Material guide · 173
Material guide: delta-decalactone — same molecular formula as gamma-decalactone, and the odor family field splits them anyway
· 21 min read
CAS 705-86-2, 104 suppliers. It shares a molecular formula with the gamma-decalactone already covered here, C10H18O2, and the same molecular weight of 170.25. The only difference is whether the ring has five members or six. The database's odor family field splits them regardless: gamma is fruity, delta is coconut. Line the series up from C8 to C12 and the delta column stays coconut throughout while the gamma column jumps to fruit at C10 and C12. Longevity does not follow ring size at all: delta-nonalactone records 24 hours while delta-octalactone, one carbon shorter, records 400. There is one interesting word in the natural occurrence list: margarine. And a 2022 Tokyo University of Marine Science paper is about exactly that. Measuring lactone enantiomer ratios in butter, fermented butter and margarine by enantioselective GC-MS, butter gave (R)-delta-decalactone while margarine gave only racemic forms, which the authors read as added synthetic aroma chemicals. A 1997 paper pulls it back, though: a yeast produces gamma-lactones at a fixed enantiomer ratio unaffected by the growth medium, and that too is a legal natural flavour. Enantiomer ratios are evidence, not a verdict.
About a 5 minute read.
Too long, didn't read
- Name: delta-decalactone, properly decano-1,5-lactone, CAS 705-86-2, 104 suppliers
- Formula C10H18O2, MW 170.25, both identical to gamma-decalactone
- Odor family coconut (gamma's is fruity); descriptors: fresh, sweet, oily, coconut, fruity, peach, creamy, dairy, lactonic, fatty, milky
- Longevity 336 hours @100%, strength medium, vapour pressure 0.001 mmHg
- Listed in all four regulatory indexes: JECFA 232, FEMA GRAS 2361, CoE 621, FLAVIS 10.007, and FCC listed
- The natural occurrence list in the notes includes margarine
- Shelf life 12 months, flash point > 110 °C
Gamma and delta differ by one atom in the ring
Take the name apart first. A lactone is a molecule that has joined its own carboxyl group to its own hydroxyl group to make a ring. Which carbon it joins to sets the ring size:
- gamma-lactone: the 4th carbon, a five-membered ring (1,4-lactone)
- delta-lactone: the 5th carbon, a six-membered ring (1,5-lactone)
The database's proper-name field states it directly: delta-decalactone's head synonym is decano-1,5-lactone.
Same carbon count, same atoms, same formula, same molecular weight. The only difference is one more atom in the ring.
And the odor family field splits them anyway:
| gamma-decalactone | delta-decalactone | |
|---|---|---|
| CAS | 706-14-9 | 705-86-2 |
| Formula | C10H18O2 | C10H18O2 |
| MW | 170.25 | 170.25 |
| Suppliers | 111 | 104 |
| Odor family | fruity | coconut |
| First descriptors | fresh, oily, waxy, peach, coconut, buttery | fresh, sweet, oily, coconut, fruity, peach |
| Longevity (hr) | 256 | 336 |
The descriptor words overlap heavily; peach and coconut appear on both. What splits them is the order. Gamma puts peach first, delta puts coconut first, and the odor family field takes whichever came first.
One formula, 217 materials made the point that a formula throws away every edge of the structure. C10H18O2 covers 171 materials in this database, and these two are just two of them.
Line up the series
From C8 to C12, gamma beside delta:
| Carbons | γ suppliers | γ family | γ longevity | δ suppliers | δ family | δ longevity |
|---|---|---|---|---|---|---|
| C8 | 92 | coconut | 144 | 42 | coconut | 400 |
| C9 | 96 | coconut | 309 | 48 | coconut | 24 |
| C10 | 111 | fruity | 256 | 104 | coconut | 336 |
| C11 | 119 | fruity | 338 | 54 | coconut | 400 |
| C12 | 82 | fruity | 400 | 92 | tropical | 336 |
Two things stand out.
First, the delta column is coconut nearly all the way down, turning tropical only at C12. The gamma column changes gear at C10, jumping from coconut to fruit and staying there for C11 and C12. The six-membered ring sits steadily in coconut and dairy territory, while the five-membered ring drifts towards peach as the chain lengthens.
Second, longevity does not track ring size at all. Delta-nonalactone records 24 hours while delta-octalactone and delta-undecalactone, its neighbours in the same column, both record 400. A sixteen-fold gap in the middle square, one carbon apart. The dodecanal piece measured this same shape: longevity numbers are what individual suppliers reported from their own blotters, not one set of experiments.
