What's in a peach and what it takes to build one are two different lists

Someone on r/DIYfragrance asked a well-defined question:

"Hey, I'm new and I know nothing about peach in perfumery. There are accords that you can buy, but how can you intensify peach and how can you play with the peach flavour?"

"For example, if you want to make a fresh peach perfume, what are the typical and most important ingredients you should know? Because a fresh peach is a little bit different than the sweet peach."

The top reply (10 points) gave both a list and a mechanism:

"C14 it's the most important for peach. Gamma undecalactone is another name that you'll find it. Also gamma decalactone and veloutone are similar and important."

"Fruits generally are difficult to be realistic. Most of the times you need some green materials like cis 3 hexenol, triplal, hexyl acetate etc and C6 is a very important aldehyde which smells very fatty but it's there almost on all fruits. Also linalool is in many many fruits." (AdministrativePool2)

That reply contains four checkable claims, and both the database and the corpus can answer them. Last round's leather question had only 9 formulas and I returned a blank; fruity has 122, so this one can actually be done.

The short version

• "Fruit accords need green materials" holds. Of 122 fruity formulas, 74 (61%) contain a green material, against a corpus baseline of 37%. 1.65×.
• "C14 is the most important for peach" holds at the formula level. γ-undecalactone appears in 34.4% of fruity formulas against an 11.7% baseline, 2.93×. The whole lactone family runs 45.9% against 20.0%, 2.29×.
• "Linalool is in many many fruits" holds in nature and reverses in formulas. Linalool has 558 natural sources, the third most widespread molecule in the database. Its rate in fruity formulas is 28.7% against a 35.4% baseline — 0.81×, below average.
• "C6 is there almost on all fruits" is half right. Hexanal has 107 natural sources, 22 of them fruit. But it appears in 1.6% of fruity formulas against a 1.4% baseline, 1.20×, essentially no enrichment. Widespread in nature, almost never written into a formula.
• The database holds 160 materials whose natural occurrence field says "peach fruit", and ranked by supplier count, seven of the top twenty-five are lactones.
• And a 2020 paper reports that the greatest contributor to characteristic peach aroma is γ-decalactone, not the γ-undecalactone perfumery uses. Both are right; they are not in the same domain.

What's in a peach: 160 materials

Pulling every material whose natural occurrence field contains "peach fruit" gives 160. Of those, 41 have 50 or more suppliers (obtainable) and 12 have zero (not obtainable).

The top fifteen by supplier count:

Material	Suppliers	Natural sources	Odour field
Linalool	135	558	Citrus, floral, sweet, bois de rose, woody
Benzyl alcohol	125	82	Floral, rose, phenolic, balsamic, sweet
γ-undecalactone (aldehyde C-14 so-called)	119	10	Fruity, peach, creamy, fatty, lactonic, apricot
Linalyl acetate	117	143	Sweet, green, citrus, bergamot, lavender
γ-decalactone	111	21	Fresh, oily, waxy, peach, coconut, buttery
Phenethyl alcohol	110	90	Floral, rose, sweet
Benzaldehyde	108	126	Sharp, sweet, bitter, almond, cherry
Ethyl acetate	105	35	Ethereal, fruity, sweet, green, grape
δ-decalactone	104	25	Fresh, sweet, oily, coconut, fruity, peach
(Z)-3-hexen-1-yl acetate	103	32	Fresh, green, sweet, fruity, banana, apple
α-terpineol	103	490	Pine, terpenic, lilac, citrus, woody
Benzyl acetate	100	37	Sweet, floral, fruity, jasmin
Eugenol	97	199	Sweet, spicy, clove, woody, phenolic
γ-nonalactone (aldehyde C-18)	96	23	Coconut, creamy, waxy, sweet
δ-dodecalactone	92	16	Fresh, sweet, metallic, peach, oily, coconut

What to notice in this table is the ranking. The molecules with the most suppliers inside a peach are linalool and benzyl alcohol, and neither smells like peach. The first one that actually does comes third.

And seven of the top twenty-five are lactones: γ-undecalactone, γ-decalactone, δ-decalactone, γ-nonalactone, δ-dodecalactone, γ-octalactone, γ-dodecalactone.

Peach is not one molecule; it is a lactone family. That is the structure behind the forum's list, and the reply named two of them.

Aside: C-14 is not an aldehyde

The database's formal name for γ-undecalactone is:

gamma-undecalactone (aldehyde C-14 (so-called))

That "so-called" is the database's own addition.

