Flavor ingredient regulatory record
Methyl thiobutyrate
Methyl thiobutyrate is an ester in the fruity family, FEMA GRAS under FEMA number 3310 (CAS 2432-51-1). Its odor is sweet, fruity, tropical, apple, sulfurous.
- FEMA
- 3310
- CAS
- 2432-51-1
- JECFA
- 484
- EU FL
- 12.032
- Formula
- C5H10OS
- EC
- 219-407-1
GRAS status: FEMA GRAS, publication 5. Recorded by FDA in the Substances Added to Food inventory under CAS 2432-51-1.
Structure
Identity
Also known as: Butanethioic acid, S-methyl ester, Butyric acid, thio-, S-methyl ester, Methanethiol butyrate, S-Methyl butanethioate, 1-(Methylsulfanyl)butan-1-one, s-methyl butanethioate, butanethioic acid, s-methyl ester, methanethiol butyrate, methyl thiolbutyrate, butyric acid, thio-, s-methyl ester, 1-(methylsulfanyl)butan-1-one, s-methyl thiobutyrate.
Can Methyl thiobutyrate be labeled natural?
Since methyl thiobutyrate is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when methyl thiobutyrate is synthesized. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic methyl thiobutyrate 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
Methyl thiobutyrate is FEMA GRAS under FEMA number 3310. 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 12.032, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 484, evaluated at the 55th meeting in 2000. 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. Methyl thiobutyrate appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 2432-51-1, where EPA names it Butanethioic acid, S-methyl ester.
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, tropical, apple, sulfurous.
Where it is used
Methyl thiobutyrate is used in beverage, confection, fruit flavors, savory dishes and seasonings, typically as a fruity note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Methyl thiobutyrate by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| S-Methyl 2-methylbutanethioate | 3708 | 93% | Not determined |
| Propyl thioacetate | 3385 | 91% | In nature |
| 3-Hexanone | 3290 | 90% | In nature |
| 4-Hexen-3-one | 3352 | 90% | In nature |
| 2,3-Hexanedione | 2558 | 89% | In nature |
More esters in this index
Lauryl acetate · 1-Octen-3-yl acetate · Ethyl hexadecanoate · Pinocarvyl acetate · Ethyl p-anisate · Ethyl formate
Methyl thiobutyrate FAQ
Does methyl thiobutyrate have FEMA GRAS status?
Methyl thiobutyrate holds FEMA GRAS status under FEMA number 3310. It is also codified at 21 CFR 172.515.
How do I cite methyl thiobutyrate by FEMA or CAS number?
Cite methyl thiobutyrate as FEMA 3310 or CAS 2432-51-1; both point to the same entry. FEMA files it in the fruity flavor category.
Can methyl thiobutyrate be labeled a natural flavor?
Methyl thiobutyrate occurs in nature, so the label depends on the route: methyl thiobutyrate won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized methyl thiobutyrate is artificial. The EU and UK grant the natural claim only to that natural route; Mercosur and Mexico call synthetic material identical-to-natural.
Can methyl thiobutyrate be used in the EU and UK?
Methyl thiobutyrate is on the EU Union List of flavouring substances as FL 12.032 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated methyl thiobutyrate?
Yes. JECFA number 484, evaluated at the 55th meeting in 2000. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
What does methyl thiobutyrate smell and taste like, and where is it used?
The odor of methyl thiobutyrate is sweet, fruity, tropical, apple, sulfurous. Typical uses are beverage, confection, fruit flavors, savory dishes and seasonings.
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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 METHYL THIOBUTYRATE under CAS 2432-51-1 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.