Inferred Primary Odors (61)
The following aroma perceptual notes can be associated with specific olfactory receptors. Many of these notes are associated with more than one receptor; in some cases, such as the musky note, activation of any one of the receptors is probably sufficient to produce the perceptual note, while in other cases, a combination of listed receptors may be necessary. Notes with multiple names represent the intersection of their descriptors. Where multiple receptors from different subfamilies are present, the aroma note might be combinatorial rather than primary. Some notes were identified by smelling receptor agonists with and without an antagonist. An asterisk means an aroma compound produces the indicated perceptual note, but the receptor for that note in that compound is unknown. This list is neither exhaustive nor final and may change (and hopefully grow) over time.
| Aroma Note | Receptors | Example agonists |
|---|---|---|
| acetic | OR51E2 | acetic acid, beta-ionone |
| Reminiscent of vinegar, but not so much the sourness. More the specific quality that makes vinegar smell like vinegar as opposed to any other acid. | ||
| acetonic-plasticky | OR2F1, OR2T34 | cyclohexanone, floralozone, geranyl acetate, fructone |
| Probably like the note of isopropyl alcohol that distinguishes it from ethyl alcohol, or the plasticky facet of floralozone, a common sea breeze fragrance. It's possible that these receptors contribute two different notes, but both would be recognizable as plasticky. | ||
| allium-winey | OR4Q3, OR4X2 | diallyl disulfide, 2-aminoacetophenone, butyl anthranilate |
| Some kind of note shared between garlic and grapes/wine. | ||
| ambery | OR7C1, OR7E24 | (-)-ambroxide, ysamber K, ambermax, timberol |
| A note present in ambergris that distinguishes it from similar aromas. The receptors for this are closely related to the receptor for androstenone, so the note these two receptors encode is probably an ambery/animalic note uniquely recognizable as ambergris. | ||
| anisic-herbal | OR6C65, OR6C70 | anethole, estragole*, ethyl vanillin |
| Possibly the same note for the entire OR6C subfamily, though not enough is known to be sure. A specifically anise-like note, but not the sweetness of licorice, which seems to be associated instead with OR2M4. The note associated with the OR6C receptors is mostly specific to anise, licorice, fennel, basil, tarragon, etc., and probably represents an herbal facet of the anisic character. But notice it also shows up in ice-cream-smelling ethyl vanillin. | ||
| apic | OR5B12, OR5B17, ??? | dihydrojasmone, (Z)-jasmone*, jasmonyl, floralozone |
| Derived from the name Apium. This is the ozone-like sharpness that bridges celery and jasmine. | ||
| apple-rosy | OR8K3 | beta-damascenone, pomarose, ethyl safranate |
| Not the sweet fruitiness of apples nor the floral stemmy balsamic character of roses, but some kind of intersection between the two. This note is especially present in damascones, a group of related molecules that occur in small amounts in natural rose and add a berry-like sweetness. | ||
| balsamic | OR10G3, OR10G4, OR10G6, OR10G7, OR10G9 | vanillin, eugenol, creosol, guaiacol, para-anisaldehyde, 1-butanol, n-amyl acetate |
| A widely distributed note prominent in clove, vanilla, leather, anise, nutmeg, wood smoke, rose, whisky, cinnamon, rubber, and also present in banana. It is a hard to describe smooth leathery oily-like or bubblegummy benzoin-like quality that adds a great deal of pleasantness to every scent it occurs in. | ||
| bright-fresh | OR1D2 | bourgeonal, floralozone, gamma-undecalactone, tetrahydromyrcenol |
| A sort of shimmering brightness perceptible in citrus, milk, Sweet Tarts, and certain perfumes especially aldehydic and aquatic scents. | ||
| citrus-zesty | OR2W3 | citralva, geraniol, lilial |
