thumb|"[[Grapefruit mercaptan" can be detected by humans at the ppt level.|110px ]]

A fragrance compound (or fragrance) is a chemical compound with a pleasant odor. Fragrances affect only the sense of smell, whereas flavors can affect both the sense of taste and smell. Fragrances are often mixtures of individual fragrance compounds. Although many fragrances are derived from natural sources, many are synthetic. Fragrances are widely used in cosmetics and are the basis for a large industry.

Stench compounds have unpleasant odors. Some are used as odorizer or an odorant usually have an intense odor, which may be pleasant or not. They are sometimes used to confer a detectable odor to an odorless substance, like propane, natural gas, or hydrogen, as a safety measure.

Occurrence

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. Generally, fragrance compounds have molecular weights of less than 310.

Fragrance compounds are found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form during the ripening of fruits and other crops. Wines have more than 100 aromas that form as byproducts of fermentation. 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.

The invention of gas chromatography was very important to the development of fragrances. Gas chromatography-olfactometry sometimes involving a human operator sniffing the GC effluent is particularly relevant to the analysis of fragrances. GC-O and related techniques have also been developed to characterize individual enantiomers of chiral aromatic compounds.

Studies on synthetic musk reveal that the odors of some compounds are noticeably affected by deuteration.

Various fragrant fruits are commercially cultivated to have appealing or intensified aromas.

Fragrance compounds classified by chemical structure

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.

Esters

{| class="wikitable" style="font-size: 110%"

! Compound name

! Fragrance

! Natural occurrence

! Chemical structure

|-align=center

| Geranyl acetate

| Fruity, <br/>Floral

| Rose

| x40px|center|class=skin-invert-image

|-align=center

| Methyl formate

| Ethereal

| synthetic

| x40px|center|class=skin-invert-image

|-align=center

| Methyl acetate

| Sweet, nail polish <br/> Solvent

| synthetic

| x40px|center|class=skin-invert-image

|-align=center

| Fructone

| fruity, apple-like

| synthetic

|100px|center|class=skin-invert-image

|-align=center

|Ethyl methylphenylglycidate

|Strawberry

|synthetic

| 100px|center|class=skin-invert-image

|-align=center

| Methyl propionate<br />

| Sweet, fruity, rum-like

|

| x40px|center|class=skin-invert-image

|-align=center

| Methyl butyrate <br/>

| Fruity

| Apple <br/> Pineapple

| x40px|center|class=skin-invert-image

|-align=center

| Ethyl acetate

| Sweet, solvent

| Wine

| x40px|center|class=skin-invert-image

|-align=center

| Ethyl butyrate <br/>

| Fruity

| Orange, Pineapple

| x40px|center|class=skin-invert-image

|-align=center

| Isoamyl acetate

| Fruity, Banana, <br/> Pear

| | Banana plant

| x40px|center|class=skin-invert-image

|-align=center

| Pentyl butyrate <br/>

| Fruity

| Pear <br/> Apricot

| x40px|center|class=skin-invert-image

|-align=center

| Pentyl pentanoate

| Fruity

| Apple

| x40px|center|class=skin-invert-image

|-align=center

| Octyl acetate

| Fruity

| Orange

| x40px|center|class=skin-invert-image

|-align=center

| Benzyl acetate

| Fruity, Strawberry

| | Strawberries

| x40px|center|class=skin-invert-image

|-align=center

| Methyl anthranilate

| Fruity

| Grape

| x50px|center|class=skin-invert-image

|-align=center

| Methyl salicylate

| Minty, root beer

| Wintergreen

| x50px|center|class=skin-invert-image

|-align=center

| Hexyl acetate

| Floral, Fruity

|Apple, Plum

| x50px|center|class=skin-invert-image

|}

Linear terpenes

{| class="wikitable" style="font-size: 110%"

