Flavor ingredient regulatory record
Diacetyl
Diacetyl is a diketone in the dairy family, FEMA GRAS under FEMA number 2370 (CAS 431-03-8). Its odor is butter, creamy, rich, slightly cheesy.
- FEMA
- 2370
- CAS
- 431-03-8
- JECFA
- 408
- EU FL
- 07.052
- Formula
- C4H6O2
- EC
- 207-069-8
GRAS status: FEMA GRAS, publication 3. Recorded by FDA in the Substances Added to Food inventory under CAS 431-03-8.
Structure
Identity
Also known as: 2,3-Butanedione, Biacetyl, 2,3-Diketobutane, Dimethyl diketone, Dimethylglyoxal, Butanedione, 2,3-Butadione, 2,3-Dioxobutane, NSC 8750, MeSH ID: D003931, 2,3-butanedione, biacetyl.
Can Diacetyl be labeled natural?
Since diacetyl is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when diacetyl is synthesized. In the EU and UK the natural claim likewise needs the natural route, while Mercosur and Mexico keep a third class, identical-to-natural, for the synthetic material.
- 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
Diacetyl is FEMA GRAS under FEMA number 2370. It is cited in the Code of Federal Regulations at 21 CFR 184.1278.
European Union and United Kingdom
Listed on the Union List of flavouring substances as FL 07.052, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 408, evaluated at the 51st meeting in 1998. No safety concern at current levels of intake when used as a flavouring agent.
Other US flags
Not on the California Proposition 65 list. Listed on the EPA TSCA inventory.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. Diacetyl appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 431-03-8, where EPA names it 2,3-Butanedione.
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: Butter, creamy, rich, slightly cheesy. Detectable at about 0.005 ppm.
Taste: Buttery, creamy, rich dairy. Taste threshold about 0.01 ppm.
Where it is used
Diacetyl is used in butter, dairy, margarine and popcorn, typically as a dairy note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Diacetyl by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| 2-Butanone | 2170 | 91% | In nature |
| Acetoin | 2008 | 91% | In nature |
| Isobutyric acid | 2222 | 83% | In nature |
| Hydroxyacetone | 4462 | 79% | In nature |
| Pyruvic acid | 2970 | 79% | In nature |
More diketones in this index
Diacetyl FAQ
Is diacetyl FEMA GRAS?
Yes. The FEMA Expert Panel lists diacetyl as GRAS under FEMA number 2370. It is also codified at 21 CFR 184.1278.
What are the FEMA and CAS numbers for diacetyl?
Diacetyl is FEMA 2370, CAS 431-03-8. FEMA files it in the dairy flavor category.
Does diacetyl count as natural in the US and the EU?
Diacetyl occurs in nature, so the label depends on the route: diacetyl won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized diacetyl is artificial. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic diacetyl identical-to-natural.
Is diacetyl on the EU Union List?
Diacetyl is on the EU Union List of flavouring substances as FL 07.052 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated diacetyl?
Yes. JECFA number 408, evaluated at the 51st meeting in 1998. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
How is diacetyl described, and where does it show up?
Flavorists describe diacetyl as butter, creamy, rich, slightly cheesy. On the palate it is buttery, creamy, rich dairy. Its odor threshold is about 0.005 ppm. It is used in butter, dairy, margarine and popcorn.
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Guides: What Is FEMA GRAS? · Natural vs artificial · Filing a GRAS notification
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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 DIACETYL under CAS 431-03-8 and carries its FEMA number, its JECFA flavor number and its 21 CFR citations. 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.