1391

3: Dye and tannin-producing plants

Bixa orellana L.

Sp. Pl. 1: 512 (1753).

BIXACEAE

2n = 14, 16

Annatto (anatto, arnatto) tree, lipstick tree (En). Rocouyer, annato (Fr). Indonesia: kesumba (general), galuga (Sundanese). Malaysia: jarak belanda, kesumba, kunyit jawa. Philippines: echuete (Tagalog), sotis (Bisaya), achuete (Ilokano). Cambodia: châm'-puu, châm'-puu chrâluëk'. Laos: kh'am, satii, sômz phuu. Thailand: kam tai, kam sêt. Vietnam: diêù nhuôm.

Annatto tree is native to Central America, and tropical South America. It is widely planted and naturalized in the tropical regions of the world, including South-East Asia.

The main product of trade obtained from annatto tree is an organic dye present in the fruits, commercially called 'annatto'. It is widely used in the food industry for colouring rice, candy, margarine, oils, butter, ice-cream and bakery products. It owes its success in the dairy sector to the comparative instability of equivalent certified synthetic materials in these applications. It is also used in the cosmetic industry in the production of nail gloss, hair oil, lipstick, soap and home improvement products like floor wax, furniture polish, shoe polish, brass lacquer and wood stain. The dye is used to paint the body as a decoration, for instance in Papua New Guinea, and when used in this way it is believed to repel insects. Annatto has also been used for dyeing cotton, silk and wool, giving an orange-red colour which becomes more yellow if the fabric is passed through a weak solution of tartaric acid, a colour popular with oriental and Buddhist monks since early days. For colouring textiles, annatto has largely been replaced by synthetic dyes, because it is not a fast dye.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 resistant to soap, alkalies, and acids. Formerly in Indonesia bamboo matting and rattans were dyed with it. Sometimes annatto is used in mixtures with other vegetable dyes such as curcumin (from Curcuma longa L.).
The fibres extracted from the bark are used for cordage. The gum extracted from the bark is similar to gum arabic. The wood from the aged tree makes good firewood. Annatto is often planted as an ornamental in home gardens and public parks, valued for its beautiful white and pink flowers and red fruits. The seeds and leaves have been used in traditional medicine. The dye from the seeds is reported to purge gently, the leaves are said to be febrifugal.

The main commercial producers are countries in South America (especially Peru), Central America, the Caribbean, and also India and Sri Lanka. In South-East Asia annatto is produced on a rather small scale in Malaysia and the Philippines. Production statistics are not usually available, and besides they would not provide a reliable guide to international trade since many of the producing countries utilize significant quantities domestically. However, the available statistics suggest that the world market for internationally traded annatto during the 1970s was 2000—3000 t/year of seed. In recent years, the volume of trade has been slowly increasing as a result of increased consumption of the products in which annatto is used, and may well exceed 3000 t/year by now.
The main market for annatto is the United States, with 1500—2000 t/year, followed by western Europe, the Soviet Union, Puerto Rico and Japan. Some 70% of the product is used in the importing countries in cheese-making.

The principal colouring matter present in the seeds is bixin, C₂₅H₃₀O₄, a carotenoid carboxylic acid, and a harmless organic dye. The ethyl ester of bixin, C₂₇H₃₄O₄, is used as a suspension in vegetable oil for colouring foods. It imparts a golden yellow colour. The dye is sensitive to light and contains sulphur dioxide, which limits its use in food products and beverages. It has no provitamin A activity, and is therefore not much used for colouring margarine. The remainder of the pigment mass surrounding the seed (20—30%) consists mainly of an uncharacterized yellow pigment with little tinctorial strength, and small quantities of related compounds including norbixin.
Annatto is prepared as a solution in vegetable oil, as an aqueous solution of norbixin, as bixin crystals, and as a spray-dried water-soluble powder.
The bixin content of the seeds is 1.6—5.3% on an oven-dry basis in Papua New Guinea, but elsewhere contents up to 12% have been reported. The proportion of bixin present in annatto varies considerably, and depends on the nature of the product. Norbixin concentrations of commercially available spray-dried annatto powder ranges from 7.5% to 15%; a solution in vegetable oil usually contains 0.2—5% bixin. The seeds contain a small amount of fatty oil (5%), and about 13% of protein. The seed-coat contains a wax-like substance which acts as a vermifuge. A very poisonous substance has been found in the embryo. The fruit-wall contains tannin. Ellagic acid and cyanidin have been isolated from the leaves.
The wood is soft, light (air-dry weight about 400 kg/m³, yellowish to light brown, porous, and not durable.

