Turmeric: curcumin content and colour

Curcumin percentage is the number most turmeric buyers ask for first, and it is the right question. But it is not the only one that decides whether a lot is fit for your process.

This page covers what the percentage actually measures, how finger and bulb differ, and the adulteration issue that any serious turmeric buyer should be testing for.

Curcumin is the compound that gives turmeric its colour and most of its claimed functional properties. It is reported as a percentage of curcuminoids by weight, measured in a laboratory.

Indian export turmeric commonly falls in the 2-5% range, and where in that range depends heavily on the growing region and the variety. Erode and Salem material sits in the middle of it with good consistency, which is why the belt is well established for export.

Higher figures exist — some regional varieties test considerably above this range — but they trade at a premium and are not always available in container volume. If you are being offered a very high curcumin figure at an ordinary price, ask for the lab report before you go further.

The turmeric plant produces a central mother rhizome and secondary rhizomes growing off it. The secondary rhizomes are the fingers; the mother rhizome is the bulb.

Fingers are the higher-value material: better colour, more uniform, and what most buyers mean when they say turmeric. Bulbs are larger, cheaper, generally lower in curcumin, and are usually destined for grinding.

Fingers are also supplied polished or unpolished. Polishing removes the rough outer skin and gives a brighter, more uniform appearance; unpolished keeps more of the surface intact. Neither is better — it depends on whether the buyer is selling whole turmeric on appearance or grinding it anyway.

Turmeric has a documented history of adulteration, most seriously with lead chromate — a bright yellow industrial pigment added to improve the colour of poor material. It is a genuine public health issue and has triggered recalls in several import markets.

This is the single strongest argument for buying against lab reports rather than on appearance. A brilliantly coloured lot at a low price is a reason for suspicion, not enthusiasm.

Any turmeric you import should be tested for heavy metals, particularly lead, alongside the curcumin assay. Ask for the reports. A supplier who cannot produce them is telling you something.

Moisture, normally held around 10% maximum for stable transit. Whole versus ground, since ground material has a shorter useful life and is harder to verify. Any pesticide residue limits your market enforces. And packing — bulk, retail-ready or private label all price differently.