NUTRITIONAL VALUE OF DIOSCOREA BULBIFERA (AERIAL YAM)
ABSTRACT
Dioscorea bulbifera is a major stable food crop which is a species of yam widely distributed around the world in tropical and subtropical regions. Dioscorea bulbifera have been traditionally used to lower glycemic index, thus providing a more sustained form of energy and better protection against obesity and diabetics, it also has anti-cancer properties. The present study was undertaken to investigate the nutritional profile and phytochemical screening of Discorea bulbifera. Which contain protein 7.47%, moisture 14.74%, ash 2.56%, fiber 0.35%, carbohydrate 73.62%. It also show the presence of some minerals like, Ca, Mg, K, P, and Na with some phytochemical analysis like saponin, tannin, flavoured and alkaloids.   
CHAPTER ONE
1.0    INTRODUCTION
        Dioscorea bulbifera is a species of yam, it is one of the early foods, it was extensively cultivated and used by the generation of individual as an house hold name, means of survival, medicine and food etc. with different method of cooking, some roast, boil, and eat with oil and condiment, depending an individual. It has been agreed upon that people of old leave longer and the healthy, in respective of their none exposure, low health care system, poor sanitation and hygiene than the present century, even with all these facility close to our door step yet many fall appeal to various type of sickness and many wonder why?
        An evaluation on the kind o food people of old depend on was found out to be the secret in other to verify, and confirm. (Oke, 1990). The most common tubers that were feed on by the old was picked and worked on. This was to check for the nutritive value, importance and uses of the aerial yam. Surprisingly most people dose not know such yam exist, and it is rarely sold in market. Only few people in this part of the eastern land still cultivate this yam species because of the value and importance.
        This study is to help you found at the nutritive content of the aerial yam being one of the food eaten by people of the old which is their secret for healthy living and to inspire many people to revisit most the crop being cultivated and harvested by people of old and more light should be thrown on them.
1.1    LITERATURE REVIEW
        Dioscorea bulbitera is one of the various species of yam. Yam is the common name of some species in the genus dioscorea, they are perennial herbacocous vines cultivated for the consumption of their starchy tubers in African, Asia, Latin America etc. yam is a versatile vegetable it can be barbecued (using less heat). Roasted, fried, boiled, etc. yam are stable crops of the Igbo people in Nigeria in their language it is known as “ji” and they commemorate it by having a yam festival as a symbolism of fresh crop and availability of fresh food in abundance all over Nigeria. The new yam festival is known as “iri-ji” or iwa-ji” depending on the dialect. Yams are primary agricultural, and commonly important in west Africa, where over 95% of worlds yam crop is harvested, they are important for survival, they serve as a means of lively hood for some people. There are over 600 varieties of yam and 95% of it are grown in African (library congress 2011). Example of the varieties of yam are the white yam which is known as dioscorea volundata, Chinese yam (D. oposita), yellow (D. cayenesis) water yam (D. alatal) lesser yam (D. esculenta) Bitter yam (D. dumetorum), cush yam (D. trifida) and Air potato (D. bulbifera) etc. (key 1937)
        D. bulbitera is a yam species it is also know as varahi in Sanskrit, kaachi in malayalam, Dukkar kand in maraitu, Aldo in some part of Igbo land in Nigeria or Aerial yam the English name or Air potato. The Air potato plant is a nature of Africa and Asia; it is an invasive species in many tropical including Florida (Duke et al 1993). The Air potato was introduce to the Americans from African in 1905 it was introduced in Florida due to its ability to displace native species and disrupt natural processes such as fire and water flow air potato has been listed as one of the Florida’s most invasive plant spp since 1993 and was placed on the Florida Noxious weed list by the Florida Department of Agriculture and consumer since (1999)
1.2    SCIENTIFIC CLASSIFICATION OF D. BULBIFERA (TAXONOMY)
Kingdom – plantea
(unranked) – angiosperms
(unranked) – monocots
Order – Dioscoreales
Family – Dioscoreacece
Germs – Dioscorea
Species – D. bulbifera
Binomial name Dioscorea bulbifera, Air potato, aerial yam (Duke, James et al 1993)
1.3    D. BULBIFERA SPECIES DESCRIPTION
Aerial yam is a perennial vine with broad leaves and two types of storage organs. The plant form bubils in the leaf axils of the twining stems and tubers beneath the ground. These rigorously twining long stemmed herbaceous which may arise from under ground tuber although often tubers are inconspicuous or absent. The stems are round to slightly angled in cross section and they twine counter- clockwise. Conspicuous aerial tubers called bulbils are pale round to globose in shape up to 13cm wide and are formed in leaf axils it is this bulbils that give D. bulbifera the common name air potato. The leaves are attractive, alternate, broady heart shaped up to 20cm long and attached by long petiole. They are divided longitudinally into lobes by proximate arching vieas all radiating out from a single point of origin where the petiole attached to the leaf flowers rarely occur in D. bulbifera where occurring, they are small pale green and fregnants arising from leaf axils. The fruit is a capsule and the seeds are partially winged (langland and Buks 1998, langeland 2001).
