| Chufa sedge | |
|---|---|
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Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Clade: | Commelinids |
| Order: | Poales |
| Family: | Cyperaceae |
| Genus: | Cyperus |
| Species: | C. esculentus |
| Binomial name | |
| Cyperus esculentus | |
| Synonyms[2] | |
Synonymy
| |
Cyperus esculentus (also calledchufa,[3]tiger nut,[4]atadwe,[5]yellow nutsedge,[6]earth almond, and in Chishona,pfende[7]) is a species of plant in thesedge family widespread across much of the world.[8] It is found in most of the Eastern Hemisphere, includingSouthern Europe,Africa andMadagascar, as well as theMiddle East and theIndian subcontinent.[9][10][11]C. esculentus is cultivated for its edibletubers, called earth almonds or tiger nuts (due to the stripes on their tubers and their hard shell), as asnack food and for the preparation ofhorchata de chufa, a sweet, milk-like beverage.[12][13]
Cyperus esculentus can be found wild, as a weed, or as a crop. It is aninvasive species outside its native range, and is readily transported accidentally to become invasive. In many countries,C. esculentus is considered a weed.[12][14] It is often found in wet soils such as rice paddies and peanut farms as well as well-irrigated lawns and golf courses during warm weather.
Cyperus esculentus is anannual orperennial plant, growing to 90 centimetres (3 feet) tall, with solitary stems growing from a tuber. The plant is reproduced by seeds, creeping rhizomes, and tubers.[15] Due to itsclonal nature,C. esculentus can take advantage of soil disturbances caused by anthropogenic or natural forces.[16][17] The stems are triangular in section and bear slenderleaves 3–10 millimetres (1⁄8–3⁄8 inch) wide. The spikelets of the plant are distinctive, with a cluster of flat, oval seeds surrounded by four hanging, leaf-likebracts positioned 90 degrees from each other. They are5 to 30 mm (1⁄4 to1+1⁄8 in) long and linear to narrowly elliptic with pointed tips and 8 to 35 florets. The color varies from straw-colored to gold-brown. They can produce up to 2420 seeds per plant. The plant foliage is very tough and fibrous and is often mistaken for agrass. The roots are an extensive and complex system of fine, fibrous roots and scaly rhizomes with small, hard, spherical tubers and basalbulbs attached.
The tubers are0.3–2.5 cm (1⁄8–1 in) in diameter and the colors vary between yellow, brown, and black.[18][19] One plant can produce several hundred to several thousand tubers during a single growing season. With cool temperatures, the foliage, roots, rhizomes, and basal bulbs die, but the tubers survive and resprout the following spring when soil temperatures remain above 6 °C (43 °F).[15] They can resprout up to several years later.[20] When the tubers germinate, many rhizomes are initiated and end in a basal bulb near the soil surface. These basal bulbs initiate the stems and leaves above ground, and fibrous roots underground.C. esculentus is wind pollinated and requirescross pollination as it is self–incompatible.
Cyperus esculentus is a highly invasive species inOceania,Mexico, some regions of theUnited States, and theCaribbean, mainly by seed dispersion.[12] It is readily transported internationally, and is adaptable tore-establish in varied climate and soil environments.[12] InJapan, it is an exotic clonal weed favorable to establish in wet habitats.[12]Cyperus esculentus serves as a larval host forEuphyes vestris (dun skipper)[21]andDiploschizia impigritella (yellow nut-sedge moth) in North America.[22]Cyperus esculentus likely reached thenew world through ocean currents before theHolocene.[23]
Cyperus esculentus is cultivated inEgypt,Spain,Nigeria, theUnited States,Guatemala,Mexico,Chile,Brazil,Lebanon,Syria,Jordan,Saudi Arabia,Oman,Iran,Iraq,Pakistan,India,Yemen,Morocco,Ivory Coast,Sudan,South Sudan,Gambia,Guinea Bissau,Ghana,Niger,Burkina Faso,Togo,Benin,Cameroon, andMali, where they are used primarily as animal feed or as a side dish, but inHispanic countries they are used mainly to makehorchata, a sweet, milk-like beverage.
Cyperus esculentus cultivation requires a mild climate. Low temperature, shade, and light intensity can inhibit flowering.[18] Tuber initiation is inhibited by high levels of nitrogen, long photoperiods, and high levels ofgibberellic acid. Flower initiation occurs under photoperiods of 12 to 14 hours per day.
