Aroma compound

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Fragrance bottles Perfume shelf 536pix.jpg
Fragrance bottles

An aroma compound, also known as an odorant, aroma, fragrance, flavoring or flavor, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, [1] particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds. [1] [2]

Contents

Generally, molecules meeting this specification have molecular weights of less than 310. [3] Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and the term fragrances may also apply to synthetic compounds, such as those used in cosmetics. [4]

Aroma compounds can naturally be found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form biochemically during the ripening of fruits and other crops. [1] [5] Wines have more than 100 aromas that form as byproducts of fermentation. [6] Also, many of the aroma compounds play a significant role in the production of compounds used in the food service industry to flavor, improve, and generally increase the appeal of their products. [1]

An odorizer may add a detectable odor to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure. [7]

Aroma compounds classified by structure

Esters

Compound nameFragranceNatural occurrenceChemical structure
Geranyl acetate Fruity,
Floral
Rose
Geranyl acetate skeletal.svg
Methyl formate Ethereal
Structural formula of methyl formate.svg
Methyl acetate Sweet, nail polish
Solvent
Methyl-acetate-2D-skeletal.svg
Methyl propionate
Methyl propanoate
Sweet, fruity, rum-like
Methyl propionate.svg
Methyl butyrate
Methyl butanoate
Fruity Apple
Pineapple
Buttersauremethylester.svg
Ethyl acetate Sweet, solvent Wine
Ethyl-acetate-2D-skeletal.svg
Ethyl butyrate
Ethyl butanoate
Fruity Orange, Pineapple
Ethyl butyrate2.svg
Isoamyl acetate Fruity, Banana,
Pear
Banana plant
Isoamyl acetate.svg
Pentyl butyrate
Pentyl butanoate
Fruity Pear
Apricot
Pentyl butyrate.svg
Pentyl pentanoate Fruity Apple
Pentyl pentanoate.svg
Octyl acetate Fruity Orange
Octyl acetate.svg
Benzyl acetate Fruity, Strawberry Strawberries
Benzyl acetate-structure.svg
Methyl anthranilate Fruity Grape
Methyl anthranilate.svg
Methyl salicylate Minty, root beer Wintergreen
Methyl salicylate.svg
Hexyl acetate Floral, Fruity Apple, Plum
Hexyl acetate.png

Linear terpenes

Compound nameFragranceNatural occurrenceChemical 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
Nerol structure.svg
Citral, lemonal
Geranial, neral
Lemon Lemon myrtle, Lemongrass
Geranial structure.png
Citronellal Lemon Lemongrass
Citronellal-2D-skeletal.png
Citronellol Lemon Lemongrass, rose
Pelargonium
Citronellol-2D-skeletal.png
Linalool Floral, sweet
Woody
Coriander, Sweet basil, Lavender, Honeysuckle
Linalool skeletal.svg
Nerolidol Woody, fresh bark Neroli, ginger
Jasmine
Nerolidol.png
Ocimene Fruity, Floral Mango, Curcuma amada
Alpha-ocimene.svg

Cyclic terpenes

Compound nameFragranceNatural occurrenceChemical structure
Limonene Orange Orange, lemon
Limonene-2D-skeletal.svg
Camphor Camphor Camphor laurel
Camphor structure.png
Menthol Menthol Mentha
Menthol skeletal.svg
Carvone 1 Caraway or Spearmint Caraway, dill,
spearmint
Carvone.svg
Terpineol Lilac Lilac, cajuput
Terpineol alpha.svg
alpha-Ionone Violet, woody Violet
Alpha-ionone-label.png
Thujone Minty Wormwood, lilac,
juniper
Beta-Thujone.svg
Eucalyptol Eucalyptus Eucalyptus
Eucalyptol.png
Jasmone spicy, fruity, floral in dilution Jasmine, Honeysuckle
Jasmon structural formation V1.svg

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

Aromatic

Compound nameFragranceNatural occurrenceChemical structure
Benzaldehyde Almond Bitter almond
Benzaldehyde.svg
Eugenol Clove Clove
Eugenol acsv.svg
Cinnamaldehyde Cinnamon Cassia
Cinnamon
Zimtaldehyd - cinnamaldehyde.svg
Ethyl maltol Cooked fruit
Caramelized sugar
Ethyl maltol.png
Vanillin Vanilla Vanilla
Vanillin.svg
Anisole Anise Anise
Anisol.svg
Anethole Anise Anise
Sweet basil
Anethole-structure-skeletal.svg
Estragole Tarragon Tarragon
Estragole acsv.svg
Thymol Thyme Thyme
Thymol2.svg

Amines

Compound nameFragranceNatural occurrenceChemical structure
Trimethylamine Fishy
Ammonia
Trimethylamine chemical structure.png
Putrescine
Diaminobutane
Rotting fleshRotting flesh
Diaminobutane.svg
Cadaverine Rotting fleshRotting flesh
Pentane-1,5-diamine 200.svg
Pyridine Fishy Belladonna
Pyridin.svg
Indole Fecal
Flowery
Feces
Jasmine
Indol2.svg
Skatole Fecal
Flowery
Feces
(diluted) Orange Blossoms
Skatole structure.svg

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. Aroma compounds can then be identified by gas chromatography-olfactometry, which involves a human operator sniffing the GC effluent. [12]

In mammals, olfactory receptors are expressed on the surface of the olfactory epithelium in the nasal cavity. [5]

