Turmeric is the product where buyers most often discover that a specification without a method is not a specification. Two suppliers quote “3% curcumin”. Two certificates say 3%. The powders are not the same powder, and one of them will underperform in your formulation.
Curcuminoids, not curcumin
What the trade calls curcumin content is almost always total curcuminoids: curcumin itself plus demethoxycurcumin and bisdemethoxycurcumin. The three occur together in the rhizome in a ratio that varies by variety and season, and they are not interchangeable in a finished product. If your application depends on the profile rather than the total, say so, because the total alone will not tell you what you are getting.
Indicative ranges by growing region
India grows turmeric across several distinct zones, and the differences are real rather than marketing. These are indicative ranges: every lot varies with season, soil and curing:
| Region | Typical total curcuminoids | Notes |
|---|---|---|
| Erode and Salem, Tamil Nadu | 2.5 – 3.5% | Large, consistent volumes; the trade benchmark |
| Nizamabad, Telangana | around 3% | Bulk supply, strong availability year-round |
| Alleppey finger, Kerala | 3.5 – 5.5% | Higher volatile oil; favoured for colour and aroma |
| Lakadong, Meghalaya | 6% and above | Small volumes, premium price, allocate early |
A supplier offering Lakadong-level curcumin at Erode pricing is offering one of two things: a blend, or a number produced by a method that flatters it.
The method matters more than the number
Curcuminoids can be measured spectrophotometrically or by high-performance liquid chromatography. Spectrophotometry reads total absorbance in a region where other pigments also absorb, so it tends to return a higher figure. HPLC separates the three curcuminoids and quantifies each against a reference standard. Same powder, two laboratories, two honest results, and a gap wide enough to matter commercially.
So write the method into the specification. “Total curcuminoids, minimum 3.0% by HPLC” is a specification. “Curcumin 3%” is a hope.
What else belongs on the sheet
- Moisture: a ceiling, typically around 10%, measured at packing.
- Total ash and acid-insoluble ash: acid-insoluble ash is the practical proxy for sand and soil. It is the cheapest adulteration test in the trade and the one buyers most often forget.
- Volatile oil: drives aroma, and separates culinary grades from colour-only material.
- Colour value: reported on the ASTA scale where your market expects it.
- Granulation: mesh size, stated as a percentage passing a named sieve.
- Added colour: none: with explicit screening for metanil yellow and Sudan dyes, plus a starch and foreign-matter screen.
- Sterilisation method: steam, stated in writing, if the destination is the EU or UK.
Fingers or powder
Whole fingers travel well, can be inspected by eye, and can be milled at destination to your own grind. Powder is convenient and is also where adulteration hides, because nobody can see rice flour in a bag of yellow dust. Buyers taking their first Indian lots often start with fingers and mill locally, then move to powder once the supplier relationship and the certificate history justify the trust.
A specification paragraph you can reuse
Turmeric powder, Curcuma longa, Alleppey origin. Total curcuminoids minimum 3.5% by HPLC. Moisture maximum 10.0%. Total ash maximum 7.0%, acid-insoluble ash maximum 1.5%. Granulation: minimum 95% through 60 mesh. Steam sterilised; no ethylene oxide. No added colour; screened for metanil yellow and Sudan I–IV. Aflatoxins, pesticide residues and heavy metals within destination-market limits, on a lot-specific Certificate of Analysis dated after packing.
We supply turmeric as both fingers and powder, with lot-specific HPLC results. Request a sample and spec sheet and tell us the curcumin level your formulation needs.