        The tubers often have a bitter taste which can be removed either by socking or boiling for detoxication (Kay, 1987) before eating. It is not grown much commercially since the flavour of other yams is preferred by most people. They are prepared like other yams. The air potato is the most widely consumed yam species in 1960’s it can grow up to 150ft tall, it grows extremely quickly, roughly 8 inches per day and eventually reach over 60ft long. It typically climbs to the tops of trees and have the tendency to take over native plants. New plants develop from bulbils an underground tuber. The primary means of spread and reproduction are via bubils, the smallest bubils make, control of air potato difficult due to their ability to sprout at a very small stage the vine produces small white flowers, are rarely seen when it grows. The fruit are capsules (National Tropical Botanical Garden 2007)
1.4    INVASION INFORMATION
The plant was first introduce to the world during the share trade and subsequently transported to Florida in 1905 as USDA sample, sent for Horticulural examination (Coursey 1967 and Sehults 1993). They receive and example the sample in which they saw the potential danger that the aggressive potential invader post for the state. Vigorous a sexual, reproduction via bubils has facilitated the continued spread of invasive vine throughout most of the state (mantinez 1993) bubils can last a year or more on the ground and still sprout and spoil contact D. Bubifera have become rampart on undeveloped land around Tapa by 1996 the plant had been reported from natural areas in Florida countries (large land and Burk 1998). As of 2007 the Florida exotic pest plant concil early detection and mapping system states that D. bulbilfera now occurs in at least 46 (of 67) Florida countries
1.5    POSSIBLE ECONOMICS CONSEQUENCES OF INVASION
        D. bulbifera is listed as an invasion exotic plant in Florida, indicating that the species is currently altering native plant community by displacing native species and changing community structure or ecological functions. Asexual propagation by means of bulbils that drop off, of parent vines to the ground in abundance ensure that eradication of the plant is exceedingly difficult once it has invaded an area. If the plant is cut to the ground the tubers can survive for extended periods and send up New short latter. In many part of the world the tubers and bulbils of D. bulbifera are used as food and the plant has also long been used as a flok medicine including use as an analgesic, aphrodisiac, diuretic and a rejuvenative tonic. The steroid diosgenin, an active component of birth control pills is extracted from the plant as is the anti-fungal compound dihydrorodio scor
1.6    SALINITY
          Air potato is not salt tolerant and is an in successful invader of marine and esluarine shorelines (Morisawa, 1999)
1.7    TOXICITY
        Aerial yams have anti-nutritional factors. In Asia detoxication and roasting of the grated tuber are used for better cultivars of this yam. The bitter compounds in yams also known locally as air potato including disobulbin and possibly saponins. These substance are toxic causing paralyses (Oke 1990). Also the wild from of bitter hence are referred to as bitter yam. Yam are usually detoxified in a vessel of salt and H20 in cold, hot, fresh or in stream. The bitter compound of the yam are H20 soluble alkaloids which on ingestion produced several and distressing symptoms. Severe cases of alkaloid intoxication may prove fatal.
        Uncultivated forms such as those found growing wild in Florida can be poisonous. These varieties contain the steroid, diosgenin which is a principal material used in the manufacture of a number of synthetic steroidal hormones such as those used in hormonal contraception (National Tropical Botanical Garden 2007). There have been claims by pest plant air potato 2010 that even the wild form are rendered edible after drying and boiling leading to confusion over actual toxicity
 1.8    EMBROYOLOGY
        In areas where they are produced D. bulbifera seeds are wind –dispersed (Hammer, 1998) even where flowering occurs more regularly sexual reproduction via seed in still likely of secondary importance. Seed of D. Bulbefera and other members of genus are believed to undergo an obligate dormancy period of several months before they germinate. This strategy is probably and evolutionary by adaptation to ensure that the presence of viable seeds in the seed bank when breaks in forest canopy cover occur. A laboratory genuine regime for viable non-dormant D. bulbifera seed indicate that germination occurs in approximate twenty one days at 300c (Elis et al 1985). They also and be dispersed by flood H20 and appear to be little impacted by feeding from raccoons feral pigs and other animals (Coursey 1967 Morisawe 1999)
1.9    REPRODUCTION
        Reproduction in D. bulbifera can propagate through sexual and asexual means. Discorea species are doccious with male and female flowers occurring in separate plant. The chief of reproduction in D. bulbifera is asexual and is dependent on dedicative growth from under ground and above-ground bulbils.
