Curcuma longa (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Vegetable
Spice / condiment
Dye / tannin
Medicinal
Forage / feed
Food security

1, plant habit; 2, rhizome. Source PROSEA

flowering plant (B. Loison, mytho-fleurs.com)

plant habit

rhizomes (Kazuo Yamasaki)

turmeric powder for sale on the market of Limbe, Malawi

rhizome and adhering roots

Curcuma longa L.

Protologue: Sp. pl. 1: 2 (1753).

Family: Zingiberaceae

Chromosome number: 2n = 63

Synonyms

• Curcuma domestica Valeton (1918).

Vernacular names

• Turmeric (En).
• Curcuma, safran pays, safran des Indes (Fr).
• Curcuma, rizoma dos Índios, açafroeira da Índia, terra merita (Po).
• Mmanjano (Sw).

Origin and geographic distribution

The origin of Curcuma longa is not certain but it is thought to originate from southern Asia, most probably from India. Curcuma longa does not occur in a true wild state, although in some regions it appears to have become naturalized. It is a sterile triploid and is thought to have arisen by continued selection and vegetative propagation of a hybrid between the diploid wild turmeric (Curcuma aromatica Salisb., native to India, Sri Lanka and the eastern Himalayas) and another closely related tetraploid Curcuma species.

India is considered a centre of domestication and Curcuma longa has been grown there since time immemorial. It reached China before the 7^th century, East Africa in the 8^th century and West Africa in the 13^th century. It was introduced into Jamaica in the 18^th century. At present turmeric is widely cultivated throughout the tropics, but commercial production is concentrated in India and South-East Asia. In Africa it is cultivated in home gardens in many countries and is for sale in numerous markets.

Uses

Curcuma longa is cultivated for its rhizome, primarily as a dye source, secondly as a culinary spice. In West Africa its major use is as a dye to colour products such as tanned leather, cotton cloth, thread and palm fibres a golden-yellow. Rhizomes are also used in Africa and Asia as a cosmetic for body and face. They are an auspicious article in all religious observances in Hindu households, and have many other uses in daily life in connection with birth, marriage, death, and in agriculture. In Asia turmeric is widely used as an important constituent of curry powder (contains up to 25% turmeric). In Western countries, ground turmeric rhizome is widely used in the food industry, in particular as a colouring agent (E 100 in the European Union) in processed foods and sauces. It is also applied as a colouring agent in pharmaceuticals, confectionery and textile dyes, and is a cheaper substitute for the true saffron (Crocus sativus L.).

Young shoots and young rhizomes can be eaten fresh as a spicy vegetable. Turmeric oil and oleoresin find similar applications as the ground spice. In the United States the regulatory status ‘generally recognized as safe’ has been accorded to turmeric oil (GRAS 3085) and turmeric oleoresin (GRAS 3087). The maximum permitted level of turmeric oil in fragrances is 1%, but it is now rarely used.

Turmeric rhizomes are part of numerous traditional compound medicines used as stomachic, stimulant and blood purifier, and to treat liver complaints, biliousness and jaundice. Mixed with warm milk they are used to cure common cold, bronchitis and asthma. Juice from fresh rhizomes is applied against many skin infections, while a decoction is effective against eye infections. Research since the 1970s has found promising pharmaceutical activity against cancer, dermatitis, AIDS, inflammation, high cholesterol levels and dyspeptic conditions. Turmeric also has insecticidal, fungicidal and nematicidal properties. In Madagascar ground rhizomes are mixed with grains to protect them from storage pests. The leaves are used in preparing a special medicinal bread in Nepal and India.

