View source for Aroma compound

{{short description|Chemical compound that has a smell or odor}}
{{Redirect-several|dab=off|Fragrance (disambiguation)|Fragrant, Kentucky|The Odorants}}
{{distinguish|Aromatic compound}}
{{Use American English|date=March 2021}}
{{Use mdy dates|date=March 2021}}
[[File:Perfume shelf 536pix.jpg|thumb|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 [[Volatility (chemistry)|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,<ref name="elhadi">{{cite journal | last1=El Hadi | first1=Muna | last2=Zhang | first2=Feng-Jie | last3=Wu | first3=Fei-Fei | last4=Zhou | first4=Chun-Hua | last5=Tao | first5=Jun | title=Advances in fruit aroma volatile research | journal=Molecules | volume=18 | issue=7 | date=2013-07-11 | issn=1420-3049 | pmid=23852166 | pmc=6270112 | doi=10.3390/molecules18078200 | pages=8200–8229| doi-access=free }}</ref> particularly strawberries which are [[plant breeding|commercially cultivated]] to have appealing aromas, and contain several hundred aroma compounds.<ref name=elhadi/><ref name="ulrich">{{cite journal | last1=Ulrich | first1=Detlef | last2=Kecke | first2=Steffen | last3=Olbricht | first3=Klaus | title=What do we know about the chemistry of strawberry aroma? | journal=Journal of Agricultural and Food Chemistry | volume=66 | issue=13 | date=2018-03-13 | issn=0021-8561 | pmid=29533612 | doi=10.1021/acs.jafc.8b01115 | pages=3291–3301}}</ref>

Generally, molecules meeting this specification have [[molecular weight]]s of less than 310.<ref>{{cite journal |last1=Rothe |first1=M |last2=Specht |first2=M |title=[Notes about molecular weights of aroma compounds] |journal=Nahrung |date=1976 |volume=20 |issue=3 |pages=281–6 |doi=10.1002/food.19760200308 |pmid=958345 }}</ref> Flavors affect both the sense of [[taste]] and [[Olfaction|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]].<ref name=Ullmann>{{Ullmann|first1=Karl-Georg|last1=Fahlbusch|first2=Franz-Josef|last2=Hammerschmidt|first3=Johannes|last3=Panten|first4=Wilhelm|last4=Pickenhagen|first5=Dietmar|last5=Schatkowski|first6=Kurt|last6=Bauer|first7=Dorothea|last7=Garbe|first8=Horst|last8=Surburg|title=Flavors and fragrances|doi=10.1002/14356007.a11_141}}</ref>

Aroma compounds can naturally be found in various [[food]]s, such as fruits and their [[peel (fruit)|peels]], [[wine]], [[spices]], [[floral scent]], [[perfume]]s, [[fragrance oil]]s, and [[essential oil]]s. For example, many form [[biochemical]]ly during the [[ripening]] of [[fruit]]s and other crops.<ref name=elhadi/><ref name="haug">{{cite journal | last1=Haugeneder | first1=Annika | last2=Trinkl | first2=Johanna | last3=Härtl | first3=Katja | last4=Hoffmann | first4=Thomas | last5=Allwood | first5=James William | last6=Schwab | first6=Wilfried | title=Answering biological questions by analysis of the strawberry metabolome | journal=Metabolomics| volume=14 | issue=11 | date=2018-10-26 | issn=1573-3882 | pmid=30830391 | pmc=6394451 | doi=10.1007/s11306-018-1441-x | page=145}}</ref> Wines have more than 100 aromas that form as byproducts of [[Fermentation (wine)|fermentation]].<ref name="ilc">{{cite journal | last1=Ilc | first1=Tina | last2=Werck-Reichhart | first2=Danièle | last3=Navrot | first3=Nicolas | title=Meta-analysis of the core aroma components of grape and wine aroma | journal=Frontiers in Plant Science| volume=7 | date=2016-09-30 | page=1472 | issn=1664-462X | pmid=27746799 | pmc=5042961 | doi=10.3389/fpls.2016.01472| doi-access=free }}</ref> 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.<ref name=elhadi/>

