Turmeric

Turmeric (Curcuma longa) is a small plant of the ginger family (Zingiberaceae). The part used is the rhizome, which lies beneath the soil. When the rhizome is dried, ground, and processed, it yields a powder of golden-yellow colour, known for its warm, slightly bitter taste.

Turmeric is widely used in Asian cooking, particularly in India and East Asia, and forms part of curry powder. Somali people and those of the Gulf region add turmeric to rice, meat, and broth to impart a yellow colour. It has also been used to dye textiles and in traditional medicine.

Plant characteristics and cultivation

Turmeric is a perennial plant with large leaves, though it is usually replanted each year. It requires warm conditions, good rainfall, and well-draining soil. Cultivation begins by planting pieces of rhizome; after several months, the rhizomes are dug up, dried, and exposed to the sun.

Curcumin and colour

The yellow colour comes from a group of chemical compounds called curcuminoids, of which curcumin is the most abundant. Curcumin does not dissolve readily in water, but dissolves in oil and alcohol—which is why turmeric is typically infused in oil. Its colour changes with pH level, making it sometimes used as a pH indicator in school laboratories.

Other uses and health research

Turmeric is used as a food colourant (designated E100 under European standards) and for dyeing textiles, though the colour fades in sunlight. Ayurvedic medicine and traditional remedies use turmeric for inflammation and infections. Considerable modern research has been conducted on curcumin, but health effects in humans have not been established with certainty, partly because the body absorbs only small amounts of curcumin.