Production and international trade

Curcuma longa enters into international trade mainly in the form of dried whole rhizomes. Trade in ground turmeric is less important than it used to be. India is the largest producer, with 400,000 t from 130,000 ha and dominates the international trade which is estimated at 20,000 t annually. Other producers in Asia include Bangladesh, Pakistan, Sri Lanka, Taiwan, China, Myanmar and Indonesia. It is also cultivated in the Caribbean, and in Central and South America, with Jamaica, Haiti and Peru being the most important producing countries. All Asian producers are heavy consumers as well and some are even net importers, whereas non-Asian countries export most of their production. Trade in turmeric from Asian countries is mainly routed through Singapore. Leading importers are Iran, Sri Lanka, most of the Middle East and North African countries. Taiwan is the main supplier of Japan, whereas Jamaican turmeric goes mainly to the North American market. In the 1980s and 1990s the United States imported about 1850 t turmeric annually, with a value of about US$ 2 million.

Properties

Per 100 g edible portion ground turmeric contains approximately: water 11.4 g, energy 1481 kJ (354 kcal), protein 7.8 g, fat 9.9 g, carbohydrate 64.9 g, dietary fibre 21.1 g, Ca 183 mg, Mg 193 mg, P 268 mg, Fe 41.4 mg, Zn 4.4 mg, vitamin A 0.0 IU, thiamin 0.15 mg, riboflavin 0.23 mg, niacin 5.14 mg, folate 39 μg, ascorbic acid 25.9 mg (USDA, 2004). On steam distillation the rhizomes yield 2–7% essential oil, which is orange-red and slightly fluorescent. Its major constituents are the sesquiterpene zingiberene 25% and the ketonic derivatives turmerone 35% and ar-turmerone 12%. Extraction of the rhizome with ethyl alcohol, acetone or methylene chloride yields 6–10% oleoresin, which contains 35–45% curcumin and its derivatives demethoxycurcumin and bis-demethoxycurcumin, collectively known as curcuminoids. These compounds give turmeric the characteristic yellow-orange colour (Natural Yellow No 3 of the Colour Index), the essential oil gives it the typical aroma and flavour. The contents of the rhizome are very variable and depend on the site of cultivation, type of cultivar, moment of harvest, method of processing and method of analysis.

Turmeric is recognized in the dyeing industry as one of the ‘direct colours’, capable of dyeing cotton without a mordant. However, as the pigment is extremely sensitive to light, it easily discolours, and when applied to cotton, wool or silk it is usually used in a weak solution of acetic acid or alum. Alkali in the dye bath would impart a reddish hue. In West Africa tamarind pulp is added to the turmeric dye bath, probably to purify the colour and to remove any red tint.

The essential oil of turmeric is composed mainly of oxygenated monoterpenes, with smaller quantities of sesquiterpene hydrocarbons and monoterpene hydrocarbons. The relative contribution of individual components to the aroma and flavour is not well known. The aroma of steam-distilled essential oil differs in character from that of the spice and this is believed to arise from artefact formation during the distillation process. A monograph on the physiological properties of turmeric oil has been published by the Research Institute for Fragrance Materials (RIFM).

Curry powder usually contains, in addition to turmeric, spices such as coriander, cumin, cinnamon, cardamom, fenugreek, chilli, nutmeg, clove, ginger, pepper and dill. The proportions of the different ingredients vary with the sort of food being curried, but turmeric and coriander are usually most abundant. Modern medicinal research (in tests with animals such as rats and mice) has revealed that curcumin and its allies possess anti-oxidant, anti-inflammatory and anti-carcinogenic properties. Turmeric can lower lipid peroxidation by maintaining the activities of anti-oxidant enzymes like superoxide dismutase, catalase and glutathione peroxidase at higher levels. These enzymes play an important role in the regulation of lipid peroxidation (curcumin was effective in acute as well as chronic models of inflammation). The lipid peroxidation has a main role in inflammations, heart diseases and cancer. In tests turmeric has also shown antiprotozoal, nematicidal, antibacterial, antivenom, antiviral and antitumour activities. In clinical studies promising results were obtained by oral administration of turmeric to patients with rheumatoid arthritis, respiratory diseases, peptic ulcers and dyspepsia.

