Flavor ingredient regulatory record
Leucine
Leucine is an amino acid in the savory family, FEMA GRAS under FEMA number 3297 (CAS 61-90-5). Its odor is umami, savory, broth, meaty.
- FEMA
- 3297
- CAS
- 61-90-5
- JECFA
- 1423
- EU FL
- 17.012
- Formula
- C6H13NO2
- EC
- 200-522-0
GRAS status: FEMA GRAS, publication 5. Recorded by FDA in the Substances Added to Food inventory under CAS 61-90-5.
Structure
Identity
Also known as: L-Leucine, Leucine, L-, Pentanoic acid, 2-amino-4-methyl-, (S)-, Leu, (S)-2-Amino-4-methylvaleric acid, (S)-(+)-Leucine, (S)-2-Amino-4-methylpentanoic acid, (S)-Leucine, L-α-Aminoisocaproic acid, L-(+)-Leucine, L-Norvaline, 4-methyl-, NSC 46709.
Can Leucine be labeled natural?
Nature makes leucine, which is why the US label turns on process. A natural route gives natural flavor; synthesis gives artificial leucine, same molecule. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic leucine 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
Leucine is FEMA GRAS under FEMA number 3297. It is cited in the Code of Federal Regulations at 21 CFR 172.320.
European Union and United Kingdom
Listed on the Union List of flavouring substances as FL 17.012, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (EFSA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 1423, evaluated at the 63rd meeting in 2004. 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. Leucine appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 61-90-5, where EPA names it L-Leucine.
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: Umami, savory, broth, meaty.
Where it is used
Leucine is used in savory foods, snacks, seasonings and protein supplements, typically as a savory note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to Leucine by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| dl-Isoleucine | 3295 | 93% | In nature |
| 4-Aminobutyric acid | 4288 | 80% | In nature |
| l-Valine | 3444 | 78% | In nature |
| 4-Methyl-2-oxopentanoic acid | 3871 | 77% | In nature |
| 2-Methylvaleric acid | 2754 | 75% | In nature |
More amino acids in this index
L-Methionylglycine · L-Glutamine · L-Isoleucine · L-Ornithine monochlorohydrate · Glycine · l-Valine
Leucine FAQ
Is leucine FEMA GRAS?
Yes. The FEMA Expert Panel lists leucine as GRAS under FEMA number 3297. The Code of Federal Regulations lists it at 21 CFR 172.320.
What are the FEMA and CAS numbers for leucine?
Leucine is FEMA 3297, CAS 61-90-5. Its flavor category is savory.
How is leucine described, and where does it show up?
Flavorists describe leucine as umami, savory, broth, meaty. It is used in savory foods, snacks, seasonings and protein supplements.
What did JECFA conclude about leucine?
JECFA evaluated leucine at the 63rd meeting in 2004 under JECFA number 1423. The panel concluded: No safety concern at current levels of intake when used as a flavouring agent.
Is leucine on the EU Union List?
Yes. FL 17.012 is the Union List entry for leucine, annex I Part A, under Regulation 1334/2008, and the UK keeps the same list.
Does leucine count as natural in the US and the EU?
The process decides for leucine. It occurs in nature, so a natural-source, natural-process material is natural flavor in the US and synthetic leucine is artificial. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic leucine identical-to-natural.
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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 L-LEUCINE under CAS 61-90-5 and carries its FEMA number, its JECFA flavor number and its 21 CFR citations. The inventory is searchable at FDA. FDA records its technical effect as flavor enhancer, flavoring agent or adjuvant, nutrient supplement.
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.