Aroma compound

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 <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 an odorant to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure.

Aroma compounds classified by structure

Esters

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

Linear terpenes

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

Cyclic terpenes

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

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

Aromatic

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

Amines

Compound name Fragrance Natural occurrence Chemical structure
Trimethylamine Fishy
Ammonia
Putrescine
Diaminobutane		 Rotting flesh Rotting flesh
Cadaverine Rotting flesh Rotting flesh
Pyridine Fishy Belladonna
Indole Fecal
Flowery		 Feces
Jasmine
Skatole Fecal Feces
(diluted) Orange Blossoms

Other aroma compounds

Alcohols

Aldehydes

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

Esters

Ketones

Lactones

Thiols

Miscellaneous compounds

Aroma-compound receptors

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.

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

Safety

Patch test

In 2005–06, fragrance mix was the third-most-prevalent allergen in patch tests (11.5%).[6]

'Fragrance' was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. 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.[7]

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.[8]

List of chemicals used as fragrances

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.[9]

See also

References

  1. ↑ Karl-Georg Fahlbusch, Franz-Josef Hammerschmidt, Johannes Panten, Wilhelm Pickenhagen, Dietmar Schatkowski, , Kurt Bauer, Dorothea Garbe and Horst Surburg "Flavors and Fragrances" Ullmann's Encyclopedia of Industrial Chemistry, 2003, 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. PMC 3555824 Freely accessible. PMID 23372854. doi:10.1371/journal.pone.0055780.
  3. 1 2 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. PMID 17009284. doi:10.1002/anie.200602100.
  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. PMID 15724148. doi:10.1038/nature03414.
  6. ↑ 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.
  7. ↑ Toxic chemicals linked to birth defects are being found at alarming levels in women of childbearing age
  8. ↑ Randall Fitzgerald. The Hundred Year Lie. Dutton, 2006. p. 23. ISBN 0-525-94951-8.
  9. ↑ "IFRA Survey:Transparency List". IFRA. Retrieved December 3, 2014.
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