C-14 is a historical leftover. It is not a fourteen-carbon aldehyde; it is an eleven-carbon lactone. The reply says "Gamma undecalactone is another name that you'll find it", which points the right way with the relationship inverted: γ-undecalactone is the name, and C-14 is the misnomer.

This has a practical consequence for a beginner. Understand it as "aldehyde C-14" and you will assume it belongs with aldehyde C-10 (decanal) and C-12 (lauric aldehyde), which are genuinely aldehydes. Their chemistry, volatility and handling are different.

Check one: green materials

This is the most interesting claim in the reply, because it is a mechanism rather than a list.

Pulling corpus formulas with fruit, apple, peach, pear, berry, melon, apricot, plum, cherry, banana, pineapple or mango in the title gives 122. For green materials I matched cis-3-hexenol and hexenols generally, triplal, hexyl acetate, hexenyl esters, galbanum, violet leaf, stemone and liffarome.

	Containing a green material
Fruity formulas (122)	74 = 61%
All formulas (954)	357 = 37%
	1.65×

It holds. And it rests on 122 formulas, not 9.

More useful than the ratio is how to read it: six in ten fruity formulas carry a green material, and four in ten do not. Green material is not a requirement of fruit; it is a very common option. The reply's "most of the times you need" is placed exactly right.

Check two: lactones

Material	Fruity formulas	Corpus baseline	Ratio
γ-undecalactone	34.4%	11.7%	2.93×
All lactones	45.9%	20.0%	2.29×
Hexyl acetate	16.4%	5.7%	2.90×
γ-decalactone	12.3%	4.9%	2.50×
cis-3-hexenol	17.2%	10.5%	1.64×
β-ionone	12.3%	11.8%	1.04×

γ-undecalactone at 2.93×, the lactone family at 2.29×. "C14 is the most important" stands up at the formula level.

Note hexyl acetate at 2.90× as well — it is on the reply's green materials list, and its enrichment matches γ-undecalactone's. The corpus agrees with both categories the reply named.

β-ionone at 1.04× shows no enrichment. It is the one item on that list the corpus does not support. I am not going to conclude it is useless (it may work in specific fruit directions and be diluted out across a set mixing a dozen fruits), but its difference from the others is clear.

The reversal: linalool

This is the row worth writing this round.

The reply says "linalool is in many many fruits". That is strikingly correct.

The ten molecules with the most natural sources in the database:

Material	Natural sources	Suppliers
α-pinene	619	57
Limonene (dipentene)	595	37
Linalool	558	135
Myrcene	525	56
β-pinene	519	44
β-caryophyllene	508	61
p-cymene	503	57
α-terpineol	490	103
4-carvomenthenol	423	49
γ-terpinene	413	61

Linalool is the third most widespread molecule in the database, with 558 natural sources. The reply's instinct is exactly right.

And its rate in fruity formulas is 28.7% against a 35.4% baseline. 0.81×, below average.

Put another way: peaches contain linalool, and people building peach use less linalool than an average formula does.

That is not a contradiction; it is two different things. And the "most widespread" table explains why. Nine of the top ten are terpenes — α-pinene, limonene, myrcene, β-pinene, p-cymene. They are everywhere in nature and not one of them smells like a particular fruit. They are the plant kingdom's background level.

Being ubiquitous in nature and being able to stand for something are different axes.

C6 is the same story

The reply says C6 is "there almost on all fruits".

Hexanal (aldehyde C-6, CAS 66-25-1) has 107 natural sources in its occurrence field, 22 of them fruit (21%). Its notes field reads "Constit. of many foodstuffs. A prod. of aerobic enzymatic transformations of plant constits."

So "almost all fruits" is slightly overstated, and the direction is right. It is genuinely widespread, and its presence has a mechanism.

But in formulas: 1.6% of fruity against a 1.4% baseline, 1.20×. Effectively no enrichment.

Common in fruit, almost never written into a formula for fruit. The same pattern as linalool, only more extreme. This round's material guide covers hexanal and goes after why it gets skipped.

The papers name a different lactone

Up to here the formula-level conclusion is that γ-undecalactone matters most. Ask about actual peaches and the answer changes.

Peng and colleagues, Plant Physiology, 2020, open with this:

"Among the many volatiles in peach (Prunus persica) fruits, γ-decalactone has the greatest contribution to the characteristic peach aroma."

What they studied is more specific: some peach cultivars have γ-decalactone contents too low to detect.