An [[odorizer]] may add a detectable odor to a dangerous odorless substance, like [[propane]], [[natural gas]], or [[Hydrogen odorant|hydrogen]], as a safety measure.<ref>{{Cite journal |last=Mouli-Castillo |first=Julien |last2=Bartlett |first2=Sam |last3=Murugan |first3=Arul |last4=Badham |first4=Pete |last5=Wrynne |first5=Aidan |last6=Haszeldine |first6=Stuart |last7=Wheeldon |first7=Mark |last8=McIntosh |first8=Angus |date=2020-04-14 |title=Olfactory appraisal of odorants for 100% hydrogen networks |url=https://www.sciencedirect.com/science/article/pii/S0360319920306595 |journal=International Journal of Hydrogen Energy |volume=45 |issue=20 |pages=11875–11884 |doi=10.1016/j.ijhydene.2020.02.095 |issn=0360-3199|url-access=subscription }}</ref>

== Aroma compounds classified by structure ==

=== Esters ===

{| class="wikitable" style="font-size: 110%"
! Compound name
! Fragrance
! Natural occurrence
! Chemical structure
|-align=center
| [[Geranyl acetate]]
| Fruity, <br/>Floral
| [[Rose]]
| [[File:Geranyl acetate skeletal.svg|x40px|center]]
|-align=center
| [[Methyl formate]]
| Ethereal
| 
| [[File:Structural formula of methyl formate.svg|x40px|center]]
|-align=center
| [[Methyl acetate]]
| Sweet, nail polish <br/> Solvent
| 
| [[File:Methyl-acetate-2D-skeletal.svg|x40px|center]]
|-align=center
| [[Methyl propionate]]<br />Methyl propanoate
| Sweet, fruity, [[rum]]-like
| 
| [[File:Methyl propionate.svg|x40px|center]]
|-align=center
| [[Methyl butyrate]] <br/> Methyl butanoate
| Fruity
| [[Apple]] <br/> [[Pineapple]]
| [[File:Buttersauremethylester.svg|x40px|center]]
|-align=center
| [[Ethyl acetate]]
| Sweet, solvent
| [[Wine]]
| [[File:Ethyl-acetate-2D-skeletal.svg|x40px|center]] 
|-align=center
| [[Ethyl butyrate]] <br/>  Ethyl butanoate
| Fruity
| [[Orange (fruit)|Orange]], [[Pineapple]]
| [[File:Ethyl butyrate2.svg|x40px|center]]
|-align=center
| [[Isoamyl acetate]]
| Fruity, [[Banana]], <br/>  [[Pear]]
| | [[Banana plant]]
| [[File:Isoamyl acetate.svg|x40px|center]]
|-align=center
| [[Pentyl butyrate]] <br/>  Pentyl butanoate
| Fruity
| [[Pear]] <br/>  [[Apricot]]
| [[File:Pentyl butyrate.svg|x40px|center]]
|-align=center
| [[Pentyl pentanoate]]
| Fruity
|  [[Apple]]
| [[File:Pentyl pentanoate.svg|x40px|center]]
|-align=center
| [[Octyl acetate]]
| Fruity
| [[Orange (fruit)|Orange]]
| [[File:Octyl acetate.svg|x40px|center]]
|-align=center
| [[Benzyl acetate]]
| Fruity, [[Strawberry]]
| | [[Strawberries]] 
| [[File:Benzyl acetate-structure.svg|x40px|center]]
|-align=center
| [[Methyl anthranilate]]
| Fruity
| [[Grape]]
| [[File:Methyl anthranilate.svg|x50px|center]]
|-align=center
| [[Methyl salicylate]]
| Minty, [[root beer]]
| [[Wintergreen]]
| [[File:Methyl salicylate.svg|x50px|center]]
|-align=center
| [[Hexyl acetate]]
| [[Floral]], Fruity
|[[Apple]], [[Plum]]
| [[File:Hexyl_acetate.png|x50px|center]]
|}

