Flavor ingredient regulatory record
Methyl isothiocyanate
Methyl isothiocyanate is an isothiocyanate in the sulfur family, FEMA GRAS under FEMA number 4426 (CAS 556-61-6). Its odor is pungent, mustard, sulfurous, sharp.
- FEMA
- 4426
- CAS
- 556-61-6
- JECFA
- 1884
- Formula
- C2H3NS
- EC
- 209-132-5
GRAS status: FEMA GRAS, publication 23. Recorded by FDA in the Substances Added to Food inventory under CAS 556-61-6.
Structure
Identity
Also known as: Methane, isothiocyanato-, Isothiocyanic acid, methyl ester, Isothiocyanatomethane, WN 12, Methyl mustard oil, Morton EP-161E, Trapex, Trapexide, Tropex, Methyl thioisocyanate, Methyl mustard, MIT.
Can Methyl isothiocyanate be labeled natural?
Since methyl isothiocyanate is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when methyl isothiocyanate is synthesized. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic methyl isothiocyanate 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 isothiocyanate is FEMA GRAS under FEMA number 4426. 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 Methyl isothiocyanate. 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 1884, evaluated at the 69th meeting in 2008. 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 isothiocyanate appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 556-61-6, where EPA names it Methane, isothiocyanato-.
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: Pungent, mustard, sulfurous, sharp.
Where it is used
Methyl isothiocyanate is used in seasoning, condiment, food preservation and flavor enhancer, typically as a sulfur note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Methyl isothiocyanate by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| Ethyl isothiocyanate | 4420 | 70% | In nature |
| Isopropyl isothiocyanate | 4425 | 59% | In nature |
| Butyl isothiocyanate | 4082 | 57% | In nature |
| Acetaldehyde | 2003 | 57% | In nature |
| 2-Butyl isothiocyanate | 4419 | 56% | In nature |
More isothiocyanates in this index
Isopropyl isothiocyanate · 5-(Methylthio)pentyl isothiocyanate · Isoamyl isothiocyanate · Hexyl isothiocyanate · 2-Butyl isothiocyanate · 3-(Methylthio)propyl isothiocyanate
Methyl isothiocyanate FAQ
Does methyl isothiocyanate have FEMA GRAS status?
Methyl isothiocyanate holds FEMA GRAS status under FEMA number 4426. It is also codified at 21 CFR 172.515.
How do I cite methyl isothiocyanate by FEMA or CAS number?
Cite methyl isothiocyanate as FEMA 4426 or CAS 556-61-6; both point to the same entry. FEMA files it in the sulfur flavor category.
Can methyl isothiocyanate be labeled a natural flavor?
Methyl isothiocyanate occurs in nature, so the label depends on the route: methyl isothiocyanate won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized methyl isothiocyanate is artificial. The EU and UK grant the natural claim only to that natural route; Mercosur and Mexico call synthetic material identical-to-natural.
Is methyl isothiocyanate approved in the EU?
No EU FL number is on file for methyl isothiocyanate. It has a JECFA evaluation (JECFA 1884), which the EU list draws on, but the Union List entry itself should be confirmed before EU use.
Has JECFA evaluated methyl isothiocyanate?
Yes. JECFA number 1884, evaluated at the 69th meeting in 2008. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
What does methyl isothiocyanate smell and taste like, and where is it used?
The odor of methyl isothiocyanate is pungent, mustard, sulfurous, sharp. Typical uses are seasoning, condiment, food preservation and flavor enhancer.
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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 ISOTHIOCYANATE under CAS 556-61-6 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.