Prota 3: Dyes and tannins/Colorants et tanins
Sp. pl. 1: 512 (1753).
2n = 16
Annatto, lipstick tree (En). Rocouyer, rocou, roucou (Fr). Anato, urucuzeiro, urucu, açafrão do Brasil (Po). Mzingifuri (Sw).
Origin and geographic distribution
Bixa orellana is native to tropical America, where since antiquity the red dye extracted from its seeds has been endowed with symbolic power (representing eternal life, sun, fire and blood, majesty and power) and used to colour and flavour food. Bixa orellana became popular worldwide and at present it is planted and naturalized almost pantropically. In tropical Africa it is cultivated on a commercial scale in Kenya and on a small scale in all countries. It has become naturalized very locally, e.g. in Kenya and Tanzania.
The main product obtained from Bixa orellana is an organic dye present in the seed coat, commercially called ‘annatto’ in English, ‘rocou’ in French, ‘achiote’ in Spanish and ‘orlean’ in German. Due to its solubility in lipids, it is widely used in the food industry for giving red to orange-yellow colours to cheese, butter, oils, margarine, ice-cream, candy, bakery products and rice. It owes its success in the dairy sector to the comparative instability of equivalent certified synthetic materials as well as to its proven non-toxicity and vitamin A content. In Latin American cuisine, annatto is not only used to give an attractive red colour to meat, fish and rice dishes but also to impart distinctive flavour notes. It is used in the cosmetic industry in the production of nail gloss, hair oil, lipstick, soap and in household products like floor wax, furniture polish, shoe polish, brass lacquer and wood stain. The dye, mixed with oil, is used to decorate the body, for instance in West Africa, Guyana and New Guinea, and when used in this way it is believed also to repel insects and to protect against sunburn. Annatto has been used for dyeing cotton, wool and particularly silk, giving an orangered colour which becomes more yellow if the dye is mixed in the dye-bath with wood-ash or sodium carbonate and if the dyed fabric is passed through a weak solution of tartaric or citric acid. For colouring textiles, annatto has largely been replaced by synthetic dyes because it is not a fast dye. Exposure to light soon causes fading. However, the dye is somewhat resistant to soap, alkalis and acids. Wood, bamboo, rattan and wickerwork can be dyed with it. In West Africa, the Baoulé people of Côte d’Ivoire use a paste of crushed seeds, lemon juice and water as paint for door posts, wooden masks and toys. Sometimes annatto is used in mixtures with other vegetable dyes such as curcumin from turmeric (Curcuma longa L.).
The presscake of the seed and fruit is used as fodder. Fibres extracted from the bark are used for cordage. The wood from the aged tree makes good firewood. Bixa orellana is often planted as an ornamental in homegardens and public parks, valued for its beautiful white and pink flowers and red fruits. It is also planted as a hedge. The seeds and leaves are used in traditional medicine. The seeds are edible and nutritive but slightly purgative and said to be effective against fever, dysentery, kidney diseases and poisoning by cassava. In DR Congo a paste of fruits and seeds is applied against itch. In Gabon a leaf decoction is taken to stop vomiting, in DR Congo as a gargle for sore throat and tonsillitis, in the Seychelles and Mauritius as a bath against muscular pain. In Ethiopia the leaves are applied as a wound dressing and in Mauritius against headache. In Mexico and Paraguay seeds and sap have been used against mouth diseases.
Production and international trade
The main commercial producers of Bixa orellana are countries in South America, Central America, the Caribbean, Africa, and also India and Sri Lanka. Peru is the largest exporter of annatto seed, annually about 4000 t, Brazil the largest producer with about 5000 t. Kenya exports annually about 1500 t annatto seed and extracts and after Peru is the largest exporter, particularly to Japan. Côte d’Ivoire and Angola are also exporters. In Kenya Bixa orellana is grown by smallholders, particularly near the coast in Kilifi District, Kwale escarpment and Shimba hills area. In many tropical American countries the dye is collected both from plants cultivated in homegardens and from plants growing in the wild. Production statistics are not usually available, and would not provide a reliable guide to international trade since many of the producing countries utilize significant quantities domestically (e.g. Brazil is a large producer and consumer, needing additional imports). Annual world production of dried annatto seed at the beginning of the 21st century is estimated at about 10,000 t of which 7000 t enters international trade. The average market price per t seed varies strongly; between 1984 and 1990 it fluctuated between US$ 600 and US$ 2300. The main market for annatto is the United States with 3000 t/year, followed by western Europe (2500 t) and Japan (1500 t). Some 70% of the product is used in the importing countries to colour cheese. Trade in annatto extracts (instead of dried seeds) has increased strongly since the 1980s, with the water soluble norbixin extract being largest in volume, followed by vegetable oil extracts, and solvent-extracted bixin in third place.
