Aroma compound

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Not to be confused with Aromaticity.

An aroma compound, also known as 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, perfumes, fragrance oils, and essential oils. For example, many form biochemically during ripening of fruits and other crops. In wines, most form as byproducts of fermentation. Odorants can also be added to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a warning. 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.

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
Terpineol Lilac Lilac, Cajuput
alpha-Ionone Violet, woody Violet
Thujone Minty Wormwood, lilac
Juniper

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

  • gamma-Decalactone intense peach flavor
  • gamma-Nonalactone coconut odor, popular in suntan lotions
  • delta-Octalactone creamy note
  • Jasmine lactone powerful fatty fruity peach and apricot
  • Massoia lactone powerful creamy coconut
  • Wine lactone sweet coconut odor
  • Sotolon (maple syrup, curry, fenugreek)

Thiols

Miscellaneous compounds

Aroma compound receptors

Animals that are capable of smell detect aroma compounds with olfactory receptors. Olfactory receptors are cell membrane receptors on the surface of sensory neurons in the olfactory system that detect air-borne aroma compounds.

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

Safety

'Fragrance' was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. The composition of fragrances are usually not disclosed in the label of products, hiding the actual chemicals of the formula, which raises concerns among some consumers.[6]

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. doi: 10.1371/journal.pone.0055780
  3. ↑ 3.0 3.1 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., and Katz, L.C. (2005). "Encoding social signals in the mouse main olfactory bulb." Nature 434, 470–477.
  6. ↑ Toxic chemicals linked to birth defects are being found at alarming levels in women of childbearing age

See also

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