FlavScents AInsights Entry for Nootkatone (CAS: 91416-23-8)

1. Identity & Chemical Information

Nootkatone is a sesquiterpenoid commonly associated with the characteristic aroma of grapefruit. Its IUPAC name is (4R,4aS,6R)-4,4a-Dimethyl-6-(propan-2-ylidene)decahydronaphthalen-2-one. The CAS number for nootkatone is 91416-23-8. It is also identified by FEMA number 3166. The molecular formula of nootkatone is C15H22O, with a molecular weight of 218.34 g/mol. The compound features a ketone functional group, which contributes to its distinctive odor profile. The structure-odor relevance is significant as the bicyclic structure and the presence of the isopropenyl group are crucial for its grapefruit-like aroma.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

Nootkatone is renowned for its potent grapefruit aroma, characterized by a fresh, citrusy, and woody scent. It is often described as having a medium to high intensity with a long-lasting diffusion. The taste and odor thresholds are not clearly reported, but it is known to be effective at low concentrations, making it a valuable impact note in flavor formulations. Nootkatone is primarily used to impart a realistic grapefruit note, enhancing the freshness and complexity of citrus flavors.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

Nootkatone naturally occurs in grapefruit (Citrus paradisi) and is also found in other citrus fruits, albeit in smaller quantities. It can be formed through the oxidation of valencene, a sesquiterpene present in citrus oils. This transformation can occur naturally or be catalyzed by enzymatic processes. Nootkatone's presence in grapefruit contributes to its designation as a "natural flavor" in regulatory terms, provided it is derived from natural sources.

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

4. Use in Flavors

Nootkatone is extensively used in flavor formulations, particularly in citrus and tropical fruit categories. It serves as a key impact note, providing authenticity and depth to grapefruit and other citrus flavors. Typical use levels in finished food or beverage products range from 0.1 to 5 ppm, with industry-typical levels around 1 ppm. Nootkatone is relatively stable under acidic conditions but may degrade under high heat or oxidative environments, necessitating careful formulation considerations.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

In the fragrance industry, nootkatone is valued for its ability to impart a fresh, citrusy, and woody note. It is commonly used in citrus, woody, and chypre fragrance families. Nootkatone acts as a modifier and impact note, often used in concentrations ranging from trace amounts to 0.5% in fragrance formulations. It contributes primarily to the top and middle notes due to its moderate volatility.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

In the United States, nootkatone is recognized as GRAS (Generally Recognized As Safe) by FEMA for flavor use. In the European Union, it is approved under Regulation (EC) No 1334/2008 with an assigned FL number. The United Kingdom follows similar regulations post-Brexit. In Asia, nootkatone is accepted in Japan and China, though specific regulations may vary. In Latin America, countries like Brazil and those in MERCOSUR generally align with international standards, but local regulations should be consulted for specific applications.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

Nootkatone is considered safe for oral exposure in flavor applications, with an ADI not clearly reported but generally recognized as safe at typical use levels. For dermal exposure in fragrances, it is not known to be a significant irritant or sensitizer, aligning with IFRA guidelines. Inhalation exposure is considered low risk due to its moderate volatility, but occupational exposure should be managed with standard safety practices. The risk profiles for food and fragrance applications are generally similar, with no significant differences noted.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

Nootkatone is a valuable material for its ability to impart a realistic grapefruit note, enhancing both flavor and fragrance formulations. It synergizes well with other citrus and tropical notes, adding complexity and freshness. Formulators should be cautious of its stability under heat and oxidative conditions, and it is often under-used due to its cost. Proper balancing with other components can prevent overpowering effects.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

The data on nootkatone is well-established, particularly regarding its sensory profile and regulatory status. Industry practices are well-documented, though specific numeric values for thresholds and ADI are not always available. Known data gaps include detailed toxicological studies and specific regional regulatory nuances.

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 2026-07-09 11:18:19 GMT (p2)