The colouring matter present in the seedcoat of Bixa orellana is annatto, known in the European Union as E160(b). Other codes used for annatto are CI 75120 and Natural Orange 4. In the European Union the use of annatto is permitted in a variety of food products; in the United States it has FDA GRAS (Generally Recognized As Safe) status for use in food, drugs and cosmetics. The principal components of annatto are the carotenoids bixin and norbixin. Bixin, the monomethyl ester of a dicarboxylic carotenoid (C25H30O4), is the naturally occurring form, norbixin (C24H26O4) is the saponified form of the same carotenoid. They are chemically related to lycopene and saffron. Bixin and norbixin normally occur in the cis form, but small amounts of the more stable trans forms are formed on heating. The cis forms are redder than the trans forms and thus are the pigments used commercially. The carboxylic acid portions of the norbixin molecule contribute to its solubility in water, while the ester component of bixin makes it more soluble in oil. As the ratio bixin : norbixin in annatto can vary this provides flexibility for its use in a wide variety of applications and a range of colours from orange to red. Norbixin provides the golden-yellow colour of cheddar cheese and is also preferred in cheese production because it associates with the curd rather than the whey. Annatto also contains small quantities of other carotenoids and degradation products of bixin. A yellow degradation product, termed C17 yellow pigment, is produced on heating. The ethyl ester of bixin, named ethyl bixin (C27H34O4), is used as a suspension in vegetable oil for colouring foods. It imparts a golden-yellow colour. Bixin itself has no provitamin A activity, but other fractions of the dye do have it, which adds to its usefulness in colouring margarine and butter. Three methods of extraction from the seed are in general use, which yield 3 products each with its own characteristics. Annatto can be prepared by extraction with an edible vegetable oil yielding a solution of mainly bixin in the oil. Extraction with an aqueous solution yields annatto rich in norbixin. Finally, extraction with solvents followed by removal of the solvent yields mixtures of bixin and norbixin crystals or powder. For numerous special applications special formulations are made.
The bixin content of the seed varies strongly, usually 2–4%. The proportion of bixin present in commercial annatto extracts varies considerably, and depends on the nature of the product. A solution in vegetable oil usually contains 0.2–5% bixin. Norbixin concentrations of commercially available spraydried annatto powder range from 7.5% to 15%.
The seeds have a high nutritive value, containing a small amount of fatty oil (5%) and about 13% of protein. The seedcoat contains a waxlike substance which acts as a vermifuge and the flowery scent of the seed is caused by the tetracyclic sesquiterpene ishwarane. The fruit wall contains tannin. Ellagic acid and cyanidin have been isolated from the leaves. Extracts of the fruit and the leaf showed antibacterial activity against Staphylococcus aureus, Escherichia coli and Salmonella typhi. A gum extracted from the bark is similar to gum arabic. The wood is soft, light (air-dry weight about 400 kg/m3), yellowish to pinkish yellow and not durable.
Adulterations and substitutes
The main competitor for annatto extracts in certain food applications is synthetic β-carotene.
Evergreen shrub or small tree up to 6(–8) m tall; trunk up to 10 cm in diameter; bark pale to dark brown, tough and smooth, sometimes fissured, lenticellate, inner bark with orange sap; branches greenish and densely rustyscaly when young, later becoming dark brown, ringed at nodes. Leaves arranged spirally, simple and entire; stipules quickly caducous, leaving horseshoe-shaped scars; petiole terete, thickened at both ends, 1–13 cm long; blade ovate, 5–25 cm × 3.6–16 cm, shallowly cordate to truncate at base, longacuminate at apex, dark green above, greyish or brownishgreen beneath, scaly when young but glabrescent, 5-veined from the base. Inflorescence a terminal, 8–50flowered panicle or corymb. Flowers bisexual, regular, fragrant; pedicel 0.5–1 cm long, scaly, thickened at the apex bearing 5–6 large glands; sepals 4–5, free, obovate, 10–12 mm long, caducous; petals (4–)5–7, free, obovate, 1.5–3 cm × 1–2 cm, pinkish, whitish or purplish tinged; stamens numerous, free, anthers violet; ovary superior, 1-celled, style 12–15 mm long, thickened upwards. Fruit a globose or broadly to elongated ovoid capsule 2–4.5 cm × 2–4 cm, more or less densely clothed with long bristles, green, greenish brown or red when mature, 2valved, manyseeded. Seeds obovoid and angular, 4–5 mm long, with bright orangered fleshy seedcoat and small whitish aril around the top of the long funicle. Seedling with epigeal germination, cotyledons thin, ovate, veined, hypocotyl fairly long.
