Turmeric - production & trade

India is the biggest producer of turmeric, supplying 94% of the world's demand. It is cultivated on a commercial scale and enters the market usually in the form of dried rhizomes which are then prepared according to their end use. It is widely used in South Asia as a spice.

Trade and production

A photograph of powdered turmeric rhizome from Kew's Economic Botany Collection.
Image: Powdered rhizomes of turmeric.

The main producing countries of turmeric include India, Pakistan and Bangladesh. India is the biggest producer, supplying some 20,000 t each year. It enters the international market in the form of dried whole rhizomes, or as ground rhizomes. The major importers of this spice are Iran, Sri Lanka, Middle Eastern and North African countries.

It is cultivated commercially as an annual crop, by planting small rhizomes or pieces of rhizome either on flat soil or in furrows between ridges. The growing plants require heavy manuring to get the best yield possible.

Turmeric is ready for harvesting 7 to 10 months after planting, when the lower leaves turn yellow. Harvesting is done by digging the rhizomes up. Leafy tops are then cut off and the roots and adhering earth is removed. Rhizomes are then washed. Some of these are retained for replanting as a future crop. The remainder are processed into turmeric.

To develop the yellow colour and characteristic aroma, cleaned rhizomes are cooked in boiling water for one hour under slightly alkaline conditions. The cooked rhizomes are then dried either artificially or in the sun for 6 to 8 days. Dried rhizomes are polished to smooth their exterior and also to improve the colour. They are then sold in this form or ground into a powder.

Adulteration and substitutes

In India, the deliberate contamination and bulking out of turmeric is a serious problem in local markets. On an international scale, the problems may not be so serious, but closely related species are frequently substituted for true turmeric. Fortunately, chemical analysis can to some extent establish how pure a product is.

Ground turmeric is the most vulnerable product, particularly in local markets. Here, it is not uncommon to find turmeric powder adulterated with lead chromate, yellow earth, sand or even cheap talc.

In the international market, concern over possible adulteration is associated mainly with the mixing of related Curcuma species containing similar pigments. Species that have been used as a substitute include C. xanthorrhiza, C. aromatica and C. zedoaria.

In Asian producing countries, these three species are used as a source of starch, dyes and in folk medicine as a substitute for true turmeric. It is often difficult to identify these species by microscopic examination of the powder. But, adulteration of true turmeric by C. aromatica and C. zedoaria can be detected by chemical methods.