Tubers can develop in soil depths around 30 cm, but most occur in the top or upper part. They tolerate many adverse soil conditions including periods of drought and flooding and survive soil temperatures around −5 °C (23 °F). They grow best on sandy, moist soils at a pH between 5.0 – 7.5.[18] The densest populations ofC. esculentus are often found in low-lying wetlands.[24] They do not tolerate salinity.[18]
Cyperus esculentus is normally planted on previously tilled flat soils with ridges to facilitate irrigation. Seeds are planted manually on these ridges, which are approximately 60 cm (2 ft) apart. Distances between seeds may vary from 15 to 20 cm (6 to 8 in) and seeding depth is around 8 cm (3 in). A typical seeding rate for chufa is about 120 kg of tubers/ha (107 lbs/acre).[25]
They are planted between April and May and must be irrigated every week until they are harvested in November and December. Tubers develop about 6–8 weeks after seedling emergence and grow quickly during July and August. The maturing is around 90–110 days. The average yield can approach between 10 and 19 t/ha.[26][27]
Cyperus esculentus is extremely difficult to remove completely once established. This is due to the plant having a stratified and layered root system, with tubers and roots being interconnected to a depth of 36 cm or more.[18] The tubers are connected by fragile roots that are prone to snapping when pulled, making the root system difficult to remove intact. Intermediate rhizomes can potentially reach a length of 60 cm. The plant can quickly regenerate if a single tuber is left in place. By competing for light, water and nutrients it can reduce the vigour of neighbouring plants. It can develop into a dense colony. Patch boundaries can increase by more than one meter per year. Tubers and seed disperse with agricultural activities, soil movement or by water and wind. They are often known as a contaminant in crop seeds. When plants are small they are hard to distinguish from other weeds such asDactylis glomerata andElytrigia repens. Thus it is hard to discover in an early stage and therefore hard to counteract. Once it is detected, mechanical removal, hand removal, grazing, damping, and herbicides can be used to inhibitC. esculentus.
Harvest usually occurs in November or December and the leaves are scorched during the harvest. With a combine harvester, the tiger nut is pulled out of the ground. Immediately after harvesting, the tiger nuts are washed with water in order to remove sand and small stones. The drying occurs usually in the sun and can take up to three months.[28] The temperatures and humidity levels have to be monitored very carefully during this period. The tiger nuts have to be turned every day to ensure uniform drying. The drying process ensures a longer shelf life. This prevents rot or other bacterial infections, securing quality and high nutrition levels.Disadvantages in the drying process are shrinkage, skin wrinkles and hard nut texture.[citation needed]
Tiger nut loses a considerable amount of water during drying and storage. The starch content of the tiger nut tubers decreases and the reducing sugar (invert sugar) content increases during storage.[29] Tiger nut can be stored dry and rehydrated by soaking without losing the crisp texture. Soaking is often done overnight. Dried tiger nuts have a hard texture and soaking is required to render them more easily edible and to ensure acceptable sensory quality.[18]
According to theConsejo Regulador de Chufa de Valencia (Regulating Council for Valencia's Tiger Nuts),[30] the nutritional composition/100 ml of the Spanish beverage horchata de chufas is as follows: energy content around 66 kcal,proteins around 0.5 g,carbohydrates over 10 g withstarch at least 1.9 g,fats at least 2 g.
Dried tiger nut has a smooth, tender, sweet, and nutty taste. It can be consumed raw, roasted, dried, baked or astiger nut milk,tiger nut drink or oil.
In Spain, the drink now known as horchata de chufa (also sometimes called horchata de chufas or, in West African countries such as Nigeria and Mali,kunun aya) is the original form of horchata.[dubious –discuss] It is made from soaked, ground and sweetened tiger nuts mixed with sugar and water.[31]It remains popular in Spain, where a regulating council exists to ensure the quality and traceability of the product in relation to the designation of origin. There it is served ice-cold as a natural refreshment in the summer, often served withfartons.The majority of the Spanish tiger nut crop is utilised in the production of horchata de chufa.Alboraya is the most important production centre.
