
There is no specific allergen declaration requirement for E150c. People who consume large daily amounts of high-caramel-colour foods, such as regular dark beer, soy sauce, cola drinks and gravies in combination, are the group most likely to approach or exceed the ADI. Check ingredient lists for 'caramel colour', 'colour (ammonia caramel)' or 'colour (E150c)'.
The honest read
E150c sits in a different position from plain caramel (E150a): the manufacturing route with ammonia generates two trace by-products, THI and 4-MEI, each with documented signals in animal or regulatory science. The animal data on THI lymphopenia is consistent across multiple studies and was taken seriously enough by EFSA to lower the ADI specifically for this class. The 4-MEI carcinogenicity data produced a confirmed IARC Group 2B classification, though the doses used in NTP mouse studies were far higher than typical food exposure, and no human cancer studies have confirmed the association. The exposure concern is real but contested: EFSA's 2012 refined assessment brought estimates down considerably, though it left open a residual concern for high-consumption toddlers and adults. The science here is live, not settled.
Related additives
Common questions
Is E150c banned in the UK?
No. E150c is listed on the UK FSA approved-additives register and is permitted in a range of foods. It is also authorised under retained EU Regulation 1333/2008. However, it has a lower individual acceptable daily intake than other caramel colour classes because of concerns about a by-product called THI.
What is the concern about 4-MEI in ammonia caramel?
4-methylimidazole (4-MEI) forms as a trace by-product when sugars are heated with ammonia. High-dose animal studies found lung tumours in mice, and IARC classified 4-MEI as Group 2B, possibly carcinogenic to humans, in 2013. The doses used in those studies were much higher than typical food exposure, and no human studies have confirmed a cancer link. California requires Prop 65 warning labels on products where a daily serving delivers more than 29 micrograms of 4-MEI.
What foods contain E150c?
Beer and dark ales, soy sauce and bouillon, gravies, certain cola drinks, dark bread, vinegar and various sauces. On the label it appears as 'caramel colour', 'colour (ammonia caramel)' or 'colour (E150c)'.
Is E150c vegan?
Yes. Ammonia caramel is made from plant-derived sugars and ammonia compounds; no animal-derived ingredients are used in its production.
Sources
- Approved additives and E numbers - UK Food Standards Agency
- EFSA ANS Panel: Scientific Opinion on the re-evaluation of caramel colours (E150a,b,c,d) as food additives - EFSA Journal 2011;9(3):2004
- EFSA ANS Panel: Refined exposure assessment for caramel colours (E150a, c, d) - EFSA Journal 2012;10(12):3030
- IARC Monographs Volume 101: Some Chemicals in Industrial and Consumer Products, Food Contaminants and Flavourings, and Water Chlorination By-products (4-methylimidazole, Group 2B)
- NTP Technical Report TR-535: Toxicology and carcinogenesis studies of 4-methylimidazole in F344/N rats and B6C3F1 mice
- Smith et al.: Caramel Color in Soft Drinks and Exposure to 4-Methylimidazole: A Quantitative Risk Assessment, PLoS ONE 2015
- Akbari et al.: 4-Methylimidazole, a carcinogenic component in food - systematic review, PMC 2023
- Immunosuppressive effects of 2-acetyl-4-tetrahydroxybutyl imidazole (THI) in the rat - PubMed
- Lymphopenic effects on mice of a component of ammonia caramel, THI - PubMed
- California OEHHA Proposition 65 listing of 4-methylimidazole (2011)
- Genotoxicity assessment of 4-methylimidazole: regulatory perspectives, PMC 2016
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
See this on every food you scan
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
Get NutraSafe on the App Store