Flavor ingredient regulatory record
Isobutyric acid
Isobutyric acid is an acid in the dairy family, FEMA GRAS under FEMA number 2222 (CAS 79-31-2). Its odor is sour, cheesy, rancid butter, sweaty.
- FEMA
- 2222
- CAS
- 79-31-2
- JECFA
- 253
- EU FL
- 08.006
- Formula
- C4H8O2
- EC
- 201-195-7
GRAS status: FEMA GRAS, publication 3. Recorded by FDA in the Substances Added to Food inventory under CAS 79-31-2.
Structure
Identity
Also known as: Propanoic acid, 2-methyl-, 2-Methylpropanoic acid, Dimethylacetic acid, Isopropylformic acid, α-Methylpropionic acid, 2-Methylpropionic acid, iso-Butyric acid, Isobutanoic acid, α-Methylpropanoic acid, i-Butyric acid, NSC 62780, 2-Propanecarboxylic acid.
Can Isobutyric acid be labeled natural?
Since isobutyric acid is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when isobutyric acid is synthesized. 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
Isobutyric acid is FEMA GRAS under FEMA number 2222. 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 08.006, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 253, 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.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. Isobutyric acid appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 79-31-2, where EPA names it Propanoic acid, 2-methyl-.
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 regulatory flags
| Flag | EPA definition | What it obliges |
|---|---|---|
| TP | Indicates a substance that is the subject of a proposed TSCA section 4 test rule or order. | Nothing yet. Worth tracking, because a final rule carries testing obligations and a lower reporting threshold. |
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: Sour, cheesy, rancid butter, sweaty.
Taste: Sour, cheesy, buttery.
Where it is used
Isobutyric acid is used in cheese, butter and dairy, typically as a dairy note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Isobutyric acid by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| Propionic acid | 2924 | 94% | In nature |
| Lactic acid | 2611 | 93% | In nature |
| L-Alanine | 3818 | 93% | In nature |
| Acetoin | 2008 | 89% | In nature |
| 2-Mercaptopropionic acid | 3180 | 86% | In nature |
More acids in this index
Pentadecanoic acid · Tridecanoic acid · Decanoic acid · Butyric acid · Citric Acid · 3-Methyl-2-oxobutanoic acid
Isobutyric acid FAQ
Is isobutyric acid on the FEMA GRAS list?
It is. FEMA number 2222 covers isobutyric acid. It is also codified at 21 CFR 172.515.
What is the FEMA number for isobutyric acid?
The FEMA number for isobutyric acid is 2222 and its CAS registry number is 79-31-2. FEMA files it in the dairy flavor category.
Is isobutyric acid natural or artificial?
Isobutyric acid occurs in nature, so the label depends on the route: isobutyric acid won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized isobutyric acid is artificial. 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.
Is isobutyric acid approved in the EU?
Isobutyric acid is on the EU Union List of flavouring substances as FL 08.006 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated isobutyric acid?
Yes. JECFA number 253, evaluated at the 51st meeting in 1998. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
What is isobutyric acid used for?
Isobutyric acid is described as sour, cheesy, rancid butter, sweaty. On the palate it is sour, cheesy, buttery. It shows up in cheese, butter and dairy.
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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 ISOBUTYRIC ACID under CAS 79-31-2 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.