| An ebullient shiny tart zesty note present in citrus peel. | ||
| curry-caramellic | OR8D1 | sotolone, p-cymene |
| A note dominant in burnt sugar and in curry, but also noticeable in maple, fenugreek, and caramel. | ||
| dairy-sour | OR51E1 | isovaleric acid, caprylic acid, butyl butyryl lactate, propanal |
| Reminiscent of sour milk, sour cream, or buttermilk, perhaps even a bit garbagey. | ||
| earthy-humus | OR14J1 | patchoulol, geosmin, (Z)-3-hexen-1-ol |
| A note like fresh topsoil or patchouli. Earthy, but not chalky, more like living biomass. Also a component of the smell of leaf alcohol (hexenol) which occurs in virtually all plants and is largely responsible for the leafy-green smell. | ||
| earthy-musty-chalky | OR11A1 | geosmin, 2-ethyl fenchol, 2-methylisoborneol, patchoulol |
| Chalky, earthy, like wet rocks. Also a major component of musty smells, especially molds that smell like dry powder. | ||
| earthy-papery | OR3A1, OR3A4, OR5V1 | 2,4,6-trichloroanisole, bean pyrazine, cyclamal, 2-methylisoborneol, methyl salicylate |
| A note important for newspaper smell, wet dog odor, or cork taint in wine. | ||
| estery-ethereal | OR52D1 | isoamyl acetate, acetophenone, beta-ionone, estragole |
| An ethereal, almost painty note present in the aromas of pears, many kinds of cheese, and certain herbs such as oregano and basil. Also important for the taste of artificial banana flavor, but less so for real banana which leans more into green-vegetable notes. | ||
| fishy-prawny | TAAR5 | trimethylamine, N-methylpiperidine |
| Probably the kinda-sorta fleshy note in shrimp and prawns that distinguishes them from fish. | ||
| full-bodied | OR10A6 | melafleur, cinnamyl alcohol, gamma-dodecalactone, cyclamal |
| Suggestive of floral notes or a very insipid perfume. Like a flowery bottomness without any sweet, fruity, or leafy aspects. | ||
| green-stemmy | OR2AG1, OR2AG2 | (Z)-3-hexen-1-ol, bean pyrazine, isoamyl acetate, cinnamyl alcohol |
| The sharp crisp stemmy quality of green vegetables, green beans, plant stems, cortex, pith, fresh cut grass. A major component of foliage smells in general, and certain flowers such as rose. Also important to the aroma and flavor of banana. | ||
| gritty-coconut | OR5AU1 | (no data, see https://doi.org/10.1101/2025.04.21.649882) |
| Coconut is one of the lactonic scents, as are milk, peach, apricot, etc. However, coconut has a tropical sort of almost-earthiness that the others lack. That facet is most likely the contribution from this receptor. | ||
| gritty-faenous | OR8B3 | (no data, see https://doi.org/10.1101/2025.04.21.649882) |
| A facet of hay aroma. Hay is green-grassy smelling, and also lactonic, like coconut, peach, and milk. This note is likely the gritty, dusty, almost woody aspect that distinguishes hay from other lactonic scents as well as from other green scents. | ||
| gritty-sandalwood | OR2AT4, ??? | alpha-santalol*, sandalore, sandranol |
| Part of the character that distinguishes sandalwood from other woods. Either a dark, almost earthy, almost sulfury quality, or more likely a somewhat pine-like greenish note. It's likely that at least two receptors are involved in this sandalwood uniqueness, in order to account for the separate dark earthy-sulfur and brighter green-pine facets. | ||
| ketonic | OR2AP1, OR10A3, OR10C1, OR10J1 | 2-butanone, gamma-undecalactone, isoeugenol |
| Like the buttery side of fusel oil, but not creamy, or like the lactonic note (think milk, coconut, peach, tamarind) without the full-bodied creaminess. | ||
| minty | OR2Y1, OR5R1, OR8B8, OR8B12, OR10X1, OR11H12 | (-)-menthol, (R)-carvone, acetophenone, coumarin |
| Almost certainly a mixture of notes. Recognizable as resembling mint or wintergreen, but also present in cherry, almond, vanilla, and hay aromas. | ||
