| Root crops |
ARROWROOT, Bermuda arrowroot, St. Vincent arrowroot, West Indian arrowroot.
Maranta arundinacea L.
Aloro (Philipp.); Amaranta (P. Rico); Araru (Philipp.); Ararut (Beng.); Araruta (Braz.); Aroro (Philipp.); Arraroet (Cur.); Arruruz (Fr.); Aru-aru (Braz.); CarÃ¡ maco (S. Am.); Envers blanco (Ant.); Guate (gallina) (Venez.); Hoangting (Viet.); Kuzuukon (Japan); Maranta/e (S. Am.); Mouchasse (St. Lucia); Pfeilwurz (Ger.); Pijlwortel (Nether.); SagÃº (Cur.); SagÃº belanda (Mal.); SagÃº bribri (C. Rica); SalÃº (S. Am.); Uraro (Philipp.); Yuquilla (S. Am.).
An erect, herbaceous, dichotomously branched perennial, 60-180 cm high, with large, fleshy, cylindrical, obovoid subterranean rhizomes, large lanceolate leaves and white flowers arranged in twin clusters, which very rarely produce red seeds. Two main cultivars are recognised in St. Vincent: 'Creole', which has long thin rhizomes, which spread more widely and penetrate more deeply into the soil and 'Banana', which has shorter, thicker, less fibrous rhizomes, produced near the soil surface. The latter is more easily adapted to mechanical harvesting. There are, however, many other cultivars, twenty-two of which were reported to be growing in a Philippine germplasm nursery.
Origin and distribution
Arrowroot is indigenous to tropical America and has long been cultivated in the West Indies, particularly St. Vincent, which produces about 95 per cent of the world's commercial supply. Cultivation has spread to many other tropical countries, including Brazil, India, Sri Lanka, Indonesia and the Philippines.
Temperature-arrowroot is a tropical plant that grows best at temperatures of 20-30°C.
Rainfall-a minimum annual rainfall of 95-150 cm is required, but a sufficient water supply in the soil throughout the growing period of the plant is of primary importance, and optimum yields are only obtained where the rainfall is evenly distributed throughout the year or where the dry season is of short duration.
Soil-arrowroot requires deep, well-drained, slightly acid, loam soils for the best results. Badly-drained and heavy clay soils are unsuitable. When grown on light soils, a degree of shade has been found beneficial. The sandy loam soils of St. Vincent, containing minerals of volcanic origin, have proved admirably suitable for arrowroot cultivation. Fertilising is important. It is recommended that on the St. Vincent soils the crop should receive an 8:5:14 NPK mixture at the rate of 900 kg/ha, 14 weeks after planting.
Altitude-arrowroot normally grows from sea level up to about 900 m but does particularly well near the sea at elevations of 60-90 m.
Material-arrowroot is normally propagated from 'bits' which are small pieces of rhizomes 4-7 cm in length, with buds on them. In parts of Asia the 'bits' are sometimes treated with smoke to aid germination. Suckers are also used occasionally for propagation.
Method-planting usually starts at the beginning of the rainy season, after the soil has been thoroughly ploughed and harrowed to obtain a fine filth (forking may be necessary on steep terrain where mechanisation is not possible). Holes about 8 - 15 cm deep are made and the pieces of rhizome are dropped in and covered with soil. The crop must be kept clean-weeded during the first 3 or 4 months and the flowers removed as they appear. Pre-emergence applications of 2,4-D, MCPA, monuron and diuron at the rate of 1.7 kg/ha have been recommended for weed control.
In St. Vincent, where cultivation usually follows a 5-7 year rotation, small pieces of the rhizomes are usually left in the ground at harvest to produce the root crop.
Field spacing-an average spacing of 75 x 37.5 cm is recommended.
Seed rate-approximately 3 000-3 500 kg of 'bits' are required to plant one hectare.