Other botanical information
Bixa is the only genus of the family Bixaceae and comprises about 5 species confined to Central and South America, with only Bixa orellana cultivated and sometimes naturalized in many other tropical regions of the world. The variation in shape and colour of the fruits of Bixa orellana is considerable. The shape varies from globose to ovoid, broadtopped and shortly acuminate to elongateovoid and longacuminate. The colour varies from white to green and red. The types with ovoid, broadtopped and shortly acuminate fruits are reported to have a lower bixin content than the ones with globose or elongated fruits, and are consequently considered inferior. Types with white flowers occur, but pinkflowered plants are much more common. Although many cultivated types exist, there is no official cultivar classification.
Growth and development
Mature seeds taken directly from fresh fruits germinate readily in 7–10 days under moist conditions. Cleaned, sundried seeds retain viability for over one year, but their germination rate falls to 12% in 3 years. Seedgrown plants take comparatively long to flower and initially do so sparingly; they are very tall and exhibit much variation. Plants propagated by cuttings flower early and profusely and bear fruit within two years. Pollination is by insects; honeybees are observed in plenty around the plant. Fruits mature 5–6 months after pollination. Production of seed reaches a maximum in 4–12-year-old plants, which can remain productive for more than 20 years.
Bixa orellana requires a frostfree, warm, humid climate and a sunny location. Optimum conditions are an average temperature of 20–26°C in areas with an average annual rainfall of 1250–2000 mm, well distributed over the year but with a dry season for seed ripening. However, Bixa orellana can grow in a wide variety of tropical to subtropical climates and needs little care, though in regions where rainfall is not distributed evenly throughout the year, irrigation may be necessary. It grows on almost any type of soil, with a preference for neutral to slightly alkaline soils. It grows into a larger tree when planted in deeper and more fertile soil, rich in organic matter. It does well on limestone, where the topsoil is only a few cm thick and overlies a coral base. In Africa it is grown from sea-level up to about 2000 m altitude.
Weeding is necessary only in the initial stages of plant growth. Once the canopy is formed, periodic slashing of the weed cover and light pruning to remove dead and weak stems and to balance the shape of the plant are required to increase yield. Lower branches are either trained or pruned to ease management operations. Apical pruning is done to encourage branching and to reduce plant height for ease of harvest. Suckers arising from the roots need to be removed. Earthing up the plants after application of fertilizer will help rejuvenation as a ratoon crop. No artificial pollination is required, but if bees are kept near the plantation, seed yield may increase. Bixa orellana grows easily and is tolerant of nutrient-poor soil, rarely showing deficiency symptoms. Chemical fertilizers are not usually applied. Trash is usually collected and burnt outside the field and the ash is added to the field along with poultry or farmyard manure. However, application of NPK fertilizer enriched with boron and molybdenum encourages faster early growth and higher yield.
Propagation and planting
Bixa orellana can be propagated by seed and stem cuttings. Seed is sown directly in the field, 2–5 seeds per hole in well-prepared soil, usually at the beginning of the rainy season. After germination only one seedling per hole is retained. Seedlings may be raised in planting trays; they are transferred to 1 kg bags containing a soil mixture and kept in the nursery for 3–4 months before they are transplanted into the field. Hardwood cuttings of 8 mm or more in diameter readily root when a root hormone suitable for hardwood cuttings is applied. Roots are produced in abundance in 7–9 weeks. Rooted cuttings are first transferred into pots or bags and kept in a nursery and can be transplanted to the field after 3 months. For commercial production Bixa orellana is planted in rows 3–4 m apart, with plants spaced at 2–3 m within the row, depending on soil and climate.
In vitro production of active compounds
Attempts have been made to produce bixin artificially by introducing the 3 genes of Bixa orellana that govern bixin synthesis in the plant into a strain of the bacterium Escherichia coli, which had been engineered to produce lycopene. This induced the bacterium to convert lycopene into bixin. Tests were promising and the average production level of bixin in Escherichia coli was 5 mg per g dry weight. It might be possible to use the 3 genes in sink organs such as tomato fruits, where massive amounts of lycopene are accumulated, to create a competitive alternative source for natural bixin production.
