E150d

Sulphite Ammonia Caramel

Last reviewed: 11 May 2026

Class IV caramel — the colour of cola drinks. Its production yields 4-MEI.

What it is

E150d belongs to the four-member caramel-colour family (E150a, E150b, E150c, E150d). All four are made by heating carbohydrates (sugars), but with different processing aids that produce different chemistry:

• E150a — plain caramel (heat alone). No 4-MEI generated.
• E150b — caustic-sulphite caramel (heat plus sulphite). No 4-MEI generated.
• E150c — ammonia caramel (heat plus ammonia). Can generate 4-MEI.
• E150d — sulphite ammonia caramel (heat plus ammonia plus sulphite). Can generate the highest 4-MEI levels of the family.

The ammonia-and-sulphite chemistry that makes E150d stable in acidic, carbonated drinks is also what produces 4-MEI as a process byproduct. The amount depends on production conditions: process tuning has substantially reduced 4-MEI in commercial caramels since 2012, but it is not eliminated.

Where you'll see it on a UK label

E150d is the workhorse colour of the dark soft-drink and dark sauce categories. Look for it (named as "caramel colour E150d", "colour E150d" or just "E150d") in:

• Cola drinks — Coca-Cola, Pepsi, supermarket own-brand colas, regular and diet variants
• Other dark soft drinks — root beer, some dark fruit sodas, brown malt drinks
• Dark beers — porters, stouts, some brown ales (used to standardise colour batch-to-batch)
• Soy sauce and Worcestershire sauce
• Brown sauces — HP-style, BBQ sauces, gravy granules
• Dark spirits — colour-standardised whiskies, brandies and dark rums
• Pre-mixed iced coffees and some bottled cold-brew drinks

What the science shows

4-MEI on California Proposition 65

In January 2011, the California Office of Environmental Health Hazard Assessment added 4-methylimidazole to the Proposition 65 list of chemicals "known to the state to cause cancer", with a No Significant Risk Level (NSRL) set at 29 micrograms per day. Products sold in California exceeding that threshold per serving became subject to a cancer warning label. The major cola manufacturers responded by reformulating their caramel-colour specification to reduce 4-MEI; Coca-Cola and PepsiCo announced reformulations from 2012 onward and the change rolled out across most of their global supply.

IARC Group 2B classification

The International Agency for Research on Cancer evaluated 4-methylimidazole in IARC Monograph Volume 101 (2013) and classified it as Group 2B — possibly carcinogenic to humans. The classification reflects sufficient evidence of carcinogenicity in experimental animals (rodent studies showed increased lung tumours in mice and increased mononuclear-cell leukaemia in rats at chronic high doses) combined with inadequate evidence in humans. Group 2B is the same category as aloe vera whole-leaf extract and progestin-only oral contraceptives — it signals enough laboratory evidence to merit caution, not the firm "known human carcinogen" status of Group 1.

EFSA exposure assessment

EFSA's 2011 re-evaluation of the caramel-colour group set a group acceptable daily intake of 300mg/kg body weight per day for E150a, E150b, E150c and E150d, and concluded that estimated dietary exposure to 4-MEI in Europe was below the level at which animal tumour incidence increased. The position has been retained in UK food law. Industry process-control improvements since 2012 — and the reformulation prompted by California — have lowered typical 4-MEI levels in cola products further.

What this leaves on the consumer side

The chemistry that produces 4-MEI has not changed; the levels in commercial product have. For an occasional cola drinker, current dietary exposure to 4-MEI is well below the levels that produced tumours in rodent feeding studies. For someone drinking multiple colas a day, the exposure stacks — and the 4-MEI question sits alongside the much larger concerns about sugar, phosphoric acid (see our E338 page), caffeine load and dental erosion that come with heavy cola consumption.

Reading a UK label

E150d may be declared as "colour: E150d", "caramel colour (E150d)", "sulphite ammonia caramel", or — in some legacy UK packaging — simply "colour: caramel" without specifying the class. Class IV caramel (E150d) is the dominant caramel in dark soft drinks; class I (E150a) is more common in baking, biscuits and desserts where acid-stability isn't needed. If a label declares only "caramel colour" with no class designation and the product is a dark cola or soy sauce, it is most likely E150d.

Regulatory status

UK and EU: authorised as E150d with a group ADI of 300mg/kg body weight per day across the four caramel classes. Permitted uses are listed in Annex II of Regulation (EC) No 1333/2008.

United States: authorised by the FDA. In California specifically, products containing more than 29 micrograms of 4-MEI per serving require a Proposition 65 cancer warning unless the manufacturer demonstrates the NSRL is not exceeded — which most major beverage brands now do via reformulation.

IARC: 4-methylimidazole (the process byproduct, not E150d itself) classified Group 2B — possibly carcinogenic to humans (IARC Monograph 101, 2013).

Last updated: 11 May 2026