Pests and diseases
Arrowroot is not normally subject to serious attacks by pests or diseases. In St. Vincent the only pest of any importance is the leaf roller, Calopodes ethlius, which has proved resistant to many common insecticides but has been controlled by deltamethrin. In Brazil and Venezuela, the crop is attacked occasionally by Ascia monuste orseis, Neocurtilla hexedactyla and Scapteriscus vicinus. In parts of the Caribbean, particularly in wet districts, arrowroot sometimes suffers from a rot caused by Rosellinia bunodes. Two leaf blights, caused by Rhizoctonia solani and Pellicularia filamentosa, are reported to infect arrowroot in India. A condition known as 'cigar roots', in which the rhizomes become elongated and very fibrous, has also been reported from the Caribbean but is thought to be due to nutritional deficiencies.
The rhizomes mature in 10-11 months.
Harvesting and handling
The rhizomes are ready for harvesting when the leaves begin to wilt and die down. At this stage the plants are usually dug up by hand and the rhizomes separated from the leafy stem. In St. Vincent a modified potato spinner has been used with limited success to harvest 'Banana' arrowroot. The rhizomes are normally left in the ground until required for processing. Once harvested, deterioration is rapid and the 'Banana' cultivar must be processed within 2 days and the 'Creole' within 7 days.
Rhizomes - these are fleshy, cylindrical, covered with regular scales, and grow to approximately 2.5 cm thick and 20-45 cm long.
Yields of rhizomes normally average about 12.5 t/ha, although under favourable conditions yields as high as 31 t/ha have been recorded. In St. Vincent the normal commercial yield of starch at the factories is 8-16 per cent. Average production of starch per hectare is 2 500 kg, though farmers using improved methods recommended by the St. Vincent Ministry of Agriculture have reported average yields of 3 700 kg (up to 5 600 kg at the maximum).
The rhizomes are used for the production of a very fine, easily-digested starch, which appears on world markets as a dry white powder known as arrowroot starch. It is valued as a foodstuff, particularly for infants and invalids, and is used in biscuits, cakes and puddings.
Arrowroot starch possesses demulcent properties and is sometimes used in the treatment of disorders of the intestine. It may also be employed in the preparation of barium meals and in the manufacture of tablets where rapid disintegration is desirable. The starch is also used as a base for face powders, in the preparation of certain specialised glues and, more recently, in the manufacture of carbonless paper for computers.
Secondary and waste products
(i) The rhizomes are sometimes eaten boiled or roasted.
(ii) In the West Indies the pounded rhizomes may be used for poulticing wounds and ulcers.
(iii) The plant leaves are occasionally used as local packing material.
(iv) The fibrous material, known as 'bittie', which remains after the extraction of the starch can be used as cattle feed or manure. Typical analyses of 'bittie' from 'Creole' rhizomes are: water 12.5 per cent; protein 3.7 per cent; fat 0.3 per cent; starch 64 per cent; fibre 14 per cent; ash 2.2 per cent. Analyses of 'bittie' from 'Banana' rhizomes give: water 11.9 per cent; protein 2.3 per cent; fat 0.3 per cent; starch 50.4 per cent; fibre 14.8 per cent; ash 2.6 per cent.
Arrowroot starch is one of the purest forms of natural carbohydrate and has a high maximum viscosity, although this is adversely affected by the salinity of the processing water.
Typical analyses of 'Creole' rhizomes are: water 69.1 per cent; protein I per cent; fat 0.1 per cent; starch 21.7 per cent; fibre 1.3 per cent; ash 1.4 per cent.
Typical analyses of 'Banana' rhizomes are: water 72 per cent; protein 2.2 per cent; fat 0.1 per cent; starch 19.4 per cent; fibre 0.6 per cent; ash 1.3 per cent.
Arrowroot starch is composed of simple oval grains 15-70 microns in length; the 'Banana' type has a slightly higher proportion of large grains than 'Creole'. Commercial good-quality arrowroot starch should be pure white, clean and free from specks, and have a moisture content of not more than 18.5 per cent, with low ash and fibre content, an initial pH of 4.5-7 and a maximum viscosity of between 512 and 640 Brabender units, according to the grade.