An evergreen shrub or small tree, 2—6(—8) m tall, trunk up to 10 cm in diameter. Bark light to dark brown, tough and smooth, sometimes fissured, lenticellate; inner bark with orange sap. Branches greenish and densely rusty-scaly when young, later becoming dark brown, ringed at nodes. Leaves spirally arranged, simple, herbaceous, stipulate, ovate, 7.5—24 cm x 4—16 cm, shallowly cordate to truncate at base, long-acuminate at apex, dark green above, greyish or brownish-green beneath, scaly when young but glabrescent; petiole terete, thickened at both ends, 4.5—12 cm long. Flowers in terminal, 8—50-flowered panicles, fragrant, 4—6 cm across; pedicel scaly, thickened at the apex bearing 5—6 large glands; sepals 4—5, free, obovate, 10—12 cm long, caducous; petals (4—)5—7, obovate, 2—3 cm x 1—2 cm, pinkish, whitish or purplish tinged; stamens numerous, anthers violet; ovary superior, unilocular, style 12—15 mm long, thickened upwards. Fruit a spherical, or broadly to elongated ovoid capsule, 2—4 cm x 2—3.5 cm, flattened, 2-valved, more or less densely clothed with long bristles, green, greenish-brown or red when mature, many-seeded. Seeds obovoid and angular, 4—5 mm long, with bright orange-red fleshy seed-coat. Germination epigeal, seedling with thin, ovate, nervate cotyledons, a fairly long hypocotyl, and alternate, cordate first leaves.

Mature seeds taken directly from fresh fruits germinate readily in 7—10 days under moist conditions. The harvested, cleaned, sun-dried seeds retain viability for over one year, but fall to 12% in 3 years. Pollination is by insects; honeybees are observed in plenty around the plant. Fruits mature 5—6 months after pollination. Seed-grown plants take longer to flower and do so sparingly; they are very tall and exhibit much variation. Plants propagated by cuttings, which allows selection of high-yielding, rapidly growing cultivars, flower early and profusely and bear fruit within two years. These plants are also more uniform in growth and external characteristics.

The variation in shape and colour of the fruits of different forms of annatto tree is considerable. The shape varies from spherical to ovoid, broad-topped and shortly acuminate to elongate-ovoid and long-acuminate. The colour varies from white to green and red. The form with ovoid, broad-topped and shortly acuminate fruits is reported to have a lower bixin content than the forms with spherical or elongated fruits, and is consequently considered inferior. Forms with white flowers occur, but pink-flowered plants are much more common. The species is not subdivided into cultivars.

Annatto tree requires a frost-free, warm, humid climate and a sunny location. It can grow in a wide variety of tropical to subtropical climates and needs little care, though in places where rainfall is not distributed equally throughout the year, irrigation may be necessary. It grows on almost all types of soils, with a preference for neutral and 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 centimetres thick and overlies a coral base. In Indonesia it is planted up to 2000 m altitude.

Annatto tree can be propagated from seeds or stem cuttings. Seeds are sown directly in the field, 2—5 seeds per hole in well prepared beds, usually in the beginning of the rainy season. After germination only one seedling per hole is retained. The seeds may be raised in planting trays, and transferred to 1 kg bags containing soil mixture and raised in the nursery for 3—4 months before they are transplanted. Hardwood cuttings of 0.75 cm or more in diameter readily root when any of the commercial root hormones for hardwood cuttings is used. Roots are produced in abundance in 7—9 weeks. Rooted cuttings are first transferred into pots or bags and kept protected in the nursery and can be transplanted to the field after 3 months. For commercial production, annatto tree should be planted in rows 3—4 m apart, with plants spread 2—3 m within the row, depending on soil and climate.

