Flavor ingredient regulatory record
3-Mercaptopropionic acid
3-Mercaptopropionic acid is a thiol in the sulfur family, FEMA GRAS under FEMA number 4587 (CAS 107-96-0).
- FEMA
- 4587
- CAS
- 107-96-0
- JECFA
- 1936
- Formula
- C3H6O2S
- EC
- 203-537-0
GRAS status: FEMA GRAS, publication 24. Recorded by FDA in the Substances Added to Food inventory under CAS 107-96-0.
Structure
Identity
Also known as: Propanoic acid, 3-mercapto-, Propionic acid, 3-mercapto-, Propionic acid, β-mercapto-, 3-Mercaptopropanoic acid, β-Mercaptopropionic acid, β-Thiopropionic acid, 3-Thiopropionic acid, Mercaptopropionic acid, 3-Thiopropanoic acid, β-Mercaptopropanoic acid, MPA, Thiohydracrylic acid.
Can 3-Mercaptopropionic acid be labeled natural?
The process decides for 3-Mercaptopropionic acid. It occurs in nature, so a natural-source, natural-process material is natural flavor in the US and synthetic 3-Mercaptopropionic 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
3-Mercaptopropionic acid is FEMA GRAS under FEMA number 4587. It is cited in the Code of Federal Regulations at 21 CFR 172.515.
European Union and United Kingdom
No EU FL number is on file for 3-Mercaptopropionic acid. That is not a finding either way. The Union List covers defined flavouring substances, so natural complex materials are handled as flavouring preparations under Parts B to F and never receive a number, and substances used as additives sit under Regulation 1333/2008 instead. Confirm the position before EU or UK use.
JECFA (WHO / FAO)
JECFA number 1936, evaluated at the 73rd meeting in 2010. 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. 3-Mercaptopropionic acid appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 107-96-0, where EPA names it Propanoic acid, 3-mercapto-.
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
Taste: Bitter, sour, pungent.
Where it is used
3-Mercaptopropionic acid is used in savory dishes, seasoning, sauces and condiments, typically as a sulfur note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to 3-Mercaptopropionic acid by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| l-Cysteine | 3263 | 90% | In nature |
| Butyric acid | 2221 | 82% | In nature |
| Alanine | 3252 | 78% | In nature |
| 2-Methylbutyric acid | 2695 | 71% | In nature |
| 2-Mercaptopropionic acid | 3180 | 71% | In nature |
More thiols in this index
4-Mercapto-4-methyl-2-hexanone · S-Methyl benzothioate · Methyl mercaptan · 2-Mercapto-3-butanol · 3-Mercaptohexanol · 1-(2-Thienyl)ethanethiol
3-Mercaptopropionic acid FAQ
Is 3-Mercaptopropionic acid FEMA GRAS?
Yes. The FEMA Expert Panel lists 3-Mercaptopropionic acid as GRAS under FEMA number 4587. The Code of Federal Regulations lists it at 21 CFR 172.515.
What are the FEMA and CAS numbers for 3-Mercaptopropionic acid?
3-Mercaptopropionic acid is FEMA 4587, CAS 107-96-0. Its flavor category is sulfur.
What did JECFA conclude about 3-Mercaptopropionic acid?
JECFA evaluated 3-Mercaptopropionic acid at the 73rd meeting in 2010 under JECFA number 1936. The panel concluded: No safety concern at current levels of intake when used as a flavouring agent.
Is 3-Mercaptopropionic acid approved in the EU?
No EU FL number is on file for 3-Mercaptopropionic acid. It has a JECFA evaluation (JECFA 1936), which the EU list draws on, but the Union List entry itself should be confirmed before EU use.
Does 3-Mercaptopropionic acid count as natural in the US and the EU?
Nature makes 3-Mercaptopropionic acid, which is why the US label turns on process. A natural route gives natural flavor; synthesis gives artificial 3-Mercaptopropionic 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 3-MERCAPTOPROPIONIC ACID under CAS 107-96-0 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.