Odorant
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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 two conditions are met: the compound needs to be volatile, so it can be transported to the olfactory system in the upper part of the nose, and it needs to be in a sufficiently high concentration to be able to interact with one or more of the olfactory receptors.

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 natural gas or hydrogen, as a warning. As well many of the aroma compounds plays a significant role in the production of flavorants, which are used in the food service industry to flavor, improve and increase the appeal of their products.

Aroma compounds classified by functional group

Alcohols

• Benzyl alcohol (oxidises to benzaldehyde, almond)
• Ethyl maltol (sugary, cooked fruit)
• Furaneol (strawberry)
• 1-Hexanol (herbaceous, woody)
• cis-3-Hexen-1-ol (fresh cut grass)
• Menthol (peppermint)

Aldehydes

• Acetaldehyde (pungent)
• Benzaldehyde (marzipan, almond)
• Hexanal (green, grassy)
• Cinnamaldehyde (cinnamon)
• Citral (lemongrass, lemon oil)
• cis-3-Hexenal (green tomatoes)
• Furfural (burnt oats)
• Neral (citrus, lemongrass)
• Vanillin (vanilla)

Amines

• Cadaverine (rotting flesh)
• Indole (jasmine flowery, feces)
• Putrescine (rotting flesh)
• Pyridine (very unpleasant)
• Skatole (bad breath, feces)
• Substituted pyrazines: 2-ethoxy-3-isopropylpyrazine, 2-methoxy-3-sec-butylpyrazine, 2-methoxy-3-methylpyrazine (toasted seeds of fenugreek, cumin, and coriander)
  • Alkylpyrazines
  • Methoxypyrazines
• Trimethylamine (fish)

Esters

• Ethyl acetate (fruity, solvent)
• Ethyl butanoate (fruity) - also known as ethyl butyrate
• Ethyl decanoate - also known as ethyl caprate
• Ethyl hexanoate - also known as ethyl caproate
• Ethyl octanoate - also known as ethyl caprylate
• Hexyl acetate (apple, floral, fruity)
• Isoamyl acetate (banana)
• Methyl butanoate (apple, fruity) - also known as methyl butyrate
• Methyl salicylate (oil of wintergreen)
• Pentyl butanoate (pear, apricot)
• Pentyl pentanoate (apple, pineapple)
• Sotolon (maple syrup, curry, fenugreek)
• Strawberry aldehyde (strawberry)
• Fructone (fruity, apple-like)

Ethers

• Anethole (liquorice, anise seed, ouzo, fennel)
• Anisole (anise seed)
• Eugenol (clove oil)
• 2,4,6-Trichloroanisole (cork taint)

Ketones

• Dihydrojasmone (fruity woody floral)
• Oct-1-en-3-one (blood, metallic, mushroom-like)^[1]
• 2-Acetyl-1-pyrroline (fresh bread, jasmine rice)
• 6-Acetyl-2,3,4,5-tetrahydropyridine (fresh bread, tortillas, pop corn)

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

Terpenes

• Camphor (Cinnamomum camphora)
• Citronellol (rose)
• Linalool (floral, citrus, coriander)
• Nerol (sweet rose)
• Nerolidol (wood, fresh bark)
• alpha-Terpineol (lilac)
• Thujone (juniper, common sage, Nootka cypress, and wormwood)
• Thymol (Thyme-like)

Thiols

• Ethanethiol, formerly called Ethyl mercaptan (Durian or leek, added to natural gas)
• Grapefruit mercaptan (grapefruit)
• Methanethiol, formerly called Methyl mercaptan (added to natural gas)

Miscellaneous compounds

• Methylphosphine and dimethylphosphine (garlic-metallic, two of the most potent odorants known)^[1]

• Nerolin (orange flowers)
• Tetrahydrothiophene (added to natural gas)

Aroma compound receptors

Animals which 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 which detect air-borne aroma compounds.

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

References

1. ^ ^{a b} D. Glindemann, A. Dietrich, H. Staerk, P. Kuschk, (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. 

See also

• Odor
• Olfaction
• Olfactory system
• Olfactory receptor
• Pheromone
• Odor detection threshold

External links

• Leffingwell, commercial odorant information resource.
• The Good Scents Company, commercial odorant information resource.
• Fantastic-Flavour, commercial odorant/flavour information resource.