“Curcuma oil” is used in trade for at least three different materials: the steam-distilled essential oil of turmeric, the solvent-extracted oleoresin, and oil-soluble curcumin made to color fat-based products. They come from the same rhizome but carry different compounds, and only two of the three contain curcumin at all. This guide separates them by process, composition and use, and shows how to read the color value on an oil-soluble curcumin COA.
Curcuma oil in the strict sense is turmeric essential oil: aromatic, rich in turmerones, and essentially free of curcumin. If you need yellow color in an oil phase, you need oil-soluble curcumin or turmeric oleoresin, specified by color value or curcuminoid content rather than by aroma.
Curcuma Oil, Turmeric Oleoresin and Oil-Soluble Curcumin Compared
The three materials differ first in how they are made, and everything else in the table follows from that.
| Property | Curcuma oil (turmeric essential oil) | Turmeric oleoresin | Oil-soluble curcumin |
|---|---|---|---|
| Process | Steam or hydro-distillation of rhizome | Solvent extraction of rhizome | Curcumin color formulated into an edible oil carrier |
| Key compounds | ar-Turmerone, α- and β-turmerone | Curcuminoids plus volatile oil and resins | Curcuminoids in oil |
| Curcumin content | Not reported in the oil | About 25–35% coloring matter in first-pass oleoresin | Set by specification; about 2.5% in our product |
| Appearance | Thin liquid with strong turmeric aroma | Dark, viscous paste or liquid | Brownish-red viscous liquid (our COA) |
| Main function | Flavor and fragrance | Flavor and color together | Color in fat-based systems |
| Specified by | Turmerone profile (GC) | Color value or curcuminoids, volatile oil | Color value (E1%1cm at about 425 nm) |
What Is Curcuma Oil (Turmeric Essential Oil)?
Curcuma oil is the volatile fraction of turmeric, obtained by hydro- or steam distillation of fresh or dried rhizome[1]. It carries the aroma of turmeric, not its color: curcumin has not been reported in the essential oil; the volatile oil gives turmeric its aroma, while the curcuminoids give its yellow color[1].
In the turmeric essential oil assessed by EFSA, distillation yielded oil equal to 3–6% of the dried rhizome, and the specification set ar-turmerone at 40–60% and β-turmerone at 5–15% (GC area)[2]. Five production batches averaged 47.45% ar-turmerone[2]. A buyer specifying curcuma oil should therefore ask for a GC turmerone profile, not a curcumin assay.
Industrial uses follow from the composition. The oil is a flavoring and fragrance raw material, and EFSA assessed it as a sensory additive (flavouring) in animal feed[2]. It will not tint an oil, a softgel fill or a margarine yellow.
Composition also varies with the plant. Essential oils from different Curcuma species and different plant parts are reported with different profiles[1], so a turmeric oil specification should name Curcuma longa rhizome and the distillation method, not just “curcuma oil”.
Steam-Distilled vs CO2-Extracted Turmeric Oil
Both are sold as “turmeric oil”, but they are different extracts. Steam or hydro-distillation collects only the volatile fraction, while supercritical carbon dioxide (CO2) extraction pulls a broader lipophilic fraction, and curcumin has been found in turmeric CO2 extract although it has not been reported in the distilled oil[1]. In other words, a CO2 extract can carry part of the color that a steam-distilled oil does not.
Volatile fraction only: turmerones and other sesquiterpenes, with no curcumin reported[1]. Specified by GC profile. Used for flavor and fragrance.
For a buyer, the practical rule is to state the extraction method on the purchase order and check it against the COA. A steam-distilled oil and a CO2 extract are not interchangeable in fragrance work, and neither replaces a standardized curcumin color. Valeherb does not supply turmeric essential oil; our turmeric range covers the color and curcuminoid side, described in the sections below.
What Is Turmeric Oleoresin?
Turmeric oleoresin is the solvent extract of the rhizome, and it holds both the color and the flavor fractions. US color additive rules define it as “the combination of flavor and color principles” obtained from turmeric by extraction with listed solvents, including acetone, ethyl alcohol, hexane, isopropyl alcohol and methyl alcohol[4].
A first solvent pass typically gives an oleoresin with 25–35% coloring matter[5]. Further purification by crystallization removes most of the volatile oil and resin and produces curcumin powder above 90%[5], which in the EU is the E 100 specification of at least 90% total coloring matters[6]. Oleoresin sits between the two: more concentrated than ground turmeric, but with a strong turmeric taste that limits its use in neutral-tasting products. For how the powder grades that follow crystallization are made and specified, see our guide to curcumin grades by process and assay.
