*2.4.2 Dioscorea bulbifera*

It is usually cultivated in Africa and Asia, with slight differences between those found in each place. It is a large vine of about 6 meters (20 ft.) or more in length and produces tubers (bulbils) which grow at the base of its leaves. It is an important food product and it is about the size of potatoes (hence the name "air potato"), weighing from 0.5 to 2 kg (1 to 5 lbs.) [40]. Some known varieties of air potato can be eaten raw while some need to be detoxified by either soaking or boiling before eating. Its growth for commercial purpose is hampered by its moderately unpleasant


**199**

*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects*

flavor, making other yam to be mostly preferred by consumers [41, 42]. The aerial or air yam is popular in home vegetable gardens, because it produces its first bubils only after four months of growth and thereafter throughout the life of the vine, as

This yam specie got its common name from its yellow flesh, due to the presence of carotenoids. It is a West African native; it has a longer period of vegetation and a shorter dormancy than white yam [44]. Yellow and white yam were considered in past as two separate species, but now they are been considered as same specie by most taxonomists with about over 200 cultivated varieties between them [44]. They are large and their vines are as long as 10 to 12 meters (35 to 40 feet). The tubers can weigh up to about 2.5 to 5 kg (6 to 12 lbs.) each for an average size, but extra large tubers can weigh as much as 25 kg (60 lbs.) [40]. The maturation stage after planting is 7 to 12 months [45]. It is commonly used in Africa for the traditional popular

The tuber is commonly referred to as cluster yam, bitter yam or trifoliate yam. It is called *"ona*" by the Igbos of Southeast Nigeria and 'esuru' by the Yorubas in Southern Nigeria [42, 47]. The tuber contains fleshy edible part having a yellowish or whitish color which can be boiled and eaten as snacks. Extract from the tubers can be used for the treatment of *diabetes mellitus* in traditional medicine [48, 49]. It has been reported that the tuber is rich in fiber and contains an

alkaloid, dioscorentine, which possesses hypoglycemic activity [50, 51]. It is fairly high in protein and possesses a well balanced amino acid profile, making it the most nutritious of the commonly consumed yam species. It has been established that trifoliate yam contain 15–38% starch on wet weight basis and 70–80% dry

This type of tuber is popularly referred as 'Chinese yam'; it is smaller than other known yam species grown in Africa [24]. It possesses ability to tolerate cold temperature and can be grown in much cooler conditions than other yams. It is commonly grown in China, Korea, and Japan and it was introduced to Europe in the 1800s when the potato crop was affected by diseases [53]. In France, it is still grown for Asian food market. The tubers mature in 6 months and can be eaten immediately after harvest, while others are used as ingredients for other dishes, including

This yam specie is native to Africa. It produces edible tubers that possess economic importance [55]. It is among the most important cultivated yam species and it is mostly consumed in West Africa and Cameroon [56]. It has a long shelf-life which makes it available all year round. White yam are subjected to different cooking methods in Western and Central Africa, however, the most common ones are boiling, frying and roasting [29]. It is mostly used in Africa for the traditional popular dish known as "iyan" (pounded yam). Sun-drying of parboiled yam pieces and then milled into a light-brownish powder (*elubo*) is another method of processing

*DOI: http://dx.doi.org/10.5772/intechopen.95020*

dish known as "iyan" (pounded yam) [46].

noodles and traditional medicines [24, 54].

*2.4.6 Dioscorea rotundata Poir (white yam)*

long as two years [41, 43].

*2.4.4 Dioscorea dumetorum*

weight basis [52].

*2.4.5 Dioscorea esculenta*

*2.4.3 Dioscorea cayenesis*

#### **Table 2.**

*Nutrient content of white yam in comparison with other crops.*

flavor, making other yam to be mostly preferred by consumers [41, 42]. The aerial or air yam is popular in home vegetable gardens, because it produces its first bubils only after four months of growth and thereafter throughout the life of the vine, as long as two years [41, 43].
