CHUFA, Earth nut, Tiger nut, Yellow nutsedge
Cyperus esculentus L.
Amande de terre (Fr.); Aya (Nig.); Chichoda (Ind.); Earth or ground almond, Enensa (Nig.); Erdmandel (Ger.); Imumu (Nig.); Kaseru (Ind.); Motha (Beng.); Omu (Nig.); Rush nut; Souchet comestible (Fr.); Zulu nut.
An erect perennial, grass-like sedge, usually 30-90 cm high, with long narrow dark-green leaves arranged in three rows around the triangular stem. The plant develops as a series of shoots, bulbs and stem tubers connected by brown wiry rhizomes which are strengthened by lignification of the inner cortex. Tubers are small, 1-2 cm in diameter, and are borne at intervals along the rhizomes. Basal bulbs grow from rhizome tips, producing shoot growth and new plants. The plant, when growing wild, is extremely difficult to eradicate and is stated to be the fifteenth worst weed in the world.
Origin and distribution
Chufa is thought to have originated in the Mediterranean area and western Asia but has spread (mainly as a weed) to many parts of the world. It will grow in a very wide range of climatic conditions, and occurs in the tropics, subtropics and warm temperate regions and is cultivated in several countries.
Temperature - although the plant can be grown in relatively cool climates, optimum yields are obtained with moderately high temperatures throughout the growing season.
Rainfall - a moderate well-distributed rainfall is required for optimum yields. Although chufas are fairly drought resistant, commercial crops receive copious and repeated irrigation during the dry summer season (eg in Valencia, Spain) in order to ensure maximum yields.
Soil - maximum yield is obtained in light sandy loams of pH 5.5-6.5, but chufas can be grown on any well-drained soil. Alluvial sands containing relatively high quantities of manganese, sulphur, calcium, magnesium and boron are particularly suitable. They can be grown on saline soils in coastal areas and are of use in reclaiming such areas. There is little information on the precise fertiliser requirements of chufas but nitrogen is often limiting under natural conditions. The application of a 6:6:8 complete (NPK) fertiliser at the rate of I 000 kg/ha has been recommended. In many areas growers give a heavy dressing of FYM, if available, and wood ash, before or immediately after planting. In Florida, however, the crop has been found to respond very erratically to applications of fertilisers.
Material - tubers are used for propagation.
Method - the tubers are soaked in water for 24-36 hours and then planted, either by hand or drill. Sprouting can be stimulated by treatment with ethylene at 3-10 ppm in air or by ethephon (ethrel) at 10-100 ppm in water.
Field spacing - spacing is extremely variable according to the soil conditions, local cultural methods and the purpose for which the crop is grown. Reports from Florida indicate that when grown for pig feed, chufas are usually drilled in rows 60-90 cm apart, with either 30 cm or 15 cm between the plants. Reports from other countries refer to tubers frequently being planted at 10 cm intervals along rows 60 cm apart. With spacing in the row of 10x60 cm a single tuber is placed in a hole and covered with 2.5-4 cm of soil, with IS x 60 cm spacing two tubers are used and at 30 x 60 cm, four tubers are used.
Seed rate - chufa tubers vary in size so that it is difficult to give even an approximate seeding rate; 16-22 kg/ha has been reported but calculations suggest that over 500 kg may be required when spacing is close and medium-sized tubers are used.
Pests and diseases
In Florida the negro bug, Thyreocoris pulicaria, has been reported to damage the crop; the larvae develop inside the tubers. Proper crop rotation is the best means of control. Chufas are seldom seriously affected by diseases.
Chufas normally take 3-4 months to reach maturity.
Harvesting and handling
The tubers are ready for harvesting when the plants begin to die back; they are usually dug by hand or by running a small lifting plough under them. In Florida groundnut harvesters are sometimes used. The entire plant is laid on the soil and allowed to dry for 1-3 days before the tubers are separated for storage in thin layers in sheds. Tubers for human consumption are washed in running water and then dried either in the sun or artificially, after which they are graded and stored.
Tubers - tubers are normally 1.5-2 cm in length, with a maximum diameter of approximately 1-2 cm. They have very thin skins and the flesh is slightly yellowish-white in newly-formed tubers, but darkens with increasing maturity; the flavour is sweet and nutty.
On sandy soils the yields of tubers are reported to average
800-900 kg/ha, although in Spain, with large-scale cultivation, yields as high
as 8 000
14 000 kg/ha are reported.
The tubers are used as a foodstuff, particularly in Africa, where they are an important food crop with certain tribes. They may be eaten raw, baked as a vegetable, roasted like groundnuts or grated and used to make icecream, sherbets or a milky beverage which is known as 'horchata' in Spain and Latin American countries. In Spain the major proportion of the crop (approximately 1000 t) is used in this manner, and horchata continues to be a popular beverage, in spite of severe competition from carbonated drinks.