The tubers can be roasted and ground into acoffee substitute.[32]
The tubers areedible raw or cooked.[33] They have a slightly sweet, nutty flavour, compared to the more bitter-tasting tuber of the relatedCyperus rotundus (purple nutsedge). They are quite hard and are generally soaked in water before they can be eaten, making them much softer and giving them a better texture. They are a popular snack in West Africa. The tubers can also be dried and ground into flour.[33]
InNorthern Nigeria, it is calledaya and it is usually eaten fresh. It is sometimes dried and later rehydrated and eaten. A snack made by toasting the nuts and sugar coating it is popular among theHausa children ofNorthern Nigeria. Also, a drink known askunun aya is made by processing the nuts withdates and later sieved and served chilled.
In Egypt, tiger nuts are known by the nameHab el-Aziz and after softening it by soaking in water, it is sold on hand carts as a street food.[34] Its popularity was depicted in movies, such as the song named after it, "Hab el Aziz".
Flour of roasted tiger nut is sometimes added to biscuits and other bakery products as well as in making oil, soap, and starch extracts. It is also used for the production of nougat, jam, beer, and as a flavoring agent in ice cream and in the preparation ofkunu (a local beverage in Nigeria).[citation needed] Kunu is a nonalcoholic beverage prepared mainly from cereals (such as millet or sorghum) by heating and mixing with spices (dandelion, alligator pepper, ginger, licorice) and sugar. To make up for the poor nutritional value of kunu prepared from cereals, tiger nut was found to be a good substitute for cereal grains. Tiger nut oil can be used naturally with salads or for deep frying. It is considered to be a high-quality oil. Tiger nut "milk" has been tried as an alternative source of milk in fermented products, such as yogurt production, and other fermented products common in some African countries and can thus be useful replacingmilk in the diet of people intolerant tolactose to a certain extent.[14]
Since the tubers ofC. esculentus contain 20-36% oil, it has been suggested as potential oil crop for the production ofbiodiesel.[35] One study found that chufa produced 1.5 metric tonnes of oil per hectare (174 gallons/acre) based on a tuber yield of 5.67 t/ha and an oil content of 26.4%.[36] A similar 6-year study found tuber yields ranging from 4.02 to 6.75 t/ha, with an average oil content of 26.5% and an average oil yield of 1.47 t/ha.[37] The oil of the tuber was found to contain 18% saturated (palmitic acid andstearic acid) and 82% unsaturated (oleic acid andlinoleic acid)fatty acids.[35]
The boiled nuts are used in the UK as a bait forcarp. The nuts have to be prepared in a prescribed manner to prevent harm to the fish. The nuts are soaked in water for 24 hours, and then boiled for 20 minutes or longer until fully expanded. Some anglers then leave the boiled nuts to ferment for 24–48 hours, which can enhance their effectiveness. If the nuts are not properly prepared, they can be toxic to carp. This was originally thought to have been the cause of death ofBenson, a large, well-known female carp weighing 54 lb (24 kg) found floating dead in a fishing lake, with a bag of unprepared tiger nuts lying nearby, empty, on the bank. An examination of the fish by ataxidermist concluded tiger nut poisoning was not the cause of death, but rather the fish had died naturally.[38]
It has been suggested that the extincthomininParanthropus boisei (the "Nutcracker Man") subsisted on tiger nuts.[39]
Cyperus esculentus was one of the oldest cultivated plants in prehistoric andAncient Egypt, where it was an important food. Roots of wild chufa have been found atWadi Kubbaniya, north ofAswan, dating to around 16,000 BC.[40] Dry tubers also appear later in tombs of thePredynastic period, around 3000 BC. During that time,C. esculentus tubers were consumed either boiled in beer, roasted, or as sweets made of ground tubers with honey.[41] The tubers were also used medicinally, taken orally, as an ointment, or as an enema, and used in fumigants to sweeten the smell of homes or clothing.[42] Chufa continued to be an important source of food in theDynastic period, and cultivation of the plant remained exclusively in Egypt.[43] The tomb of thevizierRekhmire from the 15th century BCE, shows peasants preparing and measuring tiger nuts to make votive cakes as offerings to the godAmun.[44][45] The modern name for tiger nuts in Egypt is حب العزيز(Hab el Aziz = grains ofAl-Aziz) named after the Fatimid ruler who was reputedly fond of it.[34]
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