Turmeric is a spice valued in international market more for the bright yellow colour than as a flavouring material. Nevertheless, it is valued from olden days in India for food flavouring, for colouring and for therapeutic uses so much so that it is regarded as an auspicious material.
Turmeric is a rhizome, an underground stem growth from which roots and shoot grow. This is an annual herbaceous plant, with leaves in sheaths and which grows to a maximum height of 1 metre. The plant is harvested in about 9 month’s time with crop coming in January to March period in India.
Several cultivars are grown in South India. Although many South and South East Asian countries and other tropical areas grow turmeric, India remains not only as the major producer but also as producer of superior quality. Some of the major trade varieties are Alleppey, Erode, Sangli, Pazhangali, Rajapore etc. with Alleppey showing highest in yellow colour. Both the bulb (mother turmeric) and secondary rhizome (finger turmeric) are used, but the latter is valued higher.To facilitate drying, rhizomes are boiled in water for about an hour or so when the starch get gelatinized. This is followed by sun drying. It is common to cut the bulb into 2 or 4 longitudinal pieces. In some markets, turmeric fingers are polished by rotating in a drum with rough side walls. Polishing gives a bright yellow eye-appeal and higher price.
Turmeric when dry has an essential oil content of 1.5 to 3% but is not valued for its aroma. The active component of turmeric is curcumin, the bright yellow food colour which is present to the level of 2 to 5%.Turmeric is used mostly in ground form. Solvent extraction gives an oleoresin which is used in processed food industry. Since colour is the main attribute with aroma not valued, there is great demand for near pure curcumin crystals. Curcumin also finds use as an antioxidant and as an anti-cancer nutraceutical.