Adulterations and substitutes

The early history of Curcuma longa is bound up with that of saffron, for which it is a much cheaper substitute. In India adulteration of turmeric itself is a serious problem in local markets and ground turmeric is more vulnerable to such practice. It is not uncommon to find turmeric powder locally adulterated with lead chromate, yellow earth, sand, or cheap talc. However, in the international market, concern over possible adulteration relates mainly to the mixing of related Curcuma species containing curcuminoid pigments into turmeric rhizome material. There are three other curcumin-containing species that are significant with regard to adulteration: Curcuma xanthorrhiza Roxb., Curcuma aromatica Salisb. (wild turmeric or yellow zedoary) and Curcuma zedoaria (Christm.) Roscoe (zedoary). In the producing countries of Asia these three species are variously used as a source of starch, dyes and in folk medicine and as a substitute for true turmeric (not as a spice but in other applications). Identifying these species by microscopy of ground material is often difficult, particularly if the starch grains and oleoresin cells have been destroyed by boiling. Adulteration of Curcuma longa by Curcuma aromatica or Curcuma zedoaria can be detected from the presence of camphor and camphene, which occur as minor components in the essential oil of the latter two species.

Description

• Perennial, erect, strongly tillering herb (often cultivated as an annual), up to 1(–1.5) m tall; rhizome a fleshy complex with an ellipsoid primary tuber c. 5 cm × 2.5 cm, ringed with the bases of old scale leaves and when mature bearing numerous straight or slightly curved, cylindrical, branched, lateral rhizomes (called fingers) 5–10 cm × 1–1.5 cm, the whole forming a dense clump; rhizomes inside and outside bright orange-yellow, young tips white, with a spicy smell when bruised; roots filiform, tough.
• Leaves alternate, distichous, simple, with sheaths forming a short pseudostem; petiole 0.5–10 cm long, broadly furrowed and narrowly winged; blade oblong-lanceolate, 7–70 cm × 3–18 cm, base cuneate to rounded, apex acute or acuminate, above dark green, below very pale green, densely studded with pellucid dots.
• Inflorescence a terminal spike up to 20 cm long, erect, appearing between the leaf sheaths; peduncle 3–20 cm long, densely hairy, covered by bladeless sheaths or scales; bracts elliptical-lanceolate, 5–7.5 cm × 2.5 cm, densely hairy, pale green to white.
• Flowers in pairs in axils of bracts, bisexual, zygomorphic, 5–6 cm long, opening one at a time; calyx tubular, short, with 3 unequal teeth; corolla tubular at base, upper half much widened and with 3 unequal lobes, white; labellum (central staminode) orbicular to obovate, 12–17 mm in diameter, with 2 small lateral lobes and a large emarginate central lobe, white with a yellow central streak, lateral staminodes 2, elliptical-oblong, c. 1 cm × 6 mm, creamy-white, functional stamen 1, for larger part connate with staminodes, 5–6 mm × 3 mm, anther with a broad, curved large spur at base; ovary inferior, 3-celled, with 2 erect glands at top, style slender, passing between and held by the anther thecae, stigma expanded.
• Fruit never produced.

Other botanical information

Curcuma comprises about 50 species and is native from India to northern Australia; several species have been introduced in other tropical regions. The identity of Curcuma longa as a species needs better investigation. In Asia a group of closely related species is now distinguished solely by the different colours of the bracts, corolla, leaves or rhizomes, but in fact they form a single complex species around Curcuma longa. In some countries, especially India, several not officially recorded cultivars are distinguished by the names of the localities in which they are grown, some types being preferred for spice use (e.g. Madras type with up to 3.5% curcuminoid pigments), others for dyeing (e.g. Alleppey type, with up to 6.5% curcuminoid pigments). A thorough revision is needed to establish reliable cultivar groups and cultivars.

