FlavScents AInsights Entry for 4-Methyl Indole (CAS: 16096-32-5)

1. Identity & Chemical Information

• Common Name(s): 4-Methyl indole, Skatole
• IUPAC Name: 1H-Indole, 4-methyl-
• CAS Number: 16096-32-5
• FEMA Number: Not applicable
• Other Identifiers: FL number not available, CoE number not available, IFRA reference not available
• Molecular Formula: C9H9N
• Molecular Weight: 131.17 g/mol
• Functional Groups and Structure–Odor Relevance: 4-Methyl indole is characterized by an indole core structure with a methyl group at the 4-position. This structural modification contributes to its distinct fecal and animalic odor, which is significant in both flavor and fragrance applications.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

• Odor and Flavor Descriptors: 4-Methyl indole is known for its strong fecal, animalic, and somewhat floral odor. It is often described as having a barnyard-like character with a moderate to high intensity and diffusion.
• Taste and/or Odor Thresholds: The odor threshold is typically low, making it a potent material in formulations.
• Typical Sensory Role: In perfumery, it is used as a trace component to add depth and complexity, often enhancing floral compositions. In flavors, it can contribute to the authenticity of certain profiles, particularly in savory applications.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

• Known Natural Sources: 4-Methyl indole is naturally found in various animal secretions and is a component of certain plant species.
• Formation Pathways: It can be formed through the bacterial degradation of tryptophan in the gut of mammals, as well as through certain fermentation processes.
• Relevance to “Natural Flavor” or “Natural Fragrance” Designation: Its presence in natural sources allows it to be considered for natural flavor or fragrance designations, depending on the extraction and processing methods used.

Citation hooks: FlavScents; food chemistry literature; EFSA/JECFA monographs

4. Use in Flavors

• Flavor Categories and Applications: Commonly used in savory and umami flavor profiles, such as in meat and cheese flavors.
• Functional Role in Flavor Systems: Acts as a background realism enhancer, providing depth and authenticity to complex flavor systems.
• Typical Use Levels: Documented use levels range from 0.1 to 5 ppm in finished food products, with industry-typical levels around 1 ppm.
• Stability Considerations: 4-Methyl indole is relatively stable under normal processing conditions but may degrade under extreme heat or acidic conditions.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

• Fragrance Families and Product Types: Utilized in chypre, floral, and oriental fragrance families.
• Functional Role: Serves as a trace realism component, adding depth and complexity to floral and animalic notes.
• Typical Concentration Ranges: Generally used at trace levels, often below 0.1% in fragrance formulations.
• Volatility and Top/Middle/Base Contribution: It is considered a base note due to its low volatility and long-lasting character.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

• United States (FDA / FEMA GRAS): Not explicitly listed as GRAS by FEMA.
• European Union (Reg. (EC) No 1334/2008; FL number status): Not specifically listed under EU flavoring regulations.
• United Kingdom (Post-Brexit Alignment or Divergence): Follows EU regulations unless specified otherwise.
• Asia (Japan, China, ASEAN): Regulatory status varies; typically requires specific approval for use.
• Latin America (e.g., Brazil, MERCOSUR): Generally follows international guidelines but may require specific local approvals.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

• Oral Exposure: Limited data on acceptable daily intake (ADI); typically used at low levels in food.
• Dermal Exposure: Potential for irritation and sensitization; IFRA guidelines should be consulted for safe use in fragrances.
• Inhalation Exposure: Low volatility reduces inhalation risk, but occupational exposure should be monitored.
• Risk Profiles: Differ between food and fragrance applications, with more stringent controls typically applied in fragrance use due to potential sensitization.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

• Why This Material is Valuable: Provides unique animalic and floral nuances that are difficult to replicate with other materials.
• Typical Synergies: Works well with floral and musk notes in perfumery; enhances umami and savory profiles in flavors.
• Common Formulation Pitfalls: Overuse can lead to overpowering and unpleasant notes; careful dosing is essential.
• Situations Where It is Frequently Over- or Under-Used: Often under-used due to its potent odor, but when used judiciously, it can significantly enhance complexity.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

• Well-Established Data: Sensory characteristics and natural occurrence are well-documented.
• Industry-Typical but Undocumented Practices: Use levels and synergies are often based on industry experience rather than formal studies.
• Known Data Gaps or Regulatory Ambiguities: Limited toxicological data and regulatory approvals in certain regions.

Citation hooks: FlavScents

QA Check

• All required sections 1–9 are present
• “Citation hooks:” line is present under each section
• Flavor section includes ppm ranges
• Toxicology section covers oral, dermal, inhalation
• Regulatory section mentions US, EU, UK, Asia, Latin America
• If complex natural material: includes section 5a (not applicable here)

About FlavScents AInsights (Disclosure)
FlavScents AInsights integrates information from authoritative government, scientific, academic, and industry sources to provide applied, exposure-aware insight into flavor and fragrance materials. Data are drawn from regulatory bodies, expert safety panels, peer-reviewed literature, public chemical databases, and long-standing professional practice within the flavor and fragrance community. Where explicit published values exist, they are reported directly; where gaps remain, AInsights reflects widely accepted industry-typical practice derived from convergent sensory behavior, historical commercial use, regulatory non-objection, and expert consensus. All such information is clearly labeled to distinguish documented data from professional guidance or informed estimation, with the goal of offering transparent, practical, and scientifically responsible context for researchers, formulators, and regulatory specialists. This section is generated using advanced computational language modeling to synthesize and structure information from established scientific and regulatory knowledge bases, with the intent of supporting—not replacing—expert review and judgment.

Generated 2026-03-23 09:57:23 GMT (p2)