Aroma compound

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Fragrance bottles.

An aroma compound, also known as an odorant, aroma, fragrance, or flavor, is a chemical compound that has a smell or odor. A chemical compound has a smell or odor when it is sufficiently volatile to be transported to the olfactory system in the upper part of the nose.

Generally molecules meeting this specification have molecular weights of less than 300. Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and fragrances tend to be synthetic.[1]

Aroma compounds can be found in food, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form biochemically during the ripening of fruits and other crops. In wines, most form as byproducts of fermentation. Also, many of the aroma compounds play a significant role in the production of flavorants, which are used in the food service industry to flavor, improve, and generally increase the appeal of their products.

An odorizer may add a detectable odor to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure.

Aroma compounds classified by structure[edit]


Compound name Fragrance Natural occurrence Chemical structure
Geranyl acetate Fruity, Rose Rose,
Geranyl acetate skeletal.svg
Methyl formate Ethereal
Methyl acetate Sweet, nail polish
Methyl propionate
Methyl propanoate
Sweet, fruity, rum-like
Methyl propionate.svg
Methyl butyrate
Methyl butanoate
Fruity, Apple
Ethyl acetate Sweet, solvent Wine
Ethyl acetate2.svg
Ethyl butyrate
Ethyl butanoate
Fruity, Orange
Ethyl butyrate2.svg
Isoamyl acetate Fruity, Banana
Banana plant
Isoamyl acetate.png
Pentyl butyrate
Pentyl butanoate
Fruity, Pear
Pentyl butyrate.png
Pentyl pentanoate Fruity, Apple
Pentyl pentanoate.png
Octyl acetate Fruity, Orange
Octyl acetate.svg
Benzyl acetate Fruity, Strawberry Strawberries
Benzyl acetate.png
Methyl anthranilate Fruity, Grape
Methyl anthranilate.png

Linear terpenes[edit]

Compound name Fragrance Natural occurrence Chemical structure
Myrcene Woody, complex Verbena, Bay leaf
Myrcene beta straight acsv.svg
Geraniol Rose, flowery Geranium, Lemon
Geraniol structure.png
Nerol Sweet rose, flowery Neroli, Lemongrass
Citral, lemonal
Geranial, neral
Lemon Lemon myrtle, Lemongrass
Geranial structure.png
Citronellal Lemon Lemongrass
Citronellol Lemon Lemongrass, rose
Linalool Floral, sweet
Woody, Lavender
Coriander, Sweet basil
Linalool skeletal.svg
Nerolidol Woody, fresh bark Neroli, ginger

Cyclic terpenes[edit]

Compound name Fragrance Natural occurrence Chemical structure
Limonene Orange Orange, lemon
Camphor Camphor Camphor laurel
Camphor structure.png
Menthol Menthol Mentha
Menthol skeletal.svg
Carvone1 Caraway or Spearmint Caraway, dill,
Terpineol Lilac Lilac, cajuput
Terpineol alpha.svg
alpha-Ionone Violet, woody Violet
Thujone Minty Wormwood, lilac,
Eucalyptol Eucalyptus Eucalyptus globulus

Note: Carvone, depending on its chirality, offers two different smells.


Compound name Fragrance Natural occurrence Chemical structure
Benzaldehyde Almond Bitter almond
Eugenol Clove Clove
Eugenol acsv.svg
Cinnamaldehyde Cinnamon Cassia
Zimtaldehyd - cinnamaldehyde.svg
Ethyl maltol Cooked fruit
Caramelized sugar
Ethyl maltol.png
Vanillin Vanilla Vanilla
Anisole Anise Anise
Anethole Anise Anise
Sweet basil
Estragole Tarragon Tarragon
Estragole acsv.svg
Thymol Thyme Thyme


Compound name Fragrance Natural occurrence Chemical structure
Trimethylamine Fishy
Trimethylamine chemical structure.png
Rotting flesh Rotting flesh
Cadaverine Rotting flesh Rotting flesh
Pyridine Fishy Belladonna
Indole Fecal
Skatole Fecal Feces
(diluted) Orange Blossoms
Skatole structure.svg

Other aroma compounds[edit]



High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas.