Comparing the transcriptomes and metabolomes of a high-aroma cultivar, Fenghuayulu, and a low-aroma cultivar, Achutao, they concluded that amino acid substitutions in ALCOHOL ACYLTRANSFERASE (PpAAT1) are responsible for the undetectable levels in the latter. Modelling and molecular docking indicated the substituted residues might determine substrate recognition or act as control channels to the active site. In vitro enzyme assays on PpAAT1 expressed and purified from E. coli, and in vivo assays using transient expression in Nicotiana benthamiana and the oleaginous yeast Yarrowia lipolytica, showed that PpAAT1 from high-aroma cultivars converts 4-hydroxydecanoyl-coenzyme A into γ-decalactone more efficiently.

So "peach smell" depends on one enzyme, and some peaches genuinely lack it.

That bears directly on the question asked. He wrote that a fresh peach is a little different from a sweet peach — part of that difference is cultivar and ripeness, and the cultivar part traces to a single gene.

And Liu and colleagues in 2022 tie the two material classes together. Studying controlled atmosphere storage of cold-stored peaches, they measured:

"A total of 14 volatiles were positively correlated with consumer acceptability, mainly including three C6 compounds, three esters and four lactones derived from the fatty acid lipoxygenase (LOX) pathway."

Three C6 compounds, three esters, four lactones, all from one metabolic pathway.

The paper supports both halves of that forum reply: lactones matter, and C6 matters. And it adds something the reply did not say — they are not two unrelated categories but products of the same LOX pathway. Green materials and fruit lactones are relatives inside the plant.

The limits of both papers should be stated. They measure actual peaches and consumer acceptability of fruit, not perfume. From "these 14 volatiles correlate with liking a peach" to "put these in your formula" is a gap I cannot cross. What they establish is which molecules matter in a peach, not which matter in a peach perfume. And the subject of this whole piece is that those two are different.

What I noticed this round

I set out to write a verification piece: take four claims to the data and see which hold. The first two held cleanly, and then the third — linalool — went the other way.

I initially read that as the reply being wrong. Rereading, it isn't. What he wrote was "linalool is in many many fruits", a statement about fruit, not about formulas. I was the one who read it as formula advice.

Corrected, that row became the most useful part of the piece. Discussions of materials on forums slide between "this molecule in nature" and "this molecule in formulas", and the answers to those two can be opposite.

Last round I learned that the sentence the asker throws in casually is often where the answer is. This round the lesson is different: before testing a claim, establish which domain it is about.

What you can actually do

• Start peach from the lactone family, not one molecule. γ-undecalactone, γ-decalactone, δ-decalactone and γ-nonalactone all have 96 or more suppliers and are easy to obtain.
• The difference between "fresh" and "sweet" lives on the green side. Six in ten fruity formulas carry green material, and green is the fresh end.
• Green materials and fruit lactones come from the same LOX pathway. That is not just a formulation trick; it is how the plant does it.
• Do not add a molecule because it is present in the fruit. Linalool has 558 natural sources and sits below baseline in fruity formulas. Ubiquity is not signature.
• C-14 is not an aldehyde. It is γ-undecalactone, and the database itself appends "so-called" to the name.
• Don't chase what you can't buy. Twelve of the 160 peach materials have zero suppliers.

What this doesn't establish

• The 122 fruity formulas mix a dozen fruits (apple, pear, berry, melon, apricot, plum, cherry, banana, pineapple, mango). Every ratio is "fruity as a whole" against the corpus, not "peach" against the corpus. There are too few peach-specific formulas to analyse separately.
• The green materials match list is mine. I used cis-3-hexenol and hexenols, triplal, hexyl acetate, hexenyl esters, galbanum, violet leaf, stemone and liffarome. A different list moves the 61%.
• The natural occurrence field is not quantitative. That 160 materials list "peach fruit" says nothing about comparable concentrations inside a peach; only a few carry a percentage.
• Supplier count is not importance. I sorted by it because it represents whether you can buy the material, not its role in a peach.
• I did not pursue β-ionone's 1.04×. It may work in specific fruit directions (berry, peach) and be diluted out across 122 mixed formulas. I have no conclusion for that row.
• Both papers measured actual peaches, not perfume. They establish which molecules matter in the fruit and the genetics and metabolism behind that. Any inference towards formulation is mine, not theirs.
• Peng 2020 compared two Chinese cultivars. The PpAAT1 amino acid substitution cannot be generalised as the cause of every low-aroma peach.