Turmeric (), or Curcuma longa (), is a flowering plant in the ginger family Zingiberaceae. It is a perennial, rhizomatous, herbaceous plant native to the Indian subcontinent and Southeast Asia that requires temperatures between and high annual rainfall to thrive. Plants are gathered each year for their rhizomes, some for propagation in the following season and some for consumption or dyeing.

The rhizomes can be used fresh, but they are often boiled in water and dried, after which they are ground into a deep orange-yellow shelf-stable spice powder commonly used as a coloring and flavoring agent in many Asian cuisines, especially for curries (curry powder). Turmeric powder has a warm, bitter, black pepper-like flavor and earthy, mustard-like aroma. Curcumin, a bright yellow chemical produced by the turmeric plant, is approved as a food additive by the World Health Organization, European Union, and United States Food and Drug Administration.

History

Turmeric has been used in Asia for centuries and is a major part of Ayurveda, Siddha medicine, traditional Chinese medicine, Unani, and the animistic rituals of Austronesian peoples.

In Maritime Southeast Asia, there is linguistic and circumstantial evidence of the ancient use of turmeric among the Austronesian peoples soon after dispersal from Taiwan (starting ), before contact with India. In Indonesia and the Philippines, turmeric was used for food, dyeing textiles, medicine, as well as body painting. It was commonly an important ingredient in various animistic rituals. Kikusawa and Reid (2007) have concluded that , the oldest reconstructed Proto-Malayo-Polynesian form for "turmeric" in the Austronesian languages, is primarily associated with the importance of its use as a dye. Other members of the genus Curcuma native to Southeast Asia (like Curcuma zedoaria) were also used for food and spice, but not as dyes. It was noted as a dye plant in the Assyrians' cuneiform medical texts from Ashurbanipal's library at Nineveh from 7th century BCE.

Description

Turmeric is a perennial herbaceous plant that reaches up to tall.

The hermaphrodite flowers are zygomorphic and threefold. The three sepals are long, fused, and white, and have fluffy hairs; the three calyx teeth are unequal. The three bright-yellow petals are fused into a corolla tube up to long. The three corolla lobes have a length of and are triangular with soft-spiny upper ends. While the average corolla lobe is larger than the two lateral, only the median stamen of the inner circle is fertile. The dust bag is spurred at its base. All other stamens are converted to staminodes. The outer staminodes are shorter than the labellum. The labellum is yellowish, with a yellow ribbon in its center and it is obovate, with a length from . Three carpels are under a constant, trilobed ovary adherent, which is sparsely hairy. The fruit capsule opens with three compartments.

In East Asia, the flowering time is usually in August. Terminally on the false stem is an inflorescence stem, long, containing many flowers. The bracts are light green and ovate to oblong with a blunt upper end with a length of ., 3–7% dietary minerals, 3–7% essential oils, 22% dietary fiber, and 1–6% curcuminoids. Some 34 essential oils are present in turmeric, among which turmerone, germacrone, atlantone, and zingiberene are major constituents.

Uses

Culinary

Turmeric is one of the key ingredients in many Asian dishes, imparting a mustard-like, earthy aroma and pungent, slightly bitter flavor to foods. It is used mostly in savory dishes, but also is used in some sweet dishes, such as the Lebanese cake sfouf. In India, turmeric leaf is used to prepare special sweet dishes, patoleo, by layering rice flour and coconut-jaggery mixture on the leaf, then closing and steaming it in a special utensil (chondrõ).

Most turmeric is used in the form of rhizome powder to impart a golden yellow color.

Turmeric is approved for use in the European Union and other countries as a food color, assigned the code E100. Turmeric is used to give a yellow color to some prepared mustards, canned chicken broths, and other foodsoften as a less-expensive substitute for saffron. For oil-containing products, the turmeric oleoresin is used.

Turmeric grows wild in the forests of South and Southeast Asia, where it is collected for use in classical Indian medicine (Siddha or Ayurveda).

In Tamil Nadu and Andhra Pradesh, as a part of the Tamil–Telugu marriage ritual, a dried turmeric tuber tied with a string is used to create a Thali necklace. In western and coastal India, during weddings of the Marathi and Konkani people, Kannada Brahmins, turmeric tubers are tied with strings by the couple to their wrists during a ceremony, Kankana Bandhana. In many Hindu communities, turmeric paste is applied to the bride and groom as part of pre-wedding festivities known as the haldi ceremony.

Turmeric makes a poor fabric dye, as it is not light fast, but is commonly used in Indian clothing, such as saris and Buddhist monks' robes. Friedrich Ratzel reported in The History of Mankind during 1896, that in Micronesia, turmeric powder was applied for embellishment of body, clothing, utensils, and ceremonial uses. Native Hawaiians who introduced it to Hawaii () make a bright yellow dye out of it.

Indicator

thumb|Turmeric dispersed in water is yellow under acid and red under alkaline conditions

Turmeric paper, also called curcuma paper or in German literature , is paper steeped in a tincture of turmeric and allowed to dry. It is used in chemical analysis as a pH indicator. The paper is yellow in acidic and neutral solutions and turns brown to reddish-brown in alkaline solutions, with transition between pH of 7.4 and 9.2.

Adulteration

As turmeric and other spices are commonly sold by weight, the potential exists for powders of toxic, cheaper agents with a similar color to be added, such as lead(II,IV) oxide ("red lead"). These additives give turmeric an orange-red color instead of its native gold-yellow, and such conditions led the US Food and Drug Administration (FDA) to issue import alerts from 2013 to 2019 on turmeric originating in India and Bangladesh. Imported into the United States in 2014 were approximately of turmeric, some of which was used for food coloring, traditional medicine, or dietary supplement. Researchers identified a chain of sources adulterating the turmeric with lead chromate: from farmers to merchants selling low-grade turmeric roots to "polishers" who added lead chromate for yellow color enhancement, to wholesalers for market distribution, all unaware of the potential consequences of lead toxicity.

Medical research

Turmeric and curcumin have been studied in various, low-quality clinical trials, with no good evidence of an anti-disease effect or health benefit. There is no scientific evidence that curcumin reduces inflammation, . and lower muscle pain following physical exercise.

Turmeric supplements are associated with rare but potentially serious liver injuries, particularly in genetically susceptible individuals.

See also

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References

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