| minty-fresh | OR2L13 | (R)-(-)-carvone, 1-dodecanol |
| Contributes something to the smell of spearmint, something apparently lacking in its mirror-image molecule the caraway molecule. However, smelling the difference between dodecanol with and without octanol (an inverse agonist) reveals a note like the fresh-clean facet of peppermint. It is not known whether peppermint excites this specific receptor, so there may be other receptors for this particular note. | ||
| muguet | OR10J5 | bourgeonal, lyral, nympheal, alpha-cedrene, (E,Z)-2,6-nonadienal |
| A wonderful enchanting perfumy lily-of-the-valley note with an almost styrofoam-like texture. | ||
| musky | OR5A2, OR5AN1 | muscone, musk ketone, tonalide |
| The characteristic musky note; the common animalic quality between all musks, independent of any powdery, floral, fruity, plushy, peppery, or hot cloth facets. | ||
| musty-hyacinth | OR6P1 | phenylacetaldehyde, para-anisaldehyde, benzaldehyde |
| Musty and dark-floral, a note that distinguishes hyacinth from other flowers, but is also important in honey and almond. | ||
| myristic | OR10D3 | isoeugenol |
| A note that distinguishes nutmeg from clove. | ||
| naphthyl-icy | OR8H1 | 1,1,6-trimethyl-1,2-dihydronaphthalene, vanillin, indole, (R)-carvone, oranger crystals |
| A note important for naphthyl or petrol odors, but also for vanilla, spearmint, and orange blossom. Naphthyl itself, or the similar phenolic note, might be encoded by a combination of this receptor and OR5P3. | ||
| powdery | OR11H4, OR11H6 | isovaleric acid, phenethyl alcohol, oranger crystals |
| Suggestive of clean laundry. A major component of neroli, rose, floral aromas in general, strawberry, and foot odor. | ||
| pruny | OR1A1 | 3-methyl-2,4-nonanedione |
| A note common to dried fruits, honey, and molasses, and especially prominent in raisins, giving them their almost jammy character. | ||
| pyrazinic | OR5K1 | hazelnut pyrazine, furaneol, methyl eugenol, hexanal |
| Somewhere between nutty and earthy, a dusty dried-leaf note also important to the smells of cocoa and bell pepper. | ||
| rancid | OR56A1 | citronellic acid, caprylic acid, 2-methylundecanoic acid |
| The added note in cooking oil that has sat too long and gone bad, or tortilla chips that are well past their expiration date. Note in both cases, the original aroma of the oil or the chip will be mixed with the rancidity. | ||
| salicylic | OR52I2 | benzyl salicylate, hexyl salicylate, delta-decalactone |
| DIY perfumers know the salicylic note well, since salicylates are used extensively in perfume formulations and they all have a common je ne sais quoi that's easily recognizable. For those who have played with silly putty, it's a bit like that. Otherwise, try to think of wintergreen without the minty or waxy notes, and you'll be close-ish. | ||
| spermous | TAAR6, TAAR8 | cadaverine, putrescine |
| Possibly two separate notes. Cadaverine and putrescine are often said to smell "like death", but in reality both compounds can be described as smelling more like wet animal fur or semen, with even a dry pasta note. The contribution(s) from TAAR6 and TAAR8 would be one or two of the facets thereof. | ||
| spicy-clove | OR9G1, OR10AG1 | cinnamaldehyde, eugenol |
| A spiciness like that of clove, cinnamon, or ginger, suggesting the holiday season or spice drops. | ||
| spicy-peppery | OR7A10 | rotundone, pepperwood |
| The spiciness of black pepper, distinct from woody and herbal qualities; the unique nuance that only black pepper has. | ||
| stinkbug | OR4N5, OR6A2 | 2-decenal, octanal, decanal |
| The note or notes perceived by those who dislike cilantro. Both receptors are implicated in contributing a soapy or stinkbug character to this herb, though whether they contribute the same note or separate notes in unknown. | ||