Weeding is necessary only in the initial stages of plant growth. Once the canopy is formed periodic slashing the weed cover, light pruning to remove the dead, dried and weak stems and to balance the shape of the plant are required to increase economic yield. Lower branches are either tied or pruned to ease farming 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, seed yield may increase.
Annatto tree grows easily and does not exhibit any nutritional deficiencies. Artificial fertilizers are not usually applied. The 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.

Annatto tree is sometimes infested by powdery mildew caused by Oidium bixae and Oidium heveae; the latter fungus causes powdery mildew on rubber, too. A foliar disease of minor importance, caused by a fungus (Phyllosticta bixina) has been recorded for Guam.
Insect pests are of minor importance. The pests include spiralling whitefly (Aleurodicus dispersus), pink wax scale (Ceroplastes rubens), transparent scale or coconut scale (Aspidiotus destructor), Seychelles scale (Icerya schellarum), and red banded thrips (Selenothrips rubrocinctus). In Indonesia, annatto tree is reported liable to be attacked by tropical mirid bugs of the genus Helopeltis.

The capsules should be harvested after they start to turn brown and before they split open. The harvested pods 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 too ripe, or when allowed to stay on the plant long after maturity reduce the quality of the product.

No reliable statistics 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 seed yield is 800—1200 kg/ha. From 1 kg of seed 20—50 g of dye can be obtained.

Seeds that have been properly harvested, dried and threshed retain their quality for a long time provided they are cleaned and dried adequately to about 4—6% moisture and stored in a cool and dry place.
The dye is extracted from seeds by soaking them in water and squeezing to dissolve the aril which contains the dye. It 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 method of extracting the dye is to boil the seeds with sodium carbonate solution, filter, and acidify the filtrate, after which the dye is coagulated by boiling with salt, and is then filter-pressed, washed and dried.
Annatto seed is usually exported in sacks containing 50—80 kg. Processed annatto is packed in polythene bags if powder or crystals, and in high density cans or drums if liquid.
For dyeing cotton, annatto is dissolved in boiling water and a solution of carbonate of soda. The cloth is left in this solution for about 20 minutes, then squeezed dry and washed in acidulated water or 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 the water solution of annatto, without addition of other compounds. For 100 g of wool 100 g of annatto is needed.

Many natural dyes have been superseded by chemical dyes. However, there is still a demand for annatto in the food and cosmetic industry because of the reported carcinogenic activity of many synthetic dyes. Although ß-carotene with its vitamin A activity competes with annatto to some extent in household margarine, the lower price and the lesser complexity associated with the use favour annatto. The major use of annatto is in the cheese-making industry, and the prospects are dependent on the growth of this industry. However, the existing exporters of annatto which are located outside South-East Asia appear to be capable of servicing any conceivable level of demand for the foreseeable future, and opportunities for new suppliers seem to be limited. The scope for rapid improvement in this crop is still considerable.

Anand, N., 1983. The market for annatto and other natural colouring materials, with special reference to the United Kingdom. Tropical Development and Research Institute, London. pp. 10—16.
Backer, C.A., 1951. Bixaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1. Vol. 4. pp. 239—241.
Bhatnagar, S.S. (Editor), 1948. The wealth of India. Raw materials. Vol. 1. Delhi. p. 196, pl. 31.
Crevost, Ch. & Pételot, A., 1941. Catalogue des produits de l'Indochine. Tome 6. Tannins et tinctoriaux. Gouvernement général de l'Indochine, Hanoi. p. 6.
Hart, G., 1964. Bixin content of Bixa orellana in Papua and New Guinea. Papua and New Guinea Agricultural Journal 17: 8—11.
Rajendran, R., 1989. Achiote, Bixa orellana L., a natural food color and dye. AES Publication No 73, College of Agriculture and Life Sciences, University of Guam. 8 pp.

R. Rajendran

Rajendran, R., 1991. Bixa orellana L.. In: Lemmens, R.H.M.J. and Wulijarni-Soetjipto, N. (Editors): Plant Resources of South-East Asia No 3: Dye and tannin-producing plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea