Flavor ingredient regulatory record
L-Isoleucine
L-Isoleucine is an amino acid in the savory family, FEMA GRAS under FEMA number 4675 (CAS 73-32-5). Its odor is umami, savory, broth, meaty.
- FEMA
- 4675
- CAS
- 73-32-5
- JECFA
- 2118
- Formula
- C6H13NO2
- EC
- 200-798-2
GRAS status: FEMA GRAS, publication 25. Recorded by FDA in the Substances Added to Food inventory under CAS 73-32-5.
Structure
Identity
Also known as: Isoleucine, L-, Isoleucine, erythro-L-Isoleucine, 2-Amino-3-methylvaleric acid, (2S,3S)-α-Amino-β-methylvaleric acid, L-(+)-Isoleucine, [S-(R*,R*)]-2-Amino-3-methylpentanoic acid, (S)-Isoleucine, (2S,3S)-α-Amino-β-methyl-n-valeric acid, (2S,3S)-2-Amino-3-methylpentanoic acid, (S,S)-Isoleucine, 2S,3S-Isoleucine.
Can L-Isoleucine be labeled natural?
The process decides for L-Isoleucine. It occurs in nature, so a natural-source, natural-process material is natural flavor in the US and synthetic L-Isoleucine 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.
- 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
L-Isoleucine is FEMA GRAS under FEMA number 4675. It is cited in the Code of Federal Regulations at 21 CFR 172.320.
European Union and United Kingdom
No EU FL number is on file for L-Isoleucine. 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 2118, evaluated at the 76th meeting in 2012. 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. L-Isoleucine appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 73-32-5, where EPA names it L-Isoleucine.
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
L-Isoleucine is used in seasoning, sauces, snack foods and meat products, typically as a savory note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to L-Isoleucine by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| Leucine | 3297 | 93% | In nature |
| 3-Methyl-2-oxopentanoic acid | 3870 | 87% | In nature |
| l-Valine | 3444 | 87% | In nature |
| Methyl-3-pentenoic acid | 3464 | 86% | In nature |
| L-Threonine | 4710 | 78% | In nature |
More amino acids in this index
L-Glutamine · Leucine · L-Methionylglycine · L-Ornithine monochlorohydrate · Glycine · L-Alanine
L-Isoleucine FAQ
Does L-Isoleucine have FEMA GRAS status?
L-Isoleucine holds FEMA GRAS status under FEMA number 4675. The Code of Federal Regulations lists it at 21 CFR 172.320.
How do I cite L-Isoleucine by FEMA or CAS number?
Cite L-Isoleucine as FEMA 4675 or CAS 73-32-5; both point to the same entry. Its flavor category is savory.
What does L-Isoleucine smell and taste like, and where is it used?
The odor of L-Isoleucine is umami, savory, broth, meaty. Typical uses are seasoning, sauces, snack foods and meat products.
What did JECFA conclude about L-Isoleucine?
JECFA evaluated L-Isoleucine at the 76th meeting in 2012 under JECFA number 2118. The panel concluded: No safety concern at current levels of intake when used as a flavouring agent.
Is L-Isoleucine approved in the EU?
No EU FL number is on file for L-Isoleucine. It has a JECFA evaluation (JECFA 2118), which the EU list draws on, but the Union List entry itself should be confirmed before EU use.
Can L-Isoleucine be labeled a natural flavor?
Nature makes L-Isoleucine, which is why the US label turns on process. A natural route gives natural flavor; synthesis gives artificial L-Isoleucine, same molecule. The EU and UK follow the same logic without a middle class; Mercosur and Mexico label synthetic L-Isoleucine 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-ISOLEUCINE under CAS 73-32-5 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 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.