| sulfurous-thiolic | OR2T1, OR2T2, OR2T4, OR2T6, OR2T11, OR2C1 | hydrogen sulfide, diallyl disulfide, octanethiol |
| Strongly redolent of sulfur, like rotten egg, garlic, chicken, or skunk, but more specifically the volcanic devil-ass facet of each of these. | ||
| sulfurous-vegetal | OR2M2, OR2M3, OR2M7 | nootkatone, (S)-(-)-citronellol, 3-mercapto-2-methylpentan-1-ol, geraniol |
| Present in the aromas of cooked vegetables, but especially cabbage, onion, and cruciferous vegetables. Also part of the aroma of grapefruit, gardenia, and, for those who can smell it, asparagus urine. Geranium and citronella also feature this note as a nuance. Since each of these receptors is narrowly tuned to a specific class of molecule, it's possible that each of these receptors contributes a slightly different note to their respective aromas: OR2M2 to grapefruit/gardenia, OR2M3 to onion, and OR2M7 to cabbage, citronella, geranium, and the asparagus excretion molecule. | ||
| sweaty-cuminic | OR52E8 | 3-hydroxy-3-methyl hexanoic acid |
| According to our sources, this is supposedly the note in underarm sweat that smells like cumin. It seems strange that a class I receptor would be associated with this note that seems more consistent with class II receptor notes, particularly spicy and balsamic. We wonder if OR52E8 actually picks up on the stale, rancid, almost watery facet of day-old sweat, as this would be a better fit for a class I receptor. But without access to smell a pure sample of the specific acid, only conjecture is possible. | ||
| sweaty-goaty | OR52A5 | 4-ethyloctanoic acid, 4-methyloctanoic acid, caprylic acid |
| A note that supposedly distinguishes goat milk and goat cheese from their more usual cow equivalents. | ||
| sweaty-podal | OR11H7 | isovaleric acid |
| The most unpleasant facet of foot odor. Not everyone has a functional OR11H7 gene, but those who do show much more sensitivity to this odor and find the smell unbearable. | ||
| sweet-fruity | OR2G2, OR2L5, OR2M4, OR2T10, OR5AC2 | alpha-damascone, vanillin, maltyl isobutyrate, fructone, cinnamaldehyde |
| Probably multiple related notes. Sweet notes reminiscent of fruits, fruit punch, and candy. If these are indeed separate notes then OR2G2 seems to lean more berry/sugary, OR2L5 more pear, OR2M4 more anise, OR2T10 more generally sweet, and OR5AC2 more tropical, however note that other receptors are separately identifiable as contributing important aspects to notes of sugar, pear, anise, and tropical fruit. | ||
| sweet-honeyed | OR51L1 | allyl phenylacetate, phenylacetaldehyde, phenoxyacetic acid, caproic acid |
| A facet of the aroma of honey, but divorced of the sugary and pruny facets. A sort of clear-yellow, almost juicy, aroma note. The part of honey's flavor that makes it taste good with chicken. | ||
| sweet-sugary | OR5M3 | maltol, furaneol, sotolone |
| The common note between caramellic and berry aromas, a granular sugary quality. | ||
| tabagique-dried-rosy | OR2A25 | geranyl acetate, (S)-(-)-citronellol, peony acetonitrile, quinoline |
| Suggestive of dried leaves, especially tobacco leaves, but also of dried rose petals. Seems to be especially important in the smell of roses, where it combines with floral-waxy, green-stemmy, and balsamic notes to produce that combination uniquely recognizable as rose. | ||
| tart | OR12D2 | acetic acid, propionic acid, isovaleric acid |
| Like vinegar or any strong acid. Sour, but not like milk. The olfactory equivalent of sour candy. | ||
| terpenic-bright | OR2A1, OR2A7 | alpha-pinene, lilial, farnesol |
| Part of a group of receptors that work together to produce the characteristic accord of scents like pine, eucalyptus, camphor, and to a lesser extent, peppermint and citrus. These specific receptors are associated with a lily-like solventy shimmering aspect to the aroma. | ||