(i) The rhizomes are washed and the skin scales carefully peeled from the white fleshy core, otherwise they impart a bitter taste to the final product.
(ii) The peeled rhizomes are washed again and grated into a coarse pulp.
(iii) The pulp is mixed with a large quantity of clean water and the mixture passed over a series of sieves to separate the fibre.
(iv) The liquid is allowed to stand and the starch to settle out on long tables.
(v) The starch is removed from the tables, mixed with more water and resettled overnight.
(vi) The lumps of starch are placed on racks to air-dry, a process which can take from 4 to 14 days according to the weather; slow drying can result in the material becoming discoloured.
(vii) After drying, the lumps of starch are pulverised and prepared for marketing in different grades according to viscosity ratings. The pulverised starch is packed in moisture-proof bags.
Most of the St. Vincent factories operate on a combination of the small scale and large-scale techniques.
(i) On arrival at the factory the rhizomes are first thoroughly washed in special tanks.
(ii) They are then cut into small pieces, rasped and crushed into a pulp.
(iii) The pulp is passed in a continuous flow of water into a series of three vibratory sieves.
(iv) The starch milk then passes to the separator.
(v) The residues remaining on the sieves are crushed and sieved twice more to effect the maximum extraction of starch. The resultant starch milk is passed to the separator.
(vi) The separator divides the starch from the water within 4 minutes and it is next mixed with fresh water, passed through a fine sieve of 120 mesh wire cloth and re-centrifuged.
(vii) The starch is then mixed with fresh water, treated with sulphurous acid and fed into settling tanks.
(viii) After the starch has settled, the supernatant liquid is run off and the upper layers of sediment are washed away by vigorous hosing to remove as much as possible of the residual fibrous tissue.
(ix) The starch is then dried in low temperature driers at 55-60°C for 2-3 hours, to a moisture content of approximately 17 per cent or slightly less.
(x) When dry, the starch is pulverised as in the small-scale processing procedure.
Production and trade
Production - St. Vincent accounts for the major proportion of the world's output of arrowroot, but for several years it has been grown to a moderate extent in Brazil, mainly in the Otujai valley, Santa Catarina. Arrowroot starch facilities are known to exist in China. Following an exceptionally heavy crop resulting in 4 000 t of unsold stock, production in St. Vincent declined steadily and might have collapsed entirely, but in recent years there has been renewed interest, particularly from buyers in the USA where arrowroot starch is used in the manufacture of carbonless paper for computers.
Production in St. Vincent during the period 1960-80 was: 1960, 2 952 1964, 5 400 t; 1968, 1 272 t; 1972, 784 t; 1976, 740 t; 1980, 630 t.
Current production in each of St. Vincent and Brazil is less than I 000 t/a.
Trade - Exports - St. Vincent: 1961-65 average, 2 939 t/a; 1966-69, 2 097 t/a; 1972, 842 t; 1974, 930 t; 1976, 720 t; 1978, 810 t. Brazil: 1961-65 average, 159 t/a; 1966-69, 139 t/a The export market in 1983 was about I 000 t/a.
Imports - most countries do not show arrowroot separately. Imports of 'arrowroot' starch, which includes sago (ie cassava) starch and flour, into the USA, were reported as: 1961-65 average, 2 158 t/a; 1966-70, 1 492 t/a.
The demand for arrowroot starch tends to be limited by its high price compared with other starches and the fact that its manufacture requires large quantities of very pure water. In St. Vincent, recent attempts to increase production to meet the increased demand from the USA for arrowroot starch for use in the manufacture of carbonless paper for computers have been handicapped by the shortage and cost of labour to harvest the crop, and there is an urgent need to mechanise field production. Even so, as arrowroot starch is sold entirely on the basis of its 'special properties', and recent developments in starch technology have produced cheaper substitutes, eg fractionated wheat starch, market competition is becoming more severe and a decline rather than an increase in demand seems likely.
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