Material guide · 98
Material guide: thyme oil, white and red, one CAS and two FEMA numbers
· 18 min read
White thyme oil has 55 suppliers, red thyme oil (Spain) 38 and red thyme oil (India) 18, and all three share CAS 8007-46-3. FEMA gives white 3065 and red 3064. The substantivity fields are measured under matching conditions (both neat) and differ by 2.1-fold: white 83 hours, red 172. The appearance differs too, white being colorless to pale yellow and red amber to orange red. Thyme has six chemotypes, and the thymol content recorded across origins in this database runs from 0.2 to 71.84 percent. Also, the notes field on the white thyme record describes an entirely different plant, which is a clear cataloguing error.
In short: white and red thyme are two records, one CAS and two FEMA numbers in this database. What you can see is the colour and the substantivity; what you cannot see is the chemotype.
Fields
| Field | White thyme oil #39414 | Red thyme oil (Spain) #39423 |
|---|---|---|
| CAS | 8007-46-3 | 8007-46-3 |
| FEMA | 3065 | 3064 |
| Suppliers | 55 | 38 |
| Appearance | colorless to pale yellow clear liquid | amber to orange red clear liquid |
| Specific gravity | 0.915-0.935 @ 25 C | 0.915-0.935 @ 25 C |
| Refractive index | 1.495-1.505 @ 20 C | 1.495-1.505 @ 20 C |
| Flash point | 55.56 C | 55.00 C |
| Water solubility | 437.4 mg/L @ 25 C (est) | 437.4 mg/L @ 25 C (est) |
| Odour type | herbal | herbal |
| Odour | thyme; herbal; camphoreous; medicinal; phenolic; terpenic; spicy | herbal; spicy; phenolic; camphoreous; medicinal; aromatic; terpenic |
| Strength | high, evaluate at 10% or less (rank 3) | high, evaluate at 10% or less (rank 3) |
| Substantivity | 83 hours (neat) | 172 hours (neat) |
| Regulatory | FEMA GRAS | FEMA GRAS |
| Oral toxicity | rat LD50 2840 mg/kg | same |
| Dermal toxicity | rabbit LD50 > 5000 mg/kg | same |
Red thyme oil (India) #39418 carries the same FEMA number, substantivity and odour field as the Spanish one, with a slightly lower specific gravity (0.911-0.918) and 18 suppliers.
One CAS, two FEMA numbers
This is the fourth pattern of registry disagreement I have run into across these articles, and the direction is new.
Previously:
- Amber ethers: CAS splits into two, FEMA and the Council of Europe merge into one
- Rose oxide: CAS splits into two, FEMA and CoE merge, FLAVIS splits
- Ylang: three fractions share one CAS, and five records share one FEMA number
This time: CAS merges white and red into one number (8007-46-3), and FEMA splits them into 3065 and 3064.
Somebody on the forum complained about exactly this:
"goodscents gives the same CAS number for White and Red Thyme and we all know they have different odor profile." (imgustavog)
He is right, and he can take it one step further: FEMA agrees with him. To distinguish these two on paper, the FEMA number is more useful than the CAS.
(I quoted that thread in the rose oxide article, where he was explaining why CAS numbers cannot be trusted for essential oils.)
Substantivity differs 2.1-fold, and this time it is comparable
White 83 hours, red 172 hours. Both measured neat.
The substantivity field has caught me out in two consecutive articles: the same rose oxide molecule at 8 hours and 388 hours, where the conditions differed, and ylang's 140 against 319, where the direction contradicted the trade description.
Here the conditions match and the direction makes sense. Red thyme is the higher-phenolic material, phenols boil higher than the monoterpenes, and lasting longer follows.
So the field is not broken. It needs its conditions read first.
The colour means something
White is colorless to pale yellow; red is amber to orange red.
Red thyme oil is the first steam distillation; white thyme oil has been rectified. Rectification removes the coloured higher-boiling components, and takes some of the phenols with them.
That lines up with the substantivity difference.
(The database does not state that white is rectified. I am inferring it from the appearance and substantivity fields.)
Six chemotypes
Thyme's variation is not origin noise; it is botanical typing.
Thompson and colleagues studied Thymus vulgaris in J Chem Ecol in 2003. It has six chemotypes with marked spatial segregation in nature. Some populations have a single chemotype in majority; many have two or three.
Two quantitative findings:
One, phenolic chemotypes (thymol, carvacrol) have a significantly lower proportion of their oil composed of the dominant monoterpene than nonphenolic ones (geraniol, alpha-terpineol, linalool), because the phenolic oils contain high amounts of precursors (gamma-terpinene and para-cymene).
Two, at sites where a chemotype is not the majority type, the percentage of its dominant monoterpene decreases significantly.
So composition depends not only on which chemotype you bought, but on the population mix where it was harvested.
The database numbers agree. Scanning the occurrence field across the library, the content ranges recorded in thyme oil:
| Molecule | Origins | Range | Fold |
|---|---|---|---|
| thymol | 9 | 0.2% – 71.84% | 359x |
| myrcene | 9 | 0.06% – 39.1% | 652x |
| geraniol | 6 | 0.04% – 11.8% | 295x |
| geranyl acetate | 5 | 0.09% – 25.0% | 278x |
| alpha-pinene | 9 | 0.01% – 2.28% | 228x |
(Those are ranges of literature values, not repeat measurements on one lot. The method and its limits are in How much does a natural actually vary.)
The notes field has a clear error
The white thyme record's head_synonym reads white thymus vulgaris oil, which is fine.
The notes field on the same record reads:
"Obtained from the fruit of the Ptychotis Ajowan in India... Locally it is used as a spice and is sometimes distilled and sold as Oman water. Ajowan oil..."
That is ajowan, not thyme. Both are thymol-rich, so two sources were probably merged during cataloguing.
The notes on the two red thyme records are correct: "Red Thyme Oil is water and steam distilled from the partially dried herb of the wild growing Thymus Vulgaris."
It makes no difference when buying, because what is wrong is the description rather than the spec. If you use that field as a source, though, it takes you to a different plant.
How to buy it
- White and red are two materials, not two grades. Red is the first distillation: higher phenol, longer lasting, darker. White is rectified: cleaner, shorter.
- CAS cannot distinguish them; FEMA can. 3064 is red, 3065 is white.
- To specify thymol content, ask the seller or read a COA. Under one name, the literature range runs from 0.2% to 71.84%.
- Ask about the chemotype separately. A linalool-type thyme and a thymol-type thyme are entirely different materials, and both are sold as thyme oil.
- Evaluate both at 10% or less.
- It carries phenols, so dose conservatively. (I did not look up its IFRA limit.)
What this doesn't establish
- I have not smelled either. This is database fields plus one paper.
- "White is rectified" is my inference from the appearance and substantivity fields; the database does not say so.
- That red is higher in phenols is also an inference. The database gives no component percentages for these two records, only library-level ranges.
- On 83 versus 172 hours I only established that the conditions match (both neat); whether the same protocol was used, I cannot tell.
- The content ranges are literature values, mixing origins, years and analytical methods. They are not repeat measurements on one lot, nor the range you would meet buying three bottles.
- Thompson 2003 studied wild populations in southern France, not commercial cultivation.
- On the notes error I only established that the content describes ajowan. Whether the mistake is in the original source or in the import, I cannot tell.
- I did not look up IFRA limits. Thyme oil contains phenols and will have practical limits, but that is not a field in this database.
- I did not run corpus statistics. I have not checked its frequency in the 954-formula corpus.