=== Linear terpenes ===
{| class="wikitable" style="font-size: 110%"
! Compound name
! Fragrance
! Natural occurrence
! Chemical structure
|-align=center
| [[β-myrcene|Myrcene]]
| Woody, complex
| [[Verbena]], [[Bay leaf]]
| [[File:Myrcene beta straight acsv.svg|140px|center]]
|-align=center
| [[Geraniol]]
| [[Rose]], flowery
| [[Geranium]], [[Lemon]]
| [[File:Geraniol structure.png|center|140px]]
|-align=center
| [[Nerol]]
| [[Sweet rose]], flowery
| [[Neroli]], [[Lemongrass]]
| [[File:Nerol structure.svg|140px|center]]
|-align=center
| [[Citral]], lemonal <br/> Geranial, neral
| [[Lemon]]
| [[Lemon myrtle]], [[Lemongrass]]
| [[File:Geranial structure.png|140px|center]]
|-align=center
| [[Citronellal]]
| [[Lemon]]
| [[Lemongrass]]
| [[File:Citronellal-2D-skeletal.png|140px|center]]
|-align=center
| [[Citronellol]]
| [[Lemon]]
| [[Lemongrass]], [[rose]] <br/> [[Pelargonium]]
| [[File:Citronellol-2D-skeletal.png|140px|center]]
|-align=center
| [[Linalool]]
| Floral, sweet <br/> Woody
| [[Coriander]], [[Sweet basil]], [[Lavender]], [[Honeysuckle]]
| [[File:Linalool skeletal.svg|140px|center]]
|-align=center
| [[Nerolidol]]
| [[Wood|Woody]], fresh bark
| [[Neroli]], [[ginger]] <br/> [[Jasmine]]
| [[File:Nerolidol.png|140px|center]]
|-align=center
| [[Ocimene]]
| Fruity, Floral
| [[Mango]], [[Curcuma amada]]
| [[File:Alpha-ocimene.svg|140px|center]]
|}

=== Cyclic terpenes ===
{| class="wikitable" style="font-size: 110%"
! Compound name
! Fragrance
! Natural occurrence
! Chemical structure
|-align=center
| [[Limonene]]
| [[Orange (fruit)|Orange]]
| [[Orange (fruit)|Orange]], [[lemon]]
| [[File:Limonene-2D-skeletal.svg|x60px|center]]
|-align=center
| [[Camphor]]
| [[Camphor]]
| [[Cinnamomum camphora|Camphor laurel]]
| [[File:Camphor structure.png|x60px|center]]
|-align=center
| [[Menthol]]
| [[Menthol]]
| [[Mentha]]
| [[File:Menthol skeletal.svg|x60px|center]]
|-align=center
| [[Carvone]]<sup>1</sup>
| [[Caraway]] or [[Spearmint]]
| [[Caraway]], [[dill]], <br/> [[spearmint]]
| [[File:Carvone.svg|x60px|center]]
|-align=center
| [[Terpineol]]
| [[Lilac]]
| [[Lilac]], [[cajuput]]
| [[File:Terpineol alpha.svg|x60px|center]]
|-align=center
| [[Ionone|alpha-Ionone]]
| [[Viola (plant)|Violet]], woody
| [[Viola (plant)|Violet]]
| [[File:Alpha-ionone-label.png|x60px|center]]
|-align=center
| [[Thujone]]
| Minty
| [[Artemisia absinthium|Wormwood]], [[lilac]], <br/> [[juniper]]
| [[File:Beta-Thujone.svg|x60px|center]]
|-align=center
| [[Eucalyptol]]
| Eucalyptus 
| [[Eucalyptus]]
| [[File:Eucalyptol.png|x60px|center]]
|-align=center
| [[Jasmone]]
| spicy, fruity, floral in dilution
| [[Jasmine]], [[Honeysuckle]]
| [[File:Jasmon_structural_formation_V1.svg|x60px|center]]
|}

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

=== Aromatic ===
{| class="wikitable" style="font-size: 110%"
! Compound name
! Fragrance
! Natural occurrence
! Chemical structure
|-align=center
| [[Benzaldehyde]]
| [[Almond]]
| [[Bitter almond]]
| [[File:Benzaldehyde.svg|x60px|center]]
|-align=center
| [[Eugenol]]
| [[Clove]]
| [[Clove]]
| [[File:Eugenol acsv.svg|x60px|center]]
|-align=center
| [[Cinnamaldehyde]]
| [[Cinnamon]]
| [[Cinnamomum aromaticum|Cassia]] <br/>[[Cinnamon]]
| [[File:Zimtaldehyd - cinnamaldehyde.svg|x60px|center]]
|-align=center
| [[Ethyl maltol]]
| Cooked fruit <br/>Caramelized sugar
| 
| [[File:Ethyl maltol.png|x60px|center]]
|-align=center
| [[Vanillin]]
| [[Vanilla]]
| [[Vanilla]]
| [[File:Vanillin.svg|x60px|center]]
|-align=center
| [[Anisole]]
| [[Anise]]
| [[Anise]]
| [[File:Anisol.svg|x60px|center]]
|-align=center
| [[Anethole]]
| [[Anise]]
| [[Anise]] <br/>[[Sweet basil]]
| [[File:Anethole-structure-skeletal.svg|x60px|center]]
|-align=center
| [[Estragole]]
| [[Tarragon]]
| [[Tarragon]]
| [[File:Estragole acsv.svg|x60px|center]]
|-align=center
| [[Thymol]]
| [[Thyme]]
| [[Thyme]]
| [[File:Thymol2.svg|x60px|center]]
|}

=== Amines ===
{| class="wikitable" style="font-size: 110%"
! Compound name
! Fragrance
! Natural occurrence
! Chemical structure
|-align=center
| [[Trimethylamine]]
| Fishy <br/> Ammonia
| 
| [[File:Trimethylamine chemical structure.png|x40px|center]]
|-align=center
| [[Putrescine]] <br/> Diaminobutane
| Rotting flesh
| Rotting flesh
| [[File:Diaminobutane.svg|x40px|center]]
|-align=center
| [[Cadaverine]]
| Rotting flesh
| Rotting flesh
| [[File:Pentane-1,5-diamine 200.svg|x40px|center]]
|-align=center
| [[Pyridine]]
| Fishy
| [[Atropa belladonna|Belladonna]]
| [[File:Pyridin.svg|x60px|center]]
|-align=center
| [[Indole]]
| Fecal <br/> Flowery
| Feces <br/> Jasmine
| [[File:Indol2.svg|x60px|center]]
|-align=center
| [[Skatole]]
| Fecal <br/> Flowery
| [[Feces]] <br/> (diluted) Orange Blossoms
| [[File:Skatole structure.svg|x60px|center]]
|}

== Other aroma compounds ==

=== Alcohols ===

* [[Furaneol]] ([[strawberry]])
* [[1-Hexanol]] ([[herbaceous]], woody)
* [[cis-3-Hexen-1-ol|''cis''-3-Hexen-1-ol]] ([[Smell of freshly cut grass|fresh cut grass]])
* [[Menthol]] ([[peppermint]])

=== Aldehydes ===
High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas.
* [[Acetaldehyde]] (ethereal)
* [[Hexanal]] (green, grassy)
* [[cis-3-Hexenal|''cis''-3-Hexenal]] (green [[tomato]]es)
* [[Furfural]] (burnt [[oat]]s)
* [[Hexyl cinnamaldehyde]]
* [[Isovaleraldehyde]] – nutty, fruity, cocoa-like
* [[Anisic aldehyde]] – floral, sweet, hawthorn. It is a crucial component of chocolate, vanilla, [[strawberry]], [[raspberry]], apricot, and others.
* [[Cuminaldehyde]] (4-propan-2-ylbenzaldehyde) – Spicy, cumin-like, green

=== Esters ===

* [[Fructone]] (fruity, apple-like)
* [[Ethyl methylphenylglycidate]] ([[Strawberry]])
* [[alpha-Methylbenzyl acetate]] ([[Gardenia]])

=== Ketones ===
* Cyclopentadecanone (musk-ketone)<ref>{{cite journal | last1 = Gane | first1 = S | last2 = Georganakis | first2 = D | last3 = Maniati | first3 = K | last4 = Vamvakias | first4 = M | last5 = Ragoussis | first5 = N | last6 = Skoulakis | first6 = EMC | last7 = Turin | first7 = L | year = 2013 | title = Molecular-vibration-sensing component in human olfaction | journal = PLOS ONE | volume = 8 | issue = 1| article-number = e55780 | doi = 10.1371/journal.pone.0055780 | pmid=23372854 | pmc=3555824| bibcode = 2013PLoSO...855780G | doi-access = free }}</ref>
* [[Dihydrojasmone]] (fruity woody floral)
* [[Oct-1-en-3-one]] (blood, metallic, mushroom-like)<ref name="metallic" />
* [[2-Acetyl-1-pyrroline]] (fresh bread, jasmine rice)
* [[6-Acetyl-2,3,4,5-tetrahydropyridine]] (fresh bread, tortillas, popcorn)

===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 ===
{{Main|Thiol}}
* [[Thioacetone]] (2-propanethione) A lightly studied organosulfur. Its smell is so potent it can be detected several hundred meters downwind mere seconds after a container is opened.
* [[Allyl thiol]] (2-propenethiol; allyl mercaptan; CH<sub>2</sub>=CHCH<sub>2</sub>SH) ([[garlic]] volatiles and [[garlic breath]])<ref>{{cite book |author=Block, E. |title=Garlic and Other Alliums: The Lore and the Science |publisher=Royal Society of Chemistry |year=2010 |isbn=978-0-85404-190-9 }}</ref>
* (Methylthio)methanethiol (CH<sub>3</sub>SCH<sub>2</sub>SH), the "mouse thiol", found in mouse urine and functions as a [[semiochemical]] for female mice<ref>{{cite journal | last1 = Lin | first1 = D.Y. | last2 = Zhang | first2 = S.Z. | last3 = Block | first3 = E. | last4 = Katz | first4 = L.C. | s2cid = 162036 | year = 2005 | title = Encoding social signals in the mouse main olfactory bulb | journal = Nature | volume = 434 | issue = 7032| pages = 470–477 | doi=10.1038/nature03414 | pmid=15724148| bibcode = 2005Natur.434..470L }}</ref>
* [[Ethanethiol]], commonly called ethyl mercaptan (added to [[propane]] or other liquefied-petroleum gases used as fuel gases)
* [[tert-Butylthiol|2-Methyl-2-propanethiol]], commonly called ''tert''-butyl mercaptan, is added as a blend of other components to natural gas used as fuel gas.
* [[Butanethiol|Butane-1-thiol]], commonly called butyl mercaptan, is a chemical intermediate.  
* [[Grapefruit mercaptan]] (grapefruit)
* [[Methanethiol]], commonly called methyl mercaptan (after eating [[asparagus]])
* [[Furan-2-ylmethanethiol]], also called furfuryl mercaptan (roasted [[coffee]])
* [[Benzyl mercaptan]] (leek or garlic-like)

=== Miscellaneous compounds ===

* [[Methylphosphine]] and [[dimethylphosphine]] (garlic-metallic, two of the most potent odorants known)<ref name="metallic">{{cite journal
| author= Glindemann, D.
| author2= Dietrich, A.
| author3= Staerk, H.
| author4= Kuschk, P.
| title = The Two Odors of Iron when Touched or Pickled: (Skin) Carbonyl Compounds and Organophosphines
| journal = [[Angewandte Chemie International Edition]]
| year = 2005
| volume = 45
| issue = 42
| pages = 7006–7009
| doi = 10.1002/anie.200602100
| pmid= 17009284| doi-access = 
}}
</ref>
* [[Phosphine]] ([[zinc phosphide]] poisoned bait)
* [[Diacetyl]] ([[butter]] flavor)
* [[Acetoin]] (butter flavor)
* [[Nerolin]] ([[orange (fruit)|orange flowers]])
* [[Tetrahydrothiophene]] (added to [[natural gas]])
* [[2,4,6-Trichloroanisole]] ([[cork taint]])
* [[Substitution (chemistry)|Substituted]] [[pyrazine]]s

== Aroma-compound receptors ==

Animals that are capable of [[olfaction|smell]] detect aroma compounds with their [[olfactory receptor]]s. Olfactory receptors are cell-membrane [[receptor (biology)|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.<ref>{{cite journal |last1=Brattoli |first1=M |last2=Cisternino |first2=E |last3=Dambruoso |first3=PR |last4=de Gennaro |first4=G |last5=Giungato |first5=P |last6=Mazzone |first6=A |last7=Palmisani |first7=J |last8=Tutino |first8=M |title=Gas chromatography analysis with olfactometric detection (GC-O) as a useful methodology for chemical characterization of odorous compounds. |journal=Sensors (Basel, Switzerland) |date=5 December 2013 |volume=13 |issue=12 |pages=16759–800 |doi=10.3390/s131216759 |pmid=24316571 |pmc=3892869|bibcode=2013Senso..1316759B |doi-access=free }}</ref>

In [[mammal]]s, olfactory receptors are [[gene expression|expressed]] on the surface of the olfactory epithelium in the [[nasal cavity]].<ref name=haug/>