! Compound name

! Fragrance

! Natural occurrence

! Chemical structure

|-align=center

| Myrcene

| Woody, complex

| Verbena, Bay leaf

| 140px|center|class=skin-invert-image

|-align=center

| Geraniol

| Rose, flowery

| Geranium, Lemon

| center|140px|class=skin-invert-image

|-align=center

| Nerol

| Sweet rose, flowery

| Neroli, Lemongrass

| 140px|center|class=skin-invert-image

|-align=center

| Citral, lemonal <br/> Geranial, neral

| Lemon

| Lemon myrtle, Lemongrass

| 140px|center|class=skin-invert-image

|-align=center

| Citronellal

| Lemon

| Lemongrass

| 140px|center|class=skin-invert-image

|-align=center

| Citronellol

| Lemon

| Lemongrass, rose <br/> Pelargonium

| 140px|center|class=skin-invert-image

|-align=center

| Linalool

| Floral, sweet <br/> Woody

| Coriander, Sweet basil, Lavender, Honeysuckle

| 140px|center|class=skin-invert-image

|-align=center

| Nerolidol

| Woody, fresh bark

| Neroli, ginger <br/> Jasmine

| 140px|center|class=skin-invert-image

|-align=center

| Ocimene

| Fruity, Floral

| Mango, Curcuma amada

| 140px|center|class=skin-invert-image

|}

Cyclic terpenes

{| class="wikitable" style="font-size: 110%"

! Compound name

! Fragrance

! Natural occurrence

! Chemical structure

|-align=center

| Limonene

| Orange

| Orange, lemon

| x60px|center|class=skin-invert-image

|-align=center

| Camphor

| Camphor

| Camphor laurel

| x60px|center|class=skin-invert-image

|-align=center

| Menthol

| Menthol

| Mentha

| x60px|center|class=skin-invert-image

|-align=center

| Carvone<sup>1</sup>

| Caraway or Spearmint

| Caraway, dill, <br/> spearmint

| x60px|center|class=skin-invert-image

|-align=center

| Terpineol

| Lilac

| Lilac, cajuput

| x60px|center|class=skin-invert-image

|-align=center

| alpha-Ionone

| Violet, woody

| Violet

| x60px|center|class=skin-invert-image

|-align=center

| Thujone

| Minty

| Wormwood, lilac, <br/> juniper

| x60px|center|class=skin-invert-image

|-align=center

| Eucalyptol

| Eucalyptus

| Eucalyptus

| x60px|center|class=skin-invert-image

|-align=center

| Jasmone

| spicy, fruity, floral in dilution

| Jasmine, Honeysuckle

| x60px|center|class=skin-invert-image

|}

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

| x60px|center|class=skin-invert-image

|-align=center

| Eugenol

| Clove

| Clove

| x60px|center|class=skin-invert-image

|-align=center

| Cinnamaldehyde

| Cinnamon

| Cassia <br/>Cinnamon

| x60px|center|class=skin-invert-image

|-align=center

| Ethyl maltol

| Cooked fruit <br/>Caramelized sugar

|

| x60px|center|class=skin-invert-image

|-align=center

| Vanillin

| Vanilla

| Vanilla

| x60px|center|class=skin-invert-image

|-align=center

| Anisole

| Anise

| Anise

| x60px|center|class=skin-invert-image

|-align=center

| Anethole

| Anise

| Anise <br/>Sweet basil

| x60px|center|class=skin-invert-image

|-align=center

| Estragole

| Tarragon

| Tarragon

| x60px|center|class=skin-invert-image

|-align=center

| Thymol

| Thyme

| Thyme

| x60px|center|class=skin-invert-image

|}

Other aroma compounds

Alcohols

  • Furaneol (strawberry)
  • 1-Hexanol (herbaceous, woody)
  • cis-3-Hexen-1-ol (fresh cut grass)

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 (green tomatoes)
  • Furfural (burnt oats)
  • 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 – Spicy, cumin-like, green

Ketones

  • Dihydrojasmone (fruity woody floral)
  • Oct-1-en-3-one (blood, metallic, mushroom-like)
  • 2-Acetyl-1-pyrroline (fresh bread, jasmine rice)
  • 6-Acetyl-2,3,4,5-tetrahydropyridine (fresh bread, tortillas, popcorn)
  • Diacetyl (butter flavor)
  • Acetoin (butter flavor)

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)

Detection and interpretation

Fragrances are detected by the nose when the movement of inspired air contacts olfactory sensory neurons, which in humans, number between 6 and 10 million over a surface area of of olfactory epithelium. Fragrance signals are conveyed from the epithelium to the olfactory nerves, and then to the olfactory bulbs, which relay neural impulses about fragrance properties into the primary olfactory cortex of the brain.

Safety and regulation

thumb|right|[[Patch test]]

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

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. In the United States, this is because the law regulating cosmetics protects trade secrets.

In the United States, fragrances are regulated by the Food and Drug Administration if present in cosmetics or drugs, by the Consumer Product Safety Commission if present in consumer products.

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

See also

  • 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
  • The Hundred Year Lie
  • Vabbing

References