Flavor ingredient regulatory record
Cyclopentanethiol
Cyclopentanethiol is a thiol in the sulfur family, FEMA GRAS under FEMA number 3262 (CAS 1679-07-8). Its odor is pungent, garlic, onion, earthy, sulfurous.
- FEMA
- 3262
- CAS
- 1679-07-8
- JECFA
- 516
- EU FL
- 12.029
- Formula
- C5H10S
- EC
- 216-841-3
GRAS status: FEMA GRAS, publication 5. Recorded by FDA in the Substances Added to Food inventory under CAS 1679-07-8.
Structure
Identity
Also known as: Cyclopentyl mercaptan, Mercaptocyclopentane, Cyclopentylthiol, cyclopentyl mercaptan, mercaptocyclopentane, cyclopentylthiol, cyclopentanethiol [fhfi], 4-06-00-00015 (beilstein handbook reference), cyclopentyl thiol, cyclopen-tanethiol, cyclopentane thiol, cyclopentylmercaptan.
Can Cyclopentanethiol be labeled natural?
Since cyclopentanethiol is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when cyclopentanethiol is synthesized. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic cyclopentanethiol 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
Cyclopentanethiol is FEMA GRAS under FEMA number 3262. 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 12.029, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 516, 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. Listed on the EPA TSCA inventory.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. Cyclopentanethiol appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 1679-07-8, where EPA names it Cyclopentanethiol.
Inactive in US commerce
EPA designates this substance inactive, so a Notice of Activity Form B is required before anyone manufactures or processes it again. Being FEMA GRAS does not change that. 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, garlic, onion, earthy, sulfurous.
Where it is used
Cyclopentanethiol is used in savory dishes, seasoning, sauces and meat products, typically as a sulfur note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Cyclopentanethiol by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| 2-Methyl-3-tetrahydrofuranthiol | 3787 | 90% | In nature |
| 2-Mercapto-3-butanol | 3502 | 73% | In nature |
More thiols in this index
S-Methyl benzothioate · Dimercaptomethane · Furfuryl mercaptan · Hydrogen sulfide · 3-Methylbutanethiol · Ammonium hydrogen sulphide
Cyclopentanethiol FAQ
Does cyclopentanethiol have FEMA GRAS status?
Cyclopentanethiol holds FEMA GRAS status under FEMA number 3262. It is also codified at 21 CFR 172.515.
How do I cite cyclopentanethiol by FEMA or CAS number?
Cite cyclopentanethiol as FEMA 3262 or CAS 1679-07-8; both point to the same entry. FEMA files it in the sulfur flavor category.
Can cyclopentanethiol be labeled a natural flavor?
Cyclopentanethiol occurs in nature, so the label depends on the route: cyclopentanethiol won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized cyclopentanethiol 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 cyclopentanethiol be used in the EU and UK?
Cyclopentanethiol is on the EU Union List of flavouring substances as FL 12.029 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated cyclopentanethiol?
Yes. JECFA number 516, evaluated at the 53rd meeting in 1999. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
What does cyclopentanethiol smell and taste like, and where is it used?
The odor of cyclopentanethiol is pungent, garlic, onion, earthy, sulfurous. Typical uses are savory dishes, seasoning, sauces 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 CYCLOPENTANETHIOL under CAS 1679-07-8 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.