Flavor ingredient regulatory record
S-Methyl 3-methylbutanethioate
S-Methyl 3-methylbutanethioate is a thiol in the fruity family, FEMA GRAS under FEMA number 3864 (CAS 23747-45-7). Its odor is sweet, fruity, tropical, sulfurous, apple.
- FEMA
- 3864
- CAS
- 23747-45-7
- JECFA
- 487
- EU FL
- 12.157
- Formula
- C6H12OS
GRAS status: FEMA GRAS, publication 18. Recorded by FDA in the Substances Added to Food inventory under CAS 23747-45-7.
Structure
Identity
Also known as: Butanethioic acid, 3-methyl-, S-methyl ester, Butyric acid, 3-methylthio-, S-methyl ester, methanethiol isovalerate, s-methyl thioisovalerate, butanethioic acid, 3-methyl-, s-methyl ester, s-methyl 3-methylthiobutyrate, methylthiol isovalerate, 3-methyl-1-(methylsulfanyl)butan-1-one, s-methyl 3-methylbutanethioate [fhfi], butyric acid, 3-methylthio-, s-methyl ester, s-methyl isovalerate, s-methyl thio-3-methylbutyrate.
Can S-Methyl 3-methylbutanethioate be labeled natural?
S-Methyl 3-methylbutanethioate occurs in nature, so the label depends on the route: S-Methyl 3-methylbutanethioate won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized S-Methyl 3-methylbutanethioate 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
S-Methyl 3-methylbutanethioate is FEMA GRAS under FEMA number 3864. 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 12.157, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 487, 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. S-Methyl 3-methylbutanethioate appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 23747-45-7, where EPA names it Butanethioic acid, 3-methyl-, 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, sulfurous, apple.
Where it is used
S-Methyl 3-methylbutanethioate is used in beverage, confection, fruit flavors and savory dishes, typically as a fruity note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to S-Methyl 3-methylbutanethioate by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| Methyl thiobutyrate | 3310 | 86% | In nature |
| S-Methyl 2-methylbutanethioate | 3708 | 77% | Not determined |
| Propyl thioacetate | 3385 | 76% | In nature |
| 2-(Methylthio)methyl-2-butenal | 3601 | 68% | In nature |
More thiols in this index
2,5-Dimethyl-3-tetrahydrofuranthiol, cis and trans isomers · 2-Hexylthiophene · Ethyl 2-Mercapto-2-methylpropionate · (+/-)-cis- and trans-2-Pentyl-4-propyl-1,3-oxathiane · 1-(3-(Methylthio)-butyryl)-2,6,6-trimethylcyclohexene · 2-Pentenyl-4-propyl-1,3-oxathiane
S-Methyl 3-methylbutanethioate FAQ
Is S-Methyl 3-methylbutanethioate FEMA GRAS?
Yes. The FEMA Expert Panel lists S-Methyl 3-methylbutanethioate as GRAS under FEMA number 3864. It is also codified at 21 CFR 172.515.
What are the FEMA and CAS numbers for S-Methyl 3-methylbutanethioate?
S-Methyl 3-methylbutanethioate is FEMA 3864, CAS 23747-45-7. FEMA files it in the fruity flavor category.
Does S-Methyl 3-methylbutanethioate count as natural in the US and the EU?
Since S-Methyl 3-methylbutanethioate is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when S-Methyl 3-methylbutanethioate is synthesized. The EU and UK grant the natural claim only to that natural route; Mercosur and Mexico call synthetic material identical-to-natural.
Is S-Methyl 3-methylbutanethioate on the EU Union List?
S-Methyl 3-methylbutanethioate is on the EU Union List of flavouring substances as FL 12.157 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated S-Methyl 3-methylbutanethioate?
Yes. JECFA number 487, evaluated at the 53rd meeting in 1999. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
How is S-Methyl 3-methylbutanethioate described, and where does it show up?
Flavorists describe S-Methyl 3-methylbutanethioate as sweet, fruity, tropical, sulfurous, apple. It is used in beverage, confection, fruit flavors and savory dishes.
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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 S-METHYL 3-METHYLBUTANETHIOATE under CAS 23747-45-7 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.