Flavor ingredient regulatory record
2,6,6-Trimethylcyclohex-2-en-1,4-dione
2,6,6-Trimethylcyclohex-2-en-1,4-dione is a ketone in the fruity family, FEMA GRAS under FEMA number 3421 (CAS 1125-21-9). Its odor is sweet, fruity, caramel, buttery, rich.
- FEMA
- 3421
- CAS
- 1125-21-9
- JECFA
- 1857
- EU FL
- 07.109
- Formula
- C9H12O2
- EC
- 214-406-2
GRAS status: FEMA GRAS, publication 7. Recorded by FDA in the Substances Added to Food inventory under CAS 1125-21-9.
Structure
Identity
Also known as: 2-Cyclohexene-1,4-dione, 2,6,6-trimethyl-, 2,6,6-Trimethyl-2-cyclohexene-1,4-dione, 3,5,5-Trimethyl-2-cyclohexene-1,4-dione, 4-Oxoisophorone, 2,6,6-Trimethylcyclohex-2-ene-1,4-dione, Oxophorone, Ketoisophorone, 6-Oxoisophorone, Oxopholone, 2,6,6-Trimethyl-2-cyclohexen-1,4-dione, 4-Ketoisophorone, 4-Oxo-α-isophorone.
Can 2,6,6-Trimethylcyclohex-2-en-1,4-dione be labeled natural?
Nature makes 2,6,6-Trimethylcyclohex-2-en-1,4-dione, which is why the US label turns on process. A natural route gives natural flavor; synthesis gives artificial 2,6,6-Trimethylcyclohex-2-en-1,4-dione, same molecule. The EU and UK grant the natural claim only to that natural route; Mercosur and Mexico call synthetic material identical-to-natural.
- United States
- Natural or artificial, by process
- European Union and UK
- Natural only from natural material
- Mercosur and Mexico
- Natural or identical-to-natural
How each market defines the classes: natural vs artificial flavor under 21 CFR 101.22.
Regulatory status, with citations
United States
2,6,6-Trimethylcyclohex-2-en-1,4-dione is FEMA GRAS under FEMA number 3421. It is cited in the Code of Federal Regulations at 21 CFR 172.515.
European Union and United Kingdom
Listed on the Union List of flavouring substances as FL 07.109, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (EFSA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 1857, evaluated at the 69th meeting in 2009. no safety concern at current levels of intake.
Other US flags
Not on the California Proposition 65 list.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. 2,6,6-Trimethylcyclohex-2-en-1,4-dione appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 1125-21-9, where EPA names it 2-Cyclohexene-1,4-dione, 2,6,6-trimethyl-.
Active in US commerce
EPA designates this substance active, so no Notice of Activity Form B is required before manufacturing. What active and inactive mean.
EPA publishes no regulatory flags on this listing. What the flags mean.
From the EPA non-confidential TSCA Inventory, July 2026 release. EPA also maintains a confidential portion it does not publish. Search the Inventory by CAS number.
Odor and taste
Odor: Sweet, fruity, caramel, buttery, rich.
Taste: Sweet, rich, caramel.
Where it is used
2,6,6-Trimethylcyclohex-2-en-1,4-dione is used in beverage, confection, bakery and desserts, typically as a fruity note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to 2,6,6-Trimethylcyclohex-2-en-1,4-dione by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| Isophorone | 3553 | 88% | In nature |
| 2,6,6-Trimethylcyclohexanone | 3473 | 76% | In nature |
| d-Fenchone | 2479 | 62% | In nature |
| l-fenchone | 4519 | 62% | In nature |
| 2,4,6-Trimethylphenol | 4329 | 61% | In nature |
More ketones in this index
Cyclohexanone diethyl ketal · Tetramethyl ethylcyclohexenone · 3,5-Dimethyl-1,2-cyclo-pentanedione · 2,6-Dimethyl-4-heptanone · 1-(4-Methoxyphenyl)-4-methyl-1-penten-3-one · 4-Phenyl-3-buten-2-one
2,6,6-Trimethylcyclohex-2-en-1,4-dione FAQ
Does 2,6,6-Trimethylcyclohex-2-en-1,4-dione have FEMA GRAS status?
2,6,6-Trimethylcyclohex-2-en-1,4-dione holds FEMA GRAS status under FEMA number 3421. The Code of Federal Regulations lists it at 21 CFR 172.515.
How do I cite 2,6,6-Trimethylcyclohex-2-en-1,4-dione by FEMA or CAS number?
Cite 2,6,6-Trimethylcyclohex-2-en-1,4-dione as FEMA 3421 or CAS 1125-21-9; both point to the same entry. Its flavor category is fruity.
What does 2,6,6-Trimethylcyclohex-2-en-1,4-dione smell and taste like, and where is it used?
The odor of 2,6,6-Trimethylcyclohex-2-en-1,4-dione is sweet, fruity, caramel, buttery, rich. On the palate it is sweet, rich, caramel. Typical uses are beverage, confection, bakery and desserts.
What did JECFA conclude about 2,6,6-Trimethylcyclohex-2-en-1,4-dione?
JECFA evaluated 2,6,6-Trimethylcyclohex-2-en-1,4-dione at the 69th meeting in 2009 under JECFA number 1857. The panel concluded: no safety concern at current levels of intake.
Can 2,6,6-Trimethylcyclohex-2-en-1,4-dione be used in the EU and UK?
Yes. FL 07.109 is the Union List entry for 2,6,6-Trimethylcyclohex-2-en-1,4-dione, annex I Part A, under Regulation 1334/2008, and the UK keeps the same list.
Can 2,6,6-Trimethylcyclohex-2-en-1,4-dione be labeled a natural flavor?
The process decides for 2,6,6-Trimethylcyclohex-2-en-1,4-dione. It occurs in nature, so a natural-source, natural-process material is natural flavor in the US and synthetic 2,6,6-Trimethylcyclohex-2-en-1,4-dione is artificial. The EU and UK grant the natural claim only to that natural route; Mercosur and Mexico call synthetic material identical-to-natural.
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Sources and attribution. The identity and regulatory facts on this page are taken from the FDA Substances Added to Food inventory, a US government record, which lists this substance as 2,6,6-TRIMETHYLCYCLOHEX-2-ENE-1,4-DIONE under CAS 1125-21-9 and carries its FEMA number, its JECFA flavor number. The inventory is searchable at FDA. FDA records its technical effect as flavoring agent or adjuvant.
A FEMA GRAS conclusion is reached by the Expert Panel of the Flavor and Extract Manufacturers Association of the United States, and the FEMA number names that conclusion. FEMA publishes its own entry for this substance in the FEMA Flavor Library, which is the authoritative record of what the Panel decided and is worth reading alongside this page.
Ambrose Compliance is not affiliated with, endorsed by, or sponsored by FEMA. FEMA and FEMA GRAS are used here as identifiers for a published regulatory determination, not as marks of any relationship between FEMA and Ambrose.
About this page. Facts come from the FDA Substances Added to Food inventory, the Code of Federal Regulations, the EPA TSCA Inventory, the EU Union List, JECFA and the Ambrose database, with FEMA's published determination cited where it applies; parts of the text are written by Ambrose AI, which can make mistakes. Check the cited source before relying on anything here. This is not regulatory or legal advice.