Animal feeding - chufas can be used for animal feed and are grown as pig feed in parts of the southern USA.
Confectionery - chufas are sometimes used in certain types of confectionery, often as a substitute for almonds.
Coffee and cocoa adulterant - the ground tubers are sometimes used as a substitute or adulterant of coffee and cocoa.
Secondary and waste products
Oil - the tubers contain 20-28 per cent of a yellow non-drying pleasantly flavoured oil, similar to olive or sweet almond oil. It is used in Spain and Italy for culinary purposes and for the manufacture of soap.
Starch - chufa tubers are potentially a rich source of starch which may be extracted after the oil has been removed from the tubers.
Flour - the tubers can be ground to produce a nutritious flour, which can be used mixed with wheat flour in baking. It has the following composition: protein 3.4 per cent; fat 27 per cent; starch 38 per cent; ash 2.5 per cent.
Alcohol - chufa tubers can be used for the production of alcohol by fermentation. In Sicily, a cultivar with a very high sucrose content is grown and used commercially for this purpose.
Leaves - it has been suggested that the leaves of the chufa could be utilised for papermaking; simple digestion with soda lye will give a yield of 35-40 per cent of a deep-yellow coloured pulp.
Tubers - chufa tubers are rich in both starch and oil. They are variable in composition: the dry matter of fresh tubers is from about 70 per cent to about 90 per cent. Average analytical figures of the dry matter have been quoted as: residual moisture 9.3 per cent; protein 8.6 per cent; fat 21.8 per cent; carbohydrate 48 per cent; ash 1.7 per cent; magnesium 0.1 mg/100 g; phosphorus 211.5 mg/100 g; potassium 0.5 mg/100 g.
The carbohydrate consists of 33.4 g starch and 14.6 g total sugars. Quinones occur and have been used as an aid to the classification of the genus Cyperus.
Starch - chufa starch has the following approximate composition: moisture 9 per cent; nitrogenous material 0.3 per cent, fat traces; starch 89.8 per cent; cellulose 0.3 per cent; ash 0.5 per cent. It is a white flavourless product and when heated in water forms a transparent gelatinous paste.
Oil - the oil has the following characteristics: SG (15°C) 0.917-0.924; ND (20°C) 1.4680; sap. val. 190-194; iod. val. 74-89; acetyl val. 4.5-12; RM val. 0.2; Poll val. 0.3; unsap. 0.6 per cent. The oil consists of 17-18 per cent saturated acids of which 12 per cent is palmitic and 5 per cent stearic; of the unsaturated fatty acids present, 75 per cent is oleic acid and 6 per cent linoleic, though this varies to some extent with growing conditions and from cooler areas the proportions have been reported as 67.5 per cent and 15.2 per cent respectively, with a corresponding increase in the iodine value. Chufa oil is resistant to oxidative changes and it has been suggested that it could be added to oils such as coconut oil to retard rancidity.
Horchata, the milky white beverage, is prepared as follows:
(i) The tubers are left to soak in water for 12 hours and then thoroughly washed to remove adhering soil, etc.
(ii) The clean swollen tubers are ground in a crusher and the resultant paste stirred with water and passed through a 25 mesh sieve.
(iii) The residues left on the sieve are stirred with water twice more and the milky liquid obtained added to that from (ii).
(iv) The liquids from (ii) and (iii) are passed through a 100 mesh sieve and the residues pressed to obtain maximum extraction.
(v) Sucrose is then added to the extract at the rate of 150 g/litre and the product is bottled and kept at 0-5°C.
In general, about I kg of chufas will produce 5.5 litres of horchata.
A typical analysis of horchata is: total solids 22.8 per cent; fat 2.6 per cent; starch 2.4 per cent; sucrose 2.1 per cent; reducing sugars 0.03 per cent; ash 0.24 per cent; vitamin B 0.02 mg/100 g; ascorbic acid 0.27 mg/100 g. The pH is approximately 7 and Brix 18.3°.
When prepared on a commercial scale and stored at 0.5°C horchata quickly ferments and has a storage life of only 48 hours; for this reason attempts have been made to produce a more stable commercial product, eg by the production of frozen concentrates or using infra-red radiation. Pasteurisation before bottling is stated to extend the storage life of the chilled product to about four weeks without adverse effect on flavour.
Freeze drying is a promising (though costly) technique, which, with the incorporation of the antioxidant EDTA (ethylenediaminetetracetate) and packaging in nitrogen, gives a product of excellent quality with a storage life of four months at 37°C or about one year at 25°C. Spray drying has also been investigated.
Although most of the literature on chufa is concerned with its eradication as a weed, there is continuing interest in the plant as a food and as a drink in the form of horchata. Certain vegetarian organisations have promoted chufa tubers as a complete food, in spite of the fact that their protein content is relatively low and their high cellulose content is nutritionally detrimental.
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