Last reviewed: 8 May 2026
The plant pigment behind orange cheddar, Red Leicester and smoked haddock
E160b is annatto, an extract from the seed coat of the achiote tree, Bixa orellana. The achiote is a small tropical tree native to the Americas; its pods burst open at maturity to reveal clusters of small red seeds covered in a vivid waxy pigment. That waxy coating is what gets washed, dried and processed into the colouring you find on a UK ingredients list. Unlike most food dyes on the additive register, annatto is not a synthesised compound — it is a real plant pigment with a continuous food history going back several thousand years in Mesoamerican cooking.
Two pigments do the actual work, and the labelling system reflects this:
On a UK pack you may see any of these forms: E160b, E160b(i) bixin, E160b(ii) norbixin, or simply the words annatto or annatto extract. They all refer to the same source material; the bracketed Roman numeral just tells you which of the two pigments was prepared.
Strictly speaking, cheddar curd is not naturally orange. Milk is white, the curd that comes out of it is pale cream, and the cheese that follows would be a creamy off-white if nothing else was added. The orange you associate with mature coloured cheddar, mild coloured cheddar and Red Leicester is annatto, almost without exception.
The practice has West Country roots. In 17th and 18th century Gloucestershire and Somerset, dairy farmers ran into a seasonal problem: cows out on rich summer pasture produced milk high in beta-carotene, which carried through into a slightly yellower cheese. Cows on winter feed produced paler milk and paler cheese. Buyers had come to associate the yellower summer colour with quality, so winter producers used to top up the colour with carrot juice or marigold extracts to keep their cheese looking the part. By the 19th century, annatto — already well known in the spice trade — had displaced the older plant dyes because it gave a stronger, more consistent result with very little flavour of its own.
That tradition is what survives in the modern coloured cheddar. Red Leicester goes a step further and uses a heavier dose to produce its characteristic deep orange-red. White cheddar (sometimes labelled as such, sometimes just called mild or mature cheddar) skips the annatto entirely and shows you what unstained curd actually looks like. The two are the same cheese chemistry; the difference is the bottle on the dairy floor.
Once you know what to look for, annatto shows up in more places than most shoppers realise:
One product family where annatto is uncommon is brightly coloured soft drinks; those tend to lean on beta-carotene, paprika extract, or — at the synthetic end — sunset yellow (E110) or other azo dyes. We will come back to that distinction in a moment.
Annatto has a small but well-documented allergy literature. Published case reports describe reactions to annatto-coloured foods that include urticaria (hives), angioedema (swelling, particularly around the lips and eyes) and, in rare cases, anaphylaxis. The reactions appear to be linked to residual seed-coat proteins rather than the pigment molecules themselves.
That said, annatto is not one of the 14 allergens that UK and EU food law require to be declared on a pre-packed label. The 14 mandatory allergens are: cereals containing gluten, crustaceans, eggs, fish, peanuts, soybeans, milk, nuts, celery, mustard, sesame, sulphur dioxide and sulphites, lupin, and molluscs. Annatto sits outside that list, which means a manufacturer is not legally required to flag it as an allergen risk on the pack. The ingredient must still appear in the ingredients list — under "annatto", "E160b", or "natural colour (annatto)" — but it will not be in bold or otherwise highlighted.
For most people annatto causes no detectable reaction. For the small number who do react, the trigger is usually obvious in retrospect (an orange cheese or a yellow smoked fish followed by hives within an hour or two). If you suspect a pattern, that is a conversation for your GP or an NHS-referred allergy clinic; it is not something to self-diagnose from a label.
Worth saying directly because it confuses parents reading the colourings list. The Southampton Six — the dyes that carry the FSA's hyperactivity warning ("may have an adverse effect on activity and attention in children") — are:
All six are synthetic azo or sulphonate dyes. Annatto is a plant pigment from a different chemical family entirely, and it is not on that list. UK and EU regulators have not required the hyperactivity warning for annatto, and the 2007 Southampton study that prompted the FSA action did not test it. So if you are scanning a coloured-cheddar pack with the Southampton Six in mind, E160b is not what you are looking for.
EFSA — In its 2008 re-evaluation of annatto, EFSA set separate Acceptable Daily Intake values for the two pigment forms: 6 mg/kg body weight per day for bixin and 0.3 mg/kg body weight per day for norbixin. The norbixin figure is lower because the water-soluble form is more bioavailable in the gut. Both ADIs are based on standard toxicology endpoints, not on the rare allergy reports.
UK FSA — Annatto is approved as a food colouring under the retained EU additive regulations. It does not carry the Southampton hyperactivity warning. It is not on the FSA's named-allergen list.
FDA (US) — Annatto extract is listed as Generally Recognised As Safe (GRAS) and is permitted for colouring foods in the United States, although US labels increasingly carry a voluntary mention of annatto-related allergic reactions.
For UK and EU shoppers, the relevant labelling forms are E160b, E160b(i) bixin, E160b(ii) norbixin, annatto, or annatto extract. All five mean the same source plant.
Annatto is a plant extract, full stop. It is suitable for vegans and vegetarians, and you will often see it called out on packs where the manufacturer wants to avoid synthetic dyes — "naturally coloured with annatto" is a common front-of-pack line on cheddar, especially in the organic and free-from aisles. The colour itself is one of the most common natural alternatives to the Southampton Six, so swapping a tartrazine-coloured product for an annatto-coloured one is the substitution a lot of "no artificial colours" reformulations are quietly making.
The names that all point to annatto on a UK ingredients list:
On cheddar specifically, the white-vs-coloured distinction is the easy tell. Plain block cheddar with no colouring listed will be a creamy off-white. Anything reaching towards orange, from mild golden through to Red Leicester's deep red, has annatto in it. The flavour difference between coloured and uncoloured cheddar of the same age is negligible; the colour is cosmetic, but the cosmetic is centuries old.
On smoked haddock, the giveaway is the contrast between the cut surface and the outside. Naturally smoked, undyed haddock is a fairly even pale grey-brown across the fillet. Dyed haddock has a vivid yellow surface that fades a little towards the centre — that surface tone is annatto carried in by the brining or smoking process.
Bixin is moderately heat-stable but does fade somewhat at sustained high temperatures, which is why annatto is not the colouring of choice for products that get baked or fried hard. In milder cooking — pasteurisation, gentle baking, the cheese-making process itself — it holds up well. Norbixin behaves better in dairy applications because its water solubility lets it bind into the curd rather than sit on the fat surface, and it survives cheese ageing without significant fade. That is why your two-year-old mature cheddar still looks orange rather than washing out to cream.
Light is more of an enemy than heat. Annatto-coloured products held in transparent packaging on a brightly lit shelf can lose intensity over weeks, which is one reason most annatto-coloured cheeses ship in opaque or printed wrappers.
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