FlavScents AInsights Entry for (E,Z)-2,4-Nonadienal (CAS: 21661-99-4)

1. Identity & Chemical Information

• Common Name(s): (E,Z)-2,4-Nonadienal
• IUPAC Name: (2E,4Z)-nona-2,4-dienal
• CAS Number: 21661-99-4
• FEMA Number: 3215
• Other Identifiers: FL No. 05.062
• Molecular Formula: C9H14O
• Molecular Weight: 138.21 g/mol

(E,Z)-2,4-Nonadienal is an aldehyde characterized by its conjugated diene structure, which contributes to its potent odor profile. The presence of the aldehyde group is crucial for its reactivity and sensory properties, often associated with fatty, green, and cucumber-like odors.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

(E,Z)-2,4-Nonadienal is known for its distinctive odor, often described as fatty, green, cucumber-like, and reminiscent of deep-fried or cooked fat. It has a strong intensity and is highly diffusive, making it a powerful impact note in both flavor and fragrance applications. The odor threshold is relatively low, allowing it to be perceived at minimal concentrations, which is typical for aldehydes with conjugated double bonds.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

(E,Z)-2,4-Nonadienal occurs naturally in various foodstuffs, including cooked beef, fish, and certain oils. It is formed through the oxidative degradation of polyunsaturated fatty acids, particularly linoleic acid, during cooking or processing. This compound is significant in the context of "natural flavor" designation due to its presence in naturally occurring processes and food sources.

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

4. Use in Flavors

(E,Z)-2,4-Nonadienal is utilized in flavor formulations to impart a fatty, green, and cucumber-like note, enhancing the authenticity of savory and fresh profiles. It is commonly used in meat, fish, and vegetable flavors. Typical use levels in finished food products range from 0.1 to 2 ppm, with variations depending on the desired intensity and product type. The compound is relatively stable under typical food processing conditions but can be prone to oxidation, necessitating careful formulation to maintain its sensory characteristics.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

In fragrance applications, (E,Z)-2,4-Nonadienal contributes to green and fresh accords, often used in fine fragrances and personal care products. It serves as a modifier or impact note, providing a natural and realistic touch. Concentration ranges in formulations are typically low, often below 0.1%, due to its potent odor. Its volatility places it in the top to middle notes of fragrance compositions.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

• United States: Recognized as GRAS by FEMA for flavor use.
• European Union: Listed under Regulation (EC) No 1334/2008 with FL No. 05.062.
• United Kingdom: Follows EU regulations post-Brexit.
• Asia: Approved for use in Japan and China, with specific regulations varying by country.
• Latin America: Generally accepted in Brazil and MERCOSUR countries, subject to local regulations.

Explicit approvals and harmonized assumptions are common, though specific country regulations should be verified for compliance.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

For oral exposure, (E,Z)-2,4-Nonadienal is considered safe within the typical use levels in food, with no specific ADI established but covered under general GRAS status. Dermal exposure in fragrance use is generally safe, though IFRA guidelines should be consulted to avoid irritation or sensitization. Inhalation exposure is minimal due to its low volatility, but occupational safety measures should be in place during handling to prevent overexposure.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

(E,Z)-2,4-Nonadienal is valued for its ability to impart a realistic fatty and green note, enhancing the authenticity of both flavors and fragrances. It synergizes well with other aldehydes and green notes but can be overpowering if not balanced correctly. Formulators should be cautious of its oxidation potential and consider antioxidants to preserve its sensory qualities.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

The data on (E,Z)-2,4-Nonadienal is well-established, with comprehensive sensory and regulatory information available. Industry practices are well-documented, though specific regional regulatory nuances may require further verification. Known data gaps are minimal, primarily related to specific regional regulatory updates.

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 2026-09-02 08:08:08 GMT (p2)