| terpenic-green | OR2L3 | alpha-terpineol, 4-methyl acetophenone, indole |
| A green piney note also suggestive of mint and chlorine. Since mint, conifer, camphorous, and citrus are all classes of terpene aromas and all seem to have perceptual elements in common, this pine-green note probably helps to distinguish minty and coniferous from the other terpene types. It is also perceptible in fecal odors (e.g. indole) as a chlorine-like or broccoli-like greenness. | ||
| textured-fluffy | OR2B11 | quinoline, coumarin, coffee difuran, d-limonene |
| A note reminiscent of soft fragrances such as those used in tissue paper. Strongly associated with coffee but also with hay, cinnamon, orange, and seafood, probably making this an important aroma note for all of these diverse scents and flavors. | ||
| textured-plushy | OR4K2, OR4K5, OR4M1, OR4P4, OR5L1 | benzaldehyde, isobutyraldehyde, muscone, ethylene brassylate, gamma-nonalactone, acetophenone, habanolide, ysamber K |
| A major part of new carpet smell, but also the smells of cereal, almond, certain musks, and sunscreen lotion. | ||
| textured-pointy | OR2J3 | (Z)-3-hexen-1-ol, cinnamaldehyde, hexanal, coumarin, citral |
| Sharper than the OR2J2 note, more like a biteyness in cinnamon, passionfruit, and fresh cut grass. One study found that OR2J3 is important for recognition of leaf alcohol, the natural molecule that gives nearly all plants their leafy-green smell. A different receptor is likely to convey the greenness itself, so it is probably the combination of that other receptor with OR2J3 that gives a uniquely leafy-green aroma perception. | ||
| textured-smooth | OR2J2 | methyl eugenol, phenylacetaldehyde, cinnamaldehyde, coumarin, butyl anthranilate |
| A sort of smoothness found in a variety of scents from grape to carnation to cinnamon to hay. In particular, methyl eugenol, which occurs naturally in many plant oils and smells like a clove-nuanced empty movie theater with freshly cleaned carpets, is active for OR2J2 and only a few other receptors, the others contributing the clove and butter aspects. | ||
| urinous | OR7D4, OR9Q2 | androstenone, p-cresol, p-cresyl isobutyrate |
| Very suggestive of stale urine in some city subway, or the smell of a barnyard, but also important for the aroma of narcissus. | ||
| warmed | OR5P3 | coumarin, benzaldehyde, p-anisaldehyde, indole, (R)-carvone |
| A sort of warmness perceptible in many aromas including almond, cherry, hay, neroli, spearmint, caraway, and fusel oil. Importantly, this is not a trigeminal sensaton of heat like the spiciness of chili peppers, black pepper, ginger, mustard, etc, nor is it a burnt smell per se, but more of a note suggesting something that has been gently heated. It's warm in the same way amaretto is warm. Probably combines with the bright ice-cream nuance of OR8H1 to give the perception of naphthyl odors. | ||
| watery-greasy | OR10H1, OR10H2, OR10H5 | sandranol, azurone, cinnamaldehyde, calone |
| Whatever the note in common is between watermelon, greasy smelling sandranol, and cinnamon. | ||
| waxy-fatty | OR56A4, OR56A5 | undecanal, citronellic acid, gamma-undecalactone, 2-methylheptanoic acid |
| A major component of the smell of tallow, a note reminiscent of unscented candle wax; the fatty aspect of the dominant waxy facet of the smell of crayons. | ||
| waxy-petaly | OR1G1 | vanillin, 2-undecanone, gamma-decalactone |
| A delicate white-floral waxy flower-petal note. Strongly associated with fruity, floral, lactonic (milky), and waxy aromas where this receptor probably adds a delicate pleasantness. | ||
| woody | ???, OR7A17 | guaiacol*, arborone, cedryl acetate, vetynal, cedramber |
| A note dominant in wood and wood smoke, but also in black pepper, cinnamon, graprefruit, and certain herbs. | ||