Incidentally, two entries in the gamma column have lying names. C9 appears in the catalogue as "gamma-nonalactone (aldehyde C-18 (so-called))" and C11 as "gamma-undecalactone (aldehyde C-14 (so-called))". Neither is an aldehyde. The -olide suffix covered the history of that naming.
The notes field lists margarine as a natural occurrence
Delta-decalactone's list of natural sources is long: coconut oil, butter, apricot, peach, cheese (one record at 1,680 ± 97 µg%), cane sugar, pork fat, lavender oil, and margarine.
Margarine appearing on a list of natural occurrences is worth a pause on its own. The paper in the next section is about exactly that.
The difference between butter and margarine is written in the enantiomer ratio
In 2022 Saeki and colleagues at the Tokyo University of Marine Science and Technology did something direct (PMID 35482605): they quantified the enantiomeric distributions of delta- and gamma-lactones in butter, fermented butter and margarine, using solvent extraction combined with enantioselective gas chromatography-mass spectrometry.
As reported: the main lactones in butter and fermented butter were (R)-delta-decalactone and (R)-delta-dodecalactone. In contrast, margarine samples consisted of only delta-decalactone and delta-dodecalactone in racemic forms, indicating that synthetic aroma chemicals were added to margarine.
After heat treatment, 13 types of lactones were detected in butter and fermented butter. In the heated samples the major delta-lactones were abundant in the (R) form, but only delta-octalactone was detected in the (S) form.
The principle is simple. Biosynthetic enzymes are chiral, so what they make leans one way. Chemical synthesis has no such preference and makes half of each. Read the enantiomer ratio and you know whether a cow or a factory made that flavour.
This paper carries a 2022 erratum (J Agric Food Chem 70(30):9596), to be read alongside it.
Except that yeast makes them too, at a fixed ratio
That test has a hole in it, and a 1997 paper by Dufossé and colleagues fills it in (PMID 9366027).
They worked on Sporidiobolus salmonicolor, an aroma-producing yeast that gives its culture medium a peach-like smell. Using multidimensional gas chromatography (MDGC) on a fused silica capillary column coupled to a modified beta-cyclodextrin column, they measured the enantiomeric ratios of five gamma-lactones produced by this yeast in two different media.
Two layers to the conclusion. First, those ratios remain constant during growth and are not affected by the composition of the medium. Second, the authors say it outright: with respect to consumers' preference for products considered "natural", microbial lactone production may represent a valuable alternative to fruit flavours.
So a gamma-decalactone made by yeast fermentation has a skewed enantiomer ratio, because the enzyme is chiral, and counts as a natural flavour under the regulations, while never having been near a peach.
An enantiomer ratio separates chemical synthesis from biosynthesis. It does not separate fruit from fermenter. It is evidence, not a verdict, and it has the same shape of limitation as the carbon isotopes in the vanilla extract piece.
Buying and storing
104 suppliers, well supplied. A few practical points:
- Decide gamma or delta before buying. One Greek letter apart, different prices and different directions. Peach means gamma, coconut and dairy mean delta. The assay field reads "98–100%, sum of isomers", and that "sum" is worth noticing.
- Ask about the enantiomer spec separately. Natural and synthetic grades differ in enantiomer ratio and a standard spec sheet will not carry it. If you need to support a natural claim, ask the supplier for enantiomeric purity data.
- Longevity 336 hours and vapour pressure 0.001 mmHg put it in base-note territory. Melting point −27 °C, so it will not solidify in winter.
- Shelf life 12 months is short for a single compound, where 24 is more usual. Keep it sealed and dark.
- Water solubility 393.8 mg/L (est); soluble in alcohol, fixed oils and propylene glycol.
→ Delta-decalactone in the database: full physical data, 104 suppliers and suggested blends.
What this article does not establish
- "Gamma drifts towards peach as it lengthens" is a trend read off five records, C8 to C12, and the odor families are the source data's labels, not a reclassification of mine.
- For the jump in the longevity column I offered one direction of explanation (different suppliers measuring separately) without ruling out genuine non-monotonicity.
- Saeki and colleagues did not say all margarine contains synthetic aroma chemicals. They said their samples were racemic, which indicates addition. The sample count is not in the abstract.
- Dufossé's paper is about gamma-lactones, not delta-lactones. I use it to establish that the microbial route exists, not to transfer its ratios to this article's subject.
- I did not trace the source of margarine appearing in the natural occurrence list. It may be a neutral statement that the molecule has been detected in margarine.