Growth and development

During establishment, sprouting of sets of turmeric is completed in 2–4 weeks; this is followed by a period of active vegetative growth. Flowering and rhizome development start about 5 months after planting. Active rhizome development continues for about 7–10 months, depending upon cultivar and climatic conditions; then the lower leaves turn yellow and the crop is ready for lifting.

Ecology

Turmeric requires warm and moist conditions. It can be cultivated in most areas of the tropics and subtropics provided rainfall is adequate (1000–2000 mm) or facilities for irrigation are available. A well-distributed rainfall of 1200–1400 mm in 100–120 days is optimal. Cultivation has been extended into areas with over 2000 mm rainfall. Turmeric is grown up to altitudes of 1200 m in the Himalayan foothills but it performs better at altitudes of 450–900 m. Optimum temperature ranges are 30–35°C during sprouting, 25–30°C during tillering, 20–25°C during rhizome initiation and 18–20°C during the bulking stage. Turmeric is grown in various soil types, but prefers well-drained, loose and friable, fertile loam or clay loam, with good organic matter status, and a pH of 5–7.5. It cannot stand waterlogging or alkaline soils. Gravelly, stony and heavy soils are unsuitable for the development of rhizomes. As a shade-loving plant it does well in partial shade and can be cropped under fruit trees.

Propagation and planting

Turmeric is propagated vegetatively by rhizomes. Mother rhizomes, whole or cut into pieces, and daughter rhizomes (fingers) are generally used. As seed material mother rhizomes are better than daughter rhizomes. However, it has also been stated that large daughter rhizomes sprout better and produce higher yields than mother rhizomes. Finger rhizomes store better, are more tolerant of wet soil conditions and can be planted at a lower density. It is necessary to store rhizomes for 2–3 months from harvest to planting. This may be done by spreading them thinly under a covering of turmeric leaves or storing them in heaps under a layer of straw and soil.

The field should be well prepared by ploughing or digging and turning over to a depth of about 30 cm, to provide a good tilth. Large quantities of organic manure (farmyard manure, oilseed cake, green leaves) are usually applied. The optimum is reported to be about 25 t/ha of cattle manure or compost and 65 kg/ha of N through oilseed cake. Turmeric is generally planted by one of two methods: the flat-bed method or the ridge and furrow method. The flat-bed method is generally better, but in sites with excessive or deficient moisture the ridge and furrow method is superior, facilitating drainage and irrigation. Ridges should be 20–25 cm high and 45–50 cm wide and the rhizomes planted at a distance of 30–40 cm, at a depth of 7.5 cm. A spacing of 25 cm × 25 cm for the flat-bed method is optimal. However, good results have been obtained at spacings of 30 cm × 15 cm and 15 cm × 15 cm. If turmeric is intercropped, spacing is adjusted accordingly. Planting time depends on cultivar, planting material and agroclimatic conditions. Rapid multiplication of turmeric has been reported using in vitro culture of young vegetative buds excised from sprouting rhizomes. Plantlet formation occurred throughout the year without exhibiting the usual dormancy period of field-grown plants.

Management

After planting it is beneficial to mulch with locally available leaves, straw or sugarcane trash. This practice improves rhizome establishment, suppresses weeds and increases plant height and rhizome yield. It is recommended to apply a mulch of green leaves twice at a rate of 15 t/ha, at planting and 60 days after planting. After-planting care consists of weeding, irrigation, protection against diseases and pests, and application of fertilizers. Early weeding may be avoided by the use of 2,4-D as a pre-emergence herbicide. Three to four hoeings followed by weeding at regular intervals are desirable. Earthing-up may be necessary about 8 weeks after planting.

A good soaking of the field at planting is beneficial, followed by a weekly irrigation until sprouting is completed, after which less frequent watering is required. Turmeric, being an exhaustive crop, requires heavy manuring for high yield. Under rainfed conditions the application of ammonium sulphate at a rate of 100 kg/ha has been reported to increase yield by nearly 100%. Response to phosphorus at a rate of up to 175 kg/ha and in combination with other nutrients has also been reported. Application of potassium significantly increases plant height, and the number of tillers, leaves, and mother and daughter rhizomes. Among micronutrients, responses to iron and zinc have been reported (50 kg each of FeSO₄ and ZnSO₄). However, recommendations of fertilizer application differ widely from place to place.

