*2.4.3 Dioscorea cayenesis*

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

nutrient content of yam is compared with other crops in **Table 2**.

**2.4 Yam varieties**

*2.4.1 Dioscorea alata*

*D. trifida* [39].

*2.4.2 Dioscorea bulbifera*

**COMPONENT (PER 100G PORTION)**

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

(bitter yam), *Dioscorea esculenta* (lesser yam), *Dioscorea opposita* (Chinese yam), *Dioscorea rotundata* (white yam), and *Dioscorea trifida* (cush-cush yam) [33]. Among the species mentioned above, *Dioscorea rotundata* and *Dioscorea cayenensis* are the most commonly grown for consumption and commercial production. Yam contains mainly carbohydrates with little amount of proteins, lipids and vitamins, and it can provide around 110 calories per 100 grams of products [34]. Yam possesses high in moisture, dry matter, starch, dietary fiber, vitamin B6, but low in saturated fat, sodium and vitamin A contents. Yams contain about 5–10 mg/100 g of vitamin C, and the limiting amino acids are isoleucine and sulfur containing amino acids. They also contain a compound called "diosgenin", which can be extracted and used as base for drugs such as cortisone and hormonal drugs. Some species contain alkaloids (e.g. dioscorine C 13H 19O 2N) and steroid derivatives [34]. However, the

It is widely called "water yam", "winged yam" and "purple yam". It is the most widely cultivated specie globally and it is second to white yam in popularity [36, 37]. Water yam is economically important yam specie which serve as a staple food for millions of people in tropical and subtropical countries, and with a great potential for increase in consumers demand due to its low sugar content necessary for diabetic patients [38]. Aside from being source of carbohydrate, it also possesses higher content of protein and low lipids than *D. cayenensis*, *D. escunlenta*, *D. rotundata* and

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

**Staple Maize/Corn Rice Wheat Potato Cassava Soybean** 

**Water (g)** 10 12 13 79 60 68 70 **Protein (g)** 9.4 7.1 12.6 2 1.4 13 1.5 **Fat (g)** 4.74 0.66 1.54 0.09 0.28 6.8 0.17 **Carbohydrate (g)** 74 80 71 17 38 11 28 **Fiber (g)** 7.3 1.3 12.2 2.2 1.8 4.2 4.1 **Sugar (g)** 0.64 0.12 0.41 0.78 1.7 0 0.5

**Crops**

**(Green)**

**Yam**

**198**

**Table 2.**

*Source: Kumar et al. [35].*

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