Because the oleoresin is a solvent extract, residual solvent is a standard COA item. In the US, residues may not exceed the limits set for the same solvents in spice oleoresins[4]; the EU caps ethyl acetate at 50 mg/kg in E 100 curcumin[6].
What Is Oil-Soluble Curcumin?
Oil-soluble curcumin is a curcumin color prepared to stay dissolved or evenly dispersed in an oil phase, so it can be dosed straight into fats, oils and oil-based fills. It is sold by color strength, not by aroma, and its curcumin content is far below that of curcumin powder because the oil carrier makes up most of the product.
Our oil-soluble curcumin, batch 2026060201 (160 kg, manufactured 2 June 2026, report dated 8 June 2026): brownish-red viscous liquid with characteristic turmeric odor, soluble in salad oil. Color value E1%1cm (425 ± 2 nm): 40.1. Solvent residue: 17.6 ppm against a limit of ≤50 ppm. Lead, arsenic and cadmium each ≤1 mg/kg; mercury ≤0.1 mg/kg; total heavy metals ≤10 ppm. Stored sealed at room temperature in plastic drums, with a 1-year shelf life in original packaging.
How to Convert Color Value to Curcumin Content
Divide the product’s E1%1cm by the specific absorbance of pure curcumin, 1607 at about 426 nm in ethanol, and multiply by 100. The 1607 reference value is the one given in the EU E 100 specification[6]. For our batch, 40.1 ÷ 1607 × 100 = 2.50%, which matches the UV result reported by our laboratory.
Read E1%1cm from the COA
This is the absorbance of a 1% (w/v) solution in a 1 cm cell at about 425 nm. For batch 2026060201 it is 40.1.
Divide by 1607
1607 is the E1%1cm of pure curcumin in ethanol[6]. As a cross-check, E 100 curcumin at its 90% minimum[6] would read about 1446 on the same scale.
Express as a percentage
40.1 ÷ 1607 = 0.0250, or 2.50% total coloring matter calculated as curcumin.
The UV figure counts everything that absorbs near 425 nm, so it reports total coloring matter expressed as curcumin, not curcumin alone. Demethoxycurcumin and bisdemethoxycurcumin are included in the reading. If a formulation needs individual curcuminoids, request an HPLC result in addition to the color value.
Is Turmeric Water Soluble?
No. Curcumin is practically insoluble in water at acidic and neutral pH, with solubility estimated at about 11 ng/mL[7]. That is why turmeric color is supplied in two separate formats, one for the oil phase and one for the water phase, and the choice depends on where the color has to end up.
Goes into fats, oils, shortenings, margarine, oil-based sauces and dressings, snack seasoning oils, softgel fills and cosmetic oils. Dose it into the oil phase before emulsifying or blending.
Goes into beverages, drink powders, effervescent tablets and other aqueous systems. The curcuminoids sit on a carrier or emulsifier system such as cyclodextrin, phospholipid or gum[7], which lowers the assay but lets the color disperse in water.
Valeherb supplies both directions: the oil-soluble grade described above, and water-dispersible and powder grades listed on our turmeric extract specification page. The powder grades, including 95% curcuminoids and tetrahydrocurcumin, are compared side by side in our curcumin grade comparison. For how these concentrated forms compare with culinary spice, see turmeric powder vs a standardized extract.
How Much Oil-Soluble Curcumin to Add
Work from the curcumin level you need in the finished product, then divide by the curcumin content of the oil. At 2.5%, each gram of our oil-soluble curcumin delivers 25 mg of coloring matter as curcumin, so the product addition in g/kg equals the target in mg/kg divided by 25.
| Target curcumin in finished product | Oil-soluble curcumin (2.5%) to add |
|---|---|
| 10 mg/kg | 0.4 g/kg |
| 50 mg/kg | 2 g/kg |
| 100 mg/kg | 4 g/kg |
| 250 mg/kg | 10 g/kg |
Two checks come before the final number. First, the permitted level depends on the food category and the market, so confirm the curcumin limit for your category under local additive rules before fixing the dose. Second, the oil carrier adds fat, which matters in low-fat or labeled-fat products at the higher addition rates.
Stability and Handling in Oil Systems
Curcumin’s main stability risk in finished products is pH. Its first pKa falls between pH 7.5 and 8.5, where the color shifts from yellow to red, and degradation accelerates as pH rises[3]. In a fully anhydrous fat or oil there is no aqueous pH to drive this, but the color shift can appear in emulsions and filled products whose water phase is alkaline.
For storage, keep drums sealed at room temperature and away from moisture, as stated on the COA. Mix before sampling, because a viscous oil color can stratify in the drum, and take QC samples from the homogenized lot rather than from the surface.