Diseases and pests

Leaf spot or leaf blotch, and rhizome rot are the most important diseases of turmeric. Leaf spot or leaf blotch, caused by Taphrina malucans, is characterized by the appearance of spots on both surfaces of the leaves, 1–2 mm in diameter, coalescing freely. Infected leaves are distorted, have a reddish brown appearance and soon become yellow. The disease can be controlled reasonably by Bordeaux mixture, ethion and zineb. Cultivars resistant to the disease are available. Another leaf spot disease is caused by Colletotrichum capsici, provoking spots of variable size, enlarging to 4–5 cm × 3 cm and frequently coalescing over most of the leaf, which then dries up. In very severe infestation most leaves dry up, presenting a scorched appearance, resulting in yield losses of more than 50%. The disease can be checked by spraying Bordeaux mixture once before symptoms appear. Captan and zineb, applied at monthly intervals, control the disease adequately. Planting materials should be selected from disease-free areas and treated with an authorized fungicide before planting. Excess shade and intercropping favour the disease.

Rhizome rot caused by Pythium aphanidermatum shows progressive drying-up of the leaves of infected plants. The base of the aerial shoots shows water-soaked soft lesions. As the disease progresses infection gradually passes to the rhizomes, which begin to rot and become soft. The bright orange colour of the rhizomes changes into brown. The disease may be confined to a few isolated plants or may occur in patches. In severe attacks the yield is considerably reduced. One of the effective control methods is eradication and burning of infected plants. In serious cases it may be advisable to disinfect the soil with an authorized fungicide (e.g. metalaxyl and mancozeb). Treating the planting material with a fungicide helps preventing the disease. Some cultivars (e.g. ‘Suvarna’ in India) have shown field tolerance.

Pests of turmeric include shoot borers, leaf-eating insects, sucking insects and nematodes. In Asia caterpillars of the shoot borer Conogethes punctiferalis (synonym: Dichocrocis punctiferalis) attack the central shoot, causing it to die (‘dead heart’). Monthly spraying with malathion controls the insect. In India the hesperiid caterpillar Udaspes folus (‘grass demon’) is also a serious foliage feeding insect. It is recommended to spray carbaryl, dimethoate or phosphamidon for its control. In Africa and the South Pacific the scale insect Aspidiella hartii is a sucking insect infesting rhizomes while still in the field. It multiplies on fresh rhizomes being kept for seed. The infested rhizomes ultimately desiccate. Control is achieved by dipping the seed rhizomes in phosalone, monocrotophos or quinalphos. Two hymenopteran parasites, Physcus sp. and Adelencyrtus moderatus, attack this pest. In Asia the tinged bug, Stephanitis typica, causes leaf discolouration by sucking the sap. Thrips also suck the leaves, which then roll up, turn pale and gradually dry up. The nematodes recorded in turmeric include root-knot nematode (Meloidogyne incognita) and burrowing nematode (Radopholus similis).

Harvesting

Turmeric is ready for harvest 7–10(–12) months after planting, when the lower leaves turn yellow. Harvesting is done by digging. Care should be taken not to damage the rhizomes and to ensure that the whole clump is lifted together with the dry plant. Leafy tops are then cut off, roots and adhering earth removed, and rhizomes are well washed. The finger rhizomes are separated from the mother rhizome. A few rhizomes may be used fresh and, except for those that are required for replanting, the remainder are processed.

Yield

The average yield of fresh turmeric rhizomes is 17–23 t/ha if the crop is irrigated, and 6.5–9 t/ha under rainfed conditions. However, yields depend largely upon the cultivar. Some cultivars are capable of yielding 30–35 t/ha of fresh turmeric rhizomes.

