Flavor ingredient regulatory record
2-Oxobutyric acid
2-Oxobutyric acid is an acid in the fruity family, FEMA GRAS under FEMA number 3723 (CAS 600-18-0). Its odor is fruity, sour, tangy, slightly sweet.
- FEMA
- 3723
- CAS
- 600-18-0
- JECFA
- 589
- EU FL
- 08.066
- Formula
- C4H6O3
GRAS status: FEMA GRAS, publication 13. Recorded by FDA in the Substances Added to Food inventory under CAS 600-18-0.
Structure
Identity
Also known as: Butanoic acid, 2-oxo-, Butyric acid, 2-oxo-, 2-Oxobutanoic acid, Propionylformic acid, α-Oxobutyric acid, α-Oxo-n-butyric acid, α-Ketobutyric acid, 2-Ketobutyric acid, α-keto-n-Butyric acid, 3-Methylpyruvic acid, 2-Oxo-n-butyric acid, 2-Ketobutanoic acid.
Can 2-Oxobutyric acid be labeled natural?
The process decides for 2-Oxobutyric acid. It occurs in nature, so a natural-source, natural-process material is natural flavor in the US and synthetic 2-Oxobutyric acid is artificial. 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-Oxobutyric acid is FEMA GRAS under FEMA number 3723. 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 08.066, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 589, evaluated at the 53rd meeting in 1999. no safety concern at current levels of intake when used as a flavouring agent.
Other US flags
Not on the California Proposition 65 list.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. 2-Oxobutyric acid appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 600-18-0, where EPA names it Butanoic acid, 2-oxo-.
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: Fruity, sour, tangy, slightly sweet.
Taste: Sour, tangy, slightly sweet.
Where it is used
2-Oxobutyric acid is used in beverage, confection, fruit flavors, sauces and dressings, typically as a fruity note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to 2-Oxobutyric acid by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| 3-Methyl-2-oxobutanoic acid | 3869 | 92% | In nature |
| 3-Hydroxy-2-pentanone | 3550 | 87% | In nature |
| Butyric acid | 2221 | 83% | In nature |
| 3-Hydroxy-2-oxopropionic acid | 3843 | 81% | In nature |
| 2,3-Pentadione | 2841 | 81% | In nature |
More acids in this index
3-Hydroxy-2-oxopropionic acid · cis-5-Octenoic acid · 3,4-Dihydroxybenzoic acid · 4-Methyl-2-oxopentanoic acid · 4-Hydroxybenzoic acid · 3-Methylcrotonic acid
2-Oxobutyric acid FAQ
Is 2-Oxobutyric acid FEMA GRAS?
Yes. The FEMA Expert Panel lists 2-Oxobutyric acid as GRAS under FEMA number 3723. The Code of Federal Regulations lists it at 21 CFR 172.515.
What are the FEMA and CAS numbers for 2-Oxobutyric acid?
2-Oxobutyric acid is FEMA 3723, CAS 600-18-0. Its flavor category is fruity.
How is 2-Oxobutyric acid described, and where does it show up?
Flavorists describe 2-Oxobutyric acid as fruity, sour, tangy, slightly sweet. On the palate it is sour, tangy, slightly sweet. It is used in beverage, confection, fruit flavors, sauces and dressings.
What did JECFA conclude about 2-Oxobutyric acid?
JECFA evaluated 2-Oxobutyric acid at the 53rd meeting in 1999 under JECFA number 589. The panel concluded: no safety concern at current levels of intake when used as a flavouring agent.
Is 2-Oxobutyric acid on the EU Union List?
Yes. FL 08.066 is the Union List entry for 2-Oxobutyric acid, annex I Part A, under Regulation 1334/2008, and the UK keeps the same list.
Does 2-Oxobutyric acid count as natural in the US and the EU?
Nature makes 2-Oxobutyric acid, which is why the US label turns on process. A natural route gives natural flavor; synthesis gives artificial 2-Oxobutyric acid, same molecule. 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.
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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 ALPHA-KETOBUTYRIC ACID under CAS 600-18-0 and carries its FEMA number, its JECFA flavor number. The inventory is searchable at FDA. FDA records its technical effect as flavor enhancer, 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.