Material guide: decanal (aldehyde C-10) — the waxy shine an orange peel sprays at you, and the aldehyde of "aldehydic"

Peel an orange and the skin sprays a fine mist at your face. One of the main players in that waxy brightness is decanal.

What matters

• Decanal is the waxy aldehyde of citrus peel, and when perfumery says "aldehydic" it means this row of straight-chain fatty aldehydes. High strength, evaluate at 1% or less; its 224 hours of substantivity sit oddly under such a light-seeming smell.
• A 2001 orange juice study, quantifying by odour activity value, ranked decanal among the dominant aroma contributors of fresh-squeezed juice. Part of the "fresh orange" in your nose is this molecule.
• Watch the storage: the recommended shelf life is only 12 months, the shortest in this series so far. Fatty aldehydes oxidise into a rancid edge with age. Buy small, date the bottle.

The record

CAS	112-31-2
Formula	C₁₀H₂₀O
MW	156.27
Odour	sweet, aldehydic, waxy, orange peel, citrus, floral, orange, citrus rind
Odour family	aldehydic
Strength	high (evaluate at 1% or less)
Substantivity	224 h (neat, on a strip)
Specific gravity	0.824–0.832 (25 °C)
Flash point	83 °C
Shelf life	12 months or longer (cool, dark, sealed)
Registers	GRAS, JECFA, CoE, FEMA GRAS, IFRA

Plain reading: CAS is the material's ID number. Two numbers deserve a pause: evaluation at 1% or less (banana-ester strong), and a 12-month shelf life (most materials say 24; this one is halved). The 224-hour substantivity is the family's hidden talent — the citrus impression scatters early, the wax stays and stays.

Which aldehydes "aldehydic" means

In a chemistry class, aldehyde is a broad functional group. Perfumery slang is much narrower: mainly the C₈-to-C₁₂ row of straight-chain fatty aldehydes, smelling of soap, wax and hot-ironed linen. The trade also left them numbered nicknames, and our database prints them right in the catalogue names: decanal (aldehyde C-10), octanal (aldehyde C-8). The gamma-decalactone guide already defused this numbering: C-14 is a lactone wearing an aldehyde's name, flagged "(so-called)". C-10 here is an actual aldehyde.

Perfume-history lore says the aldehydic family got its name as a style from the heavy use of fatty aldehydes in Chanel No. 5 in 1921. The story comes in many versions and I won't vouch for the details, but it is a fact that this row of materials ended up with its own odour family; our database's odor_type column simply says aldehydic.

A dominant contributor in orange juice

In 2001, Buettner and Schieberle in the Journal of Agricultural and Food Chemistry compared hand-squeezed Valencia late and Navel juices, quantified 25 aroma compounds by isotope dilution, and ranked contributors by odour activity value (concentration divided by threshold):

Fruity esters (ethyl 2-methylpropanoate, ethyl butanoate, (S)-ethyl 2-methylbutanoate), wine lactone, a grassy-smelling compound and decanal were the dominant aroma contributors in both juice types. Navel oranges showed weaker fruity character, correlating with lower ester concentrations, and higher levels of the grassy compound than Valencia late. […] Model solutions built from the quantitative data successfully replicated the sensory profiles.

The OAV tool appeared in the threshold article: a raw concentration ranking lies, and only dividing by threshold shows who is actually speaking. That is how decanal made this list. In perfumery you run the same trick in reverse: when a citrus accord has juice but no peel, a trace of decanal is often the patch.

Aldehydes also became receptor probes

A classic 1998 experiment used the fatty-aldehyde family to show that an olfactory receptor answers a small group of molecules rather than everything. That research history now sits in Why smell research keeps using the same odorants; this guide returns to decanal in orange peel and aldehydic perfumery.

Smelling it

• Evaluate at 1% or less; I smell a second pass at 0.1%. High concentrations read candle and soap; diluted, the orange-peel shine appears.
• The soapiness of an aldehydic accord is this row playing as a section. Decanal alone leans citrus; with undecanal or octanal the "aldehydic" effect turns three-dimensional.
• A few tenths of a percent in a floral flattens a crisp, ironed layer over everything; white florals take this especially well. Experience speaking.
• Past a year open, smell before you use. An oxidised fatty aldehyde carries a rancid-oil edge that no formula recovers from.

The catalogue family

Item	What it is
decanal (aldehyde C-10, 92 suppliers)	the material itself: orange-peel wax
octanal (aldehyde C-8, 73 suppliers)	two carbons shorter, sharper and more citrus; the famous ligand of receptor research
hexanal (aldehyde C-6, 70 suppliers)	shorter still, grass and apple skin, one step from the GLV family
nonanal (aldehyde C-9, 63 suppliers)	the odd-carbon one, rosy wax
undecanal (aldehyde C-11, 35 suppliers)	one carbon longer, soapier
gamma-nonalactone (aldehyde C-18 so-called, 96 suppliers)	another lactone wearing an aldehyde's number, coconut cream — don't be fooled

Every added carbon trades a little citrus for soap and wax. And the last row's C-18 is, like C-14, a lactone in disguise. Order by CAS.

Regulatory

Listed on GRAS, JECFA, CoE, FEMA GRAS, IFRA. As always, registers carry no limit values. Fatty aldehydes are regulatorily uncomplicated; for skin formulae, consult the current IFRA Standards and the supplier's specification.

Buying it

1. Buy the smallest bottle. High strength plus a 12-month shelf life makes a big bottle a waste.
2. Check CAS 112-31-2; "C-10" works as a nickname, but order by the CAS.
3. To enter the aldehydic family, a small bottle each of decanal and octanal sketches the outline. No need to collect the whole row yet.

→ Decanal in the database: full properties, supplier list, suggested pairings. → Octanal | Undecanal | Search by odour: try "aldehydic citrus" for its neighbours.

References

A. Buettner & P. Schieberle, Evaluation of aroma differences between hand-squeezed juices from Valencia late and Navel oranges by quantitation of key odorants and flavor reconstitution experiments, Journal of Agricultural and Food Chemistry, 49(5), 2387–2394 (2001). PMID 11368609

H. Zhao, L. Ivic, J. M. Otaki, M. Hashimoto, K. Mikoshiba & S. Firestein, Functional expression of a mammalian odorant receptor, Science, 279(5348), 237–242 (1998). PMID 9422698