Miscellaneous compounds[edit]

Aroma-compound receptors[edit]

Animals that are capable of smell detect aroma compounds with their olfactory receptors. Olfactory receptors are cell-membrane receptors on the surface of sensory neurons in the olfactory system that detect airborne aroma compounds. Aroma compounds can then be identified by Gas Chromatography-Olfactometry (GC-O), which involves a human operator sniffing the GC effluent.[6]

In mammals, olfactory receptors are expressed on the surface of the olfactory epithelium in the nasal cavity.


In 2005–06, fragrance mix was the third-most-prevalent allergen in patch tests (11.5%).[7] 'Fragrance' was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. A recent academic study in the United States has shown that "34.7 % of the population reported health problems, such as migraine headaches and respiratory difficulties, when exposed to fragranced products".[8]

The composition of fragrances is usually not disclosed in the label of products, hiding the actual chemicals of the formula, which raises concerns among some consumers.[9][10]

Fragrances are regulated in the United States by the Toxic Substances Control Act of 1976 that "grandfathered" existing chemicals without further review or testing and put the burden of proof that a new substance is not safe on the EPA. The EPA, however, does not conduct independent safety testing but relies on data provided by the manufacturer.[11]

List of chemicals used as fragrances[edit]

In 2010 the International Fragrance Association published a list of 3,059 chemicals used in 2011 based on a voluntary survey of its members. It was estimated to represent about 90% of the world's production volume of fragrances.[12]

See also[edit]


  1. ^ Fahlbusch, Karl-Georg; Hammerschmidt, Franz-Josef; Panten, Johannes; Pickenhagen, Wilhelm; Schatkowski, Dietmar; Bauer, Kurt; Garbe, Dorothea; Surburg, Horst, "Flavors and Fragrances", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a11_141
  2. ^ Gane, S; Georganakis, D; Maniati, K; Vamvakias, M; Ragoussis, N; Skoulakis, EMC; Turin, L (2013). "Molecular-vibration-sensing component in human olfaction". PLoS ONE. 8: e55780. doi:10.1371/journal.pone.0055780. PMC 3555824. PMID 23372854.
  3. ^ a b Glindemann, D.; Dietrich, A.; Staerk, H.; Kuschk, P. (2005). "The Two Odors of Iron when Touched or Pickled: (Skin) Carbonyl Compounds and Organophosphines". Angewandte Chemie International Edition. 45 (42): 7006–7009. doi:10.1002/anie.200602100. PMID 17009284.
  4. ^ Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. ISBN 0-85404-190-7.
  5. ^ Lin, D.Y.; Zhang, S.Z.; Block, E.; Katz, L.C. (2005). "Encoding social signals in the mouse main olfactory bulb". Nature. 434: 470–477. doi:10.1038/nature03414. PMID 15724148.
  6. ^ Brattoli, M; Cisternino, E; Dambruoso, PR; de Gennaro, G; Giungato, P; Mazzone, A; Palmisani, J; Tutino, M (5 December 2013). "Gas chromatography analysis with olfactometric detection (GC-O) as a useful methodology for chemical characterization of odorous compounds". Sensors (Basel, Switzerland). 13 (12): 16759–800. doi:10.3390/s131216759. PMC 3892869. PMID 24316571.
  7. ^ Zug KA, Warshaw EM, Fowler JF Jr, Maibach HI, Belsito DL, Pratt MD, Sasseville D, Storrs FJ, Taylor JS, Mathias CG, Deleo VA, Rietschel RL, Marks J. Patch-test results of the North American Contact Dermatitis Group 2005–2006. Dermatitis. 2009 May–Jun;20(3):149-60.
  8. ^ Anne Steinemann, "Fragranced consumer products: exposures and effects from emissions", Air Quality, Atmosphere & Health, December 2016, Volume 9, Issue 8, pp 861–866.
  9. ^ Toxic chemicals linked to birth defects are being found at alarming levels in of childbearing age, Environmental Working Group, Retrieved 7 May 2018.
  10. ^ Anne C. Steinemann et al., "Fragranced Consumer Products: Chemicals Emitted, Ingredients Unlisted", Environmental Impact Assessment Review, Vol. 31, Issue 3, April 2011, pp. 328-333.
  11. ^ Randall Fitzgerald. The Hundred Year Lie. Dutton, 2006. p. 23. ISBN 0-525-94951-8.
  12. ^ "IFRA Survey:Transparency List". IFRA. Retrieved December 3, 2014.