What to Put on the Purchase Specification
Each of the three materials needs a different set of test lines, and a curcumin assay on a curcuma oil COA is a sign the wrong material was quoted. The table lists the items that identify each one and the checks that catch the most common substitution errors.
| Material | Identity and strength | Safety and process items |
|---|---|---|
| Curcuma oil (essential oil) | GC profile with ar-turmerone and β-turmerone ranges; distillation method stated | Botanical source and plant part, heavy metals, optical rotation if specified |
| Turmeric oleoresin | Color value or curcuminoid content; volatile oil content | Extraction solvent named, residual solvent, heavy metals |
| Oil-soluble curcumin | E1%1cm at about 425 nm with the curcumin equivalent; carrier oil named; HPLC curcuminoids if needed | Residual solvent, lead, arsenic, cadmium, mercury, solubility in the target oil |
Specify curcuma oil by turmerone profile and oil-soluble curcumin by color value; the two are not substitutes for each other.
Frequently Asked Questions
Is curcuma oil the same as turmeric oil?
Usually yes. Both names normally refer to the essential oil distilled from turmeric (Curcuma longa) rhizome, which is rich in turmerones and contains essentially no curcumin. Some suppliers also use “turmeric oil” loosely for oleoresin or oil-soluble curcumin, so check the process and the COA before ordering.
Does turmeric essential oil contain curcumin?
Curcumin has not been reported in turmeric essential oil. The distilled oil carries the aroma compounds, mainly turmerones, while the yellow curcuminoids stay in the rhizome and its solvent extracts. For color, use turmeric oleoresin or oil-soluble curcumin.
Is CO2-extracted turmeric oil the same as turmeric essential oil?
No. Steam-distilled essential oil contains only the volatile fraction, and curcumin has not been reported in it. Supercritical CO2 extraction also takes up other lipophilic compounds, and curcumin has been found in turmeric CO2 extract. State the extraction method on the purchase order, because the two behave differently in color and aroma.
What does E1%1cm mean on a curcumin COA?
It is the absorbance of a 1% solution measured in a 1 cm cell at about 425 nm, a standard measure of color strength. Dividing it by 1607, the value for pure curcumin, gives the coloring matter content expressed as curcumin. An E1%1cm of 40.1 corresponds to about 2.5%.
Is turmeric water soluble?
No. Curcumin is practically insoluble in water at acidic and neutral pH, estimated at about 11 ng/mL. Aqueous products need a water-dispersible curcumin made with a carrier or emulsifier system, while fat-based products use oil-soluble curcumin.
Can oil-soluble curcumin be used in softgels?
Yes, oil-based fills are one of its main uses, because the color dissolves into the fill oil without a separate dispersion step. Confirm compatibility with the other fill ingredients and the regulatory status of curcumin as a color or ingredient in your target market.
References
[1] Dosoky NS, Setzer WN. Chemical composition and biological activities of essential oils of Curcuma species. Nutrients. 2018;10(9):1196. https://doi.org/10.3390/nu10091196 (review)
[2] EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP). Safety and efficacy of turmeric extract, turmeric oil, turmeric oleoresin and turmeric tincture from Curcuma longa L. rhizome when used as sensory additives in feed for all animal species. EFSA Journal. 2020;18(6):e06146. https://doi.org/10.2903/j.efsa.2020.6146 (regulatory scientific opinion)
[3] Priyadarsini KI. The chemistry of curcumin: from extraction to therapeutic agent. Molecules. 2014;19(12):20091–20112. https://doi.org/10.3390/molecules191220091 (review)
[4] U.S. Code of Federal Regulations. 21 CFR 73.615, Turmeric oleoresin. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.615 (government regulation, not peer-reviewed; eCFR text read directly)
[5] FAO/WHO Joint Expert Committee on Food Additives (JECFA). Curcumin: Chemical and Technical Assessment, 61st JECFA. FAO; 2004. https://www.fao.org/fileadmin/templates/agns/pdf/jecfa/cta/61/Curcumin.pdf (intergovernmental technical assessment, not peer-reviewed; original read directly)
[6] Commission Regulation (EU) No 231/2012 of 9 March 2012 laying down specifications for food additives, Annex, entry E 100 Curcumin (consolidated version). https://eur-lex.europa.eu/eli/reg/2012/231/2020-07-02/eng (government regulation, not peer-reviewed; E 100 text read from the consolidated version)
[7] Stohs SJ, Chen O, Ray SD, Ji J, Bucci LR, Preuss HG. Highly bioavailable forms of curcumin and promising avenues for curcumin-based research and application: a review. Molecules. 2020;25(6):1397. https://doi.org/10.3390/molecules25061397 (review)
