Material guide: gamma-nonalactone — only three records in the database carry (so-called) in their name, and none of the three is an aldehyde

About a 4 minute read.

Too long, didn't read

• Name: gamma-nonalactone, properly nonano-1,4-lactone, CAS 104-61-0, 96 suppliers
• Its full catalogue name is gamma-nonalactone (aldehyde C-18 (so-called))
• Odor family coconut; descriptors: coconut, creamy, waxy, sweet, buttery, oily, fatty
• Longevity 309 hours @100%, vapour pressure 0.009 mmHg, boiling point 243 °C, flash point 113 °C
• The strength field reads medium with no concentration given
• Listed in all four regulatory indexes: JECFA, FEMA GRAS, CoE, FLAVIS. GHS: H302 harmful if swallowed
• Shelf life 24 months, water solubility 1,201 mg/L (est)

Only three records carry the (so-called) parenthesis

Start with the name. Of 42,225 records, only three contain so-called:

Catalogue name	CAS	Suppliers	Odor family	Longevity
gamma-undecalactone (aldehyde C-14 (so-called))	104-67-6	119	fruity	338 hours
gamma-nonalactone (aldehyde C-18 (so-called))	104-61-0	96	coconut	309 hours
strawberry glycidate 1 (aldehyde C-16 (so-called))	77-83-8	63	fruity	241 hours

None of the three is an aldehyde. The first two are lactones and the third is a glycidate. None of the carbon counts lines up either: this molecule has nine carbons (nonalactone) under a C-18 label, gamma-undecalactone has eleven under a C-14 label, and strawberry glycidate has thirteen under a C-16 label.

The "aldehyde C-N" convention is an early twentieth-century trade naming habit in which the number is a catalogue index rather than a carbon count, and all three are not aldehydes at all. Whoever wrote this catalogue evidently knew, because they appended (so-called) to the name. That parenthesis is a rare piece of candour in this database, and it appears exactly three times.

The proper-name field is clean about it: nonano-1,4-lactone. The 1,4 is a five-membered ring, which is what gamma means; the 1,5 six-membered ring is what the delta-decalactone piece covered. The -olide suffix is the same naming problem again.

The catalogue's own accord puts all three fake aldehydes in one bottle

Wedged into this record's notes field is a demonstration accord. Copied out:

waxy floral fruity accord: 0.05 - leerall / 0.01 - aldehyde C-14 / 0.05 - aldehyde C18 10% / 0.01 - musk gx / 0.01 - raspberry ketone 10% / 0.01 - aldehyde C-16 10%

Six components, and three of them are exactly the three from the table above: C-14, C-18 and C-16, all present.

It is a little funny, and it explains something. These three were always one set of tools in a formula. Their trade names were filed into the same series not because their chemical structures are similar (they are not), but because a perfumer reaches for them in the same kind of accord. The name records a working tradition, not a chemistry.

Note also that C-18 and C-16 both appear at 10% in that accord. They go in diluted.

The strength field gives one word

This record's strength field says medium, and stops. No recommended concentration.

As measured before, of 2,451 records carrying a strength field, 1,649 give only an adjective. This is one of them. Comparing its "medium" against another material's "medium" is comparing two uncalibrated labels.

The literature does give numbers.

Of eight enantiomers, this one has the highest threshold

In 2009 Cooke and colleagues in Adelaide did a solid piece of work (PMID 19228057).

They synthesised the individual enantiomers of four 4-alkyl substituted gamma-lactones: gamma-octalactone, gamma-nonalactone, gamma-decalactone and gamma-dodecalactone. The (R) series was prepared from L-glutamic acid by deamination and reduction to an intermediate, with side chains of different lengths introduced through a series of Wittig reactions and hydrogenation to finish. The (S) series came from D-glutamic acid by the analogous route.

Aroma detection thresholds for all eight enantiomers were then determined in a "bag in a box" dry red wine by ASTM method E 679 with a panel of 25 members.

The result, verbatim: the lowest threshold determined was 8 µg/L for (R)-dodecalactone, while the highest threshold was 285 µg/L for (R)-nonalactone.

In that test, then, this article's subject is the least sensitive of the eight, 36 times higher than the sharpest in the set. The impression that a coconut lactone is a powerful material does not survive the numbers.

One more finding worth keeping: with the exception of gamma-decalactone, there were statistically significant differences (at the 5% level) in aroma detection thresholds between the two enantiomers of the same lactone. Mirror images are not a chemical footnote; they differ at the level of the threshold. Where the delta-decalactone piece used enantiomer ratios to tell butter from margarine analytically, this is the sensory counterpart.

It is in freshly cooked white rice

In 2009 Zeng and colleagues ran a narrow but concrete study (PMID 19701135): looking for gamma-nonalactone in the headspace above freshly cooked non-scented rice.

The method was a modified headspace solid-phase microextraction (SPME) with gas chromatography-olfactometry (GC-O) and GC-MS. They confirmed it as one of the important odour-active compounds of freshly cooked rice, with a mass spectrum showing a characteristic ion peak at m/z 85 (100%), and validated the GC-O odour description against the authentic compound: a strong, sweet, coconut-like aroma.

That matches the database's occurrence field, which lists apricot, wheat bread, coconut, corn silk, crispbread, and blackcurrant bud and fruit. Grains and baked goods appear on that list more densely than fruit does. There is a material sold as coconut sitting in the smell of plain rice, and that is worth remembering on its own.

Buying and storing

96 suppliers, easy to source. A few practical points:

• Do not let the name steer you. Order it by CAS 104-61-0 or as nonano-1,4-lactone. "Aldehyde C-18" alone may point at something else at a different supplier.
• Longevity 309 hours and vapour pressure 0.009 mmHg put it in base-note territory. It will not open a formula for you; it is the layer that stays.
• With no concentration in the strength field, starting at 10% is a reasonable default. Its relatives gamma-undecalactone and gamma-decalactone are reference points, not substitutes for testing.
• GHS carries only H302 (harmful if swallowed). Flash point 113 °C, so shipping and storage constraints are loose.
• The solubility field gives usable ratios: 1:2 in 60% alcohol, 1:5 in 50% alcohol. Fields that state a dilution ratio directly are uncommon in this database.
• Shelf life 24 months, sealed and dark.

→ gamma-Nonalactone in the database: full physical data, 96 suppliers and suggested blends.

What this article does not establish

• "The number in aldehyde C-N is an index, not a carbon count" is inferred from the actual carbon counts of these three; I have not traced the primary source of that trade naming.
• The accord in the notes field carries no attribution or date, and no indication of who composed it.
• 285 µg/L is the result in a red wine matrix, with a 25-member panel, by ASTM E 679. Change the matrix, the method or the panel and it moves. It is not "the threshold of this material"; it is the threshold under those conditions.
• That study covered four gamma-lactones, not the delta series, and did not test the racemate of this article's subject.
• The rice paper is a single-compound screening study, not a full quantitative aroma profile of cooked rice.