Flavor ingredient regulatory record
4,5-Dihydro-3(2H) thiophenone
4,5-Dihydro-3(2H) thiophenone is a ketone in the earthy family, FEMA GRAS under FEMA number 3266 (CAS 1003-04-9). Its odor is sulfurous, earthy, musty, pungent.
- FEMA
- 3266
- CAS
- 1003-04-9
- JECFA
- 498
- EU FL
- 15.012
- Formula
- C4H6OS
- EC
- 213-698-9
GRAS status: FEMA GRAS, publication 5. Recorded by FDA in the Substances Added to Food inventory under CAS 1003-04-9.
Structure
Identity
Also known as: 3(2H)-Thiophenone, dihydro-, Dihydro-3(2H)-thiophenone, 3-Thiophanone, 3-Thiacyclopentanone, Tetrahydrothiophen-3-one, 4,5-Dihydrothiophen-3(2H)-one, 3-Oxo-2,3,4,5-tetrahydrothiophene, 3-Oxotetrahydrothiophene, Thiolan-3-one, NSC 241151, Dihydrothiophen-3-one, Tetrahydrothien-3-one.
Can 4,5-Dihydro-3(2H) thiophenone be labeled natural?
Since 4,5-Dihydro-3(2H) thiophenone is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when 4,5-Dihydro-3(2H) thiophenone 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
4,5-Dihydro-3(2H) thiophenone is FEMA GRAS under FEMA number 3266. 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 15.012, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 498, evaluated at the 55th meeting in 2000. No safety concern at current levels of intake.
Other US flags
Not on the California Proposition 65 list.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. 4,5-Dihydro-3(2H) thiophenone appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 1003-04-9, where EPA names it 3(2H)-Thiophenone, dihydro-.
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: Sulfurous, earthy, musty, pungent.
Where it is used
4,5-Dihydro-3(2H) thiophenone is used in savory dishes, seasoning blends, snack foods and meat products, typically as a earthy note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to 4,5-Dihydro-3(2H) thiophenone by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| 4-Hydroxybutyric acid lactone | 3291 | 91% | In nature |
| 2-Pyrrolidone | 4829 | 90% | In nature |
| 1-Pyrroline | 3898 | 76% | In nature |
| 2-Methyltetrahydrothiophen-3-one | 3512 | 74% | In nature |
| 4-Methyl-3-thiazoline | 4644 | 69% | In nature |
More ketones in this index
Methyl-beta- ionone · 4-Heptanone · Methyl-delta-ionone · 2,3-Hexanedione · d,l-Isomenthone · 2-Pentanone
4,5-Dihydro-3(2H) thiophenone FAQ
Is 4,5-Dihydro-3(2H) thiophenone on the FEMA GRAS list?
It is. FEMA number 3266 covers 4,5-Dihydro-3(2H) thiophenone. It is also codified at 21 CFR 172.515.
What is the FEMA number for 4,5-Dihydro-3(2H) thiophenone?
The FEMA number for 4,5-Dihydro-3(2H) thiophenone is 3266 and its CAS registry number is 1003-04-9. FEMA files it in the earthy flavor category.
Is 4,5-Dihydro-3(2H) thiophenone natural or artificial?
4,5-Dihydro-3(2H) thiophenone occurs in nature, so the label depends on the route: 4,5-Dihydro-3(2H) thiophenone won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized 4,5-Dihydro-3(2H) thiophenone 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 4,5-Dihydro-3(2H) thiophenone approved in the EU?
4,5-Dihydro-3(2H) thiophenone is on the EU Union List of flavouring substances as FL 15.012 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated 4,5-Dihydro-3(2H) thiophenone?
Yes. JECFA number 498, evaluated at the 55th meeting in 2000. Conclusion: No safety concern at current levels of intake.
What is 4,5-Dihydro-3(2H) thiophenone used for?
4,5-Dihydro-3(2H) thiophenone is described as sulfurous, earthy, musty, pungent. It shows up in savory dishes, seasoning blends, snack foods and meat products.
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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 4,5-DIHYDRO-3(2H)THIOPHENONE under CAS 1003-04-9 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.