Handling after harvest

To develop the attractive yellow colour and the characteristic aroma, the cleaned rhizomes are cooked in boiling water for 1 hour under slightly alkaline conditions. The cooked material is dried in the sun for 6–8 days. Hot-air dryers are also used. Dried rhizomes are polished to smooth their exterior and also to slightly improve the colour. The polishing can be done in a simple rotating cylindrical galvanized iron drum turned by hand, or in other types of equipment. A small quantity of turmeric powder sprinkled in during polishing gives the product a good appearance.

In its simplest form, the method used to dye leather in Nigeria is merely to make a paste of the pulverized turmeric rhizome with water, and rub it well into the tanned hide after lightly oiling the surface. The hide is then washed with a weak mixture of lime juice and water, and dried. In the north-eastern Province of Bornu, the hides to be dyed are not oiled, and the dyestuff is prepared for use by mixing with water and a mineral containing sodium (bi)carbonate. This mixture turns the hides almost red, but the colour is purified to yellow by washing with lime juice and water. In Sokoto in north-western Nigeria, cotton cloth is dyed by dipping it into the dye paste and rubbing the paste well into the cloth with the hands. After a few minutes a piece of tamarind paste is added and the mixture again rubbed in (the tamarind paste is prepared from entire pods which are soaked in cold water and then gradually warmed in a vessel over the fire to a temperature that can still be easily handheld; the soft pulpy mass is then wrapped in leaves and kept for use). Then the cloth is taken out, shaken and exposed to the air for 2–3 minutes while wiping off any adhering moisture. Then the cloth is again dipped into the dye bath and the mixture again rubbed in for about 5 minutes, after which it is wiped clean and hung up to dry. Another simple method of dyeing with turmeric, used in Ethiopia, is to put the cloth to be dyed into a boiling decoction of the turmeric paste. In Asia turmeric is mostly used for cotton and silk cloth to obtain various shades of golden to orange-yellow. In Europe it was used in wool dyeing, to obtain special shades of golden-yellow in combination with weld (Reseda luteola L.) and bright scarlet, where turmeric was applied as a ground-dye for cochineal (Dactylopius coccus).

Genetic resources

A germplasm collection of 500–600 Curcuma longa accessions is maintained at the NBPGR Regional Station, Thrissur, Kerala, India.

Breeding

The average productivity and quality of turmeric are far from satisfactory. Until recently, there has been hardly any work on crop improvement in Curcuma longa, because conventional methods of breeding are hampered by problems of sterility. Clonal selection is now being applied to exploit the naturally occurring variation, and mutation breeding is being practised. The major breeding objectives are creating cultivars with high yield and appropriate curcumin content and colour tone, without excessive volatile oil content and with resistance against rhizome rot.

Prospects

Curcuma longa is an important food colorant, spice and medicinal plant. The growing demand for turmeric as a spice and as a safe food colouring agent in local as well as international markets indicates that its prospects are good. Crop improvement, agronomic research and pest management need to be undertaken to obtain high production levels and good quality. Turmeric is an interesting crop for incorporation in a mixed cropping system with shrubs and young trees. Studies on the bioactive compounds of the rhizomes have opened up new possibilities for the use of turmeric in pharmaceutical products. Given the dominant position of India in both production and trade, it will be difficult for the crop to expand in Africa for the international market. Expansion for local use may offer better opportunities.

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Sources of illustration

• Dahal, K.R. & Idris, S., 1999. Curcuma longa L. In: de Guzman, C.C. & Siemonsma, J.S. (Editors). Plant Resources of South-East Asia No 13. Spices. Backhuys Publishers, Leiden, Netherlands. pp. 111–116.

Author(s)

• P.C.M. Jansen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Jansen, P.C.M., 2005. Curcuma longa L. In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 17 December 2024.

• See the Prota4U database.