Diseases and pests
Bixa orellana is sometimes infested by powdery mildew caused by Oidium bixae and Oidium heveae which attack mainly young fruits; the latter fungus causes powdery mildew in rubber. A foliar disease of minor importance, caused by the fungus Phyllosticta bixina, has been recorded in Guam. Insect pests are of minor importance; they include spiralling whitefly (Aleurodicus dispersus), pink wax scale (Ceroplastes rubens), transparent scale or coconut scale (Aspidiotus destructor), Seychelles scale (Icerya seychellarum), and redbanded thrips (Selenothrips rubrocinctus). In Indonesia Bixa orellana is reported liable to attack by tropical mirid bugs of the genus Helopeltis which are destructive in tea plantations.
Under favourable conditions the first harvest of Bixa orellana can be done 1.5 year after field planting. The fruits should be harvested after they start to turn brown and before they split open. They are dried in the shade and threshed by gently beating with a stick. The seeds can then be collected, dried again, cleaned to remove dust and other plant parts, and stored. Fruits harvested when not yet ripe or when allowed to stay on the plant long after maturity reduce the quality of the product.
No reliable statistics on yield are available. Seed yield is reported to be as high as 3–5 t/ha, but in Sri Lanka yields of only 625 kg/ha have been reported. Usually annual seed yields are 800–1200 kg/ha (0.5–4 kg per tree). From 1 kg of seed 20–50 g of dye can be obtained.
Handling after harvest
Seeds of Bixa orellana that have been properly harvested, threshed, and dried to 4–6% moisture content retain their quality for a long time provided they are stored in a cool, dark and dry place. Sun drying takes about 3–10 days. Artificial drying is also done at maximum temperatures of 55–60°C. To avoid deterioration of the pigment content however, storage periods should be kept as short as possible. Clean double jute bags, containing 50–70 kg seeds, are used for export. Ocean shipment is preferably done in ventilated containers.
Traditionally the dye is extracted from seeds by soaking and squeezing in water to dissolve the fleshy seedcoat which contains the dye. The dye is only partially soluble in water and produces a turbid solution. The solution of bixin is concentrated by heating and subsequently cooled to form red crystals. The solution may also be allowed to ferment for about a week, and the dye that has settled at the bottom of the vessel is then separated and dried into cakes. A third traditional method of extracting the dye is to boil the seeds with a sodium carbonate solution, filter, and acidify the filtrate, after which the dye is coagulated by boiling with salt, filterpressed, washed and dried.
For dyeing cotton, annatto is dissolved in boiling water and a solution of sodium carbonate. The cloth is left in this solution for about 20 minutes, then squeezed dry and washed in acidulated water or an alum solution and dried in the shade. For dyeing silk, a solution is made of equal proportions (by volume) of annatto and sodium carbonate in water; soap is usually added and the dyeing is continued at 50°C for about an hour (longer duration gives a darker colour). Wool is dyed at about 90°C in a water solution of annatto, without addition of other compounds. For 100 g of wool 100 g of annatto is needed.
In its area of natural distribution, Bixa orellana is widespread and does not seem to be in danger of genetic erosion. Germplasm collections are available in tropical America, e.g. at CATIE, Turrialba, Costa Rica (about 130 accessions), Universidad Nacional de Colombia, Palmira, Colombia (100 accessions) and CENARGEN, Brasilia, Brazil (22 accessions).
Selection and breeding in Bixa orellana is directed towards improvement of planting stock by breeding high-yielding cultivars adapted to country and climate, but little work has been done so far.
Many natural dyes have been superseded by synthetic dyes. However, there is still a strong demand for annatto in the food and cosmetic industries because of the carcinogenic activity of many synthetic dyes. Although βcarotene with its vitamin A activity competes with annatto to some extent in household margarine, the lower price and the lesser complexity associated with its use favour annatto. The major use of annatto is in the cheesemaking industry, and its prospects are dependent on the growth of this industry. Existing exporters of annatto appear to be capable of servicing any conceivable level of demand for the foreseeable future, and opportunities for new suppliers seem to be limited but not impossible provided a consistent high quality is produced. It is expected that international trade will increasingly shift from seed to seed extracts. The scope for rapid improvement in Bixa orellana is still considerable.
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Sources of illustration
• Rajendran, R., 1991. Bixa orellana L. In: Lemmens, R.H.M.J. & Wulijarni-Soetjipto, N. (Editors). Plant Resources of South-East Asia No 3. Dye and tannin producing plants. Pudoc, Wageningen, Netherlands. pp. 50–53.
Correct citation of this article:
Jansen, P.C.M., 2005. Bixa orellana L. In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, flowering branch; 2, flower; 3, fruit; 4, halved fruit showing seeds
fruiting tree habit