Lemongrass oil is a steam-distilled essential oil obtained from the leaves of Cymbopogon species. Two commercial types dominate the trade: East Indian lemongrass oil from Cymbopogon flexuosus and West Indian lemongrass oil from Cymbopogon citratus. Both are traded under CAS 8007-02-1 and are valued mainly for their citral content, which is the reason the material is bought as an industrial raw material rather than only as a fragrance ingredient.
Composition and What Buyers Actually Pay For
The oil is a pale yellow to amber mobile liquid with an intense fresh lemon odour. Its principal constituent is citral, which is not a single molecule but a mixture of two geometric isomers: geranial (citral A) and neral (citral B). Commercial oil typically contains 70-85 % total citral by gas chromatography, with the geranial fraction normally the larger of the two. Minor components include geraniol, citronellal, limonene, myrcene, linalool and various sesquiterpenes. The citral figure and the geranial-to-neral ratio are the two numbers that determine both the price and the suitability of a lot for a given downstream use.
Typical Quality Specification
| Parameter | Typical Value | Method |
|---|---|---|
| Appearance | Clear to slightly hazy, pale yellow liquid | Visual |
| Odour | Strong fresh lemon, characteristic | Organoleptic |
| Total citral (GC) | 70 - 85 % | GC / GC-MS |
| Relative density at 20 °C | 0.885 - 0.905 | ISO 279 |
| Refractive index at 20 °C | 1.483 - 1.489 | ISO 280 |
| Botanical nomenclature | Cymbopogon flexuosus / C. citratus | ISO 4720 |
Fragrance, Flavour and Personal-Care Use
In perfumery the oil is used for its fresh top note in soaps, detergents, household cleaners, air-care products and candles. Because citral oxidises readily, it is normally supported by an antioxidant or by careful ageing studies before it is committed to a long-shelf-life product. In personal care it appears in cleansers, toners and foot-care products, where its odour and its antimicrobial character are both used. Flavour applications are possible but are governed by the food-additive rules of the destination market, and the material must then meet food-grade documentation requirements.
Insect Repellent and Other Non-Fragrance Applications
Citral is the recognised active behind the traditional reputation of lemongrass as a mosquito repellent, and the oil is formulated into sprays, lotions, candles and incense-type products. Performance in a formulated repellent depends on dose and on how the oil is held on the skin or released from the matrix; burn-type products release active into the air rather than onto the surface to be protected, so their effect is more limited than that of a topical formulation. Other industrial applications include use in surface cleaners and disinfectant formulations, use as a botanical active in crop-protection products, and use of purified citral as a chemical feedstock for ionones, vitamin A intermediates and menthol-type syntheses.
Stability, Oxidation and Storage
Citral is unsaturated and oxidises on exposure to air and light, producing off-odours and a measurable fall in the citral figure. Storage in full, tightly closed containers with limited headspace, in the dark and preferably at 5-25 °C, is standard practice; nitrogen blanketing further slows oxidation when drums are used slowly. A practical shelf life of 12 to 24 months can be expected under those conditions, but lots held longer should be re-tested for citral content before release, because a specification that was met at delivery may no longer hold at the point of use.
Purchasing Checklist
Ask for the botanical species and country of origin, a lot-specific gas chromatography report showing total citral and the geranial-to-neral ratio, and statements on heavy metals and pesticide residues where the material will be used on skin. For cosmetic products, note that citral is classified as a fragrance allergen and must be declared on the label when it exceeds the applicable threshold in the finished product - 0.001 % in leave-on and 0.01 % in rinse-off products in the EU. Confirm the packing material and the headspace conditions, since oxidation during transport is the most common cause of quality disputes.
Frequently Asked Questions
Q: What is the difference between East Indian and West Indian lemongrass oil?
A: They come from different Cymbopogon species. East Indian oil from C. flexuosus is generally higher in citral and is the type preferred as a citral source, while West Indian oil from C. citratus has a comparable odour profile but is often used more for fragrance purposes.
Q: How much citral should a good commercial lot contain?
A: Between about 70 % and 85 % total citral by GC is the usual commercial band. Material at the lower end of the range is normally priced lower and is less suitable for citral isolation, though it may still be acceptable in fragrance blends.
Q: Why does lemongrass oil sometimes smell different from one lot to another?
A: The citral content, the geranial-to-neral ratio and the proportions of minor aldehydes and terpenes vary with species, harvest season and distillation practice. Oxidation during storage also changes the profile, which is why an organoleptic check on receipt is worthwhile.
Q: Is lemongrass oil an effective insect repellent on its own?
A: It shows repellent activity that is attributed mainly to citral, but it is volatile and its effect fades faster than that of long-acting repellent actives. Formulated products usually combine it with fixatives or other actives and re-dose the product to compensate for evaporation.
Q: Can lemongrass oil be stored in plastic containers?
A: Concentrated essential oils can attack some plastics and cause leaching. Glass, internally lacquered steel or suitable high-density containers are the usual choice, and the oil should be kept full, dark and cool to limit oxidation.