== Safety and regulation ==
[[File:Epikutanni-test.jpg|thumb|right|[[Patch test]]]]

In 2005–06, fragrance mix was the third-most-prevalent [[allergen]] in [[patch test]]s (11.5%).<ref name="autogenerated2005">{{Cite journal |last1=Zug |first1=Kathryn A. |last2=Warshaw |first2=Erin M. |last3=Fowler |first3=Joseph F. |last4=Maibach |first4=Howard I. |last5=Belsito |first5=Donald L. |last6=Pratt |first6=Melanie D. |last7=Sasseville |first7=Denis |last8=Storrs |first8=Frances J. |last9=Taylor |first9=James S. |last10=Mathias |first10=C. G. Toby |last11=Deleo |first11=Vincent A. |last12=Rietschel |first12=Robert L. |last13=Marks |first13=James |date=2009 |title=Patch-test results of the North American Contact Dermatitis Group 2005-2006 |journal=Dermatitis: Contact, Atopic, Occupational, Drug |volume=20 |issue=3 |pages=149–160 |issn=2162-5220 |pmid=19470301}}</ref> '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".<ref>[[Anne C. Steinemann|Anne Steinemann]], [https://link.springer.com/article/10.1007/s11869-016-0442-z "Fragranced consumer products: exposures and effects from emissions"], ''Air Quality, Atmosphere & Health'', December 2016, Volume 9, Issue 8, pp 861–866.</ref>

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.<ref>Anne C. Steinemann et al., [https://www.sciencedirect.com/science/article/abs/pii/S0195925510001125 "Fragranced Consumer Products: Chemicals Emitted, Ingredients Unlisted"], ''Environmental Impact Assessment Review'', Vol. 31, Issue 3, April 2011, pp. 328-333.</ref> In the United States, this is because the law regulating cosmetics protects [[trade secret]]s.<ref name="FDA fragranaces">{{Cite web |date= |title=Fragrances in Cosmetics {{!}} FDA |url=https://www.fda.gov/cosmetics/cosmetic-ingredients/fragrances-cosmetics |website=Food and Drug Administration}}</ref>

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.<ref name="FDA fragranaces" /> 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 [[United States Environmental Protection Agency|EPA]]. The EPA, however, does not conduct independent safety testing but relies on data provided by the manufacturer.<ref>{{cite book |author=Randall Fitzgerald |author-link=Randall Fitzgerald | title=The Hundred Year Lie| publisher=[[Dutton Penguin|Dutton]], 2006 |page=[https://archive.org/details/hundredyearlieho00fitz/page/23 23] |isbn=978-0-525-94951-0|title-link=The Hundred Year Lie |year=2006 }}</ref>

A 2019 study of the top-selling [[skin moisturizer]]s found 45% of those marketed as "fragrance-free" contained fragrance.<ref>{{cite web|url=https://www.npr.org/sections/health-shots/2017/10/02/554365324/hypoallergenic-and-fragrance-free-moisturizer-claims-are-often-false |title='Hypoallergenic' And 'Fragrance-Free' Moisturizer Claims Are Often False|author=Patti Neighmond|publisher=NPR|date=2 October 2017}}</ref>

==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.<ref>{{cite web| url=http://www.ifraorg.org/en-us/ingredients#.VH-EkXsdXYg|title=IFRA Survey:Transparency List |publisher=[[International Fragrance Association|IFRA]]|
access-date=December 3, 2014}}</ref>

== See also ==
{{div col|colwidth=18em}}
* [[Aroma of wine]]
* [[Eau de toilette]]
* ''[[Flavour and Fragrance Journal]]''
* ''[[Fragrances of the World]]''
* [[Foodpairing]]
* [[Odor]]
* [[Odor detection threshold]]
* [[Odorizer]], a device for adding an odorant to gas flowing through a pipe
* [[Olfaction]]
* [[Olfactory receptor]]
* [[Olfactory system]]
* [[Pheromone]]
* [[Vabbing]]
{{end div col}}

== References ==
<references/>

{{Perfume}}

{{sister project links|auto=1|wikt=aroma}}
{{Portal|Chemistry}}

{{DEFAULTSORT:Aroma Compound}}
[[Category:Organic chemistry]]
[[Category:Olfaction]]
[[Category:Flavors]]
[[Category:Perfume ingredients]]