Safety and regulation

Patch test Epikutanni-test.jpg
Patch test

In 2005–06, fragrance mix was the third-most-prevalent allergen in patch tests (11.5%). [13] 'Fragrance' was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. An academic study in the United States published in 2016 has shown that "34.7 % of the population reported health problems, such as migraine headaches and respiratory difficulties, when exposed to fragranced products". [14]

The composition of fragrances is usually not disclosed in the label of the products, hiding the actual chemicals of the formula, which raises concerns among some consumers. [15] In the United States, this is because the law regulating cosmetics protects trade secrets. [16]

In the United States, fragrances are regulated by the Food and Drug Administration if present in cosmetics or drugs, by the Consumer Products Safety Commission if present in consumer products. [16] No pre-market approval is required, except for drugs. Fragrances are also generally regulated 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. [17]

A 2019 study of the top-selling skin moisturizers found 45% of those marketed as "fragrance-free" contained fragrance. [18]

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, identifying about 90% of the world's production volume of fragrances. [19]

See also

References

  1. 1 2 3 4 El Hadi, Muna; Zhang, Feng-Jie; Wu, Fei-Fei; Zhou, Chun-Hua; Tao, Jun (July 11, 2013). "Advances in fruit aroma volatile research". Molecules. 18 (7): 8200–8229. doi: 10.3390/molecules18078200 . ISSN   1420-3049. PMC   6270112 . PMID   23852166.
  2. Ulrich, Detlef; Kecke, Steffen; Olbricht, Klaus (March 13, 2018). "What do we know about the chemistry of strawberry aroma?". Journal of Agricultural and Food Chemistry. 66 (13): 3291–3301. doi:10.1021/acs.jafc.8b01115. ISSN   0021-8561. PMID   29533612.
  3. Rothe, M; Specht, M (1976). "[Notes about molecular weights of aroma compounds]". Nahrung. 20 (3): 281–6. doi:10.1002/food.19760200308. PMID   958345.
  4. 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. ISBN   978-3-527-30673-2.
  5. 1 2 Haugeneder, Annika; Trinkl, Johanna; Härtl, Katja; Hoffmann, Thomas; Allwood, James William; Schwab, Wilfried (October 26, 2018). "Answering biological questions by analysis of the strawberry metabolome". Metabolomics. 14 (11): 145. doi:10.1007/s11306-018-1441-x. ISSN   1573-3882. PMC   6394451 . PMID   30830391.
  6. Ilc, Tina; Werck-Reichhart, Danièle; Navrot, Nicolas (September 30, 2016). "Meta-analysis of the core aroma components of grape and wine aroma". Frontiers in Plant Science. 7: 1472. doi: 10.3389/fpls.2016.01472 . ISSN   1664-462X. PMC   5042961 . PMID   27746799.
  7. Mouli-Castillo, Julien; Bartlett, Sam; Murugan, Arul; Badham, Pete; Wrynne, Aidan; Haszeldine, Stuart; Wheeldon, Mark; McIntosh, Angus (April 14, 2020). "Olfactory appraisal of odorants for 100% hydrogen networks". International Journal of Hydrogen Energy. 45 (20): 11875–11884. doi:10.1016/j.ijhydene.2020.02.095. ISSN   0360-3199.
  8. 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 (1): e55780. Bibcode:2013PLoSO...855780G. doi: 10.1371/journal.pone.0055780 . PMC   3555824 . PMID   23372854.{{cite journal}}: CS1 maint: article number as page number (link)
  9. 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. doi:10.1002/anie.200602100. PMID   17009284.
  10. Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. ISBN   978-0-85404-190-9.
  11. Lin, D.Y.; Zhang, S.Z.; Block, E.; Katz, L.C. (2005). "Encoding social signals in the mouse main olfactory bulb". Nature. 434 (7032): 470–477. Bibcode:2005Natur.434..470L. doi:10.1038/nature03414. PMID   15724148. S2CID   162036.
  12. Brattoli, M; Cisternino, E; Dambruoso, PR; de Gennaro, G; Giungato, P; Mazzone, A; Palmisani, J; Tutino, M (December 5, 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. Bibcode:2013Senso..1316759B. doi: 10.3390/s131216759 . PMC   3892869 . PMID   24316571.
  13. Zug, Kathryn A.; Warshaw, Erin M.; Fowler, Joseph F.; Maibach, Howard I.; Belsito, Donald L.; Pratt, Melanie D.; Sasseville, Denis; Storrs, Frances J.; Taylor, James S.; Mathias, C. G. Toby; Deleo, Vincent A.; Rietschel, Robert L.; Marks, James (2009). "Patch-test results of the North American Contact Dermatitis Group 2005-2006". Dermatitis: Contact, Atopic, Occupational, Drug. 20 (3): 149–160. ISSN   2162-5220. PMID   19470301.
  14. Anne Steinemann, "Fragranced consumer products: exposures and effects from emissions", Air Quality, Atmosphere & Health, December 2016, Volume 9, Issue 8, pp 861–866.
  15. 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.
  16. 1 2 "Fragrances in Cosmetics | FDA". Food and Drug Administration.
  17. Randall Fitzgerald (2006). The Hundred Year Lie. Dutton, 2006. p.  23. ISBN   978-0-525-94951-0.
  18. Patti Neighmond (October 2, 2017). "'Hypoallergenic' And 'Fragrance-Free' Moisturizer Claims Are Often False". NPR.
  19. "IFRA Survey:Transparency List". IFRA . Retrieved December 3, 2014.