        Tubers and burbils generally sprout in the spring and the new short often climb the deed stems of the previous year to reach the tree canopy. In the summer (June-July) a large numbers of new bubils are produced which fall to the ground in late August. By the time seasonal stem die back begins around October a single vine may have out as many as 200 bubils (www.killerparts.com 2004)
1.1.0 POTENTIALLY MISIDENTIFIED SPECIES
          The water yam (D. alata) D. bulbifera are superficially similar in appearance but distinguishing the two is straight toward. D. alata and alternate in D. bulbifera. The underground tubers of D. alata are also enormous, some weighing more than 45kg where as the D. bulbifera are small and may be absent all together. (Largelan and Burks 1998)
1.1.1 STORAGE  
        Roots and tubers such as yam are living organisms when stored they continue to respire. The respiration process result in the oxidation of starch (polymer of glucose) contained in the cell of the tubers which convert it into H2o, Co2 and heat energy. During its transformation of starch the dry malter of the tubes properly stored is consider to be the least perishable. Below are the methods you can observe for successful storage and yam (Linus 2003)
Avoid bad and damage yams, used only sound and healthy yam
Proper curing, if possible combined with fungicide treatment
Adequate ventilation to remove the heat generated by respiration of tubers
Regular inspection during storage and removal of volting tuber and any sprout that develop
Protecting from direct sunlight and remain (temp 14-150c)
SAFETY PROFILE
Yams of African species must be cooked before safely eaten because various nutritional toxin substance such as dioscorina can cause illness if consumed raw. Note yams have a toxic chemical called diosegenin that can be changed through chemical reaction into useful substances. They include the medicine cortisone used for treat of joint pains as in arthritis, allergic reaction like bee stings and rashes and general body inflation and several hormones including estrogen, progesterone and testosterone. The hormones mention are in category called steroids per harps you have heard of steroid as substance used improperly to increases person as athletic ability.
Excessive skin contact with yam fluids can cause the skin to itch. If this occurs a quick cold bath or application of palm oil to the affected part of the body would stop the itching.
 1.1.3 USES
        In many part of the world the tubers and bubils of D. bulbifera are used as food and the plant is cultivated as an agricultural crop, the plant has also, long being use as a flok medicine, including use of analgesic aphrodisiac, diuretic and rejuvenate tonic. Some of the medicinal uses of D. bulbifera are in traditional/Chinese medicine; D. bulbifera is used in the treatment of soar throat, gastric cancer and carcinoma of the reticulum (GAE et al 2007)
It have been traditionally used to lower glycenic index, thus providing a more sustained form of energy and better protection against obesity and diabetics it also have anti-cancer prosperities (Jiang 1978)
Dioseorea bulbifera is used in Bangladesh for the treatment of leprosy and tumors (Murray et al 1984) and by the native people of Western highlands of came room for the treatment of pig cysticercosis through the tubers after collection during farming period, are totally destroyed and burnt because of high bitterness
The roots of D. bulbifera, although considered poisonous because of cytotoxic activity, has been used in Chinese medicine as a remedy of soar throat and for struma (Kormori, 1997)
In Zembabwe this plant is used as an infusion to apply on cuts and stores, both for humans and animals while in Cameroon and Madegascar, the rounded bulbs are applied to abscesses, boils and wound infection (Corgu 2002)
Its bulbs are used in India to treat piles, dysentery syphilis and are applied to ulcers, pain and inflammation (Gupta and Sigh, 1989)
Air potato has been used as a flok remedy or home remedy to treat conjunctivitis, diarrhea and dysentery among other ailment (Duke et al 1993). The steroid diosgenin, an active component of birth control pills is extracted from the plant as the anti-fungal compound dihydrodrodio.